LF Adaptor Extends Vector Voltmeter Magnitude and Phase Measurements down to 10 Hz

An IC single-sideband modulator is described that allows direct measurement of magnitude and phase of a voltage over 3 decades anywhere in the range 10 Hz to 1 MHz. Two modulators generate a leveled upper-sideband (USB) reference signal about a 1-MHz suppressed carrier acceptable to the HP 8405A vector voltmeter. Another modulator produces a double-sideband (DSB) replica of the output voltage of the test device. The vector voltmeter then measures the magnitude of the upper-sideband reference and test device signals and their phase difference.