Patent ID: 6947499
Filing Date: 2005-09-20
Classification: H03D,H03J

Abstract:
1. An angle demodulation apparatus comprising: a first oscillator for generating a first local oscillation signal and a first phase signal whose phase differs from that of said first local oscillation signal substantially by 90 degrees; a first mixer for externally receiving an angle modulation signal, receiving said first local oscillation signal and said first phase signal from said first oscillator, generating a first base band signal comprised of that of a product of an instantaneous value of said angle modulation signal and an instantaneous value of said first local oscillation signal from which a component with a frequency of substantially 0 is removed, and generating a second base band signal comprised of that of a product of said instantaneous value of said angle modulation signal and an instantaneous value of said first phase signal from which a component with a frequency of substantially 0 is removed; a second oscillator for generating a second local oscillation signal and a second phase signal whose phase differs from that of said second local oscillation signal substantially by 90 degrees; a second mixer for receiving said first and second base band signals from said first mixer, receiving said second local oscillation signal and said second phase signal from said second oscillator, and generating an intermediate frequency signal representing a sum of or a difference between a product of an instantaneous value of said first base band signal and an instantaneous value of said second local oscillation signal and a product of an instantaneous value of said second base band signal and an instantaneous value of said second phase signal; and a demodulator for receiving said intermediate frequency signal from said second mixer and demodulating said intermediate frequency signal to thereby generate an angle demodulation signal, said second oscillator including a reference oscillator for generating a reference oscillation signal, and a frequency divider for generating said second local oscillation signal whose frequency is substantially equal to a difference between or a sum of a predetermined intermediate frequency signal and an offset frequency of a predetermined range by frequency-dividing said reference oscillation signal by a predetermined first frequency dividing ratio, said first oscillator including a variable frequency oscillator for receiving said reference oscillation signal and generating said first local oscillation signal whose frequency is substantially equal to a sum of or a difference between a carrier frequency of said angle modulation signal and said offset frequency by generating a signal whose frequency converges to a frequency having a given ratio to a frequency of said received reference oscillation signal.