Wireless communication system

Abstract

A wireless communication system, which is provided with a PLL circuit having a plurality of oscillators and is capable of processing two or more transmit and receive signal different in frequency band from one another according to the switching between the oscillators, has a reset means which resets a voltage applied to each of filter capacitors lying within the PLL circuit to a predetermined voltage when the switching between the oscillators is performed.

1 - 11 . (canceled)  
   
   
       12 . A portable telephone, comprising: 
 an antenna which receives a radio signal from outside of the portable telephone;    an oscillation circuit which receives a first control signal and outputs an oscillation signal having one of a plurality of oscillation frequencies being different from each other and which includes: 
 an oscillator which generates the oscillation signal;  
 a phase comparator which compares a phase of a first signal based on the oscillation signal and a phase of a reference signal, and generates a second signal in accordance with a phase difference of the first signal and the reference signal,  
 a charge pump which generates a third signal in response to the second signal; and  
 a filter which receives the third signal and provides a control voltage to the oscillator for determining a frequency of the oscillation signal;  
   a reception circuit which synthesizes a signal based on the radio signal with the oscillation signal;    a switch circuit which provides a predetermined voltage to the filter controlled by a second control signal; and    a control circuit which generates the first control signal and generates a second control signal in response to the first control signal when the oscillation signal is changed from one oscillation frequency to another oscillation frequency.    
   
   
       13 . A portable telephone according to  claim 12 , 
 wherein the oscillation circuit includes a divider which divides the oscillation signal, the oscillation circuit providing a divided oscillation signal to the phase comparator as the signal based on the oscillation signal.    
   
   
       14 . A portable telephone according to  claim 13 , 
 wherein the divider is a variable divider which divides the oscillation signal in accordance with a division ratio,    wherein the control circuit includes a first circuit which generates the first control signal including an information indicating the division ratio, and a second circuit which generates the second control signal in response to the generation of the first control signal.    
   
   
       15 . A portable telephone according to  claim 14 , 
 wherein the oscillation circuit includes a first voltage controlled oscillator generating the oscillation signal having a first oscillation frequency and a second voltage controlled oscillator generating the oscillation signal having a second oscillation frequency, and    wherein the control voltage is supplied to the first voltage controlled oscillator and the second voltage controlled oscillator.    
   
   
       16 . A portable telephone, comprising: 
 an antenna which receives a radio signal from outside of the portable telephone;    an oscillation circuit which receives a first control signal and outputs an oscillation signal having one of a plurality of oscillation frequencies being different from each other and which includes: 
 an oscillator which generates the oscillation signal;  
 a phase comparator which compares a phase of a first signal based on the oscillation signal and a phase of a reference signal and generates a second signal in accordance with a phase difference of first signal and reference signal,  
 a charge pump which generates a third signal in response to the second signal; and  
 a filter which receives the third signal and provides a control voltage to the oscillator for determining a frequency of the oscillation signal;  
   a switch circuit which provides a predetermined voltage to the filter controlled by a second control signal; and    a control circuit which generates the first control signal and generates a second control signal in response to the first control signal when the oscillation signal is changed from one oscillation frequency to another oscillation frequency.    
   
   
       17 . A portable telephone according to  claim 16 , 
 wherein the oscillation circuit includes a divider which divides the oscillation signal, the oscillation circuit providing a divided oscillation signal to the phase comparator as the signal based on the oscillation signal.    
   
   
       18 . A portable telephone according to  claim 17 , 
 wherein the divider is a variable divider which divides the oscillation-signal in accordance with a division ratio,    wherein the control circuit includes a first circuit which generates the first control signal including an information indicating the division ratio, and a second circuit which generates the second control signal in response to the generation of the first control signal.    
   
   
       19 . A portable telephone according to  claim 18 , 
 wherein the oscillation circuit includes a first voltage controlled oscillator generating the oscillation signal having a first oscillation frequency and a second voltage controlled oscillator generating the oscillation signal having a second oscillation frequency, and    wherein the control voltage is supplied to the first voltage controlled oscillator and the second voltage controlled oscillator.    
   
   
       20 . A portable telephone according to  claim 16 , further comprising a reception circuit which synthesizes a signal based on the radio signal with the oscillation signal.