Theoretical Response of a Polar-Display Instantaneous-Frequency Meter

Polar-display instantaneous-frequency meters are finding increasing application as frequency monitor receivers and as modulation analyzers. These systems indicate signal frequency by the angular coordinate of a cathode-ray-tube spot and signal amplitude by the radial coordinate. This paper derives the responses (spot loci) produced by signals of interest, including the sum of two sinusoids, amplitude-modulated carriers, angle-modulated carriers, and carriers with combined amplitude and angle modulation. Differences between actual responses and responses expected from a static analysis are studied. Conditions under which the amplitudes and frequencies of two simultaneously applied sinusoids can and can not be determined from the display are derived.