VARIABLE SIGNAL DELAYING CIRCUIT, QUADRATURE FREQUENCY CONVERTER AND RADIO FREQUENCY TUNER

摘要

A variable signal delaying circuit comprising an analog delay line having a control input for controlling the variable delay. A phase detector compares the input and output signals of the delaying circuit and supplies an output signal to a charge pump and integrator. A pulse stream generating arrangement produces pulse streams of different pulse widths and pulse control logic controls a selector for selecting any one of the pulse streams. In a first mode of operation, the control logic monitors the charge pump/filter output and selects the pulse stream which minimizes change in the output. The selection is fixed and the output of the charge pump/filter is then supplied as a correction signal to the control input of the analog delay line. Such an arrangement may be used to maintain minimum phase imbalance in I and Q signal paths of a quadrature frequency converter.