A Technique for Reference Spur Eradication in Fractional-N Frequency Synthesis

This thesis details a technique of eradicating reference spurs. It involves a Fixed Width Variable Amplitude Charge Pump (FWVACP) which is inherently insensitive to current mismatch. Charge pump current pulses are modified such that they have a fixed width and occur on the falling edge of the reference signal. Phase error information is embedded in the amplitude of the current pulses. The periodic nature of these pulses creates nulls at integer multiples of the reference frequency. At the VCO output, this translates into nulls at offsets equal to integer multiples of the reference from the carrier effectively eradicating the reference spurs. The FWVACP and a standard charge pump were fabricated using IBM 0.13 micron CMOS technology. The prototype occupies less than 1 mm^2. A more than 10 dB reference spur reduction was measured with a FWVACP as compared to the standard charge pump.