7 minute read
Testing antennas in new environments
The satellite industry is undergoing a huge transformation as demand for reliable, highspeed connectivity continues to grow across the globe. A critical component of this transformation is the industry’s ability to carry out rigorous and cost-effective testing of antennas. Consequently, the approach taken to testing is having to evolve in-line with the new satcom landscape. While some antenna tests happen in dedicated test ranges, it’s becoming increasingly important to be able to test in-situ because this provides operators with a more accurate picture of how the antenna will perform, or is performing, in its operational environment.
Rasmus Hasle, R&D Director, Quadsat
In the past, in order to test antennas in-situ, operators would have had to use either on-orbit testing using a live satellite link, fixed RF beacons, or celestial bodies, each of which presents its own challenges and limitations. This made in-field testing neither cost-effective nor efficient. However, the introduction of UAV (unmanned aviation vehicle)-based test and measurement systems in recent years has made in-situ testing a viable and costeffective approach. For successful in-situ test missions using drone-based systems, there are a number of considerations that must be taken into account during the pre-test planning and preparation process.
WHY TEST IN-SITU?
Testing antennas in their operational environment has several advantages over traditional test range evaluations. Firstly, in-field testing eliminates the need to transport large and often cumbersome equipment to specialized test ranges, which can be costly, complex to coordinate, and time consuming. This is particularly beneficial when dealing with large ground station antennas, where moving the hardware is impractical.
Secondly, in-situ testing can help to identify environmental considerations such as weather attenuation and the topography that could cause signal interference and affect antenna performance. Identifying and understanding these factors is crucial for ensuring that antennas are able to perform optimally in their operational settings. This is important for both fixed communication and Communications-on-the-Move (COTM).
Testing antennas in the location where they will function ensures that any potential factors that could prevent an antenna from operating optimally can be identified, understood, and overcome as soon as possible. Testing in-situ allows operators to make the necessary adjustments to ensure that teleports are optimized for their real-life environment, rather than the test range.
Practical Considerations
Unlike in a controlled test range environment where equipment is already set up and calibrated, conducting in-situ antenna tests requires measurement equipment to be transported to the test site, installed and calibrated in the field. A ground station could well be situated in a remote location which may lack the infrastructure needed for a traditional test setup. Drone-based test equipment is ideal in these scenarios because it’s portable, quick to set up, and does not require any infrastructure to be built for tests to be conducted.
As is the case with any type of antenna testing, whether at a dedicated test range or in-situ, thorough planning is required. When testing in-situ, a comprehensive site survey is required to assess the area surrounding the antenna under test to identify any potential obstacles such as high buildings, masts, antennas, trees, and changes in terrain altitudes. These issues can then be factored in when determining the drone flight path to ensure that the test mission is safe, effective, and efficient. Drones can also be equipped with autonomous flight modes for safer and more efficient test missions.
Weather is another important consideration when carrying out in-situ testing using a drone-based system. These systems should only be flown when the weather conditions are within the system’s operation limits. It is therefore essential to check weather forecasts and be aware of system limitations. The sturdiness and built quality of the drone are extremely important because a sturdy, high quality drone provides accurate tuning and control, leading to good rejection of disturbances from external factors such as wind.
Environmental Factors And Interference
In addition to the practical considerations outlined already, environmental factors and potential sources of interference also need to be considered when carrying out in-situ testing. Environmental factors can have a significant impact on how RF signals are received, causing signal degradation and loss of throughput. Factors such as temperature, humidity, wind, precipitation, as well as topography can affect signal quality and introduce variances.
Unlike test ranges, which are designed to minimize external interference, operational environments can be filled with a variety of interference sources, from nearby cell towers and broadcast stations to industrial equipment and even other teleports. The advantage of testing an antenna in its operational environment is that you can identify potential electromagnetic interference sources and develop a mitigation strategy. This may involve adjusting the antenna’s position or modifying the site’s layout. If remedial action is not possible and the installation is for a new ground station, the test results may indicate that the location itself is not suitable.
It’s also important to note that while some negative environmental factors are easily identifiable by the naked eye, others are not. Reflectivity is a huge concern because it can’t easily be seen and can significantly impact how RF signals are received. Drones can be used to address this issue because they can be deployed to generate a reflectivity map for a test site by collecting reflectivity data across various azimuth-over-elevation angular pairs. Understanding the origin and consequences of reflectivity allows operators to reduce its impact with actions such as modifying the layout of the ground station or by installing corrective equipment.
Testing Parameters
It’s essential to have robust testing in place that determines both that the antenna is functioning correctly, and that it is operating optimally in its real-life environment. A wide range of measurements therefore need to be taken during the testing process. Drone-based testing systems have the built-in flexibility to change frequency, amplitude, and polarization of the test signal. This makes them ideal for carrying out the variable measurements needed in these scenarios.
Additionally, the flexibility that drone-based testing and measurement systems affords makes it possible to carry out diagnostic techniques that may not be easily achievable otherwise. In addition to measuring the radiation pattern, drone-based systems can also simulate satellite orbits to verify the tracking performance of antennas as they track and switch between NGSO satellites passing overhead. With this method, the satellite pass can be repeated as desired, so an antenna’s performance can be evaluated at any time without having to wait for an actual satellite to pass.
Key To Success
As the satellite industry continues to evolve, the ability to conduct effective in-situ antenna testing is becoming increasingly important. Drone-based testing technology is a key enabler on this front. It is portable, designed to be rugged for field use, and is also capable of measuring against a wide range of parameters.
By understanding the practical considerations and carrying out effective planning and preparation for testing antennas in in-field environments, antenna manufacturers and operators can ensure that their antennas perform optimally in their intended operational settings. However, maintaining flexibility throughout the test mission is crucial. A flexible approach allows the testing team to respond to any challenges that may arise by adjusting the test plan in real-time as required. By integrating these practices, operators can conduct effective in-situ testing.
With thorough planning, advanced test and measurement tools, and a proactive approach to mitigating challenges, the satellite industry can continue to push the boundaries of communication technology and deliver reliable, high-performance connectivity to customers around the world.
