Miniaturized Gps Antenna Array Technology and Predicted Anti-jam Performance

NAVSYS has developed a miniaturized GPS antenna array technology that reduces the size of the antenna elements and the array dimensions. This technology enables GPS controlled reception pattern antenna arrays (CRPAs) with anti-jamming capability to be installed on vehicles where their size has previously prohibited their use. This includes aircraft where size and weight constraints resulted in fixed reception pattern antenna (FRPA) installations instead of CRPAs and munitions where space and surface area are at a premium. BOEING has developed AGHASTTM (Another GPS High Anti-jam Simulation Tool), which allows the anti-jam performance of CRPAs and their null-steering electronics to be predicted. Using detailed antenna pattern and coupling data collected in the instrumented anechoic chamber at Boeing, AGHASTTM can accurately predict the expected installed performance of anti-jam hardware in a jamming environment. In this paper, the miniaturized antenna array technology is described, along with test results and an AGHASTTM evaluation of the mini-array anti-jam performance. GPS ANTI-JAM ANTENNA ARRAYS The low broadcast power of the GPS satellites (approximately -160 dBw) makes these signals particularly susceptible to jamming. Figure 1 shows the jammer/signal (J/S) power levels as a function of distance and jammer transmit power (assumes a line of sight path and a received P(Y) code power of -163 dBw). The current generation of GPS User Equipment (UE) relies on using the more susceptible C/A code for signal acquisition. As shown in Figure 1, this can be denied almost to the horizon with as little as 22 dB J/S. If precise time is known, then P(Y) code signal acquisition can occur directly and will not be denied until the J/S exceeds 34 dB. With advanced signal processing techniques, GPS acquisition can be achieved under J/S as high as 44 dB. However, as shown in Figure 1, even a relatively low power jammer can have drastic effect on GPS receivers at quite significant distances from the jammer source.