| 摘要 |
<p>13 An arrangement for recovering a clock signal of frequency 1/T from an angle-modulated carrier signal having a modulation index m = 0.5 comprises a frequency doubler, a circuit for generating a clock signal component from the frequency-doubled signal, a clock filter for selecting the generated clock signal component and a pulse shaper for producing a clock pulse signal. The arrangement produces a reliable clock signal within a very short time after the start of the signal reception, because the frequency doubler comprises a hard limiter, a first bandpass filter connected thereto and having a Q ? 10, a balanced modulator connected to the limiter and to the first bandpass filter and a second bandpass filter having a Q ? 10 tuned to twice the carrier frequency 2fc; and because the generating circuit comprises a frequency converter for converting the frequency-doubled signal to a frequency band around a carrier frequency fo of the order of twice the clock frequency 2/T, a bandstop filter tuned to frequency fo and having a Q ? 10 and a squaring circuit connected to the band stop filter. The arrangement is attractive for use in receivers for radio communication systems which require a very fast acquisition of the correct clock phase.</p> |
