Phase locked loop comprising a sigma-delta modulator

摘要

The invention is directed to a phase locked loop with a SigmaDelta modulator. A multimodulus divider in the feedback path of the PLL is actuated by the SigmaDelta modulator. The latter has a design which can be described by a complex transfer function H(s) in the Laplace plane, said transfer function having a complex-conjugate pair of pole points. The arrangement allows a significant reduction in the noise in critical frequency domains and hence allows adherence to transmission masks based on radio specification even when the PLL bandwidth is as large as the modulation bandwidth.