Multiband PLL arrangement and a method of controlling such arrangement
First Claim
1. 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 (Vref) 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.
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Abstract
The present invention relates to a multiband PLL arrangement comprising a single loop PLL with a phase/frequency detecting means (1), a loop filter means (2) and a Voltage Controlled Oscillator (VCO) (3), to which PLL a reference voltage signal (Vref) is input. It further comprises a control circuit for appropriately locking the VCO (3) to the correct frequency band, said control circuit comprising a multi-window circuit (4) with at least first and second window amplitudes each defined by respective upper and lower voltage levels, and comparing means (5A, 5B) are provided for comparing a first VCO control voltage output from the loop filter means (2) with the upper and lower voltage levels of a first, broadest amplitude window. If the VCO control voltage settles within said first amplitude window, a narrower window is selected, the voltage levels of which are compared with the VCO control voltage and if the VCO control voltage settles within that or a further subsequent, smaller amplitude window, phase lock is achieved, otherwise, if the VCO control voltage does not settle within said windows, this is established by the comparing means (5A, 5B), said comparing means (5A, 5B) providing a signal for providing a second control signal to the VCO (3) for switching it to another, higher or lower, frequency band. For said other frequency band, the resulting first VCO control voltage signal is compared with said first amplitude window etc. until phase lock is achieved in the appropriate frequency band.
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Citations
27 Claims
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1. A multiband Phase-Locked Loop (PLL) arrangement, comprising:
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a single-loop PLL including a phase/frequency detector, a loop filter, a Voltage-Controlled Oscillator (VCO), and a reference voltage signal (Vref) 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A method of controlling a multiband phase-locked loop (PLL) arrangement that includes a single-loop PLL having a phase/frequency detector, a loop filter, a Voltage-Controlled Oscillator (VCO), and a reference voltage signal Vref input to the arrangement, the method comprising the steps of:
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(a) providing the reference voltage signal Vref to the single-loop PLL and to a multi-window circuit; (b) setting an amplitude window defined by upper and lower voltage levels in the multi-window circuit; (c) establishing whether an analog VCO control voltage output from the loop filter settles within the set amplitude window; (d) if so, setting a narrower amplitude window narrower than the set amplitude window in the multi-window circuit and establishing if the analog VCO control voltage settles within the narrower window; (e) if not, using a result of the comparison to establish whether to switch to a higher frequency band or to a lower frequency band; (f) providing a digital control signal to the VCO to switch the VCO to the higher frequency band or to the lower frequency band; and repeating steps (a)-(e) unless a frequency band switch is required until phase lock is achieved. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27)
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Specification