Improving the accuracy of measurement of phase-amplitude response of four-pole networks

The typical block diagram of an instrument used for phase-amplitude response (PAR) measurements includes a high-frequency source (generator) and test signal generator connected in series as well as a two-channel phase difference converter and an indicating device. The investigated four-pole networks are connected between the test signal generator and phase difference converter in one or in both channels simultaneously. All circuits of the PAR meter are synchronized from a common control circuit. The test signal generator produces two high-frequency output signals with an amplitude varying with time. To reduce PAR measurements errors, the amplitude-dependent phase shifts in the investigated four-pole networks acted upon by the test signal are first transferred to a relatively low stable intermediate frequency and only then converted into a code or voltage.