Phase-locked loop using continuously auto-tuned inductor-capacitor voltage controlled oscillator

Abstract

Improved voltage controlled oscillator circuits and phase-locked loop circuits are disclosed. For example, a voltage controlled oscillator circuit comprises a first linear amplifier, the first linear amplifier generating a coarse-tuning voltage from an input voltage, a second linear amplifier, the second linear amplifier generating a fine-tuning voltage from the input voltage, and a voltage controlled oscillator comprising a coarse-tuning input coupled to the first linear amplifier, a fine-tuning input coupled to the second linear amplifier, and a clock signal output, wherein a frequency of a signal on the clock signal output is changeable as a function of the input voltage. Such a voltage controlled oscillator circuit may be employed in a phase-locked loop circuit.

1 . A voltage controlled oscillator circuit, comprising: 
 a first linear amplifier, the first linear amplifier generating a coarse-tuning voltage from an input voltage;    a second linear amplifier, the second linear amplifier generating a fine-tuning voltage from the input voltage; and    a voltage controlled oscillator comprising a coarse-tuning input coupled to the first linear amplifier, a fine-tuning input coupled to the second linear amplifier, and a clock signal output, wherein a frequency of a signal on the clock signal output is changeable as a function of the input voltage.    
   
   
       2 . The voltage controlled oscillator circuit of  claim 1 , wherein the voltage controlled oscillator further comprises: 
 a coarse-tuning varactor coupled to the coarse-tuning input; and    a fine-tuning varactor coupled to the fine-tuning input.    
   
   
       3 . The voltage controlled oscillator circuit of  claim 2 , wherein a bandwidth associated with a coarse-tuning path formed by the first linear amplifier and the coarse-tuning varactor controls a bandwidth associated with a fine-tuning path formed by the second linear amplifier and the fine-tuning varactor.  
   
   
       4 . The voltage controlled oscillator circuit of  claim 1 , wherein the voltage controlled oscillator further comprises: 
 an inductor parallel with the varactors; and    transistors coupled to the varactors and the inductor.    
   
   
       5 . The voltage controlled oscillator of  claim 1 , wherein the first linear amplifier comprises a lowpass filter.  
   
   
       6 . The voltage controlled oscillator of  claim 5 , wherein the lowpass filter in the first linear amplifier comprises at least one capacitor and at least one resistor.  
   
   
       7 . The voltage controlled oscillator circuit of  claim 1 , wherein the voltage controlled oscillator comprises a single coarse-tuning varactor responsive to the coarse-tuning voltage such that a digitally programmable varactor array is not required to provide coarse-tuning of the voltage controlled oscillator circuit.  
   
   
       8 . A phase-locked loop circuit, comprising: 
 a dual-input voltage controlled oscillator having a coarse tuning input, a fine tuning input, and a clock signal output, wherein signals on the clock signal output have a changing frequency controlled by input signals;    a frequency divider coupled to receive the output of the voltage controlled oscillator and responsive to the output of the voltage controlled oscillator to provide a frequency divided output signal;    a phase and frequency detector that compares a reference clock with an output clock of the frequency divider and generates a charge pump control voltage;    a charge pump coupled to the phase and frequency detector that generates a loop filter control current from the charge pump control voltage;    a loop filter coupled to the charge pump that generates a loop filter voltage from the loop filter control current;    a coarse-tuning linear amplifier coupled to the loop filter that generates a voltage controlled oscillator coarse-tuning voltage from the loop filter voltage; and    a fine-tuning linear amplifier coupled to the loop filter that generates a voltage controlled oscillator fine-tuning voltage from the loop filter voltage.    
   
   
       9 . The phase-locked loop of  claim 8 , wherein the dual-input voltage controlled oscillator comprises: 
 a coarse-tuning varactor coupled to the coarse-tuning linear amplifier;    a fine-tuning varactor coupled to the fine-tuning linear amplifier;    an inductor parallel with the varactors; and    transistors coupled to the varactors and the inductor.    
   
   
       10 . The phase-locked loop of  claim 8 , wherein the coarse-tuning linear amplifier comprises a lowpass filter.  
   
   
       11 . The phase-locked loop of  claim 10 , wherein the lowpass filter in the coarse-tuning linear amplifier comprises at least one capacitor and at least one resistor.  
   
   
       12 . The voltage controlled oscillator circuit of  claim 11 , wherein the coarse-tuning path serves to automatically tune the voltage controlled oscillator circuit.