| 摘要 |
<p>899,135. Pulse modulation systems. POSTMASTER GENERAL. Feb. 5, 1960 [Feb. 13, 1959], No. 5165/59. Class 40(5). A demodulator for amplitude modulated pulses includes a transistor VT connected by its base and emitter electrodes across a parallel resonant circuit LC having a resonant frequency equal to at least half the reciprocal of the duration of an input pulse, reception of an input pulse charging the resonant circuit so as to bias the transistor to a condition of non-amplification, and subsequent discharging of circuit LC causing the transistor to assume a condition of amplification, the resultant collector current being dependent on the amplitude of the input pulse. In the preferred embodiment, the current pulses in the collector circuit are supplied to a load impedance W through a low-pass filter WF, inductor L being earthed at a point intermediate its ends so that circuit LC is critically damped. The demodulator is described with reference to a time division multiplex system comprising a plurality of such demodulators activated in turn by channel pulses from a generator CP applied to unblock respective rectifiers MR. Specification 899,134 is referred to.</p> |
