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Complex phase-locked loop demodulator for low-IF and zero-IF radio receivers
Complex phase-locked loop demodulator for low-IF and zero-IF radio receivers
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机译:适用于低中频和零中频无线电接收器的复杂锁相环解调器
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摘要
A digital demodulator which coherently demodulates a low-IF or zero-IF complex signal using a complex-valued phase-locked loop (CPPL). The CPPL includes a numerical controlled oscillator, four multipliers and two combiners to provide independent phase/frequency and amplitude outputs. The CPLL exhibits in first order PLL dynamics without a loop filter in the feedback loop to the NCO. However a filter with one or more poles may be included in the feedback circuit to exhibit 2nd or higher order PLL dynamics. The CPLL allows coherent demodulation of extremely low FM modulation indexes whereby the incoming frequency drift may be larger than the frequency deviation. It can also be used to coherently demodulate signals which have combined amplitude and phase characteristics.
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