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Choice of evaluation board to generate 6.8-6.9 GHz single frequencies and ramps

Question asked by vladgavr on Aug 5, 2015
Latest reply on Aug 11, 2015 by vladgavr

Dear Analog Devices support and community,

my name is Vladislav Gavryusev and I'm a PhD researcher in Heidelberg University, Germany.


We are looking for a new microwave frequency source for our experiment with ultracold Rydberg atoms of Rubidium, tunable around 6.8 GHz (to address an atomic transition) and capable of doing frequency ramps of 1 MHz/ms or faster after being triggered by an external signal. I would like to ask few questions before moving forward with the design of our system to be sure that I'm understanding correctly how your frequency synthesizer solutions work.


After exploring your catalog I found three possible choices, the ADF4155, ADF4159 and the ADF5355. All three of them have PLL loops that cover my desired range, but if I understood correctly only the ADF4159 is capable of doing frequency ramps, is this correct? I'm not an expert, so if it is the case I would like to understand there is this difference, since from the logic block schematic their operation seems pretty similar.


All three frequency synthesizer solutions have evaluation boards (EVAL-ADF4155, EV-ADF4159EB1Z and the EV-ADF5355SD1Z), but, if I understand correctly, only the EV-ADF5355SD1Z can be used off the shelf because the other two are supplied with a VCO with a different frequency tuning range, is this right? How difficult is to change the VCO and does it require additional modifications to the board?


Using an evaluation board, can the ramp be triggered by a signal on a pin?

Concerning the RF output power, I've read in the EV-ADF5355SD1Z datasheet that it can provide up to 1dBm at 6.8 GHz on RFoutB and -1dBm on RFoutA and that I should expect some power fluctuations varying the frequency, while I didn't find any information on the output power of the other two boards. Does someone know which power output do they provide?

What are the options to program the evaluation boards (USB software, SPI, direct serial or parallel programming)? Are there some LABVIEW example VI's?


In our lab we have a very stable OCXO with a 10 MHz sinusoidal output that I thought could be used as the reference source, but after reading the datasheets I seem to understand that the REFin signal should be a higher frequency in the range of 100 MHz to allow good PFD operation. Is this correct or could the 10 MHz be successfully used?


If we have the evaluation board, an amplification system to increase the power and tunable power supplies, is there anything else that  I may need to successfully generate my desired frequency?


Thank you very much,


Best regards