Patent ID: 6925293

Claim:
An antenna diversity system for receiving frequency-modulated (FM) radio signals in an FM receiver with the phase-controlled summation of antenna signals, for motor vehicles having a multi-antenna system with antenna switches coupled to antennas for producing at least two antenna output signals, comprising: a receiver having a first input and a second input coupled respectively to the at least two antenna signals; a phase-shifter having its input coupled to said second input of said receiver, whereby the received antenna output signal at said second input has the same phase at the output of said phase shifter as the antenna signal in the first receiver input; a summation circuit for adding up the two received antenna signals in a phase-coincident manner, to produce at its output, an added-up signal, to be supplied to the frequency demodulator of the FM receiver; a phase controller, having its input coupled to the output signal of said summation circuit, and having its output coupled to said phase shifter, said controller having a low pass filter to limit its speed of shifting of said phase shifter; an interference detector having its input coupled to the output of said summation circuit for rapidly detecting a reception disturbance in said added-up signal caused by a swing in the frequency of the received FM signals, so as to produce an interference detection signal at the output of said detector; and a controllable logic switch having its output coupled to the antenna switches of said antenna system, and its input coupled to said interference detector so that when a received signal that is different in terms of diversity, is supplied to at least one of said two inputs, of said receiver from each of the different switching positions of the antenna switches said interference detector will actuate said logic switch and thus switch said antenna switches to another switching position, during the presence of a reception disturbance so that the output signal fed to the FM demodulator is free of reception interference.