A Broad-Band Impedance Indicator Employing a Phase-Shift Keying Modulator

A novel homodyne scheme for implementing a broad-band impedance indicator is proposed. It features a simple form made possible by using a modified quarternary phase-shift keying as a subcarrier modulation method. This method allows both the amplitude and the phase of a signal to be detected simultaneously by one single-ended mixer. A prototype indicator has assured the swept-frequency measurement over the band ranging from 8.6 to 10.4 GHz with the amplitude and phase errors of less than 5 percent and 5°, respectively. The capabilities are demonstrated by presenting examples of measurement.