Making the Connection in GNSS Testing
One question that regularly crops up in discussions about GNSS receiver testing concerns exactly how the signals get from the GNSS simulator to the device under test. Is it better to radiate the simulator signal to the receiver's antenna, or should you couple them directly?
The short answer to this is that a direct connection from the simulator to the receiver's antenna port will always provide the most controlled test environment with no risk of outside influence. The connection is usually performed using a simple coaxial cable that acts as a 50 ohm transmission line, or it may require the addition of a low-noise amplifier in cases where the receiver is designed to use an active antenna.
In either case, making the direct connection – always using high-quality cables and components – will enable all tests to be made under controlled conditions.
Of course, some types of location-enabled equipment have no external antenna port, and in many cases the antenna is entirely hidden from view. So here practicality dictates that a radiated signal must be used. This does, however, leave the test setup open to all manner of outside interference, and this can make results unreliable. So for full confidence in the results of the test we recommend putting the equipment under test inside an RF screened enclosure together with the radiating antenna from the simulator.
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