Tuning circuit incorporating a frequency synthesizer circuit.

摘要

In a frequency synthesizer circuit comprising a digital-to-analogue converter (90, 87) for converting a difference measured between a frequency determined by a tuning data signal source (29) and the frequency of an oscillator (97) whose frequency is controllable by a control signal, the digital-to-analogue converter (90, 87) is arranged for only pulse duration modulation (39, 41, 45, 55) of a periodically occurring pulse pattern, (from 85) above a predetermined minimum value ( DELTA fmin) of the difference measured and for only amplitude modulation (61, 67, 79) of the entire pulse pattern below a predetermined maximum value ( DELTA fmax) of the difference measured.