Abstract: A direct conversion receiver is disclosed that converts RF signal into corresponding quadrature baseband signals without requiring conversion through an intermediate frequency. The direct conversion receiver abates local oscillator leakage, increases dynamic range and increases RF selectivity as compared to conventional direct conversion circuits. The circuit includes an in-phase branch and a quadrature-phase branch, each branch including two mixers instead of the conventional one. Each mixer is provided with balanced control signals that include a primary control signal and a complementary control signal. For each branch, the signals from the mixer pass through an operational amplifier and a low pass filter to extract the corresponding baseband signal component.

Abstract: A phase shift keyed carrier recovery and demodulator circuit which includes a phase detector and subsequent feedback control loop circuitry which maintains an initial phase relationship. By comparing an incoming phase modulated carrier with the multiple phase outputs of a local oscillator, the circuit is able to generate a correcting signal which allows coherent phase tracking of the incoming phase modulated carrier. The phase detector produces a correction signal which allows the circuit to phase lock any two sequential phases of the locally generated phase outputs to phase positions on either side of the phase of the incoming phase modulated carrier. Once the circuit has obtained carrier phase lock, the multiple phases produced by the local oscillator will remain fixed (without phase change) relative to the initial detected phase of the incoming phase modulated carrier.