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RF Bandwidth and Sample Rate in TES

		
	
				

			

									
					    Cito
					
							

            
            			
				
									
											
			
			
				
			
			
			    	
			                    
                
				                on Jul 31, 2024 
				
			
			
		

		
		                    	    

        	    
Thread Summary

                The user asked about configuring TES for a 20 MHz OFDM signal with a 20 MSPS complex I/Q sample rate. The final answer confirmed that the sample rate in TES should be 4/3 of the RF bandwidth, which explains why 20 MSPS was not accepted. The accompanying answer clarified that for complex signals, the minimum I/Q sample rate is equal to the channel bandwidth, but TES requires a higher sample rate.
                        	    

                
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Category: Software

    		        		            		    
Product Number:  ADRV9002  

    		        		        		        
Software Version: TES 0.25.1

    		    		    

		    		    
		    			

			    
Hello,


Our PHY uses an OFDM signal of 20 MHz (from -10 MHz to 10 MHz) and works with a sample rate of 20 MSPS (complex I/Q samples). I've tried to set up a matching profile with TES, but the latter indicates that the configuration is invalid when I set the Dataport Sample Rate to 20 MSPS and the RF Channel Bandwidth to 20 MHz in the Device Configuration tab for the Rx1/Rx2 parts:


 


My questions are:


    

  1. Should the RF Channel Bandwidth be set to the full signal bandwidth (from the lowest negative frequency to the highest positive frequency) or only the positive frequencies part (10 MHz in my case)?
    2. 

  2. If the answer to the previous question is the full bandwidth, why using a complex sampling rate equal to the RF bandwidth is not enough? Is there a formula that gives the minimum Navassa sampling rate for a specific RF bandwidth?
    3. 



Thanks.

			

			
									    

			        
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[edited by: Cito at 8:02 PM (GMT -4) on 31 Jul 2024]
				

						
		                                 
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                 software
                
                                                    
                 ADRV9002
                
                                                    
                 software defined radio
                
                                                    
                 TES 0.25.1
                
                                                    
                 Wideband Transceiver IC
                
                                        
                                            
                
                
                                        
                                            
                
                
                                
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    •  Analog Employees  
    
            
						
                            
            
            				
            
                on Aug 1, 2024 11:10 AM
            
            
						
			            		
    
		
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    Hi,
    

    The rule of thumb is that according to the Nyquist rate "the RF channel bandwidth should be half the sampling rate" which mean that data port sampling rate is 20MSPS then the RF channel bandwidth will be 10MHz for the proper transmission of the signal.
    

    Regards
    

    Rahul 
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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                on Aug 1, 2024 11:33 AM
            
            
												
						in reply to RahulMushini
					
										
			            		
    
		
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    Thanks for your answer Rahul.
    

    However, the minimum sampling rate criterion from the Nyquist–Shannon theorem is a bit different when applied to complex signals: the I and Q components are 2 different samples, so if the sample rate of each component is equal to the channel bandwidth, the full sample rate is twice the channel bandwidth. Thus, the minimum I/Q sample rates for a 20 MHz RF bandwidth is 20 MSPS (per component).
    

    Or do you mean the sample rate field in TES is actually the full sample rate instead of the per-component sample rate?
    

    From my tests, it looks like that the minimum sample rate that TES accepts it 4/3 of the RF bandwidth. Is it expected?
    

    Thanks,
    Cito
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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    •  Analog Employees  
    
            
						
                            
            
            				
            
                on Aug 2, 2024 4:23 AM
            
            
												
						in reply to Cito
					
										
			            		
    
		
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    Hi Cito,
    

    The sample rate provided in TES will have 4/3 of the RF bandwidth. 
    

    Regards
    

    Rahul  
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
				
						
						
				
				
		
		
    
			
		
    
	
    

    

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