Multi-Antenna Diversity Set for Transmission and Reception in Car-to-Car and Car-to-X Communication

A microwave circuit for scan-phase antenna diversity for Car-to-Car and Car-to-X communication at 6 GHz is presented. Up to four independent antenna signals are selected and combined after a continuous phase alignment by 3-stage variable phase shifters. These phase shifters allow for continuous phase tuning between 0° and 360° with a nearly constant transmission factor within the complete frequency band of the IEEE 802.11p standard. Measurement results of the phase shift circuits are presented. The complete diversity circuit is evaluated by example of four monopole antennas which are mounted underneath the roof of a car. In a comparison with a single antenna, the improvement of signal-to-noise ratio can be shown. An avoidance of fades by more than 10 dB and an additional gain of around 5 dB is obtained for all azimuth directions around the car.