| 摘要 |
PROBLEM TO BE SOLVED: To provide a tone detection circuit for radio equipment capable of shortening a tone signal detection time. SOLUTION: A tone signal detection circuit 100 includes three signal detection units 20, 30 and 40, a tone discriminator 15 and a control part 16. The signal detection unit 20 has a quadrature detector 10, a narrow band low-pass filter 11, a power detector 12, a moving averaging device 13 and a reference signal generator 14. The control part 16 makes a tone frequency to be detected a detection tone signal frequency f0 and sets a tone frequency around a tone signal sequence in the reference signal generator 14. The quadrature detector 10 outputs frequency components of the sum and difference between the frequency of an FM detection output and a reference signal frequency. The narrow band low-pass filter 11 eliminates undesired frequency components, the power detector 12 at a poststage calculates a power value by the squared-sum of I0 and Q0, and the moving averaging device 13 performs moving average to smooth the power value. COPYRIGHT: (C)2008,JPO&INPIT
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