Δ-Σ Modulators in Frequency Synthsizers

Frequency synthesizers are indispensable systems in the wireless communications area. In fractional-N frequency synthesizers ΔΣ modulators allows performances like larger bandwidth, faster lock times, reduced output phase-noise, with the price of some circuitry complexity. These specifications and others are based on the modulation accuracy. The main problem in ΔΣ fractional-N synthesizers is the specific quantization noise of the ΔΣ modulator and the solutions try to suppress it. MASH (Multi-stAge noise SHapping) digital ΔΣ modulator are also performance stages used in fractional-N frequency synthesizers. This paper will present solutions for ΔΣ modulators and their implementation.