PLL NOISE SMOOTHING USING DUAL-MODULUS INTERLEAVING

摘要

The present invention, generally spreading, achieves noise spreading within a PLL using a dual-modulus prescaler by interleaving the division moduli. Within a given cycle, "ones" and "tens" are not all counted consecutively. Instead, ones and tens are interleaved. In one embodiment of the invention, the R count is doubled and the output of the R counter is toggled between high and low states. (The Q counter may remain unmodified). In another embodiment of the invention, ones and tens are interleaved in accordance with a ratio q:r. By so interleaving the modulus, the effect is to spread the noise resulting from the output signal of the dual-modulus prescaler over a wider frequency range. The prescaler noise level is greatly reduced, particularly within the frequency band of the reference frequency.