| 摘要 |
In a transmitter, a digital base-band signal drives a frequency modulator via a pulse-expanding filter. In the receiver, the received signals are fed via a bandpass filter to a frequency discriminator for demodulation. The demodulated signal is filtered in a low-pass filter and passes through a pulse-compressing filter before threshold decoding. A plurality of identical receivers can be connected in such a manner that the bandwidth of the bandpass filter becomes smaller and smaller in successive branches. The pulse-expanding filter has a constant frequency response amplitude and a linearly rising group delay time, while the pulse-compressing filter has a frequency response which is the conjugate-complex of the said filter.
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