PHASE SHIFTER AND QUADRATURE MODULATOR

摘要

PROBLEM TO BE SOLVED: To provide a phase shifter which can obtain two output signals whose phase difference precisely becomes 90 degrees. SOLUTION: An LPF 32 of a CR phase shifter 31 is set to be an integration circuit where a resistor R1 and an NPN transistor Tr1 as a variable element are connected in series. A phase difference detection circuit 34 feeds back a control signal S2 based on the phase difference of first and second carrier signals LO1 and LO2, to the transistor Tr1. Thus, the phase difference detection circuit 34 changes the junction capacity of the transistor Tr1 so that the phase difference of the first and second carrier signals LO1 and LO2 comes close to 90 degrees.