An integrated digital fast-hopping frequency synthesiser for second-generation cordless telephones

Describes a phase-locked synthesiser using a combination of a novel low-frequency switched loop filter and an adaptive digital controller, which is capable of very fast frequency switching in no more space and consuming little more current than a conventional modern non-switching UHF frequency synthesiser. The loop filter permits rapid frequency switching, and the adaptive controller compensates for spurious phase shifts introduced by the frequency switching by the vernier principle to achieve phase accuracies of a small fraction of a cycle (at frequencies of nearly 1 GHz) using normal prescalers and CMOS control logic. The problems of efficient direct data modulation have also been solved in a novel way which is fundamental to the synthesiser operation