PLL-FM demodulator

摘要

The PLL includes a mixer (100) which is connected to a voltage-controlled oscillator (230) having low-gain and high-gain control inputs (L,H) from a controlled switch (225). In one position of this switch, the input and output of a low-pass filter (205) are connected to the high and low-gain inputs respectively, and conversely in the other switch position. A control circuit (215) selects the first switch position when the two inputs (235,240) to the mixer are insufficiently converged. The second position is selected when these inputs and the signal levels at the filter input and output have converged sufficiently.