How to I correct for IQ rate that is not supported by the NI-2920 ?

[don3of4]

Hi All;

I am using Labview 11 and the NI-2920 (Ettus Radio) to build an FSK Receiver, I have the Modulation toolkit. 

My carrier is 169MHz, my data rate is 256Kbits/sec, my frequency deviation is +/-89.5KHz, I choose a samples/symbol of 16, my FSK symbols is 2 ( 0 and 1).

My receiver is close to working however I am getting an extra 5 bits in my frame data of 408 bits.

My sync bits are all lining up and the front end of my frame data which also has a 16bit frame counter in the front of the frame, which is working from 0 to 65535 without dropping data.

I think the extra bits are a result of the IQ rate which I try to set at 4096K based on 256K*16 = 4096K

The radio seems to default to 4.166667M for the IQ rate. 

The ratio of 408bits /415bits = 4096/4166 coincidence or not ?

Is there a way around this issue in the setup of the NI-2920 or in the way I handle the sampling and fetching of the data.

Any guidance would be greatly appreciated.

Don3of4

[don3of4 · Accepted solution]

For any interested:

The answer is Labview has an I/Q resample module. 

Connecting between the radio fetch and the demodulation modules, set tje input to the actual sample rate you desire = data rate* samples / symbol. 

Working thus far, not sure what happens when other clocking tolerances start to affect the data but for now its working.  Also not sure why this is not built into the demodulate or the fetch modules to get the sample rate you actually need from the beginning but I am still learning.

Don3of4