Semiconductor device

Abstract

A semiconductor device includes a controlled oscillator and a control unit. The controlled oscillator includes a resonance circuit, an amplification unit, and a current adjustment unit. The resonance circuit includes one or a plurality of inductors and a first capacitive unit having a variable capacitance value. The amplification unit is connected to the resonance circuit, and outputs a local oscillation signal having an oscillation frequency corresponding to a resonance frequency of the resonance circuit. The current adjustment unit adjusts a value of a drive current to be supplied to the amplification unit. The control unit controls the capacitance value of the first capacitive unit and the current adjustment unit. When the control unit instructs the current adjustment unit to change the value of the drive current to be supplied to the amplification unit, the control unit also changes the capacitance value of the first capacitive unit.

1 - 11 . (canceled) 
     
     
         12 . A communications instrument, comprising:
 a baseband circuit generating a baseband signal; and   a radio frequency integrated circuit,   said radio frequency integrated circuit including:
 a controlled oscillator including:
 a resonance circuit including a first capacitive unit having a variable capacitance value; 
 an amplification unit connected to said resonance circuit, and outputting a local oscillation signal having an oscillation frequency corresponding to a resonance frequency of said resonance circuit; and 
 a current adjustment unit adjusting a value of a drive current to be supplied to said amplification unit; 
 
 a modulator modulating said local oscillation signal using said baseband signal and outputting said modulated local oscillation signal; 
 an amplifier having an adjustable gain amplifying an output of said modulator; and 
 a control unit controlling the capacitance value of said first capacitive unit and said current adjustment unit, wherein: 
   when said control unit instructs said current adjustment unit to change the value of the drive current to be supplied to said amplification unit, said control unit changes the capacitance value of said first capacitive unit to keep said oscillation frequency constant, and   said control unit instructs said current adjustment unit to change the value of the drive current to be supplied to said amplification unit in accordance with the gain of said amplifier.   
     
     
         13 . A communications instrument, comprising:
 a baseband circuit generating a baseband signal; and   a radio frequency integrated circuit modulating a local oscillation signal using said baseband signal and outputting said modulated local oscillation signal,   said radio frequency integrated circuit including:
 a controlled oscillator including:
 a resonance circuit including first and second capacitive units each having a variable capacitance value; 
 an amplification unit connected to said resonance circuit, and outputting said local oscillation signal having an oscillation frequency corresponding to a resonance frequency of said resonance circuit; and 
 a current adjustment unit adjusting a value of a drive current to be supplied to said amplification unit; 
 
 a frequency divider outputting a frequency-divided signal of said local oscillation signal; 
 a phase comparator outputting a signal corresponding to a phase difference between an output of said frequency divider and a given reference signal; 
 a filter unit generating a feedback signal by removing a high-frequency component of an output of said phase comparator; 
 a switching unit provided in a path of said feedback signal between said filter unit and said controlled oscillator, and supplying one of said feedback signal and a predetermined constant signal to said second capacitive unit of said controlled oscillator; and 
 a control unit generating first and second control signals, wherein: 
   the capacitance value of said first capacitive unit varies in accordance with a value of said first control signal,   the capacitance value of said second capacitive unit varies in accordance with a value of said feedback signal or said constant signal,   said current adjustment unit adjusts the value of the drive current to be supplied to said amplification unit in accordance with a value of said second control signal,   during calibration, said control unit changes the value of said second control signal with said constant signal being supplied to said second capacitive unit by operating said switching unit, said control unit determines the value of said first control signal to be supplied after changing the value of said second control signal, such that frequencies of said local oscillation signal detected before and after changing the value of said second control signal will be equal, and said control unit stores the determined value of said first control signal as a table so as to be associated with a change in the value of said second control signal, and   when said control unit changes the value of said second control signal during normal operation in which said feedback signal is supplied to said controlled oscillator via said switching unit, said control unit determines the value of said first control signal to be supplied after changing the value of said second control signal, based on said table.   
     
     
         14 . A communications instrument, comprising:
 a baseband circuit generating a baseband signal; and   a radio frequency integrated circuit modulating a local oscillation signal using said baseband signal and outputting said modulated local oscillation signal,   said radio frequency integrated circuit including:
 a controlled oscillator including:
 a resonance circuit including first and second capacitive units each having a variable capacitance value; 
 an amplification unit connected to said resonance circuit, and outputting said local oscillation signal having an oscillation frequency corresponding to a resonance frequency of said resonance circuit; and 
 a current adjustment unit adjusting a value of a drive current to be supplied to said amplification unit; 
 
 a frequency divider outputting a frequency-divided signal of said local oscillation signal; 
 a phase comparator outputting a signal corresponding to a phase difference between an output of said frequency divider and a given reference signal; 
 a filter unit generating a feedback signal by removing a high-frequency component of an output of said phase comparator; and 
 a control unit generating first and second control signals, wherein: 
   the capacitance value of said first capacitive unit varies in accordance with a value of a first control signal generated by said control unit,   the capacitance value of said second capacitive unit varies in accordance with a value of said feedback signal,   said current adjustment unit adjusts the value of the drive current to be supplied to said amplification unit in accordance with a value of said second control signal,   during calibration, said control unit changes the value of said second control signal, said control unit determines the value of said first control signal to be supplied after changing the value of said second control signal, such that values of said feedback signal detected before and after changing the value of said second control signal will be equal, and said control unit stores the determined value of said first control signal as a table so as to be associated with a change in the value of said second control signal, and   when said control unit changes the value of said second control signal during normal operation, said control unit determines the value of said first control signal to be supplied after changing the value of said second control signal, based on said table.   
     
     
         15 . A communications instrument, comprising:
 a baseband circuit generating a baseband signal; and   a radio frequency integrated circuit modulating a local oscillation signal using said baseband signal and outputting said modulated local oscillation signal,   said radio frequency integrated circuit including:
 a controlled oscillator including:
 a resonance circuit including a first capacitive unit having a variable capacitance value; 
 an amplification unit connected to said resonance circuit, and outputting said local oscillation signal having an oscillation frequency corresponding to a resonance frequency of said resonance circuit; and 
 a current adjustment unit adjusting a value of a drive current to be supplied to said amplification unit; 
 
 a frequency divider outputting a frequency-divided signal of said local oscillation signal; 
 a phase comparator outputting a signal corresponding to a phase difference between an output of said frequency divider and a given reference signal; 
 a filter unit being capable of changing a passband width and generating a feedback signal by removing a high-frequency component of an output of said phase comparator; and 
 a control unit controlling the capacitance value of said first capacitive unit, said current adjustment unit, and the passband width of said filter unit, 
   wherein when said control unit instructs said current adjustment unit to change the value of the drive current to be supplied to said amplification unit, said control unit changes the capacitance value of said first capacitive unit to keep said oscillation frequency constant and increases the passband width of said filter unit more than a normal bandwidth.   
     
     
         16 . A communications instrument, comprising:
 a baseband circuit generating a baseband signal; and   a radio frequency integrated circuit modulating a local oscillation signal using said baseband signal and outputting said modulated local oscillation signal,   said radio frequency integrated circuit including:
 a controlled oscillator including:
 a resonance circuit including a first capacitive unit having a variable capacitance value; 
 an amplification unit connected to said resonance circuit, and outputting said local oscillation signal having an oscillation frequency corresponding to a resonance frequency of said resonance circuit; and 
 a current adjustment unit adjusting a value of a drive current to be supplied to said amplification unit; and 
 
 a control unit controlling the capacitance value of said first capacitive unit and said current adjustment unit, wherein: 
   said control unit generates a first control signal and a second control signal,   the capacitance value of said first capacitive unit varies in accordance with a value of a signal obtained by adding said first control signal and said second control signal, and   when said control unit instructs said current adjustment unit to change the value of the drive current to be supplied to said amplification unit with said second control signal being kept constant, said control unit changes a value of said first control signal to keep said oscillation frequency constant.