A new PLL-FM modulator with rapid acquisition time

摘要

A phase locked loop (PLL) FM modulator which has a frequency acquisition speed faster than 60 mu s and a lower cutoff modulation frequency below a few Hz is presented. The PLL-FM modulator is composed of digital signal processing components for a voltage-controlled oscillator (VCO). The phase error signal at the phase comparator is derived by the subtraction between a reference phase component and a feedback phase component. Therefore, it is able to have about 10/sup 3/ times faster acquisition speed than conventional PLL-FM modulators because the low-pass filter used in those is not needed.