Multiple antenna FM receiver

摘要

An FM stereo receiving system includes two or more antennae (12, 14) for receiving RF signals having a common frequency but potentially different phases, an FM receiver (80) having a detector output and a pilot output on which a pilot tone, such as a 19 kHz pilot tone, is present. A summer (76) sums the RF signals and provides the summed signal to the receiver (80). The or each amplitude modulator (84, 104) resides between one of the antennae (12, 14) and the summer (76) to amplitude modulate the antennae's RF signal at a perturbation frequency which is a whole number multiple greater than 1 of the pilot tone. The receiver (80) thus produces on its phase detector output a phase signal having a frequency equal to the perturbation frequency and a magnitude corresponding to the phase error between the RF signals which is connected in a feedback loop to align the phases.