Analog open-loop VCO calibration method
First Claim
1. A calibration circuit for a phase locked loop for selecting the frequency of a voltage controlled oscillator (VCO), the calibration circuit comprising:
- a frequency divider module coupled to receive a local oscillation signal from the VCO and a reference signal, the frequency divider module producing a divided local oscillation and a divided reference signal, wherein the local oscillation signal and the reference signal are divided by different values to produce a divided oscillation signal substantially equal to the divided reference signal;
a period-to-voltage conversion module coupled to receive the divided local oscillation and the divided reference signal, the period-to-voltage module to convert the divided local oscillation and the divided reference signal to a threshold voltage signal and a reference voltage signal, respectively;
a comparator module coupled to receive the threshold and reference voltage signals, the comparator module for comparing the threshold and reference voltage signals and for producing a frequency adjustment signal; and
a logic module coupled to receive the frequency adjustment signal, the logic module for producing a frequency compensation signal responsive to the frequency adjustment signal.
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Abstract
An analog open-loop voltage controlled oscillator (VCO) calibration circuit and method for selecting the frequency of the VCO for a phase locked loop (PLL).
A frequency divider module produces a 50% duty cycle divided local oscillation and a 50% duty cycle divided reference signal, wherein the divided signals are substantially equal. A period-to-voltage conversion module converts the divided local oscillation signal and the divided reference signal to voltages proportional to the divided signals. A comparator module produces a frequency adjustment signal based on a comparison of the proportional voltages and couples the frequency adjustment signal to a logic module which produces a frequency compensation signal based on the frequency adjustment signal. The frequency compensation signal functions to adjust the configuration of switched capacitors in a capacitor bank, coupled to the VCO tuned circuit, until the divided local oscillation signal is substantially equal to the divided reference signal.
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Citations
38 Claims
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1. A calibration circuit for a phase locked loop for selecting the frequency of a voltage controlled oscillator (VCO), the calibration circuit comprising:
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a frequency divider module coupled to receive a local oscillation signal from the VCO and a reference signal, the frequency divider module producing a divided local oscillation and a divided reference signal, wherein the local oscillation signal and the reference signal are divided by different values to produce a divided oscillation signal substantially equal to the divided reference signal; a period-to-voltage conversion module coupled to receive the divided local oscillation and the divided reference signal, the period-to-voltage module to convert the divided local oscillation and the divided reference signal to a threshold voltage signal and a reference voltage signal, respectively; a comparator module coupled to receive the threshold and reference voltage signals, the comparator module for comparing the threshold and reference voltage signals and for producing a frequency adjustment signal; and a logic module coupled to receive the frequency adjustment signal, the logic module for producing a frequency compensation signal responsive to the frequency adjustment signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method for calibrating a voltage controlled oscillation, comprising:
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receiving a local oscillation signal and a reference signal; dividing the local oscillation signal by “
N1”
to create a first divided local oscillation signal and dividing the local oscillation signal by “
N2”
to create a second divided local oscillation signal, wherein “
N1” and
“
N2”
are not equal;dividing the reference signal by “
N”
to create a divided reference signal;converting the first and second divided local oscillation signals to an upper threshold voltage signal and a lower threshold voltage signal, respectively; converting the divided reference signal to a reference voltage signal; comparing the reference voltage signal to the upper and lower threshold voltage signals and producing a first and second logic signal therefrom; and producing a frequency compensation signal based on the first and second logic signals. - View Dependent Claims (15, 16, 17)
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18. A direct conversion Radio Frequency (RF) transceiver integrated circuit comprising:
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a baseband processor for producing an outgoing baseband signal and for processing an incoming baseband signal; and wherein the baseband processor produces a frequency initiation signal for selecting and initiating a local oscillation frequency; a local oscillator that generates an RF local oscillation signal corresponding to an RF channel, the local oscillator further including a capacitor bank comprising a plurality of switched capacitors, and wherein analog open-loop VCO calibration circuitry selects at least one switched capacitor of the plurality of switched capacitors, the at least one switched capacitor for adjusting the tuning ranged of the VCO; a period-to-voltage conversion module coupled to receive a divided local oscillation and a divided reference signal, the period-to-voltage module to convert the divided local oscillation and the divided reference signal to a threshold voltage signal and a reference voltage signal, respectively; a comparator module coupled to receive the threshold and reference voltage signals, the comparator module for comparing the threshold and reference voltage signals and for producing a frequency adjustment signal; a receiver section operably coupled to the local oscillator to receive the RF local oscillation signal, wherein the receiver section receives an incoming RE signal, and wherein the receiver section down-converts, based partially upon a frequency compensation signal derived from the frequency adjustment signal by logic, the incoming RE signal based upon the RE local oscillation signal to produce the incoming baseband signal; and a transmitter section operably coupled to the local oscillator to receive the RE local oscillation signal, wherein the transmitter section receives an outgoing baseband signal, and wherein the transmitter section up-converts the outgoing baseband signal to produce an outgoing RE signal. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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34. A method for open loop calibration of a voltage controlled oscillator (VCO), the method comprising:
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receiving, in a calibration circuit logic module, a calibration initiation signal containing at least one frequency divider number; dividing a local oscillation signal and a reference signal by the at least one frequency divider number to produce a divided local oscillation signal and a divided reference signal; converting, in a period-to-voltage converter, the divided local oscillation signal into a threshold voltage signal proportional to the period of the divided local oscillation signal; converting, in a period-to-voltage converter, the divided reference signal into a reference voltage signal proportional to the period of the divided reference signal; comparing the threshold voltage signal and the reference voltage signal to produce a frequency adjustment signal; generating a frequency compensation signal from the frequency adjustment signal, said frequency compensation signal comprising a binary signal having a plurality of values; and setting, with the frequency compensation signal, at least one switched capacitor from a plurality of switched capacitors in a capacitor bank, wherein setting the at least one switched capacitor changes the VCO tuning range. - View Dependent Claims (35, 36, 37, 38)
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Specification