| 摘要 |
PURPOSE:To attain channel interference detection with less effect of noise over a wide range of reception input electric field with high accuracy and high sensitivity by transmitting a pilot signal of a prescribed frequency at no talking from a transmission side, differentiating a signal as the result of envelope detection of a reception signal at the reception side, applying once more envelope detection and detecting the level through a band pass filter. CONSTITUTION:An output of an intermediate frequency filter 3 is inputted to the 1st envelope detector 6 while being branched so as to attain envelope detection and an output of the 1st envelope detector 6 is amplified by an amplifier 7 and inputted to a low pass filter 8. An output signal is inputted to a differentiation circuit 14, whose output is inputted to the 2nd envelope detector 15, where the signal is applied again with envelope detection and an output of the 2nd envelope detector 15 is inputted to a rectifier circuit 17 through a band pass filter 16, the rectifier circuit 17 rectifies the output of the band pass filter 16 and detects an average level. Thus, a detection signal proportional to the strength of an interference wave is obtained. |
