adrf6821 questions about the data sheet parameters

I don't need the return loss info. I found the S-parameter file(s). Still need the other info though.

Hello gizmoaudio,

Sorry for our late reply. Here are the answers for some your questions:

Modulation bandwidth in Table 2 says 500MHz - is this RF or baseband bandwidth?

500MHz is I/Q IF bandwidth and 1GHz BW is for RF.

On page 28 you discuss the 60 ohm output impedance (10+25+25 = 60). What is the penalty of using 45 ohm resistors instead of 25 ohms for a better match into 100 ohms (10+45+45 = 100)?

By design, the ADRF6821 has an I/Q output impedance of 10 Ω and voltage gain/linearity is optimized to perform with an external 25 Ω in each differential leg when terminated with 100 Ω differential load.

I'm looking at substituting this ADRF6821 in an existing design that uses the obsolete ADRF6820. I use the internal LO in both cases. My reference freq is ok (38.4M) with the new part  and my freq range falls within the spec (950 to 2450M). My RF BW will be approx 30MHz.

Is there anything I need to be aware of in changing from one part to the other? I do see the gain is higher by some 8 to 9dB. Are there other areas where I should be concerned?

Your values are good for the operation. Please feel free to reach us if you find any problems during your application.

For your other questions, we are currently running some tests, and provide the answers soon.

Gokhan

Hi

The integrated balun requires an external tuning of 15nH and a DC block(0.1uF) for the optimized performance. No further optimization is required for pin-7 RFBT_FB.

Thanks

Hi gizmaudio,

Does varying the digital attenuator have any effect on IQ image rejection? 

The RF path attenuator does not effect the image rejection performance. You can improve the image rejection by adjusting the IF filter or reducing LO signal level.

Gokhan