Patent ID: 11933919
Assignee: MIXED-SIGNAL DEVICES INC.
Field: Measurement (Instruments)
Classification: CPC G  H | IPC G  H

Claim 13:
14. The direct frequency synthesizer of claim 12, wherein the codeword is a digital codeword xn;
wherein xn is converted to the analog signal through the high speed digital to analog converter (HS DAC);
wherein xn corresponds to a desired analog signal at t=nTs where Ts is a period of a sample clock;
wherein, for a non-stationary sample clock where the sample time happens at t′=nTs′ or (nTs+ΔTs), the digital codeword is adjusted and the corrected codeword xn′ is calculated by the variable interpolator/decimator (VID) by the following equation:, x
   n
   ′
  
  =
  
   
    x
    ⁡
    (
    
     t
     =
     
      nT
      s
      ′
     
    
    )
   
   =
   
    
     x
     ⁡
     (
     
      t
      =
      
       
        nT
        s
       
       +
       
        Δ
        ⁢
        
         T
         s
        
       
      
     
     )
    
    =
    
     {
     
      
       
        
         
          
           
            x
            n
           
           ⁢
           
            
             1
             -
             
              Δ
              ⁢
              
               T
               s
              
             
            
            
             T
             s
            
           
          
          +
          
           
            x
            
             n
             +
             1
            
           
           ⁢
           
            
             Δ
             ⁢
             
              T
              s
             
            
            
             T
             s
            
           
          
         
         ,
        
       
       
        
         
          Δ
          ⁢
          
           T
           s
          
         
         ≥
         0
        
       
      
      
       
        
         
          
           
            x
            n
           
           ⁢
           
            
             1
             +
             
              Δ
              ⁢
              
               T
               s
              
             
            
            
             T
             s
            
           
          
          -
          
           
            x
            
             n
             -
             1
            
           
           ⁢
           
            
             Δ
             ⁢
             
              T
              s
             
            
            
             T
             s
            
           
          
         
         ,
        
       
       
        
         
          Δ
          ⁢
          
           T
           s
          
         
         <
         0
        
       
      
     
    
   
  
 

wherein For all VID filters, codeword xn′ can be calculated as follows:, x
   n
   ′
  
  =
  
   
    x
    ⁡
    (
    
     t
     =
     
      nT
      s
      ′
     
    
    )
   
   =
   
    
     x
     ⁡
     (
     
      t
      =
      
       
        nT
        s
       
       +
       
        Δ
        ⁢
        
         T
         s
        
       
      
     
     )
    
    =
    
     
      ∑
      
       i
       =
       
        -
        L
       
      
      L
     
     
      
       h
       ⁡
       (
       i
       )
      
      *
      
       x
       
        n
        +
        i
       
      
     
    
   
  
 

wherein h(i): VID filter coefficients.