A 975-to-1960MHz fast-locking fractional-N synthesizer with adaptive bandwidth control and 4/4.5 prescaler for digital TV tuners

This paper presents a wideband fractional-N synthesizer whose loop bandwidth is controlled adaptively. A fast automatic frequency-control (AFC) technique which selects the subband of the VCO is proposed to reduce the residual fractional error to 1/16 of the reference frequency f
_ref
. A new 4/4.5 prescaler is adopted to lower the quantization noise by reducing the quantization step size to 0.5.