Analogue phase discriminator with linear characteristic within +φ interval

The present article considers a method of forming of phase discriminator linear discriminative curve (DC). As usual, existent phase discriminators have non-linear DCs, thus making designing of devices applying them more complicated and impairing their functioning.

The concept of phase discriminator DC forming is the following. To form phase discriminator DC it is necessary to use three ordinary phase detectors (PDs) with Sinφ, Cosφ and - Cos φ amplitude-phase characteristics; two voltages with equal amplitudes (i.e. Uc=Uop) are to be applied at the input. In this case cosinusoidal and sinusoidal voltages at the PD output shall become straight lines. Three univibrators, five electronic switches, two voltage sources and an output device are to be used as well.

Output voltage PD Sinφ and PD - Cos φ (in the form of straight-line segments) shall be applied to the differentiating circuits; output peaked negative polarity pulses from the circuits are applied via diodes to the univibrators controlled by electronic switches. If the signal frequency equals to 1KHz, the output pulse duration from UV2 and UV3 would be equal to 250 µs, and UV1 pulse duration would be 500µs.

Upon appearing of voltages approximated by straight-line segments at PD input, voltage from PD Sinφ is applied to Σ input, then positive voltage from the voltage source and the straight-line segment signal from - Cosφ output are summed up at the Σ output device, afterwards negative voltage from the second voltage source and straight-line segment signal from PD Cosφ output are summed up at the output device. Then the contact at the PD Sinφ output closes and the cycle of forming of linear voltage of the given PD amplitude-phase characteristic ends.