| 摘要 |
PROBLEM TO BE SOLVED: To provide a demodulator where a time constant for automatic gain control AGC is decreased while a BER characteristic in a steady-state is enhanced, and a tracking speed against level fluctuation in an input signal is increased. SOLUTION: A demodulator of quadrature amplitude modulation(QAM) type with 2<q> values is provided with an AGC amplifier 10 that receives a modulation wave to be operated to keep an average power of an output signal constant, A/D converters 61, 62 that apply A/D conversion to an output signal of the AGC amplifier 10, an equalizer 70 that eliminates an intersymbol interference component included in the output signals of the A/D converters 61, 62, AGC circuits 81, 82 that are operated so that the convergence point of the output signal of the equalizer 70 reaches an amplitude expressed by a binary number in (q/2)-bit, and a control circuit 90 that receives the output signal from the AGC circuits 81, 82 to generate a control signal for the AGC circuits 81, 82. |
