PHASE NOISE FILTERING TECHNIQUES FOR DELTA-SIGMA FREQUENCY SYNTHESIZER

Abstract

The wideband ∆Σ fractional-N PLL suffers from the out-of-band phase noise since the quantization noise from the ∆Σ modulator can be dominant over VCO phase noise at high frequencies. In this thesis, two new filtering techniques have been proposed to suppress the ∆Σ quantization noise at high frequencies. The first one is single path FIR phase noise filtering. Different from the hybrid FIR filtering technique which employs multiple PFDs and dividers in parallel, in the proposed technique, only one circuit path is needed and the high resolution fractional phase control is achieved by two-step phase interpolation. The second one is hybrid IIR phase noise filtering. We explore ways of implementing IIR quantized phase filtering for ∆Σ fractional-N PLL based on the fact that in digital filter design, IIR offers many advantages over FIR. The concept of hybrid FIR noise filtering is extended to hybrid IIR noise filtering.