Quadrature phase demodulator capable of operating under a wide input dynamic range

摘要

In a demodulator for demodulating into a demodulated signal a quadrature phase modulated signal having a large varying amplitude caused by various radio transmission link conditions, a preprocessing circuit (21) logarithmically processes the envelope to produce a first preprocessed signal having a logarithmically compressed and digitized amplitude and limits the amplitude to multiple values to produce a second preprocessed signal. A phase detecting circuit (22) detects a phase difference between a reference signal having a reference frequency and the second preprocessed signal and produces a phase difference signal representative of the phase difference. A processing circuit (23) processes the first preprocessed signal and the phase difference signal to produce first and second processed signals collectively as the demodulated signal. Preferably, the processing circuit comprises an exponential processor for exponentially processing the first preprocessed signal to produce an exponentially processed signal as the first processed signal.