Patent ID: 6466086
Filing Date: 2002-10-15
Classification: H04L

Abstract:
A quadrature demodulator comprising:(a) an oscillator section for generating a local signal with a local frequency of twice a carrier frequency-converting an input signal with a specific frequency using the local signal; (b) a quadrature demodulator section for generating two orthogonal baseband signals by frequency-converting an input signal with a specific frequency using the local signal; (c) a PLL section for stabilizing the local frequency by applying its output signal corresponding to a difference between the local frequency of the local signal and a predetermined reference frequency to the oscillator section; and (d) the oscillator section having an oscillator capable of varying its oscillation frequency by changing its driving current, the driving current being changeable according to the output signal of the PLL section; (e) the local frequency of the local signal being kept constant by adjusting the driving current of the oscillator section by way of the output signal of the PLL section and said demodulator comprises a resonant circuit with a fixed resonant frequency; wherein the resonant circuit cooperates with the oscillator section to generate the local signal.