DUPLEX COMMUNICATION TRANSCEIVER WITH MODULATION CANCELLATION

摘要

A duplex FM communication transceiver (10) in which the problem of requiring additional costly apparatus to separately generate a modulated transmit carrier signal and a receiver first mixer injection signal is solved by utilizing the modulated transmit carrier signal as the receiver first mixer (32) injection signal. The receiver portion (27-46) of the transceiver (10) comprises dual conversion circuitry, and the transmit information signal used for modulating the transmit carrier signal is phase and amplitude adjusted and then utilized to modulate the receiver second injection local oscillator (41) which provides the input injection signal to the receiver second mixer (36). The second mixer (36) substantially cancels all of the transmit information signal previously introduced into the receiver path by the first mixer (32) and provides only received information signals to a demodulator (43) which provides audio signals to a speaker (46).