Half duplex rf transceiver

Abstract

A radio frequency (RF) transceiver for modulating and demodulating RF signals with a direct modulation transmitter and a dual intermediate frequency (IF) receiver, respectively, includes a local oscillator, three frequency converters, a demodulator, a carrier generator, a modulator, a controller and two signal switches. The local oscillator (e.g. phase lock loop PLL!) provides a first local oscillator (LO) signal. One frequency converter (e.g. mixer) frequency converts an incoming modulated RF signal with the first LO signal to provide a first modulated IF signal. A second frequency converter frequency converts the first modulated IF signal with a second LO signal to provide a second modulated IF signal. The demodulator also receives the second LO signal and demodulates therewith the second modulated IF signal. The carrier generator (e.g. voltage-controlled oscillator VCO!) receives a transmitter control signal and in accordance therewith generates a transmitter carrier signal. The third frequency converter receives the transmitter carrier signal and the first LO signal and in response thereto provides the second LO signal. The modulator selectively receives and modulates the second LO signal to provide a third modulated IF signal. The controller (e.g. phase detector) receives a reference signal and selectively receives the second LO signal and the third modulated IF signal and in response thereto provides the transmitter control signal. The signal switches receive a mode control signal and in response to one state thereof connect the controller to the third frequency converter and in response to another state thereof connect the modulator to both the third frequency converter and controller.