HIDDEN PITFALLS
Hidden pitfalls of IoT antenna design It is easy for developers to get tripped up when cramming multiple antennas into the small spaces that characterize IoT applications. Traditionally there has been a wall between industrial design and RF (radio frequency) engineering when companies develop products that have wireless capabilities. The process typically starts with product designers assembling a list of design requirements that determine the look, feel and function of the product. Only with the product development process well under way are RF engineers tasked with squeezing in wireless capabilities. Simply put, the wireless antenna and its performance can be afterthoughts. The problem, of course, is that wireless products designed this way run the risk of underperforming and being impractical – perhaps forced to use off-the-shelf antennas inappropriate for the constrained location and proximity to perturbational materials. Stick-on antennas, for example, can be detuned by most plastics. Volume constraints introduced by prescribed industrial and mechanical designs often suggest the use of a “chip” antenna. However, many chip antennas require a printed circuit board (PCB) footprint and features that may not comply with the size constraints.
RICH WALTERS • BRIAN PETTED LAIRD CONNECTIVITY
It is remarkable that many manufacturers don’t integrate the RF and industrial design teams to avoid making costly changes late in development. A well-integrated team can define early boundaries for the product that could simplify antenna design later. Moreover, designing the antenna and PCB layout without input or constraints from industrial designers can lead to missed opportunities for optimizing the shape, performance, size, cost, assembly, and desirability of the product. For example, it may not occur to RF designers operating alone that it may be advantageous to integrate antennas right into the product housing, essentially creating a Molded Interconnect Device (MID) -- basically, an injection-molded plastic with integrated circuit traces. The MID can be an internal part or integrated into the exterior of the product. There are several ways to produce MIDs and some of them require less tooling than others. This sort of design thinking takes a team of industrial designers and antenna designers who work side by side, simulating antenna patterns, building prototypes, and testing real physical prototypes. In this scenario, RF engineers make sure industrial designers know about limitations as well as spatial and material challenges for the chosen antennae. They can also factor in spatial and material limitations such as those imposed by adjacent ground and dielectric planes, human body interactions, and resistive loss characteristics of metallization materials and processes.
The Revie Flex is a flexible PCB antenna with a broad frequency range for LTE CAT M1 and NB-IoT devices.
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Laird — Internet of Things HB 04-19.indd 45
4 • 2019
DESIGN WORLD — EE NETWORK
45
4/15/19 10:23 AM
