Regarding the ADF4350:

1.) Why does the value of Frac and Mod seem to be related by integer number? I noticed in the eval board software, each time the program would set frac and mod values related by an integer value.

2.) I'd like to use ADF4350 in frequency range of 200 MHz to 2 GHz, with some gain to get LO power of 17dBm over this entire range. Can you recommend best combination of parts to achieve this?

Hi Rich,

1. The modulus is related to the channel spacing or frequency steps. Gory details on how to calculate are in the ADF4153 etc. fractional N data sheets.

So as you step through channels you step through N, N+1, N+2 etc divided by the modulus.

2. The ADL5541 and ADL5542 cover this range. The ADL5542 is a better fit, 19 dB of gain and a P1dB of 20.6 dBm. Assuming somewhere from 0 to - 3 dBm from the ADF4350 this will put him at roughly 17 dBm. (All RF calculations are +-3 dB!)

Regards,

Bob