| 摘要 |
PURPOSE:To provide a circuit quality monitoring function, by supplying a control signal to an automatic equalizer in a digital transmission circuit, and thus causing frequency amplitude distortion or inter-code interference on a transmission line, and only providing a simple additional circuit. CONSTITUTION:For a 16QAM (orthogonal phase amplitude modulation) system, a signal from a transmitter 1 is inputted to an automatic equalizer 3 through a space diversity circuit 2 for compensating the multipath fading. The equalizer 3 compensates frequency amplitude distortion or compensates inter-code interference by the time axis to send the resulting signal to a demodulator 4. When the initial value of the frequency amplitude distortion is supplied to the equalizer 3 by a circuit quality monitoring control signal Ec, the code error rate of the demodulated signal is detected by a code error detecting circuit 100. When the initial value is varied by the signal Ec and the amplitude distortion is generated by the equalizer 3, the amplitude distortion due to the multipath fading is compensated by the automatic equalizer, and the amplitude distortion amount of the system includes only deviation in initial set value, so that a test is accurately performed. |
