Patent ID: 7577215

Claim:
An angle demodulation apparatus comprising: a first oscillation section 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 mixing section for externally receiving an angle modulation signal, receiving said first local oscillation signal and said first phase signal from said first oscillation section, generating a first base band signal representing 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 representing 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 oscillation section for generating (i) a 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, and (ii) a second phase signal whose phase differs from that of said second local oscillation signal substantially by 90 degrees; a second mixing section for receiving said first and second base band signals from said first mixing section, receiving said second local oscillation signal and said second phase signal from said second oscillation section, and generating an intermediate frequency signal representing a sum of or a difference between: (i) a product of an instantaneous value of said first base band signal and an instantaneous value of said second local oscillation signal and (ii) a product of an instantaneous value of said second base band signal and an instantaneous value of said second phase signal; and a demodulation section for receiving said intermediate frequency signal from said second mixing section and demodulating said intermediate frequency signal to thereby generate an angle demodulation signal; wherein said first oscillation section generates 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 receiving said first base band signal or said second base band signal from said first mixing section, extracting a carrier component of said angle modulation signal included in said received first base band signal or second base band signal and generating a signal whose frequency converges to a frequency having a given ratio to a frequency of said extracted carrier component.