Automatic calibration system for a voltage control oscillator
First Claim
1. A signal generator including periodic self-calibration, includinga reference frequency souce for producing a fixed frequency signal,a voltage controlled oscillator (VCO) for producing a variable frequency signal in accordance with a voltage input to the VCO,an adjustable dividing network coupled to the VCO and responsive to the variable frequency signal for dividing the variable frequency signal by a particular divider (N) in accordance with the adjustment of the dividing network and producing an output signal equal to the variable frequency signal divided by N,phase detector means coupled to the reference frequency source and the dividing network and responsive to the fixed frequency signal and the output signal for producing an error voltage in accordance with the difference between the fixed frequency signal and the output signal,a programmable nonvolatile storage means for storing a plurality of individual values representative of a plurality of frequency steps from the VCO,converter means coupled to the programmable nonvolatile storage means and responsive to the individual stored values for converting the stored values to a plurality of individual voltages,means coupled to the phase detector means and the converter means and responsive to the error voltage and the individual voltages for summing the voltages and applying the summed voltages to the VCO for controlling the VCO to particular frequency steps,means for providing a fixed reference voltage,second means responsive to the error voltage for comparing the error voltage to the fixed reference voltage for producing a control signal in accordance with the comparison,means responsive to a value of the control signal different from zero for incrementaly adjusting the individual voltage from the converter means in a direction to reduce the value of the control signal to zero,control means coupled to the second means and the programmable nonvolatile storage means and responsive to a zero value for the control signal for reprogramming the reprogrammable nonvolatile storage means in accordance with the value of the individual voltage providing a zero value in the control signal andmeans responsive to the reprogramming of the reprogrammable nonvolatile storage means for adjusting the value of N to initiate a calibration of the variable frequency signal divided by the new value of N.
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Accused Products
Abstract
A signal generator including a calibration circuit for providing periodic recalibration of the generator, including a reference frequency source for producing a fixed frequency signal. A voltage controlled oscillator (VCO) for producing a variable frequency signal in accordance with a voltage input to the VCO. An adjustable dividing network coupled to the VCO for dividing the variable frequency signal by a particular divider (N) to produce an output signal equal to the variable frequency signal divided by "N". A phase detector coupled to the reference frequency source and the dividing network for producing an error signal in accordance with the difference between the fixed frequency signal and the output signal. A filter coupled to the phase detector for producing an error voltage signal representative of the error signal. A programmable nonvolatile storage for storing a plurality of individual values representative of the plurality of frequency steps from the VCO. A converter coupled to the programmable storage for converting the stored values to a plurality of individual voltage signals. A summer coupled to the filter and the converter for summing the signals and applying the summed signals to the VCO for controlling the VCO to particular frequency steps. A comparator coupled to the phase detector for comparing the error signal to a fixed reference for producing a control signal in accordance with the comparison, and a controller coupled to the comparator and the programmable storage for reprogramming the plurality of individual values to recalibrate the frequency steps in accordance with the control signal.
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Citations
27 Claims
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1. A signal generator including periodic self-calibration, including
a reference frequency souce for producing a fixed frequency signal, a voltage controlled oscillator (VCO) for producing a variable frequency signal in accordance with a voltage input to the VCO, an adjustable dividing network coupled to the VCO and responsive to the variable frequency signal for dividing the variable frequency signal by a particular divider (N) in accordance with the adjustment of the dividing network and producing an output signal equal to the variable frequency signal divided by N, phase detector means coupled to the reference frequency source and the dividing network and responsive to the fixed frequency signal and the output signal for producing an error voltage in accordance with the difference between the fixed frequency signal and the output signal, a programmable nonvolatile storage means for storing a plurality of individual values representative of a plurality of frequency steps from the VCO, converter means coupled to the programmable nonvolatile storage means and responsive to the individual stored values for converting the stored values to a plurality of individual voltages, means coupled to the phase detector means and the converter means and responsive to the error voltage and the individual voltages for summing the voltages and applying the summed voltages to the VCO for controlling the VCO to particular frequency steps, means for providing a fixed reference voltage, second means responsive to the error voltage for comparing the error voltage to the fixed reference voltage for producing a control signal in accordance with the comparison, means responsive to a value of the control signal different from zero for incrementaly adjusting the individual voltage from the converter means in a direction to reduce the value of the control signal to zero, control means coupled to the second means and the programmable nonvolatile storage means and responsive to a zero value for the control signal for reprogramming the reprogrammable nonvolatile storage means in accordance with the value of the individual voltage providing a zero value in the control signal and means responsive to the reprogramming of the reprogrammable nonvolatile storage means for adjusting the value of N to initiate a calibration of the variable frequency signal divided by the new value of N.
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11. A calibration circuit for providing periodic recalibration of a signal generator of the type including a fixed reference frequency signal from a reference frequency source, a voltage controlled oscillator (VCO) for producing a variable frequency output signal, an adjustable dividing network coupled to the VCO and responsive to the variable frequency output signal for dividing the variable frequency output signal by a particular divider (N) to produce an output signal, and phase detector means coupled to the reference frequency source and the dividing network to produce an error voltage in accordance with the difference between the fixed frequency signal and the output signal, the calibration circuit including,
programmable nonvolatile storage means for digitally storing a plurality of individual values representative of a plurality of frequency steps from the VCO, converter means coupled to the programmable storage means for converting the stored values to a plurality of individual voltages, means coupled to the phase detector means and the converter means for summing the error voltage and the individual voltages and applying the summed signals to the VCO for controlling the VCO to particular frequency steps, means for providing a fixed reference voltage, second means coupled to the phase detector means for comparing the error voltage to the fixed reference voltage for producing a control signal in accordance with the comparison, means responsive to a value different from zero from the second means for incrementally adjusting the individual voltage in a direction to reduce the error voltage to zero, control means coupled to the second means and the programmable nonvolatile storage means for reprogramming the individual value in the reprogrammable nonvolatile storage means upon a value of zero in the control voltage, and means responsive to a value of zero in the control voltage for operating upon the adjustable dividing network to change the value of N and to institute another calibration of the programmable nonvolatile storage means for the new value of N.
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20. A method of providing periodic recalibration of a signal generator of the type including means for providing a fixed reference frequency signal, a voltage controlled oscillator (VCO) for producing a variable frequency signal, an adjustable dividing network coupled to the VCO and responsive to the variable frequency signal to divide the variable frequency signal by a particular divider (N) and phase detector means coupled to the reference frequency means and the dividing network to produce an error voltage in accordance with the difference between the fixed frequency signal and the frequency-divided output signal, the method including the following steps:
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storing a plurality of individual values representative of a plurality of frequency steps from the VCO, converting the stored value for the particular value of N to a plurality of individual voltages, summing the error voltage and the individual voltage and applying the summed voltage to the VCO for controlling the operation of the VCO, providing a fixed reference voltage, comparing the error voltage to the fixed reference voltage for producing a control signal in accordance with the comparison, incrementally increasing the individual voltage for the particular value of N to obtain a new sum of the error voltage and the individual voltage and a comparison of the resultant error voltage with the fixed reference, storing the incremented individual value for the particular value of N when the error voltage is reduced to zero, and converting the stored value for the next value of N to an individual voltage for the operations of summing, comparing, incrementing and storing as recited above. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27)
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Specification