Quadrature FM detector including low reactance phase shifter

Claim 1

A quadrature detector for producing a frequency demodulated signal by the detection of a phase difference between a signal, applied thereto from a limiter, and a signal applied thereto from the limiter through a tank circuit and a phase shift circuit for shifting the second mentioned signal approximatedly 90° in phase, said quadrature detector comprising in combination: a multi-mode resonator of trapped energy type included in said tank circuit, said resonator having input and output electrodes laminated on one surface thereof and common electrode element laminated on the other surface thereof; a capacitor included in said phase shift circuit, said capacitor connected between output and input terminals of the phase shift circuit; a resistor included in said phase shift circuit, said resistor connected between two output terminals of the phase shift circuit; and an inductance element coupled to said resonator for facilitating the use of said capacitor having a comparatively high capacitance necessary to prevent said second mentioned signal from being considerably attenuated during its passage through such said capacitor, thereby allowing the phase shift circuit to generate an output signal of high level.