Published:2009/7/11 3:03:00 Author:May | From:SeekIC
Measures center frequency of active bandpass filter by measuring phase angle as function of frequency. 0utput of VCO excites bandpass filter under test.Output of filter serves as input for PLL comparator. When VCO and filter signals are in phase, PLL Iocks at center frequency of filter, corresponding to 0°phase shift. Accuracy is 1% for measurements in AF range.-M. P. Prongue, Phase-Lock Loops Test Bandpass Filters, EDN Magazine, June 20, 1974, p 76 and 78.
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