Patent ID: 7738618

Claim:
A multiband Phase-Locked Loop (PLL) arrangement, comprising: a single-loop PLL including a phase/frequency detector, a loop filter, a Voltage-Controlled Oscillator (VCO), and a reference voltage signal (V ref ) input to the arrangement; a control circuit for locking the VCO to a correct frequency band, the control circuit including a multi-window circuit having at least two amplitude windows, each amplitude window being defined by respective upper and lower voltage levels; and a comparison device for comparing a VCO control voltage output from the loop filter with the upper and lower voltage levels of an amplitude window; wherein if the VCO control voltage settles within a first amplitude window, a second narrower amplitude window narrower than the first amplitude window is selected and the VCO control voltage is compared with the upper and lower voltage levels of the second amplitude window; if the VCO control voltage settles within the second amplitude window or a further subsequent even narrower amplitude window, phase lock is achieved; if the VCO control voltage does not settle within either the first or the second amplitude window, the comparison device provides a signal for providing a control signal to the VCO for switching the VCO to another frequency band; and for the other frequency band, the VCO control voltage signal is compared with at least one of the amplitude windows to determine if phase lock is achieved in the other frequency band.