Synthesizer with lock detector, lock algorithm, extended range VCO, and a simplified dual modulus divider

Abstract

The present invention provides a synthesizer having an efficient lock detect signal generator, an extended range VCO that can operate within any one of a plurality of adjacent characteristic curves defined by a plurality of adjacent regions, and a divide circuit implemented using only a single counter along with a decoder. This allows for a method of operating the synthesizer, methods of establishing or reestablishing a lock condition using the extended range VCO, and a method of designing a plurality of divide circuits which each use the same single counter and each use a different decoder.

1 . An extended range voltage controlledoscillator (VCO) comprising: 
 a variable capacitor controlled by an analog control voltage coupled to the VCO; and    a plurality of digitally selected switches, each one of the plurality of digitally selected switches is disposed to contorllably couple or decouple one of a plurality of fixed capacitors to the variable capacitor.    
     
     
         2 . An extended range VCO as set forth in  claim 1 , wherein each combination of controllably coupled ones of the plurality of fixed capacitors have a different characterstic curve associated therewith for operation of the VCO.  
     
     
         3 . An extended range VCO as set forth in  claim 2 , wherein certin of the different characteristic curves have an overlap of an output frequency range.  
     
     
         4 . An extended range VCO as set forth in  claim 2 , wherein each of the different characteristic curves has a substantially linear portion.  
     
     
         5 . An extended range VCO as set forth in  claim 2 , wherein the different characteristic curves are all adjacent.  
     
     
         6 . An extended range VCO as set forth in  claim 1 , wherein the switches are disposed to controllably couple the fixed capacitors in parallel with the variable capacitor with respect to an AC ground.  
     
     
         7 . An extended range VCO as set forth in  claim 1 , wherein the switches are digitally selected in accordance with corresponding bits stored in a register.  
     
     
         8 . An extended range voltage controlled oscillator (VCO) comprising: 
 a variable capacitor controlled by an analog control voltage; and    a plurality of fixed capacitors that are disposed to be controllably coupled or decoupled to the variable capacitor.    
     
     
         9 . An extended range VCO as set forth in  claim 8 , further comprising: 
 a plurality of switches, each of which operate to couple certain of the fixed capacitors to the variable capacitor in a first switch state, and decouple the certain fixed capacitors to the variable capacitor in a second switch state.    
     
     
         10 . An extended range VCO as set forth in  claim 9 , wherein the switch state of the switches is set in accordance with corresponding bits stored in a register.  
     
     
         11 . An extended range VCO as set forth in  claim 8 , wherein each combination of controllably coupled ones of the plurality of fixed capacitors have a different characteristic curve associated therewith for operation of the VCO.  
     
     
         12 . An extended range VCO as set forth in  claim 11 , wherein certain of the different characteristic curves have an overlap of an output frequency range.  
     
     
         13 . An extended range VCO as set forth in  claim 11 , wherein each of the different characteristic curves has a substantially linear portion.  
     
     
         14 . An extended range VCO as set forth in  claim 11 , wherein the different characteristic curvess are all adjacent.  
     
     
         15 . An extended range VCO as set forth in  claim 9 , wherein the switches are disposed to controllably couple the certain fixed capacitors in parallel with the variable capacitor with respect to an AC ground.  
     
     
         16 . An extended range voltage controlled oscillator (VCO) comprising: 
 a variable capacitor controlled by an analog control voltage; and    means for controllably coupling or decoupling a plurality of combinations of fixed capacitors to the variable capacitor.    
     
     
         17 . An extended range VCO as set forth in  claim 16 , wherein the means for controllably coupling or decoupling the fixed capacitors comprises a plurality of switches, each of which operate to couple certain of the fixed capacitors to the variable capacitor in a first switch state, and decouple the certain fixed capacitors to the variable capacitor in a second switch state.  
     
     
         18 . An extended range VCO as set forth in  claim 17 , wherein the switch state of the switches is set in accordance with corresponding bits stored in a register.  
     
     
         19 . An extended range VCO as set forth in  claim 16 , wherein each combination of controllably coupled ones of the plurality of fixed capacitors have a different characteristic curve associated therewith for operation of the VCO.  
     
     
         20 . An extended range voltage controlled oscillator (VCO) comprising: 
 a differential oscillator;    first and second variable capacitors, both controlled by an analog control voltage and coupled to a respective branch of the differential oscillator; and    a plurality of fixed capacitors disposed to be selectively coupled to the variable capacitors.    
     
     
         21 . An extended range VCO as set forth in  claim 20 , further comprising a plurality of switches, each of which operate to couple certain of the fixed capacitors to the variable capacitors in a first switch state, and decouple the certain fixed capacitors to the variable capacitor in a second switch state.  
     
     
         22 . An extended range VCO as set forth in  claim 21 , wherein the switch state of the switches is set in accordance with corresponding bits stored in a register.  
     
     
         23 . An extended range VCO as set forth in  claim 20 , wherein the fixed capacitors have different values.  
     
     
         24 . An extended range VCO as set forth in  claim 20 , wherein a first subset of the capacitors can be selectively coupled to the fist variable capacitor but not to the second variable capacitor, and a second subset of the capacitors can be selectively coupled to the second variable capacitor but not to the first variable capacitor.  
     
     
         25 . An extended range VCO as set forth in  claim 24 , wherein each of the capacitors in the first subset has a different value from the other capacitors in the first subset.  
     
     
         26 . An extended range VCO as set forth in  claim 25 , wherein each of the capacitors in the first subset has the same value as a respective one of the capacitors in the second subset.  
     
     
         27 . (New) An extended range VCO as set forth in  claim 20 , wherein each combination of selectively coupled ones of the plurality of fixed capacitors have a different characteristic curve associated therewith fbr operation of the VCO.  
     
     
         28 . An extended range VCO as set forth in  claim 27 , wherein certain of the different characteristic curves have an overlap of an output frequency range.  
     
     
         29 . An extended range VCO as set forth in  claim 27 , wherein each of the different characteristic curves has a substantially linear portion.  
     
     
         30 . An extended range VCO as set forth in  claim 27 , wherein the different characteristic curves are all adjacent.