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AD8302 Recommended for New Designs
The AD8302 is a fully integrated system for measuring gain/loss and phase in numerous receive, transmit, and instrumentation applications. It requires...
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AD8302 Eval Board – VPHS Output Behavior and SW2 Function

		
	
				

			

									
					    singam vamshi
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Aug 10, 2025 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
    
		      		            		        
    Category: Hardware
    
    		        		            		    
    Product Number:  AD8302  
    
    		        		    		    
    
		    		    
		    			
    
			    
    Hi Team,
    

    I’m testing the AD8302 Evaluation Board to measure phase difference between two RF signals at 1500 MHz, −10 dBm each. I’m seeing unexpected results at the VPHS (phase output) SMA connector:
    

      

    • 

      No input signals:
        SW2 set to “M” → VPHS fluctuates between ~1.13 V and 1.2 V
        SW2 set to “C” → VPHS steady at ~2.4 V
      

      • 

    • 

      With both RF inputs connected (same frequency, unknown phase):
        VPHS reading remains unchanged from the no-signal case.
      

      • 

    

    Could you clarify:
    

      

    1. 

      What is the exact function of SW2?
      

      2. 

    2. 

      Is ~2.4 V at VPHS a valid phase output, or is the device saturated?
      

      3. 

    3. 

      What is the correct procedure to measure phase difference in this setup?
      

      4. 

    

    Thanks in advance for your support.
    
			
    
			
									
		                             
                        

    
    
                                            
                 hardware
                
                                                    
                 EVAL-AD8302-ARDZ
                
                                                    
                 phase detector
                
                                                    
                 Vector Power Measurement
                
                                                    
                 rf & microwave
                
                                        
                                            
                
                
                                        
                                            
                
                
                                        
                                            
                
                
                                        
                                            
                
                
                                
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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Aug 11, 2025 6:29 PM
            
            
						
			            		
      
		
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      The AD8302 has two modes that are set by SW1 and SW2. If these two switches are open (VMAG not connected to MSET and VPHS not connected to PSET (see Figure 14 in datasheet), the device operates in a comparator mode, that is, the VMAG and VPHS signals are digital output that tell you whether INPA is bigger or smaller than INPB and whether the phase of INPA is greater or less than the phase of INPB.
      If you want to measure the phase between two signals, you do not want to be in this mode. So set SW1 and SW2 so that VMAG is connected to MSET and VPHS is connected to PSET. 
      If your two signals are not referenced to the same source, the phase output voltage will wander. If you have two signal generators, you should connect both to the same 10 MHz reference (or slave one off of the other). An alternative way to test the board is to use one signal generator. Feed the output of the signal generator into a power splitter and feed the two outputs of the power splitter into INPA and INPB. Then vary the relative cable lengths between the power splitter and the INPA and INPB inputs. 
       
       
      I’m testing the AD8302 Evaluation Board to measure phase difference between two RF signals at 1500 MHz, −10 dBm each. I’m seeing unexpected results at the VPHS (phase output) SMA connector:
      • No input signals:
         SW2 set to “M” → VPHS fluctuates between ~1.13 V and 1.2 V
         SW2 set to “C” → VPHS steady at ~2.4 V
      • With both RF inputs connected (same frequency, unknown phase):
         VPHS reading remains unchanged from the no-signal case.
      Could you clarify:
      1. What is the exact function of SW2?
      2. Is ~2.4 V at VPHS a valid phase output, or is the device saturated?
      3. What is the correct procedure to measure phase difference in this setup?
      Thanks in advance for your support.
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
				
				
				
		
		
      
			
		
      
	
      

      

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