Quadrature Signals and Image Reject Mixers
Stephen I. Long · River Publishers eBooks · 2023
Quadrature signals are the basis for nearly all digital communications. Mixers can be used to translate signals up or down in frequency. The downconverting mixers can either mix to a finite frequency or to baseband. The low pass filter is required in order to reject the upconverted output of the mixers. The mixer output amplitude is not extremely sensitive to local oscillator amplitude, thus reasonably good if amplitude balance can be obtained over some bandwidth. The input data would typically be generated by separating a serial data path into two channels with a serial-parallel converter. Polyphase filters can be used for quadrature signal generation and also for image rejection. Polyphase filters discriminate between positive and negative frequency signals.