Television receiver with automatic gain control (AGC)

Abstract

A receiver ( 200 ) includes a processing path ( 240 ), a plurality of power detectors ( 251, 252 ), and an automatic gain control circuit ( 250 ). The processing path ( 240 ) has an input for receiving an input signal, and an output for providing an output signal. Each of the plurality of power detectors ( 251, 252 ) has an input coupled to a different node of the processing path ( 240 ), and an output. The automatic gain control circuit ( 250 ) has inputs coupled to respective outputs of each of the plurality of power detectors ( 251, 252 ), and a first output adapted to be coupled to a first controllable gain element ( 241 ) for controlling a gain thereof in response to the outputs of the plurality of power detectors ( 251, 252 ).

1 . A receiver comprising: 
 a processing path having an input for receiving an input signal, and an output for providing an output signal;    a plurality of power detectors each having an input coupled to a different node of said processing path, and an output; and    an automatic gain control circuit having inputs coupled to respective outputs of each of said plurality of power detectors, and a first output adapted to be coupled to a first controllable gain element for controlling a gain thereof in response to said outputs of said plurality of power detectors.    
   
   
       2 . The receiver of  claim 1  wherein said input signal is a television signal and said processing path provides said output signal by mixing said input signal to another frequency.  
   
   
       3 . The receiver of  claim 1  wherein said plurality of power detectors, said first controllable gain element and said automatic gain control circuit are further combined on a single integrated circuit.  
   
   
       4 . The receiver of  claim 3  wherein said automatic gain control circuit further includes a second output adapted to be coupled to a second controllable gain element that is not on said single integrated circuit.  
   
   
       5 . The receiver of  claim 3  wherein said automatic gain control circuit further includes an input adapted to be coupled to an external power detector that is not on said single integrated circuit.  
   
   
       6 . The receiver of  claim 5  wherein said automatic gain control circuit selectively overrides said external power detector in response to one or more of said plurality of power detectors, in forming said first output thereof.  
   
   
       7 . The receiver of  claim 1  wherein said automatic gain control circuit has a second output for controlling a gain of a second controllable gain element in response to said outputs of said plurality of power detectors.  
   
   
       8 . The receiver of  claim 7  wherein said automatic gain control circuit adapts a gain of at least one of said first and second controllable gain elements in response to at least one operating characteristic of said first and second programmable gain elements.  
   
   
       9 . The receiver of  claim 1  wherein said automatic gain control circuit further includes a data input for receiving a first threshold and adjusts a gain of said first controllable gain element when a power detected by a first one of said plurality of power detectors exceeds said first threshold.  
   
   
       10 . The receiver of  claim 9  wherein said data input further receives a second threshold and said automatic gain control circuit further adjusts a gain of said first controllable gain element when a power detected by a second one of said plurality of power detectors exceeds said second threshold.  
   
   
       11 . The receiver of  claim 1  wherein said processing path comprises: 
 a low noise amplifier having a first input for receiving said input signal, and an output;    a mixing element having an input coupled to said output of said low noise amplifier, a second input for receiving a mixing signal, and an output;    a bandpass filter having an input coupled to said output of said mixing element, and an output; and    an amplifier having an input coupled to said output of said bandpass filter, and an output for providing said output signal.    
   
   
       12 . The receiver of  claim 11  wherein said automatic gain control circuit is adapted to receive a signal from an external power detector and to control a gain of said first controllable gain element further in response to an output of said external power detector.  
   
   
       13 . The receiver of  claim 11  wherein said automatic gain control circuit has a second output adapted to be coupled to a second controllable gain element for controlling a gain thereof in response to said outputs of said plurality of power detectors.  
   
   
       14 . The receiver of  claim 13  wherein said first controllable gain element comprises said low noise amplifier.  
   
   
       15 . The receiver of  claim 14  wherein said second controllable gain element comprises a PIN diode attenuator.  
   
   
       16 . The receiver of  claim 11  further comprising a data port coupled to said automatic gain control circuit for receiving a data signal indicating at least one operating mode of said automatic gain control circuit.  
   
   
       17 . The receiver of  claim 16  wherein said at least one operating mode of said automatic gain control circuit comprises an automatic gain control time constant.  
   
   
       18 . The receiver of  claim 16  wherein said at least one operating mode comprises controlling said first controllable gain element using a first power detector, using a second power detector, or using both said first power detector and said second power detector.  
   
   
       19 . The receiver of  claim 16  wherein said data signal further indicates a first threshold for a first power detector and a second threshold for a second power detector.  
   
   
       20 . The receiver of  claim 16  further comprising: 
 an analog-to-digital converter having an input coupled to an output of one of said plurality of power detectors, and an output coupled to said data port for providing a digital representation of an input thereto.    
   
   
       21 . The receiver of  claim 20  further comprising: 
 a multiplexer having a first input for receiving an external signal, a second input coupled to said output of said one of said first power detectors, and an output coupled to said input of said analog-to-digital converter.    
   
   
       22 . A receiver comprising: 
 a processing path having an input for receiving an input signal, and an output for providing an output signal;    a power detector having an input coupled to a node of said processing path, and an output; and    an analog-to-digital converter having an input coupled to said output of said power detector, and an output for providing a digital representation of said output of said power detector.    
   
   
       23 . The receiver of  claim 22  further comprising: 
 a multiplexer having a first input for receiving an external signal, a second input coupled to said output of said power detector, and an output coupled to said input of said analog-to-digital converter.    
   
   
       24 . The receiver of  claim 22  further comprising: 
 a data port having an input coupled to said output of said analog-to-digital converter, and an output for providing said digital representation.    
   
   
       25 . The receiver of  claim 24  wherein said data port comprises a register for temporarily storing said digital representation.  
   
   
       26 . A method of performing automatic gain control comprising the steps of: 
 receiving an input signal;    processing said input signal to provide an output signal and thereby forming intermediate signals;    detecting a power in a plurality of said intermediate signals;    adjusting a gain of at least one controllable gain element in response to said step of detecting said power in said plurality of said intermediate signals.    
   
   
       27 . The method of  claim 26  wherein said step of receiving comprises the step of receiving an input television signal.  
   
   
       28 . The method of  claim 26  wherein said step of processing said input signal comprises the step of: 
 mixing said input signal to another frequency to form said output signal.    
   
   
       29 . The method of  claim 26  wherein said step of processing comprises the step of: 
 filtering said input signal in a plurality of filters to provide said output signal.    
   
   
       30 . The method of  claim 29  wherein said step of filtering said input signal in said plurality of filters further comprises the steps of: 
 filtering said input signal in a bandpass filter to provide an intermediate signal; and    filtering said intermediate signal in a surface acoustic wave (SAW) filter.