Development of Smart Antenna Array Signal Processing Algorithm for Anti-Jam GPS Receiver

GPS guidance uses low power signals from satellites which are 11000 NMI away. The satellite transmitter power is modest nearly 10W orders of magnitude. Neither satellite nor receivers have the luxury of very high antenna gain since both entities have signiflcant fleld of view requirements. These factors result in a very low power density incident on a GPS receiver antenna. The signal received is generally 165dB down than the thermal noise level. Such signals are notoriously easy to jam either by intentional noise sources (Jammer) or unintentionally from harmonics of broadcasting stations or other out of band sources. Here in this paper we will show how a nulling antenna or controlled reception pattern antenna with adaptive spatial flltering technique e-ciently mitigate the intentional and non intentional interferences. A beamforming antenna array is a set of antennas whose outputs are weighted by complex values and combined to form the array output. The efiect of the complex valued weights is to steer main lobes of the array pattern to desired directions. These directions may be unknown and so the antenna weights must be adjusted adaptively until some measure of array performance is improved, indicating proper lobe or null placement. An adaptive algorithm to adjust the complex weights of an antenna array is presented that nulls high power signals while allowing reception of GPS signals as long as the signals arrive from difierent directions.