Phase-locked loop circuit with switchable outputs for multiple l

Details Phase-locked loop circuit with switchable outputs for multiple l Phase-locked loop circuit with switchable outputs for multiple l

1997-12-22

2000-08-29

Tsang, Fan

Telecommunications

Receiver or analog modulated signal frequency converter

Local control of receiver operation

455259, 455258, 455230, 4552361, 455256, 455313, 455318, H04Q 732

Patent

active

061120685

ABSTRACT:
An electronic system, such as a wireless telephone handset (10), having multiple voltage-controlled oscillators (26, 28) so that the system can operate in a selected one of multiple frequency bands, is disclosed. Each of the voltage-controlled oscillators (26, 28) is associated with one of multiple loop filters (32, 34), which filter the control voltage (CP1, CP2) responsive to which the frequency of oscillation of the voltage-controlled oscillators (26, 28) controlled. Only one of the voltage-controlled oscillators (26, 28) is enabled at any one time, responsive to a control signal (VCOSEL). Synthesizer circuitry (30) includes a phase detector (44) which is coupled to a common node (VCOCLK) at which outputs of the voltage-controlled oscillators (26, 28) are coupled; the phase detector (44) compares the phase of this signal (VCODIV) to a reference signal (REFDIV) based on a reference clock (REFCLK), and controls a charge pump (46) accordingly. A switch (48) is provided to selectably apply the output of the charge pump (46) to the loop filter (32, 34) associated with the selected voltage-controlled oscillator (26, 28).

REFERENCES:
patent: 4510461 (1985-04-01), Dickes et al.
patent: 4745371 (1988-05-01), Haine
patent: 5166642 (1992-11-01), Hietala
patent: 5519887 (1996-05-01), Lieu

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