Airborne gps guidance system for defeating multiple jammers

Abstract

A missile guidance system designed to operate on GPS signals in an anti-jamming environment. The inventive system includes first, second and third airborne vehicles (,). A GPS receiver (,) is mounted on each of the three vehicles (,) to receive signals transmitted from spaceborne satellites (,). Each vehicle (,) acts as a pseudo-satellite or 'pseudolite'. The received GPS signals are processed by a processor (,) to provide a first intermediate signal indicating the position of the vehicle (,). This signal is retransmitted from each vehicle and received by a GPS receiver mounted on a missile. The received intermediate signal is processed on the missile to provide an output signal indicating the position thereof. The pseudolites would be airborne in the vicinity of a target area. Because the pseudolites are relatively close to the targets compared to a satellite in high altitude orbit and because the pseudolites would be able to transmit a kilowatt or more power, the signal strength may be improved significantly. To succeed as a jammer, a jammer, successful against GPS satellites, would need considerably more power to succeed against aircraft carried pseudolites. The pseudolite system delivers GPS signals into the target area 40-70 dB stronger than signals coming directly from GPS satellites. By timing the signals for 100% time coverage, enemy C/A code receivers will be jammed because they are limited to a J/S capability of 30 dB.