chapter  99
A technique for countering the integer boundary spurs in fractional phase-locked loops with VCO
ByR. Vishnu, S.S. Anulal & J. Ravi
Pages 6

ABSTRACT: Integer boundary spur is a mechanism of fractional spur creation, caused by interactions between the RF VCO frequency and the reference frequency or phase detector frequency. An algorithm was developed which identifies the integer boundary frequencies and configures the synthesizer in such a way that the generated spurs are offsetted far away from the loop bandwidth, so that they are attenuated by the loop filter. The algorithm runs as a sub-routine in the micro-controller which programs the synthesizer, to modify the multiplier value accordingly. This algorithm was developed and tested on a fractional frequency synthesizer operating from 700-1000 MHz, even though the method is independent of frequency of operation.