The circuitry of the sensor readout comprises of three components namely: the phase detector, oscillator and the buffer The phase detector is connected to the transmission line of the sensor and the output of the buffer circuit.
A low pass filter is included to give an output voltage that is constant and proportional to the difference in phase between the inputs of the phase detector.
Oscillator circuit provides an output with the desired frequency.
It also includes an astable multivibrator the gives continuous state to the oscillator.