A Differential Capacitor Circuit for Very High and Low Dielectric Q-Factor Measurement at High Frequencies

This paper presents an electronic circuit system that is capable of measuringdielectric Q-factor Qx (= 1/tan δ) ranging from 0.01-10 at measuring frequencies 100 kHz-30 MHz, and from 10-105 at 1-300 MHz. For measurement of very high loss materials, a tripartite differential capacitor is used as a variable resistor to substitute for low Rx, and for measurement of very low loss materials, an ordinary differential capacitor connected in series with two fixed deposited fim resistors is used to substitute for high unknown resistance Rx. An important characteristic of the circuit is its capability of measuring capacitance and resistance of high loss materials accurately.