JPH05235702

PURPOSE:To make the entire group delay characteristic almost flat by setting a group delay characteristic of an analog filter and an IIR (infinite length impulse response) filter to be almost equal to each other. CONSTITUTION:An intermediate frequency signal from a band pass filter 6 is fed to multipliers 7,8 being components of an orthogonal detector, from which base band signals I,Q are obtained and they are fed respectively to A/D converters 13,14, in which the signals are converted into digital signals xi,yi, written and read under the control of a digital signal processor (DSP) 20 and the signals are processed by the DSP 20. That is, the digital signals xi,yi from the A/D converters 13,14 are written in dual port RAMs 15,16, the written signals are inverted timewise and read, the IIR filtering processing arithmetic operation is implemented and the result is inverted timewise and read, and demodulation processing is implemented. Then the group delay characteristic and the amplitude characteristic for the filtering processing of the band pass filter 6 and the IIR filter are set respectively almost identically.