**hello together,**

**the tuning word for the band-pass filter center frequency can be calculated as follows: **

** f(BPF) =( f(center) *( 2^16-1))/ f(DAC) = Value**

**DECinHEX(Value) = MSB in 0x1D and LSB in 0x1C.**

**But this is not true?? When i calculate a Value ex : f(Center)= 450MHz**

**i found 493D. But intern the AD9789 write another value?**

**I’m confused?**

**Can anyone tell me how I can calculate the right Value!**

**i will not use the AD9789 Evalboard, so i must know the right value to program this register?**

**Best Regards**

The NCO places the output between 0 and Fdac/16 MHz. The final output frequency is chosen with the 16x bandpass filter (BPF) by selecting one of the 16 images created by the 16x interpolation. So, to obtain the final output frequency, calculate the NCO frequency with

Fnco = (FreqTunWord/(2^24-1)) * (Fdac/16)

Then, choose your ultimate output frequency with

Fout = Fnco + Fmult * (Fdac/16)

where Fmult is an integer multiplier from 0 to 15, corresponding to the 16 images at the output of the 16x interpolator. Then, program the 16x filter as

BPFcenter = Fdac * (BPF_center_word/((2^16) - 1) .