| 摘要 |
The device includes a modulation path, a demodulation path, and electronic switchgear. The demodulation path includes an active filter of the SALLEN KEY type with TSCHEBYSCHEV behaviour, preferably of order six with a low-pass response curve, producing compensation for the distortion as (sin omega tau 2)/ omega tau 2 which is due to the demodulation, omega being the angular frequency of the low-frequency signal and the width of each sampling signal. This arrangement makes it possible to eliminate the demodulation distortion very effectively. The active filter (FAD) represented includes an input stage with operational amplifier (2) and three structures of the SALLEN KEY type of second order each including an operational amplifier with low consumption. The modulation path and the demodulation path are connected to a set by way of a line and of switchgear for the transmitted and received signals culminating respectively at a modulator and at a demodulator. The semi-conductor electronic switchgear possesses three pairs of poles, one of which is joined to the telephone set and the other two of which are joined to the modulation and demodulation paths respectively. <IMAGE> |
