Unmanned E-mag September 2015

UNMANNED Systems

E M A G

2015 Volume 2 Number 1

ññ UAS certification and DDS ññ Thermosets’ cost and reliability ññ Choosing a rugged Ethernet

switch/router solution

ññ LeddarTech optical time-of-flight

sensing technology

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Sponsored by: Verocel, Isola, Curtiss-Wright Defense Solutions, LeddarTech, GE Intelligent Platforms, Annapolis Micro Systems, Sealevel

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UNMANNED Systems

E M A G

2015 Volume 2 Number 1

Featuring Unmanned Air Systems certification and DDS

By George Romanski, Verocel, Inc.

Thermosets’ cost and reliability advantages for auto radar PCBs

By Isola Group

Choosing a rugged Ethernet switch/router solution

By Mike Southworth, Curtiss-Wright Defense Solutions

Leddar optical time-of-flight sensing technology: a new approach to detection and ranging

By Pierre Olivier, LeddarTech Inc. Above: Management protocols such as Quality of Service can be use to prioritize network traffic.

Photo courtesy of Curtiss-Wright Defense Solutions.

Cover: MQ-9 unmanned aircraft system, Point Mugu, CA, July, 2015.

Photo courtesy of Department of Defense (DoD)/ Lisa Ferdinando .

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© 2015 OpenSystems Media, © Military Embedded Systems. All registered brands and trademarks within the Unmanned Systems E-mag are the property of their respective owners.

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Photo Credit: US Air Force

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MQ-9 unmanned aircraft system, Point Mugu, CA, July, 2015.

Photo courtesy of Department of Defense (DoD)/ Lisa Ferdinando .

Unmanned Air Systems Certification and DDS

By George Romanski, Verocel, Inc.

There is a lot of activity both in industry and among certification authorities directed at the adoption of Unmanned Air Systems (UASs), also known as Drones or Unmanned Air Vehicles (UAVs). As reported in headline news, the small hobby type aircraft are already causing some problems as they are currently flown under minimal regulatory guidelines. Small professional vehicles are regulated more stringently, and the FAA is currently using Section 333 of the FAA Modernization and Reform Act as a temporary measure to govern the sector. This means that small UASs must conform to some basic rules intent on keeping them in the National Air Space (NAS) separated from other aircraft and hazards.

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There is a range of Unmanned Air Systems with significant capabilities, range and weight that have flown for many hours using very controlled flight plans in the U.S., in foreign war-zones, and over international waters. The integration of these larger UASs into the NAS means that they must share space with other aircraft and must comply with air traffic regulations, including safety regulations.

Current regulatory requirements for flying in the NAS address several classes of aircraft including Air Transport, General Aviation, Rotorcraft etc; however, there are no specific regulations addressing large UASs in the U.S. at present. This limits the acceptance of UASs in the NAS for the time being.

The expectation is that as regulations for UASs are developed, they will be in-line with the existing regulations governing aircraft already flying in the NAS. Other countries have already adopted regulations for the development and verification of software for large UASs in their airspace. U.S. suppliers delivering UASs to Europe are already being asked to provide evidence of compliance with DO-178C (Software Considerations in Airborne Systems and Equipment Certification). It is widely accepted that the possibility of software failure is greatly reduced if that software has undergone the rigorous development and verification processes as required

by DO-178C. Software for the large UASs already flying was produced quickly to support the needs of the war-fighting effort. The

initial software architectures were built on single monolithic computer systems, or assembled using separate dedicated processors where each provided a single function. Some of this UAS software is on flying vehicles and some is on the control segment, typically ground-based.

Coordinating information that is shared and continuously updated between the airborne and ground-based control components is a complex task. Not only must each component send and receive information, but it must also do this within defined time limits. The components may fail for various reasons. This must be taken into account.

To improve the resilience of the UAS to total failure, its components are often designed to anticipate potential failures.

They offer robustness through redundancy, restart/recovery, switching to safer degraded modes, and so on. This adds complexity to the UAS components and they must anticipate “unforeseen� problems that may arise when some components are connected to other components.

Component Interconnections using DDS UAS component interconnections are complex. The interconnections may be via dedicated memory, various types of data-busses, radio or other links. The response to dropped message packets between the components could be a request for a re-transmission or a request for a fresh data value. A component may drop out of a network, recover, and re-establish communications. Rather than each

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application-layer component communicating on a network-node making such requests, it may be expedient to use an intermediate layer to help.

The Data Distribution Service (DDS) is a middleware software developed to support cooperation between a network of components. Connext DDS Cert is a DDS implementation developed by RealTime Innovations, Inc (RTI). It supports a DDS subset that was carefully chosen to provide a balance between the functionality needed and deterministic and verifiable behavior.

Safety critical UAS components may use Connext-Cert to provide some of the resilient communication functionality they would normally have to provide themselves. This has been embraced by the UAS-Control Segment (UCS) working group by including the DDS in the approved UCS specification. An additional endorsement comes from the Future Aviation Capability Environment specification, which also includes DDS as a middleware layer.

UCS and FACE components (known as Units of Conformance in the FACE specification) may be developed and verified to show compliance with DO-178C independently of other components.

Fortunately, Connext-Cert is available

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with a Certification Data Package (CDP) from RTI, but developed by Verocel, Inc. This CDP includes all of the information required by an auditor checking compliance with DO-178C at the highest level of design assurance, Level A.

Certification Data Package for a DDS implementation As Connext-Cert is a commercial-off-theshelf component, there are no system requirements for it. Instead, there is a specification of the interfaces to the software, and detailed high-level requirements that describe the intended behavior of Connext-Cert.

As required by DO-178C, the Plan for Aspects of Certification (PSAC) document for ConnextCert describes the approach to its certification with references to a set of process plans, standards, design documents and other materials provided in the CDP. All low-level requirements and mapping between these and the high-level requirements are provided in the CDP, together with code, test cases, tests, test results and coverage analyses.

Derived requirements (requirements introduced as part of the development process which do not trace up to higher level requirements), and Software Hazard Analysis records are provided to help the integrator perform their safety

analysis on the use of Connext-Cert in support of their system. The Software Accomplishment Summary (SAS) document for Connext-Cert summarizes the successful completion of all certification activities and processes as outlined in the PSAC.

“ Verocel’s experience is that once the final audit is presented, auditors will often search very hard to produce a ‘finding.’”

All artifacts in the CDP are reviewed using documented standards and checklists. These review records are “signed-off” by the reviewer in a lifecycle traceability tool developed by Verocel called VeroTrace. VeroTrace records the identity of the developers and reviewers, checks for independence as necessary, and automates impact analysis if any artifact is changed

throughout the lifecycle. These steps taken by VeroTrace are qualified, which means that the tool’s management of the artifacts can be trusted and does not need additional manual analysis.

In addition to the lifecycle data itself, the CDP contains Configuration Management (CM) and Quality Assurance (QA) records supporting the Connext-Cert certification effort. The histories of all artifacts managed under CM control are held in the VeroTrace tool and are presented for review on the CDP. QA records resulting from audits conducted throughout the project are also present in the CDP. These audits show that the documented processes were followed, the documented criteria were satisfied, and that all of the phases and processes were completed.

Producing a CDP is an automated process using VeroTrace to structure and link many thousands of artifacts and supporting data elements such as artifact versions, traceability links, status information, dates, times, CM locations, and so on. Certification artifacts are managed in the VeroTrace tool and a linked dedicated CM system repository.

A baseline identifier may be applied to artifacts in VeroTrace and its linked CM system at any time. Automated checks are performed to verify that VeroTrace versions align with their corresponding CM versions. The links in VeroTrace to artifacts maintained in the CM system must align perfectly. VeroTrace performs the consistency and completeness checks, and this functionality has been qualified. There is no need to manually

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review all of the relationships between these two repositories.

The baseline certification data and its links are extracted from VeroTrace and recorded on a DVD-ROM or as an ISO image. The result is an HTML based CDP that appears like a website. Information can be found in lists, can be traversed through hyperlinks, or can be searched.

Forward and reverse traceability is provided so that a requirement can be traced down to a design component, code, test cases, test results, and all supporting review records. Conversely, if a specific test is selected, it can be traced up to the test case it verifies, the code and the requirement. Forward and reverse traceability are present on a CDP for examination and navigation through a user’s browser.

Audit of the Certification Data Package In practice it is unrealistic to expect a certification auditor to review all of the artifacts and review records contained in a CDP; there are tens of thousands of them in the case of Connext-Cert. The approach usually taken by the auditors is to review the process plans very carefully. If they are convinced that, by following the documented processes, an acceptable CDP could be produced, they check that documented processes were actually followed. They inspect the QA records, which provide review evidence that an independent QA reviewer has checked that the engineering work was performed in accordance with the documented plans and procedures. Finally, the auditors select some sample data “threads” for review. Starting at the highest-level requirements, they follow all of

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the traceability links checking the consistency of the associated artifacts and their reviews. They check that the documented activities were performed as expected, and they check the history records in CM. These are very detailed checks, but they are samples of the entire CDP. The certification auditors then make a determination. If they find the threads, the process plans and the QA review evidence to be acceptable, then the complete audit is passed.

Verocel’s experience is that once the final audit is presented, auditors will often search very hard to produce a ‘finding.’ In practice, providing that good processes have been approved and followed faithfully, these findings can almost always be fixed in a few days.

The Connext-Cert CDP has been audited a number of times. It is made available to the UCS, FACE, and other communities by RTI. At Verocel, we expect Connext-Cert to be a popular component of future FACE and UCS programs as UASs are prepared for entry into the National Air Space.

George Romanski is president of Verocel, Inc. Verocel, Inc.  www.verocel.com  info@verocel.com

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Thermosets’ cost and reliability advantages for auto radar PCBs

By Isola Group The car radar market for safety and driver assistance applications is exploding, and the critical mass makes the choice of PCB materials a key consideration amid the crucial importance of cost and reliability factors that are intrinsically linked to the automotive environment. So automakers are looking beyond Polytetraflouroethylene (PTFE) and highly filled hydrocarbon resins— traditionally used in high-frequency millimeter wave applications—to lower the cost of built-in vehicle radars and ensure their reliable operation at elevated temperatures. Here, the new thermoset resins are emerging as a viable alternative for advanced automotive safety systems by offering cost and reliability advantages over thermoplastic materials.

The automotive OEMs have already introduced radars for adaptive cruise control (ACC) and collision avoidance systems in many high-end vehicles. However, the industry drive behind connected cars and autonomous or semi-autonomous vehicles is pushing automakers to consider safety and driver assistance systems for a larger percentage of cars. There is even a debate about mandating some degree of automotive safety features in new vehicles.

Not surprisingly, therefore, automotive radars are gaining attention for a variety of vehicle safety applications such as blind-spot detection, pedestrian detection, automatic braking, parking assistance and proximity warning. So far, short-range automotive radars, which support most of the above

applications, have mostly been operating at 24 GHz frequencies, while long-range radars for applications like adaptive cruise control go for the 77 GHz band.

However, there is a shift to higher frequencies of 76 to 81 GHz for both short and long-range radars for improved performance, smaller size and lower cost.

Today’s automotive radars at 24 GHz Rear Cross Traffic Alert

Lane Change Assist

Blind Spot

Side Impact Adaptive Cruise Control Amazing Braking

Backup Aid

Stop & Go Blind Spot

Side Impact

Lane Change Assist Rear Cross Traffic Alert

Figure 1 | The embedded radars are key to the advancement of connected cars and autonomous vehicles.

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are rather large, while higher frequency bands like millimeter wave allow lighter radars that employ smaller boards and lower overall volumes while achieving equal or better radar performance.

In addition, these smaller designs are easier to integrate into the automobile’s body contour.

Moreover, smaller PCBs allow radar OEMs to bring down the cost for the automotive safety market that is widening, but also requires a competitive cost structure. Here, radar makers are increasing looking to single-board solutions that combine the RF and highspeed digital parts. However, such hybrid PCB designs will require RF optimized substrates next to low-cost FR-4 materials, and that leads to a number of manufacturability challenges.

Reliability is another key driver in advanced automotive safety systems like radars. The PCB construction should be thermally robust while showing consistent dielectric constant (Dk) and dissipation factor (Df) over varying humidity and temperatures ranging from -40°C to 85°C. Furthermore, automotive safety radars require larger bandwidths—up to 5 GHz—than other millimeter wave applications to acquire necessary exposure, so it’s imperative that PCB materials are consistent over the entire bandwidth.

PTFE materials, which have long been used for RF applications because of low Dk and Df, exhibit a crystalline structure that is affected by temperature changes and processing steps like sintering above the melting point. The

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shift in crystallinity leads to changes in effective density of PCB material, which in turn, results in changes in Dk. Moreover, PTFE materials show a highly variable coefficient of thermal expansion (CTE) that leads to high expansion at elevated temperatures.

Therefore, unlike other millimeter wave applications with more a controlled environment, such as mobile communications, for automotive safety radars, PTFE shows lower yield and processing difficulties at elevated temperatures, especially for hybrid constructions. This article takes a look at the new thermoset materials that boast high glass transition temperatures and high thermal reliability, and shows how these advantages make thermoset a viable alternative to PTFE dielectrics for automotive radar PCBs in terms of lower cost and higher reliability.

Thermoset’s cost merits Automotive OEMs are challenged with reducing costs, and one way to bring down the cost is using hybrid PCB constructions, where critical layers utilize the highest performance materials while other board layers can use standard FR-4 substrates. For such boards, PTFE materials are less desirable due to high costs, high CTE and a number of processing concerns.

For instance, PTFE uses abrasive fillers to lower CTE, and that increases the drilling costs. Such processing difficulties also result in limited compatibility in hybrid PCB designs. Moreover, high CTE in PTFE materials leads to critical issues such as dimensional deformation and residual stress.

On the other hand, thermoset polymers feature low processing and drilling costs because they don’t require plasma de-smear and they don’t use ceramic fillers to shorten drill life.

Moreover, the fact that thermoset materials use the processing standard similar to FR-4 means that all the stacks and materials can be compatible with each other, a crucial benefit in hybrid PCB designs.

Figure 2 | Hybrid constructions allow designers to reduce cost by employing expensive PCB materials for high-performance parts like RF and high-speed digital, while they can use FR-4 for non-critical layers.

One of the key goals in automotive design is to reduce the number of layers on the board and reduce the number of boards needed. Today, most radar applications use two boards, one for the high-speed digital processing and one for the RF circuitry. These two boards usually communicate through a connector, and automotive OEMs want to eliminate that connector for cost, size, and reliability reasons.

Moreover, the current PCB designs have the antenna on the outer layer using a connector, while the two boards are manufactured separately. Again, having just one board eliminates the need for the antenna connector. Automakers can significantly lower radar costs by combining the RF and high-speed digital processing in one board instead of two; they can put RF on one side of the stack and high-speed digital on the back.

Thermoset polymers are lower in price compared to PTFE materials. Furthermore, radar OEMs can lower the fabrication cost

by using thermosets that exhibit very lowloss material properties while offering the processing capability that is similar to an FR-4 board. The board material for thermosets tends to drill very nicely.

Reliability: the creep factor Another important factor that favors thermoset materials as opposed to PTFE in automotive safety applications like radars is creep rate. Creep is the permanent deformation that occurs due to thermal expansion at higher temperatures. The PTFE materials exhibit creep even at room temperatures, and that makes them less desirable for automotive environment that commonly operates at elevated temperatures.

PTFE’s high degree of plastic deformation is especially a problem in the hybrid PCB designs where processing difficulties emerge while combining PTFE with the low-cost FR-4 material. Thermoset materials, on the other hand, display excellent electrical as well thermo-mechanical

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properties in prolonged exposures to high temperatures. Creep isn’t an issue in thermoset materials even at temperatures as high as 200°C. The high dimensional stability also means that yields and reliability are higher for high-frequency radar boards operating over a wide temperature range.

Thermosets exhibit consistent Dk and Df over the entire radar bandwidth, and that provides consistent transmission line impedance and prevents phase distortion of RADAR transmit waveform due to frequency dependence on phase velocity.

There are more than 100 electronic control units (ECUs) in a vehicle these days, managing nearly every aspect of vehicle’s operation. Not surprisingly, therefore, reliability is a key consideration for PCB designers in safety-conscious automotive electronics. The companies like Isola Group recognize the need for a cost-effective alternative to PTFE and other commercial microwave laminate materials to better serve the reliability aspects for advanced automotive safety and driver assistance systems.

Isola has unveiled a number of glass-reinforced thermoset materials to ensure superior thermal endurance across a wide range of elevated temperatures and thus to meet the highly demanding PCB material requirements of automotive radars.

Freescale design win Freescale Semiconductor and RFbeam Microwave have conducted PCB materials evaluation for the joint development of a 77 GHz radar, and here, Isola’s high Tg thermoset material Astra MT was reviewed for RF performance and processing advantages. Astra was found to show robust electrical as well as thermo-mechanical performance and compatibility with hybrid constructions.

Eventually, Astra MT material was selected for RF and antenna boards in Freescale’s automotive radar demonstration kit. The ultra low-loss Astra MT dielectric materials have demonstrated a very high suitability for patch antenna designs and RF front-end PCBs for 76 to 81 GHz radar applications, offering a higher yield and lower production costs.

20 15 10 5 0

Highly Filled Hydrocarbon Oxidation Resistant 3.48 r 18.42% High Tg Thermoset 3.0 r 0.61%

High Tg Thermoset 3.5 r 2.44%

High Tg Thermoset 3.56 r 5.41%

Figure 3 | Percent change in dielectric loss after 1,000 hours of aging at 125°C is low for high Tg thermosets.

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The demonstration of the Astra MT material in Freescale’s radar kit has also shown how easily thermoset polymers can be built in hybrid construction alongside a wide range of standard FR-4 materials to optimize cost. Moreover, from a reliability standpoint, Astra MT materials were thermally robust with a 200°C Tg and passed the

Figure 4 | Freescale radar kit uses Isola’s Astra MT material for RF circuitry. rigorous tests like 6X 260°C to qualify for the automotive environment.

Next up, for automotive radars operating at 24 GHz, where most of the action is right now for radar applications, Isola has released I-Tera MT materials for RF boards. I-Tera MT boasts stable electrical properties over a broad frequency and temperature range with a Dk that is stable between -55°C and +125°C up to 20 GHz. Moreover, it exhibits a lower Df that is stable between -55°C and +125°C for up to 20 GHz, which makes I-Tera MT a cost effective alternative to PTFE and other commercial RF and high-speed digital laminate materials. Thermoset polymers like Astra MT and I-Tera MT come with a full complement of laminates and prepregs to meet the diverse requirements of highspeed digital, RF and microwave designs.

Thermosets such as Astra MT and I-Tera MT fit nicely into automobile radars PCB requirements where OEMs are trying to bring down materials

cost while raising the bar for reliability because it’s important to have very high yields. These thermoset materials with performance optimized for higher frequencies are likely to play a crucial role in bringing the novelty of car radars to the mass market and thus help benefit a larger number of people.

Isola’s materials are used in a range of electronic end-markets including applications in computers, networking and communications equipment, high-end consumer electronics, as well as products designed for use in the advanced automotive, aerospace, military and medical markets.

Isola  www.isola-group.com

@IsolaGroup Watch Video

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Choosing a Rugged Ethernet Switch/Router Solution

By Mike Southworth, Curtiss-Wright Defense Solutions

Mission-critical defense and aerospace applications depend on the power and effectiveness of Ethernet networking. Rugged networking solutions come in many varieties with a host of feature options to choose from.The following article will help systems integrators and end users explore some of the key networking capabilities available in modern Ethernet switches and router systems designed to support intra- and inter-vehicle/aircraft network architectures. The various commercialoff-the-shelf (COTS) networking systems available from Curtiss-Wright will be compared and contrasted in the context of selecting the most appropriate and capable solution to satisfy mission networking requirements.

Fundamental questions about network architecture When systems integrators develop new platforms or modernize legacy vehicles or aircrafts, there are many fundamental questions asked about network architecture and the platform’s intended mission capabilities, which guide the selection of rugged switch and/or router Line Replaceable Units (LRU). Many of these architectural questions will be addressed including:

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Does the mission platform need a switch, a router, or both?

What is the difference between a Layer 2 and a Layer 3 device?

Should the network device be fully manageable or just plug-and-play?

What devices will be connected and how does the traffic need to be managed?

How many Ethernet ports and what speeds should the device support?

What physical media (copper or fiber optics) and connectors are most appropriate?

What role does size, weight, power, and cost (SWaP-C) play?

Is a multi-function appliance or standalone switch/router LRU a better option?

Is a ruggedized commercial solution or a natively rugged system a better option?

How can existing IT network

Figure 1 | OSI model of computer networking

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training and staff be leveraged to minimize support costs?

What environmental/EMI validation testing is required for networking devices?

Will the device be compatible with the aircraft generator and/or vehicle battery power input?

How will network security and information assurance requirements be satisfied?

Router or switch? Layer 2 or Layer 3?

Ethernet switches and routers form the core of network architectures. Switches connect devices on a Local Area Network (LAN) onboard ground vehicles or aircrafts. They enable computers and sensors to communicate and share information locally. Connected devices might include a mission computer, flight computer, video camera, weapons system, Ethernet-enabled radio, or other wireless device. Routers form the next layer of network connectivity. Switches often interface with routers to share information outside the vehicle or aircraft to a Wide Area Network (WAN) via a tactical radio, satellite modem, or other wired or wireless backhauls. This networking paradigm facilitates communication across applications and between vehicles in aerospace and defense platforms.

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The Open Systems Interconnection (OSI) model of computer networking (see figure 1: OSI model) defines “layers” of functionality which correspond to traditional switch and router capabilities.

Switching functionality is commonly associated with the Layer 2 data link, whereas routers are traditionally related to the Layer 3 network layer. That being said, some switches are Layer 2 and 3, providing efficient switching, as well as either static or dynamic as Internet Protocol (IP) routing capabilities. Layer 2 refers to a node-to-node frame delivery on the same link, whereas Layer 3 refers to the end-to-end (source to destination) connection including routing through intermediate hosts through optimized network protocols, such as IP.

Need for speed and port count Despite the traditional desire to get lightning fast connectivity and throughput, not every application realizes tangible benefits from the faster pipes offered by 1, 10, or 40 GbE. In fact, 10/100 Fast Ethernet may meet some network requirements for WAN routing, since real-world network backhaul speeds are often slower than 100 Mbps in the field. This is because the speed of vehicle-to-vehicle platform communications is often constrained by the wireless radio connection, which becomes the bottleneck for speed and performance. Most satellite and tactical radio systems strain to achieve 5-10 Mbps throughput.

Since intra-vehicle LAN communications Figure 2 highlights the corresponding are not limited by the bottlenecks of a OSI model layers for Curtiss-Wright’s WAN connection, on-board computing COTS network subsystems. devices certainly benefit from Ethernet switches offering 1 Gigabit/second or even faster connectivity. Relatively fewer applications require more than 1 Gbps; however the military is increasingly requesting 10 GbE switches in preparation for more bandwidth intensive applications, particularly those associated with high definition video surveillance, signal intelligence, radar, sonar, and high-performance Figure 2 | OSI model layers for Curtiss-Wright networking subsystems communications

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Figure 3 | Port count and speeds for Curtiss-Wright networking subsystems. systems. This trend is expected to increase as 10, 40, and 100 GbE technologies mature and become more commercially available.

In terms of port density, many military vehicle applications often just require 8-10 ports; however, this is largely dependent on the platform’s concept of operations (CONOPS) and its physical constraints relative to SWaP-C. With the military’s “future-proof” stance on technology insertions and the miniaturization of the modern networking technologies, 16-20 ports seems to be the “sweet spot” for a growing number of integration programs. Due to varying program requirements, the current Curtiss-Wright COTS systems portfolio includes network subsystems that support a range of speeds from Fast Ethernet up to 10 G Ethernet connectivity with port counts starting at five, going up to 53 ports (see figure 3).

Copper or fiber? Connectors types?

The type of physical media used for networking – typically copper or fiber optics – is another important choice that requires a balance of budget and functionality. Depending on the application, each has its pros and cons. Fiber optics is capable of transmitting data over long distances and providing greater data security than copper. That’s because fiber optics delivers less signal loss and is more resistant to electromagnetic interference (EMI). That being said, the bend radius of fiber optic cabling is less forgiving compared to copper and installation of optical network is often more expensive compared to traditional twisted pair copper wiring (e.g. CAT 5E/6), the mainstay of home and office networks. For a large majority of military and aerospace, copper media is considered a “good enough” solution. Some deployed systems use both, playing to each medium’s

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strengths: copper for onboard Gigabit Ethernet communications and fiber optic for higher-speed applications and network-to-network communication across considerable distance.

The type of physical network connectors to which the copper or optical cabling is wired is another important consideration to achieve reliable network connectivity onboard vehicles or aircraft. Protections against environmental factors, such as water or vibration, for example, should be considered to eliminate the possibility of damage or ports becoming disconnected. Traditional RJ-45 connectors, for example, which are found on commercial-grade networking equipment, are notoriously prone to failure under extreme vibration and provide very limited ingress protection against dust and water. Typically an IP67-rated (dust/ water proof) locking connector that rackets down or has a secure push-pull feature is recommended. Many rugged connector types abound, but the most commonly implemented approach in military and aerospace electronics application is circular MIL-DTL-38999 Series III connectors (see figure 4 – These generally meet the desired requirements up to Gigabit Ethernet speeds.) Microminiature versions of these connectors are also now available to support lower size/weight requirements.

Where cost and size are important considerations, multiple Ethernet ports can be combined on a single connector to reduce the subsystem’s physical size. Human engineering factors described in MIL-STD-1472 should also

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Figure 4 | MIL-DTL-38999 connector. be considered for users of networking equipment, including the spacing between connectors on the system, which can impact the ease of installing and/or removing the unit, particularly if installers are wearing gloves. For speeds of 10Gbps or more, or where signal integrity is paramount, new and specialized interconnects are becoming available within DTL-38999 connector shells and other connector types.

Figure 5 highlights the various types of connectors and media used by CurtissWright networking systems.

Managed or unmanaged?

Network switches come in two basic varieties, unmanaged and managed.

Unmanaged switches require no configuration and are designed for simple plug-and-play operation. A managed switch conversely can be configured over a serial Command Line Interface (CLI) and/or Ethernet ports using a Graphical User Interface (GUI) or remote terminal application.

For some military and aerospace platforms, an unmanaged switch can be an ideal solution, since these are relatively easy to use and low cost. Unmanaged switches can also be ideal for scenarios where network traffic is light and the data simply needs to pass from one device to another. Rather than giving a user the ability to configure link parameters or prioritize network traffic, unmanaged switches “auto-negotiate” the data rate and whether to use half-duplex or full-duplex mode. Unmanaged switches can also be helpful when a Virtual Local Area Network (VLAN) has already been defined and there’s a need to merely expand the port count on the edge of the network.

Although managed devices are more commonly installed for new technology insertions to provide the most flexibility for growth, unmanaged switches still play an important role as a piece in the overall networking architecture. Since managed switches support capabilities to shape and configure the network traffic, the device’s management software can be

critical to a platform’s mission success.

The most widely used network management software has been the Cisco Internetworking (Cisco IOS) software, which is accounted for in more than 50 percent of all switches and routers worldwide, according to Cisco estimates.

Consequently, even non-Cisco managed network solutions are often patterned after the command line approach and capabilities introduced by Cisco.

Key management features By providing users with options for monitoring and configuring networks, managed switches provide military and aerospace platforms with greater control and security over their LAN data. Maintaining situational awareness through the use of video, maps, radio, and satellite technologies requires a networking infrastructure that can manage and prioritize data packets to ensure mission safety and success. There are a variety of important management protocols and capabilities available to support such applications, including Quality of Service (QoS), VLANs, Spanning Tree redundancy, and

Figure 5 | Port count and speeds for Curtiss-Wright networking subsystems

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Simple Network Management Protocol (SNMP), among others.

QoS allows users to prioritize network traffic by assigning a higher priority to traffic from particular ports, VLANs, IP classes, tags, etc. This helps ensure consistent network performance for critical, time-sensitive data. QoS is especially critical for military users in a mixedtraffic environment where large data files such as map images (see figure 6) can delay important voice packets or flash messages that need to reach the vehicle operator. QoS allows the user to tag certain traffic as high priority to ensure delay-sensitive data is delivered in a timely manner.

Similarly, VLANs featured on managed switches allow connected devices to be logically grouped together and to isolate traffic between groups, even when the traffic is passing over the same physical

Figure 6 | QoS can be used to prioritize network traffic.

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switch. This segmentation and isolation of network traffic helps reduce unnecessary traffic and provides maximum bandwidth to devices that need to communicate to each other, providing better network performance, and in many cases, an additional level of security.

Another common feature of managed switches is support for redundancy – to safeguard a network in case a connection or cable fails by providing an alternate data path for traffic. Many switches incorporate Spanning Tree Protocols (STP), such as RSTP or MSTP, to provide path redundancy in the network. Using spanning tree algorithms, STP allows for one active path at a time between two network devices, preventing loops and establishing the redundant links as a backup to keep integrated systems available and to prevent expensive downtime. It is not uncommon for redundant flight electronics onboard manned and unmanned aircraft to be networked

by Ethernet switches supporting some form of STP. In this way, onboard mission computers have multiple potential data paths and can quickly recover if critical hardware fails.

Monitoring functions of network switches via the SNMP protocol can provide additional control and efficiency.

SNMP facilitates the exchange of management information between network devices, allowing users to determine the health of the network or the status of a particular device. This includes the number of bytes and/or frames transmitted and received, errors generated, and port status. By displaying this data

over a standard web browser, administrators can monitor the performance of the network and quickly detect and repair network problems without having to physically interact with the switch.

SWaP-C in unmanned systems With shrinking government budgets and program-specific technical requirements, there is mounting pressure on defense and aerospace contractors to provide networking solutions with reduced Size, Weight, Power, and Cost (SWaP-C). The objective is to fit as much functionality as possible in the smallest, lightest package for the least amount of money to empower the greatest efficiency and performance onboard defense and aerospace applications, including unmanned vehicles.

That being said, managing SWaP-C or “SWaP optimization” isn’t done in a vacuum without considering many other program priorities and tradeoffs that go well beyond SWaP. Program managers ultimately consider cost, performance requirements, supported feature and capabilities, reliability under extreme environments, cooling methods and thermal management, schedule and lead time constraints, use of COTS and open standards versus custom, length of life cycle management and obsolescence mitigation and scalability, among others.

SWaP reduction is a key focus at CurtissWright when developing next generation systems and recent advancements in technology are helping the company achieve impressive results. A noteworthy example of recent SWaP reduction is

with Parvus DuraNET Gigabit Ethernet switches. The latest model, the 20-11 (see figure 7), provides 8 ports of fully managed Gigabit Ethernet switching in an ultra-miniature form factor that is a mere 10 cubic inches in size. This represents a 90 percent size reduction from the next smallest Gigabit Ethernet switch subsystem. SWaP-sensitive platforms – like unmanned air systems (UAS) are driving demand for such small network connectivity devices – and component miniaturization is helping Curtiss-Wright achieve the improvement in SWaP optimization. This level of miniaturization is enabling integration of LAN connectivity and more payload electronics than ever before to satisfy mission requirements.

Relative size and weight comparison of Curtiss-Wright networking systems is shown in figure 9.

One newer SWaP reduction approach used by Curtiss-Wright is to consolidate networking and processor functions into a single hardware device that uses software-based networking and hypervisor

Figure 7 | Parvus DuraNET 20-11 Ultra small form.

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Figure 8 | SWaP Comparison of CW networking products. virtualization applications to provide Layer 3 secure mobile routing and/or VPN encrypted security functionality (see figure 10 – This bolt-on network software approach provides the same feature sets available in dedicated hardware-based networking devices but in a software format that can be pre-loaded on rugged, general-purpose, x86 mission computers. Logically, this software approach adds no physical size or weight to the LRU – it just utilizes some portion of the processing capabilities. The overhead from the software may not be significant for multi-core high performance systems like for the quad-core, 4th Gen

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Core i7-based Parvus DuraCOR 80-41 computer (see figure 9).

Multi-function appliance vs standalone LRU Not only can combining hardware and software yield SWaP-C reduction, but also consolidating what have been traditionally standalone hardware-based LRUs into a single multi-function system solution. Many military programs have begun to request subsystems that can combine network processing, Ethernet LAN switching and IP traffic routing in a single box (see Figure 10).

Depending on the project, this can be motivated by various factors, including SWaP constraints or objectives to simplify systems integration.

Some programs aim to reduce the number of power supplies or cables on-board a vehicle, Figure 9 | Software-based networking functionality. while others seek a solution with flexible mechanical installation options. The U.S. Army’s Vehicle Integration for C4ISR/EW Interoperability (VICTORY) initiative is an excellent example of this trend, as ground vehicle architects aim to trim unnecessary fat while leveraging modern computing and networking architectures.

Open architecture, pre-integrated products featuring modularity (mix and match functionality) are most attractive to the Department of Defense (DoD) since they do not require significant engineering expertise for customization or tailoring to program needs. To support these objectives, Curtiss-Wright has designed several scalable, rugged multi-function computing and networking subsystems based on Intel x86 or Freescale ARM processors together with various integrated network switch/router options, including DuraWORX products and Digital Beachhead systems.

The Parvus DuraWORX product line exemplifies this ultra-rugged multi-function computing and networking system concept, combining a multi-core high performance Intel Core i7 based mission processor together with a Cisco 5915 IOS-managed secure network router and optional Ethernet switch into

Figure 10 | Parvus DuraCOR 80-41 4th Gen Core i7 Mission Computer. a single modular platform designed for extended temperature, high shock, and vibration environments. DuraWORX is a scalable, all-in-one computing appliance aimed at reducing SWaP and simplifying systems integration (thermal, cabling, power, installation) in tactical computing, IP networking and situational awareness applications.

The Digital Beachhead product line includes LRUs that feature 16 ports of fully managed Layer 2 GbE switching and static Layer 3 routing together with a low-power multi-core ARM-based Freescale i.MX6 processor capable of supporting general-purpose processing requirements or optional VICTORY Data Bus Management and Shared Processor

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Figure 11 | Standalone vs Multi-function networking appliance.

Services. These multi-function computing and networking devices serve as SWaP-C optimized vetronics computers with integrated network switch and GPS receiver, providing a digital backbone over Ethernet for network devices to be plugged into a vehicle and utilize CPU processing to deliver services to the platform (see figure 12).

Environmental / EMI / Power testing Ethernet switches and routers intended for installation on tactical mobile platforms such as ground vehicles, aircraft, or maritime vessels should naturally be designed with reliability in mind, as mission effectiveness and personnel

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safety can be compromised if a device fails. Validation testing should be done to either MIL-STD-810 and/or DO-160 (or equivalent) standards to qualify the equipment to specified temperature ranges, vibration frequencies, altitude, humidity offered by the device. In addition, EMI testing for radiated and conducted emissions and susceptibility and power quality compliance testing should be performed to MIL-STD-461, MIL-STD-704, and/or MIL-STD-1275 (or equivalent) to ensure compatibility with aircraft and vehicle voltage inputs, spikes, and transient levels. All Curtiss-Wright COTS networking products come pre-validated to some combination of these tests to reduce risk,

Figure 12 | Shared network/processor services of multifunction DuraDBH-672 Digital Beachhead system.. time, and expense for systems integrators selecting switches and routers for their platform.

for as demanding of application, but was enhanced to endure airborne, ground vehicle, and/or shipboard deployments.

Rugged vs ruggedized

With military customers seeking the most robust yet economical solution, weighing the tradeoffs between a “ruggedized” product and a natively rugged one is a worthy exercise. There are many advantages of each approach.

As defense and aerospace applications typically operate in extreme environments, it is critical for network integrators to specify equipment designed for harsh deployed conditions, which may include EMI, dust, water, temperature extremes, vibration, humidity, and high altitude. The terms “rugged” and “ruggedized” are often used to describe electronics capable of enduring tough environments; however, there is a distinction between the two terms that indicates how a product for military use was created. “Rugged” systems are products designed from the ground up to meet the requirements of specific harsh environments. Conversely, the term “ruggedized” typically refers to a commercial product that was not originally intended

For example, natively rugged solutions may offer more control over the component selection and/or bill of materials (BOM) since qualification testing has validated the design and the product was specified from conception for an extreme environment. A ruggedized solution, based on a network switch from Cisco Systems (see figure 12), may need to be enhanced to operate in such environments, but can potentially reduce the time to deployment to the battlefield and expense to maintain, since many

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military personnel are already trained to operate Cisco’s network management IOS software. Consequently, several product models from Curtiss-Wright integrate natively rugged Cisco router/ switch board hardware or alternatively integrate ruggedized commercial/industrial-grade switching hardware qualified through MIL-STD testing. In cases where performance or physical form factor cannot be satisfied with Cisco hardware, Curtiss-Wright also develops its own rugged hardware to meet specialized customer requirements, including rugged 10 G switches and ultra-small form factor devices.

Leveraging IT Investment Networking products need technically trained staff to operate and maintain them, which presents an opportunity for some organizations to leverage existing IT and network training investment if they select products based on industry standards.

John Chambers, CEO of Cisco Systems, reported during a news interview that the company had more 70 percent market share in the U.S. government public sector. Cisco is also credited with helping to define many of today’s networking standards and protocols, actively contributing to the standards committees within the Internet Task Force, IEEE, and other groups. This pervasiveness of Cisco technology and its IOS software makes them the “industry standard” to which more network professionals are trained. It logically follows by selecting products based on Cisco technology or products that are standards-based and are “Cisco-like,” the cost to maintain and operate them should be reduced.

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Figure 13 | Ruggedized Cisco switch, the Parvus DuraNET 3000.

Security and information assurance Beyond configurability, the information assurance for the network is another important consideration. Many Ciscobased technologies undergo information assurance validation and testing at thirdparty laboratories for certifications to Federal Information Processing Standard Publication 140-2 (FIPS 140-2), NAIP Common Criteria Evaluation (National Information Assurance Partnership/ Common Criteria Evaluation and Validation Scheme), and/or DoD APL approval.

Network security is often achieved through a variety of secure network management protocols and authentication methods supported by switches and routers. For example, Secure Shell (SSH) and Simple Network Management Protocol (SNMP) provide encrypted administrator traffic during Telnet and SNMP sessions.

TACACS+ and RADIUS authentication facilitates centralized control and restrict unauthorized users, and Dot1x, port security and DHCP allow dynamic port-based authentication. These along with intrusion

detection firewalling, Network Address Translation (NAT), Access Control Lists (ACL), virtual local area networking, and various cryptographic technologies such as AES-256 or NSA Suite B encryption help to protect network data. Many CurtissWright systems also support a non-destructive zeroization feature to sanitize the switch or router should the platform be compromised, clearing out system firmware, as well as network addresses and configuration settings.

new options to systems integrators to achieve their network-centric operational goals. The COTS portfolio of networking solutions from Curtiss-Wright will continue to evolve to even better meet these needs and offer modern capable network solutions well suited for deployment at the network edge.

Conclusion

Curtiss-Wright Defense Solutions

Defense and aerospace integrators are expected to increasingly look to Ethernet network-based technologies to achieve fast, flexible and secure network communications onboard vehicles and aircraft. Advancements in throughput, management capabilities, and rugged (and low SWaP) system design will give many

Mike Southworth is the Product Marketing Manager for Curtiss-Wright Defense Solutions.

 www.curtisswrightds.co ďƒ ds@curtisswright.com Watch Video

Figure 14 | Cisco technologies integrated into Curtiss-Wright rugged systems.

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Leddar optical time-of-flight sensing technology: a new approach to detection and ranging

By Pierre Olivier, LeddarTech Inc.

National Optics Institute (INO) in Quebec City originally discovered Leddar optical time-of-flight sensing technology, but it was developed and commercialized by LeddarTech. It is a unique technology in the field of optical sensing. Combining fast, high-resolution analog-to-digital conversion, and innovative signal processing, Leddar light processing brings the benefits of time-domain processing to optical time-of-flight sensing.

The following will give a high-level overview of the Leddar optical time-of-flight sensing technology and its advantages compared with competing technologies.

It will also describe architectural choices for sensors incorporating Leddar technology as well as the benefits that such sensors provide.

Detection and ranging Remote sensing consists of acquiring information about a specific object in the vicinity of a sensor without making physical contact with the object. Countless applications, including automotive driver assistance, robot guidance, traffic management, and level sensing exist for this technique.

Multiple technology options are available for remote sensing; we can divide them into three broad applications:

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Presence or proximity detection, where the absence or presence of an object in a general area is the only information that is required (e.g., for security applications). This is the simplest form of remote sensing;

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Speed measurement, where the exact position of an object does not need to be known but where its accurate speed is required (e.g., for law enforcement applications); and

õõ

Detection and ranging, where the position of an object relative to the sensor needs to be precisely and accurately determined.

The most complex of the three applications is the detection and ranging, and the following will focus primarily on the technologies that provide this functionality.

From the position information, presence and speed can be retrieved so technologies capable of detection and ranging can be universally applied to all remote sensing applications.

Although it is possible to obtain distance information with passive technologies, such as stereo triangulation of camera images, these passive technologies are usually very constrained in capability. For instance, stereo triangulation requires well-defined edges for the matching algorithms to work. Therefore, the most commonly used technologies for measuring the position of an object involve sending energy towards the object to be measured, collecting the echo signal, and analyzing this echo signal to determine the position of one or several objects located in the sensor’s field of view. Since energy is intentionally emitted towards the object to be measured, we will refer to these technologies as being “active.”

Of these, some technologies rely on the geometric location of the return echo to infer position information. For instance, structured lighting involves projecting an array of dots towards the object to be measured, and analyzing the geometric dispersion of the dots on the object using a camera and image analysis.

Other technologies rely on the time characteristic of the return echo to determine the position of the object to be measured. These are generally known as “time-of-flight measurement” technologies.

Presence/Proximity

Speed

Passive

Stereo Vision

Geometric

Structured light

Radio

Remote sensing

Sound Detection and Ranging

Leddar Direct Time-of Flight

Active

Other Direct ToF Time-of-flight Range Gated Imaging

Light Phase Detection

Figure 1 | Remote sensing technologies taxonomy.

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Although the implementation differs, time-of-flight measurement can be accomplished with radio waves (radar), sound or ultrasonic waves (sonar), or light waves (lidar).

Transmit pulse

Receive echo

Pulse threshold

Figure 1 is a visual repreLeading sentation of the different edge timer remote sensing technolTrailing edge ogies currently available.

Start reference In the next section we will cover light-based, or optical, time-of-flight measurement technologies in more detail.

Optical time-of-flight measurement Optical time-of-flight measurement computes the distance to a target from the round-trip time of flight between a sensor and an object. Since the speed of light in air changes very little over normal temperature and pressure extremes, and its order of magnitude is faster than the speed of objects to be measured, optical time-offlight measurement is one of the most reliable ways to accurately measure distance to objects in a contactless fashion.

Conventional optical time-of-flight sensors fall into three broad categories: direct time-of-flight, range-gated imaging, and phase detection. Leddar is a new and unique technology for performing time-of-flight measurement. This section will describe the operating principle for each measurement technology.

Direct time-of-flight measurement In the direct time-of-flight measurement method, a discrete pulse is emitted and one or several timers are used to measure the time difference between the emitted pulse and the return echo, based on threshold detection. This time difference can be directly converted to a distance, based on the following equation: d = (C * t) / 2 C is the speed of light, which is 299,792,458 m/s in a vacuum. The division by 2 accounts for the fact that light has to travel from the sensor to the object and then back to the sensor.

The difficulty in implementing the direct time-of-flight measurement method resides in the time intervals to be measured. In order to resolve a distance to centimeter-level accuracy, the required accuracy for the timers is 67 ps. Implemented in digital logic,

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this would require a 15 GHz clock speed, which is obviously not practical. Therefore, various time-to-digital conversion methods are typically used.

Both edges of the pulse are commonly used to maintain accuracy independently of varying echo amplitude.

Range-gated imaging Whereas direct time-of-flight relies on measurements made on the immediate value of the received signal, range-gated imaging uses signal integration methods, typically with CCD or CMOS imagers.

Transmit pulse

Receive echo Integration

Integration

By measuring the energy received in successive integration intervals, it is possible to extrapolate the distance between the sensor and the measured object, based on the ratio of energy received in the different intervals.

The difficulty with range-gated imaging Start reference is that CCD and CMOS imagers have a limited dynamic range; therefore, strong ambient light can easily cause saturation and impair measurement. Furthermore, since neither the emitted and received pulses are perfect rectangle pulses, nor is the sensor perfectly linear, compensation is required and accuracy is ultimately limited.

Phase difference measurement

Transmit signal

Receive echo

Phase difference

In contrast to the previous two methods, phase difference measurement relies on a modulated light source and evaluates the phase

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difference between the transmit signal and the receive echo. This phase difference can be converted to distance, using the following formula: d = (C * Ø)/ (4 * π * f) C is the speed of light, Ø is the phase difference in radians, and f is the modulation frequency.

Correlation methods are typically used to measure the phase difference of the receive echo respective to the transmit signal as well as recover the propagation delay and therefore the distance to the object to be measured.

Of course, a phase difference greater than 2 π is not resolvable; for instance, 3 π or 5 π will be measured as a � radian phase difference. Therefore, depending on the chosen modulation frequency, an artefacting phenomenon will occur where far-away objects will appear to be much closer than in reality.

Leddar optical time-of-flight technology Leddar optical timeof-flight sensing technology is based on direct time-offlight measurement; however, rather than Receive echo working directly on the analog signal, Object 1 distance Leddar light processing starts by Object 2 distance sampling the receive Start reference echo for the complete detection range of the sensor. Through patented methods, Leddar iteratively expands the sampling rate and resolution of this sampled signal. Finally, it analyzes the resulting discrete-time signal and recovers the distance for every object.

Transmit pulse

As opposed to the preceding methods, Leddar light processing can extract the distance for every object found in the field of view.

Where the preceding methods implement detection and ranging mostly through hardware, Leddar light processing utilizes complex algorithms implemented in software. This characteristic is the key to the flexibility and performance of the technology.

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Through signal processing, Leddar is capable of computing an accurate distance for an object with a very weak echo. Using various advanced filters, it is also able to detect objects in the presence of nuisance signals, such as that returned by dust, snow or raindrops.

Finally, as opposed to the preceding methods, Leddar light processing can extract the distance for every object found in the field of view.

Therefore, the key advantages of Leddar technology are high sensitivity, immunity to noise, and powerful data extraction capabilities. Sensors integrating Leddar technology will be able to turn these advantages into measurable benefits, as will be discussed later.

At the heart of Leddar technology is a library of signal processing functions covering four distinct stages of processing as presented in Figure 2.

The Leddar sensor Leddar is the root technology enabling the development and production of high-efficiency sensor modules. Sensors incorporating Leddar optical time-of-flight technology provide three key benefits compared to competing products: a high rangeto-power ratio, target detection in low-visibility conditions, and the ability to resolve multiple targets. Below is a review of the key components of a Leddar-based sensor:

Figure 2 | Leddar light processing functional blocks.

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LeddarCore tion/Syste plica m p A Int e

Leddar

O p tic s

c

INTEGRATED SOLUTION

gi

ng

COMPLETE MODULE

ka

Int Po

er

r a t e d C ir

IC SIGNAL PROCESSING SENSOR MODULE

t

Propriety Algorithms

eg

w

Lig

ui

Pro ce Photod et e

ddarCore e L

es ac rf urce So ht

ing ss or ct

Pa

c

Figure 3 | Main components of a Leddar sensor.

Implemented in standard submicron CMOS processes, Leddar becomes an ultra-lowpower sensor core (i.e., the LeddarCore) that will maximize the performance of any optical time-of-flight sensor.

When combined with a photodetector, a pulsed light source and optics, it forms a complete sensor system that can easily be integrated into a small footprint at low cost (figure 3).

Photodetector converts light pulses

The photodetector is the component responsible for converting light pulses into an electrical signal that can be read by the LeddarCore. Therefore, its function is key to any Leddar sensor, which can leverage various types of detectors including PIN photodiodes and APDs.

PIN Photodiode achieves long detection range

Leddar technology can be used with low-cost silicon PIN photodiodes, achieving a long detection range and immunity to ambient light conditions.

The main benefit of PIN photodiodes is that the rise and fall times are very rapid (typically 10 ns or less); therefore, they are well suited for receiving short light pulses on the order of 25 ns. Furthermore, they exhibit a very high linearity, enabling very small signals to be detected even in the presence of strong incident light.

Multi-element arrays, either one- or two-dimensional, can be used to build 2-D or 3-D sensors with fast, parallel measurement and no moving parts. These sensors can be used in applications requiring rapid and accurate presence, position, or speed information.

APD enables detecting weak signals

Avalanche photodiodes can also be used. They share most of their characteristics with PIN photodiodes; however, with the use of a high reverse bias voltage (typically up to 300 V), they exhibit a current gain (typically 100 or more), enabling very weak signals to be detected.

However, one of their main drawbacks is that this gain is highly dependent on temperature and bias voltage; and that bias voltage also significantly affects the dark current.

Therefore, the bias voltage normally has to be adjusted depending on temperature.

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Although Leddar technology has been originally developed for use with PIN or avalanche photodiodes, other types of photodetectors with sufficient bandwidth may also be used.

Light source is critical Whereas the photodetector detects the return echo, it is the light source that is responsible for initially emitting the transmit pulse. It is therefore equally critical to the Leddar sensor.

Leddar technology can be used with visible or infrared light sources. Any light source that can generate sufficiently fast pulses can be utilized, including LEDs, lasers, or VCSELs.

LEDs as an inexpensive light source

LEDs constitute an ideal light source for many Leddar-based applications.

Moreover, the growth in LED illumination has driven the development of a large quantity of commercial light shaping components, such as collimators and reflectors. Furthermore, LEDs are inexpensive, available in various wavelengths, easy to assemble on printed circuit boards, and highly reliable. It is also easy to design eye-safe solutions around LEDs. For many applications, Leddar technology can make use of a LED source that is already used for illumination or signaling. The short measurement pulses of Leddar (typically less than 50 ns) can be made imperceptible to the human eye.

Leddar is not limited to single-wavelength LEDs; white LEDs can also be used, which is particularly attractive for many smart lighting and automotive applications.

The short measurement pulses and very low duty cycle required by Leddar light processing also mean that in most cases, no specific thermal management needs to be implemented.

Lasers for maximum light requirements

Pulsed laser diodes are well suited for long-range, narrow-beam applications.

They are a good choice for delivering a maximum light intensity and can be collimated with small optics.

Figure 4 | Example of wide beam and different detection zones produced by a multi-element platform.

One drawback of pulsed laser diodes is that they have very low allowable duty cycles, limiting the measurement rate.

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The cost per watt of laser diodes is also significantly higher than LEDs. For high-power applications, however, the footprint and the number of optical and electronic components required can be much smaller with a laser diode than with an equivalent number of LEDs. Finally, the regulatory environment for laser products is more complex than for LEDbased products; therefore, product approval and distribution for these products will be more expensive.

VCSEL comparable to edge emitting laser diodes

VCSELs are a type of laser diode that emits light perpendicularly to the top surface of the wafer. They can therefore be produced at much lower cost than conventional, edge-emitting laser diodes. They can also be built into arrays. Therefore, they can achieve performance comparable to edge emitting laser diodes at a cost approaching LEDs. Aside from that, the other comments on lasers stated above also apply to VCSELs.

Optics are customizable to the application Since Leddar is an optical technology, the field of view of a Leddar sensor can be easily tailored by selection of the source and reception optics.

Solutions ranging from a collimated beam to a 180-degree field of view can therefore be easily designed using simple aspheric lenses.

More complex solutions can also be engineered to address specific requirements.

For instance, it may be desirable for an automotive driver assistance sensor to have a longer detection range or higher resolution for the zone directly in front of the vehicle than for the sides. This is a scenario that is easily accomplishable with Leddar technology.

Benefits of Leddar technology The first benefit of Leddar optical time-of-flight sensing technology is its high rangeto-power ratio. What this means is that, compared with other optical time-of-flight technologies, it can detect at a farther range with an equivalent amount of light.

This benefit can be leveraged in many different ways, depending on the target application. Compared to a sensor integrating another optical time-of-flight technology, a sensor integrating Leddar technology can:

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Have a longer detection range with an equivalent light output; or

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Have a similar detection range with a lower light output.

Another way to leverage the high range-to-power ratio of Leddar is by using a diffuse light source instead of a collimated source. In this case, each detection element can cover a large area. Simple optics can then be employed to customize the emission and reception patterns for specific applications.

The second benefit of Leddar technology is its capability to detect targets in low-visibility conditions. Since each measurement is formed from hundreds or even thousands of discrete light pulses, the likelihood that the technology is able to obtain reliable measurements under environmental conditions such as rain, snow, or dust is very high. This is particularly true when using a diffuse light source.

Finally, the third benefit of Leddar technology is its ability to resolve multiple targets with a single detector element. Once again, this benefit can be fully exploited with a diffused light source, where a small object may not fully occupy the field of view, and where the distance to background objects can be simultaneously measured. Detecting multiple targets at once can represent significant added value and increased versatility for many applications. Even a single-element sensor can provide a high degree of spatial awareness.

The low-power characteristics of the technology make it suitable for mobile or portable applications. Leddar technology is applicable to sensors starting from one detection element — and ranging up to thousands or even millions such elements.

Conclusion Backed by a decade of focused R&D, Leddar technology has reached a high level of maturity and has already been deployed in commercial solutions. With its novel, highly efficient approach to optical time-of-flight sensing, Leddar technology helps developers and integrators meet the key sensor requirements sought after for ultrahigh-volume deployments: small size, low cost, low power consumption, reliability, robustness, and adaptability. With its unique characteristics, Leddar opens up an array of new possibilities in detection and ranging, and contributes to increasing efficiency, productivity, safety, or quality of life in a variety of industrial, commercial, and consumer applications.

Pierre Olivier is Vice President, Engineering and Manufacturing, of LeddarTech Inc. LeddarTech Inc.  www.leddartech.com

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ďƒ info@leddartech.com

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