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Different Tx power in consecutive repeatTransmit executions, with the same exact settings (Adalm Pluto)



		

			

									
					    arquelaus
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Nov 12, 2024 
				
			
			
		
    

				
		
    
		    		    
		    
		    		      		            		        
    Category: Hardware
    
    		        		            		    
    Product Number:  adalm pluto 
    
    		        		    		    	
			
    I am seeing that, each time I do a repeatTransmit (under the same configuration), I observe different output levels, apparently in a random way. Both output levels are influenced by the Attenuation selected. For example, the plots below are two consecutive executions of the same Matlab code:
    

    Example with "low" output power:
    

     
    

    Example with "high" output power
    

     
    

    What is the origin of this? Is this indicating a HW problem? 
    

    I would be very grateful for any guidance understanding what is happening here.
    

    Best regards,
    
									
			                
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    Tags: 
                                            
                 distortion
                
                                                    
                 hardware
                
                                                    
                 tx
                
                                                    
                 adalm
                
                                                    
                 pluto
                
                                        
                                            
                
                
                                
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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Nov 12, 2024 6:11 PM
            
            
					
      
	
      

		
		
      
					
      Can you try setting the Frequency in band on your dsp.SineWave object? You are generating a baseband signal for the radio so it needs to be < fs/2.
      

      -Travis
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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													0
							
			
				
									
							        
			
			
			
        
            
						
                            
            
            				
            
                on Nov 12, 2024 6:53 PM
            
            
												
						in reply to travisfcollins
					
									
        
	
        

		
		
        
					
        Hi Travis, thank you for your suggestion & prompt response. Selecting an in-band frequency provides the same inconsistent output power between runs. I am using the following code:
        

        txGain = -50;
        

        

        Fs = 3e6;
        

        fc = 1.290e9;
        

        

        

        tx = sdrtx(deviceNameSDR);
        

        tx.RadioID = 'ip:192.168.2.1';
        

        

        tx.CenterFrequency = 1.290e9;
        

        tx.BasebandSampleRate = Fs;
        

        tx.Gain = txGain;
        

        

        

        sw = dsp.SineWave;
        

        sw.Amplitude = 10;
        

        sw.Frequency = Fs/4;
        

        sw.ComplexOutput = true;
        

        sw.SampleRate = Fs;
        

        sw.SamplesPerFrame = 20000; 
        

        txWaveform = sw();
        

        

        

        

        

        transmitRepeat(tx,txWaveform);
        

        

        

        

        release(tx);
        

        

        
Any further idea? I also tried DDS with the same result.
        

        

        Thanks again for your help.
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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													+1
							
			
				
									
							        
			
			
			
          
            
						
                            
            
            				
            
                on Nov 12, 2024 7:49 PM
            
            
												
						in reply to travisfcollins
					
									
          
	
          

		
		
          
					
          After further testing, I've managed to solve this issue. This seems originated by an incompatibility between the firmware in the Pluto (v0.38) and the firmware expected by Matlab (v0.34). If v0.34 is installed in the Pluto, the issue is resolved.
          

          Thanks again Travis for your assistance.
          
			
          

		
			
	      

		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
						
						
						
				
				
		
		
          
			
		
          
	
          

          

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