Satellite In-the-loop Test of Stabilized Antennas
Stabilized gimbal performance is often tricky to measure. Characterizing pointing accuracy of the transmit and receive beams for RF systems on a mobile platform is notoriously difficult. In an effort to understand different vendors’ stabilized gimbal performance, a customer asked IJK Controls to design a test to measure the pointing performance of mobile satcom systems. The test was to be a full “satellite in-the-loop” test with the antenna systems mounted on an actual vehicle in actual operating conditions. The customer also hoped the test could demonstrate compliance with regulations meant to reduce adjacent satellite interface in support of FCC licensing efforts.
IJK Controls designed a “pattern calibration” procedure. The antenna gimbals were swept across two adjacent satellites in a controlled matter to capture their beam properties. The calibration data was used to build a simple antenna model. IJK Controls then supervised actual testing and data-logging. During testing, signal strengths were recorded on the target satellite, an adjacent satellite and the ground antenna itself. Data was collected under various operating conditions: still, on-road moving and off-road moving.
The test involved multiple vendor antennas, rented satellite time and use of dedicated earth stations to collect data from the satellites.
IJK Controls designed the formulas for the test as well as routines for automated processing of the results. We delivered a detailed technical report explaining the test design and statistical results. The test report was useful not only to system integrator, but the regulatory authority and vendors as well.