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ADF4351; Problem with USB interface

Question asked by Rengelink on May 23, 2013
Latest reply on Jun 17, 2013 by rbrennan

I am using the ADF4351 to generate 20-1500 MHz sidebands on a laser using an electronically driven optical phase modulator. I am very happy with the quality of the sidebands I get in this way so the RF output seems to work fine. I'm having some problems with the control however, if anyone could help me out that would be very much appreciated.


I basically have two issues:


1. I would like to be able to sweep the frequency of the sideband in steps of 100 kHz and a step time of 10 milliseconds or so (faster is better but in this regard I'm already close to another bottleneck that I'm not sure I'll be able to improve) Putting these settings in the sweep function of the software is no problem but when I run the sequence it is much slower than the 10 ms per step. I see a counter popping up that displays the remaining scantime correctly (that is: 10 ms multiplied by the number of steps) but it counts down much slower than expected, roughly by a factor ten. I have a feeling that writing the registers to the device is taking much longer than the stepsize but I don't see why it would take this long. Is there something I can do about this? I'm currently communicating with the device using the USB port, is it necessary to use the SPI interface instead in order to speed the scan up?


2. In my final set-up I will generate sidebands of different frequency on two separate laserbeams. I have two separate ADF4351 evaluation boards for this purpose. Is it possible to communicate with both of them using the same computer? The frequency of one of them can remain fixed after I have set the frequency but I will want to sweep the frequency of the other one.


Thanks a lot for any help you can provide!