Testing SAASM And Carrier Phase Receivers

The new GSG Series 6 GNSS dual frequency L1/L2 simulator generates both the C/A and P code signals simultaneously for both the GPS and GLONASS navigation systems. Though it does not have an encryption capability to simulate a true classified P(Y) signal, it is still a powerful tool for acceptance testing of classified Selective Availability / Anti-Spoofing Module (SAASM) receivers. This technical note explains how to use the simulator for military SAASM receiver testing and for also testing commercial carrier phase receivers that use the L2 P(Y) signal.

SAASM receivers are capable of receiving and decoding the military’s encrypted satellite signal, called P(Y) code, to ensure it is receiving the bona fide navigation signal and not some false spoofing signal. The encryption keys for decoding the signal are highly classified and vigorously protected by the US military so they are not available for civilian use.

However, the signal structure of the P code is not classified and is widely known, so some commercial receivers use the RF carrier of the P code signal to improve their accuracy. These receivers, called carrier phase receivers, are capable of millimeter accuracy using this method. They are used routinely in the Surveying, Construction and Agriculture industries for high accuracy position and navigation. Both SAASM and carrier phase receivers can be tested using Spectracom’s L1/L2 dual frequency GSG Series 6 simulator.