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ADRV9025 DPD inquiry



		

			

									
					    Big
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Sep 9, 2023 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Hi.
    

    We are developing 5G O-RAN RU and are inquiring as the following problem occurred while testing the DPD of ADRV9025 (CFR is not applied, please refer to attached file)
    

    In TM3.1a (256QAM), DPD operates normally and ACLR characteristics are also good. However, the ACLR characteristics in TM1.1 (QPSK) are very poor. So, when I checked the PAPR at the output of ADRV9025, TM3.1a was 10.2dB (@0.001%) and TM1.1 was 11.5dB (@0.001%).
    

    1. I understand that the subcarriers of TM3.1a and TM1.1 are the same.
    In the same case, shouldn't the PAPR of TM3.1a be higher?
    Why is the PAPR of TM1.1 measured high?
    

    2. I think ACLR should improve if I lower the output due to the PAPR of TM1.1, but ACLR does not improve even if I lower the output..
    

    3. Can the ACLR performance of TM1.1 be improved if CFR is applied?
    

    Personally, I suspect there may be a problem with TM1.1 Signal.
    What do you guys think?
    

    What should I do in this case?
    

    Thanks in advance.
    

      
    

      
    

     
    
									
			        
		
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	
    
		
	
    















    
	
    
	
    
					



			


				
	









	
      
	

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      •  Analog Employees  
      •  Super User  
      
            
			                            
                        
                on Sep 11, 2023 10:16 AM
            
            
					
      
	
      

		
		
      
					
      Moved thread to the design support for ADRV9026/ADRV9029 forum. I know your inquiry is regarding ADRV9025, but they should be able to help in this forum. Similar product family.
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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      •  Analog Employees  
      
            
			                            
                        
                on Sep 12, 2023 2:44 AM
            
            
					
      
	
      

		
		
      
					
      Big said:
      In the same case, shouldn't the PAPR of TM3.1a be higher?
      Why is the PAPR of TM1.1 measured high?
      

      Yes, Ideally the PAPR of TM3.1 should be high because of its higher modulation. Have you maintained same config parameters while generating both waveforms?
      

      You are able to get proper DPD correction with TM3.1a but not with TM1.1, this seems some issue with waveform, Can you please try regenerating the TM1.1 waveform with different configuration and try again. Also  share the DPD statistics when you are getting poor results.
      

      Big said:
       Can the ACLR performance of TM1.1 be improved if CFR is applied?
      

      Yes, CFR helps to avoid saturation by clipping the peaks and thereby DPD works better without error. Please try applying CFR and try to maintain PAPR of around 8dB before applying DPD.
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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													0
							
			
				
									
							        
			
			
			
        
            
			                            
                        
                on Sep 14, 2023 4:38 AM
            
            
												
						in reply to Vinod_Mekala
					
									
        
	
        

		
		
        
					
        For TM3.1a and TM1.1, DPD conditions are as follows.
        TM3.1a is stable, but TM1.1 passes the DPD Actuator and the Peak TX Power increases intermittently.
        Why is it rising?
        Additionally, Peak ORX Power also increases, albeit slightly.
        

        Currently, DPD is applied, but CFR is not yet applied.
        

        I don't know why ACLR is bad in TM1.1.
        

         
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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        •  Analog Employees  
        
            
			                            
                        
                on Sep 15, 2023 1:30 AM
            
            
												
						in reply to Big
					
									
        
	
        

		
		
        
					
        The peak Tx. power is going beyond full scale, you need to back off the digital input signal or should use the CFR/ pre-clipped waveform to get the DPD working.
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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