Radio receiver

Abstract

A radio receiver includes a down-converter 110 for receiving a radio multiplexed signal containing a first signal and a second signal, multiplying the first signal and the second signal by a mixer 104 to thereby down-convert the radio multiplexed signal and generate an intermediate frequency signal 5 e . The mixer 104 has a control section for controlling an operating bias of the mixer 104 in response to a signal strength of at least either one of the first signal or the second signal. Thus, the dynamic range of the mixer can be widened so that stable image characteristics can be obtained over a wide range of transmission distance.

1 . A radio receiver including a down-converter for receiving a radio multiplexed signal containing a first signal and a second signal and multiplying the first signal and the second signal by a mixer to down-convert the radio multiplexed signal and generate an intermediate frequency signal, wherein 
 the mixer has a control section for controlling an operating bias of the mixer in response to a signal strength of at least either one of the first signal or the second signal.    
   
   
       2 . A radio receiver including: 
 a first down-converter for receiving a radio multiplexed signal containing a first signal and a second signal and down-converting the received radio multiplexed signal by a local oscillation signal to generate a first intermediate frequency signal;    a second down-converter for multiplying the first signal and the second signal contained in the first intermediate frequency signal by a mixer to down-convert the first intermediate frequency signal and generate a second intermediate frequency signal, wherein    the mixer has a control section for controlling an operating bias of the mixer in response to a signal strength of at least either one of the first signal or the second signal.    
   
   
       3 . The radio receiver as claimed in  claim 2 , wherein 
 the second down-converter has:    a first path;    a second path; and    a divider for dividing the first intermediate frequency signal into the first path and the second path, and wherein    the first path transmits to the mixer the first intermediate frequency signal derived from the divider,    the second path has a filter for extracting the second signal from the first intermediate frequency signal and an amplifier for amplifying the second signal extracted from the filter, and transmits the amplified second signal to the mixer.    
   
   
       4 . The radio receiver as claimed in  claim 2 , wherein 
 the second down-converter has:    a first path;    a second path; and    a divider for dividing the first intermediate frequency signal into the first path and the second path, and wherein    the first path has an amplifier for amplifying the first intermediate frequency signal, and transmits the amplified first intermediate frequency signal to the mixer, and    the second path has a filter for extracting the second signal from the first intermediate frequency signal and an amplifier for amplifying the second signal extracted from the filter, and transmits the amplified second signal to the mixer.    
   
   
       5 . The radio receiver as claimed in  claim 2 , wherein 
 the second down-converter has:    a first path;    a second path;    a third path; and    a divider for dividing the first intermediate frequency signal into the first path, the second path and the third path, and wherein    the first path has a filter for extracting a specified-band signal from the first intermediate frequency signal, and transmits the specified-band signal to a first said mixer,    the second path has a filter for extracting a specified-band signal from the first intermediate frequency signal, and transmits the specified-band signal to a second said mixer, and    the third path has a filter for extracting the second signal from the first intermediate frequency signal and an amplifier for amplifying the second signal extracted from the filter, and transmits the amplified second signal to the first and second mixers.    
   
   
       6 . The radio receiver as claimed in  claim 1 , wherein 
 the mixer has a microwave transistor.    
   
   
       7 . The radio receiver as claimed in  claim 2 , wherein 
 the mixer has a microwave transistor.    
   
   
       8 . The radio receiver as claimed in  claim 6  or  7 , wherein 
 the mixer is a base injection type mixer for injecting the first signal and the second signal to a base of the microwave transistor.    
   
   
       9 . The radio receiver as claimed in  claim 1 , wherein 
 the control section has a resistor, and    the resistor controls a current generated from the mixer to control an operating bias of the mixer.    
   
   
       10 . The radio receiver as claimed in  claim 2 , wherein 
 the control section has a resistor, and    the resistor controls a current generated from the mixer to control an operating bias of the mixer.    
   
   
       11 . The radio receiver as claimed in  claim 6  or  7 , wherein 
 the control section has a resistor, and    the resistor has 10 kΩ or more and is connected to a base terminal of the microwave transistor, and    the resistor controls a current generated from the mixer to control an operating bias of the mixer.    
   
   
       12 . The radio receiver as claimed in  claim 6  or  7 , wherein 
 the control section has a resistor, and    the resistor has 100Ω or more and is connected to an emitter terminal of the microwave transistor, and    the resistor controls a current generated from the mixer to control an operating bias of the mixer.