MASH DDSMInduced Spurs in a Fractional N Frequency Synthesizer A MASH DDSM is conventionally employed in a fractional N  frequency synthesizer as the divider controller. The quantization noise of the MASH DDSM adds to the output phase noise. It has been shown that the nonlinearity within the synthesizer causes the divider controller contribution of the noise to increase and spurious tones are generated as the result. In the past the pattern of the fractional spur has been reported and studied. In measurements as well as simulations, subharmonic spurs, i.e. spurs at a lower frequency than the expected fractional spur, have been observed. In this work, the pattern of MASH DDSMinduced spurs is studied through simulations and observations in a commercial fractional N  frequency synthesizer.

Multibit Sturdy MASH xcex94xcexa3 Modulator with Errorshaped Segmented DACs for Wideband Lowpower Applications This paper presents several techniques to enhance the resolution of sturdy multistage noise shaping (MASH) xcex94xcexa3 modulator (DSM). The proposed structure significantly suppresses the quantization noise (QN) by employing a highresolution quantizer with a segmented MSBLSB DAC feedback in the first loop as well as noise coupling techniques in both loops. Reducing QN of the first loop significantly decreases the output swings of the integrators, thus improving the stability of the first loop. Besides, the construction of one extra order shaping function mitigates the leakage of coarse QN introduced by a gain mismatch between MSB and LSB DACs of the highresolution quantizer. Simulation results demonstrate the effectiveness of the proposed architecture to achieve high resolution while employing lowgain opamps for all integrators.