Universal modulator

Abstract

A modulator generates a combined signal consisting of audio and video signals, and converts the combined signal to one of a plurality of frequencies in dependence upon a desired output frequency and broadcast standard. The modulator includes a summing amplifier, a first frequency synthesizer and a second frequency synthesizer. The summing amplifier has a first input for receiving a video signal, a second input for receiving a first audio signal, a third input for receiving a second audio signal, and an output for outputting a modulated summed signal. The first frequency synthesizer generates a first frequency for mixing with the modulated summed signal to generate a high intermediate frequency (HI-IF) signal. The second frequency synthesizer generates a second frequency for mixing with the HI-IF signal to generate a desired RF output signal.

1 . A method for combining a plurality of received signals and outputting a desired output signal, the method comprising: 
 (a) receiving a video signal;    (b) receiving a first audio signal;    (c) receiving a second audio signal;    (d) generating a first frequency;    (e) mixing the first frequency with the first audio signal to produce a modulated signal; and    (f) combining the video signal, the modulated signal and the second audio signal to generate a summed signal.    
   
   
       2 . The method of  claim 1  further comprising: 
 (g) generating a second frequency;    (h) mixing the second frequency with the summed signal to generate a high intermediate frequency (HI-IF) signal;    (i) generating a third frequency; and    (j) mixing the third frequency with the HI-IF signal to generate the desired output signal.    
   
   
       3 . The method of  claim 1  further comprising: 
 (g) limiting the amplitude of the video signal.    
   
   
       4 . The method of  claim 1  further comprising: 
 (g) adjusting the gain of the video signal.    
   
   
       5 . The method of  claim 1  further comprising: 
 (g) clipping signal peaks of the video signal.    
   
   
       6 . The method of  claim 1  further comprising: 
 (g) adjusting the gain of the first audio signal.    
   
   
       7 . A modulator for combining a plurality of received signals and outputting a desired output signal, the modulator comprising: 
 (a) a first frequency synthesizer for generating a first frequency;    (b) an audio mixer in communication with the first frequency synthesizer, the audio mixer for mixing an audio signal with the first frequency to generate a mixed audio signal;    (c) a summing amplifier having a first input for receiving a video signal, a second input for receiving the mixed audio signal, and an output for outputting a modulated summed signal;    (d) a second frequency synthesizer for generating a second frequency for mixing with the modulated summed signal to generate a high intermediate frequency (HI-IF) signal; and    (e) a third frequency synthesizer for generating a third frequency for mixing with the HI-IF signal to generate the desired output signal.    
   
   
       8 . The modulator of  claim 7  wherein the audio mixer is configured to be selectively activated or deactivated.  
   
   
       9 . The modulator of  claim 7  further comprising: 
 (f) an up-conversion mixer having an input electrically coupled to the output of the summing amplifier for receiving the modulated summed signal and outputting the HI-IF signal.    
   
   
       10 . The modulator of  claim 9  wherein the up-conversion mixer is electrically coupled to the second synthesizer for receiving the first frequency for mixing with the modulated summed signal to generate the HI-IF signal.  
   
   
       11 . The modulator of  claim 7  further comprising: 
 (f) a down-conversion mixer for receiving the HI-IF signal and outputting the desired output signal.    
   
   
       12 . The modulator of  claim 11  wherein the down-conversion mixer is electrically coupled to the third frequency synthesizer for receiving the third frequency for mixing with the HI-IF signal to generate the desired output signal.  
   
   
       13 . The modulator of  claim 7  further comprising a common communication bus, electrically coupled to the first, second and third synthesizers, for programming the first, second and third frequencies.  
   
   
       14 . The modulator of  claim 7  further comprising a clamp for limiting the amplitude of the video signal.  
   
   
       15 . The modulator of  claim 14  further comprising an adjustable amplifier, electrically coupled to the clamp, for adjusting the gain of the video signal.  
   
   
       16 . The modulator of  claim 15  further comprising a common communication bus, electrically coupled to the adjustable amplifier, for controlling the gain adjustment.  
   
   
       17 . The modulator of  claim 15  further comprising a limiter, electrically coupled to the adjustable amplifier, for clipping signal peaks of the video signal.  
   
   
       18 . The modulator of  claim 12  further comprising an adjustable amplifier for adjusting the gain of the audio signal.  
   
   
       19 . The modulator of  claim 18  further comprising a common communication bus, electrically coupled to the adjustable amplifier, for controlling the gain adjustment.  
   
   
       20 . The modulator of  claim 7  wherein the modulator is incorporated into a cable television (CATV) settop box.  
   
   
       21 . The modulator of  claim 20  wherein the desired output signal is coupled to a television receiver external to the modulator.  
   
   
       22 . A method for combining a plurality of received signals and outputting a desired output signal, the method comprising: 
 (a) receiving a video signal;    (b) receiving an baseband audio signal;    (c) generating a first frequency;    (d) mixing the first frequency with the baseband audio signal to produce a broadcast standard signal;    (e) combining the video signal and the broadcast standard signal to generate a modulated summed signal;    (f) generating a second frequency;    (g) mixing the second frequency with the modulated summed signal to generate a high intermediate frequency (HI-IF) signal; and    (h) generating a third frequency; and    (i) mixing the third frequency with the HI-IF signal to generate the desired output signal.    
   
   
       23 . A method for combining a plurality of received signals and outputting a desired output signal, the method comprising: 
 (a) receiving a video signal;    (b) processing the video signal to produce a processed video signal by: 
 (b1) limiting the amplitude of the video signal,  
 (b2) adjusting the amplitude of the video signal, and  
 (b3) clipping signal peaks of the video signal;  
   (c) receiving a baseband audio signal;    (d) processing the baseband audio signal by: 
 (d1) adjusting the amplitude of the baseband audio signal,  
 (d2) generating a first frequency,  
 (d3) mixing the first frequency with the baseband audio signal to produce a broadcast standard signal,  
 (d4) lowpass filtering the broadcast standard signal, and  
 (d5) adjusting the amplitude of the broadcast standard signal; and  
   (e) combining the processed video signal and the broadcast standard signal to generate a modulated summed signal.    
   
   
       24 . The method of  claim 23  further comprising: 
 (f) generating a second frequency;    (g) mixing the second frequency with the modulated summed signal to generate a high intermediate frequency (HI-IF) signal;    (h) generating a third frequency; and    (i) mixing the third frequency with the HI-IF signal to generate the desired output signal.    
   
   
       25 . A modulator for combining a plurality of received signals and outputting a desired output signal, the modulator comprising: 
 (a) a first input for receiving a video signal;    (b) a second input for receiving an baseband audio signal;    (c) means for generating a first frequency;    (d) means for mixing the first frequency with the baseband audio signal to produce a broadcast standard signal;    (e) means for combining the video signal and the broadcast standard signal to generate a modulated summed signal;    (f) means for generating a second frequency;    (g) means for mixing the second frequency with the modulated summed signal to generate a high intermediate frequency (HI-IF) signal;    (h) means for generating a third frequency; and    (i) means for mixing the third frequency with the HI-IF signal to generate the desired output signal.    
   
   
       26 . A modulator for combining a plurality of received signals and outputting a desired output signal, the modulator comprising: 
 (a) a video signal processing circuit including: 
 (a1) a clamp for receiving and limiting the amplitude of a video signal,  
 (a2) a first adjustable amplifier for receiving the video signal from the clamp and adjusting the amplitude of the video signal, and  
 (a3) a limiter for receiving the video signal from the first adjustable amplifier and clipping signal peaks of the video signal;  
   (b) a baseband audio signal processing circuit including: 
 (b1) a second adjustable amplifier for receiving and adjusting the amplitude of a baseband audio signal,  
 (b2) a phase-locked loop (PLL) synthesizer for generating a first frequency,  
 (b3) a baseband audio mixer for receiving the baseband audio signal from the second adjustable amplifier and mixing the first frequency with the baseband audio signal to produce a broadcast standard signal,  
 (b4) a lowpass filter for receiving the broadcast signal from the baseband audio mixer and filtering the broadcast standard signal, and  
 (b5) a third adjustable amplifier for receiving the broadcast standard signal from the lowpass signal and adjusting the amplitude of the broadcast standard signal; and  
   (c) a summing amplifier having a first input electrically coupled to an output of the third adjustable amplifier, and a second input electrically coupled to an output of the limiter, the summing amplifier for combining the processed video signal and the broadcast standard signal to generate a modulated summed signal.    
   
   
       27 . The modulator of  claim 26  further comprising: 
 (d) a switch for selectively inputting a second audio signal to a third input to the summing amplifier, wherein the summing generator combines the processed video signal, the broadcast standard signal and the second audio signal to generate the modulated summed signal.    
   
   
       28 . The modulator of  claim 27  further comprising: 
 (e) a communication bus in communication with the switch, the first adjustable amplifier, the second adjustable amplifier, the third adjustable amplifier, the PLL synthesizer and the baseband audio mixer.