| 摘要 |
PROBLEM TO BE SOLVED: To use a general A/D converter which is inexpensive and small-sized by making small the dynamic range that the A/D converter needs by compressing the signal level difference between an interference station and a desirable station with a logarithmic amplifier and inputting the result to the A/D converter. SOLUTION: A logarithmic amplifier 6 is additionally inserted between an IF band-pass filter 5 and an AGC amplifier 7, and an exponent expanding circuit 10 is further inserted between a channel separator 9 and a demodulator 11. Then the logarithmic amplifier 6 compresses and inputs the signal level difference between the interference station and desirable station to the A/D converter 8. In this receiver, the output signal of the channel separator 9 is logarithmically compressed by the logarithmic amplifier 6, so that the output signal, even if inputted to the exponent expanding circuit 10 and expanded in amplitude level by the circuit 10 is put back into a digital signal of the amplitude level. Then the demodulator 11 imposes modulation corresponding to the modulation system of a communication system to generate a data signal.
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