VARIABLE RESONANCE CIRCUIT, FILTER, COMMUNICATION APPARATUS AND METHOD FOR REGULATING TEMPERATURE CHARACTERISTICS OF VARIABLE RESONANCE CIRCUIT

摘要

A variable resonance circuit having excellent resonance frequency and temperature characteristics of resonance frequency variation rate. The variable resonance circuit comprises a variable capacitance capacitor employing a thin film dielectric layer having a dielectric constant varying with a control voltage and a temperature coefficient X equal to variation in dielectric constant for temperature, and a transmission line obtained by forming a ground conductor and a line conductor on a dielectric layer having a dielectric constant varying with a control voltage and such a temperature coefficient Y that variation in dielectric constant for temperature has a polarity reverse to that of the temperature coefficient X. Since variation in equivalent capacitance of the transmission line serves to suppress variation in capacitance of the variable capacitance capacitor for temperature variation, variation in resonance frequency of the resonance circuit due to temperature variation can be suppressed, resulting in a variable resonance circuit excellent in temperature characteristics of resonance frequency.