Phase demodulator for Hf measuring signals - is incorporated in phase-regulating loop with VCO

摘要

The phase demodulator forms part of a phase-regulating loop incorporating a difference amplifier (2), a semiconductor switch (5) and a coupling capacitor (4). A reference voltage (Uv1) is supplied directly to the negative input (3) of the difference amplifier (2), with the coupling capacitor (4) connected between the two amplifier inputs (1, 3). The positive amplifier input (1) is coupled to a constant potential, e.g. earth, via the semiconductor switch (5). The latter has its control input supplied with a second reference voltage (Uv2) and the control voltage for the oscillator (VCO) is obtained from the output (7) of the difference amplifier (2). Pref. the first reference voltage (Uv1) comprises a sawtooth waveform and the internal resistance of the voltage source is matched by the high-ohmic resistance of the positive amplifier input (1).