Vehicle navigation system using global positioning system - switches signals received from antennas positioned at front and rear of vehicle to compensate for signal fading

摘要

The vehicle GPS system includes an antenna (A1) at the front of the vehicle, and a second antenna (A2) at the rear. Both antennas are positioned inside the vehicle and signals received from them are fed to respective high frequency amplifiers (B1, B2) and then to respective demodulators (12) via an antenna selector (1). Both demodulators carry out a parallel search for different satellites, and demodulate the h.f. signals of the acquired satellites to provide GPS data. When the data from three or more satellites are present, a computer (3) controls the antenna selector such that during a search by both antennas for the same satellite, the reception is optimised. ADVANTAGE - Faster satellite acquisition in presence of fading signals.