Data transmission system between fixed beacon and vehicle - uses microwave transmitter and receiver for phase modulated signals reflected from vehicle

摘要

The data transmission system between a fixed beacon and a vehicle such as a fire engine or police car includes a microwave transmitter and receiver at the beacon and on the vehicle. The data reflected from the vehicle to the beacon is a modulated wave. The reflected wave can be phase modulated, and can consist of three components of the wave, phase displaced by 120 degrees and having nearly the same amplitude. At the beacon is a microwave assembly forming a phase modulated reflector. Pin or varactor diodes are connected with a modulator control circuit which determines the timing sequence of the control signals. Two diodes can form a T member and are spaced at different distances from the reflectiv reflective short circuit connection of the microwave line. The sender/receiver on the vehicle uses a Gunn oscillator for the microwave transmission.