One feedback, and one question.

Question

This is sunny again!
Thanks for all your help and I am now able to build a OOK tranceiver. I am now moving toward to cascade the 5610 upconverter and 5600 downconverter to 5640.
I just have one feedback for your Burst OOK demodulator IP. I modified it and used it for my tranceiver, basically it worked but two things has to be noticed(may be changed):
1. The symbol rate in the VI shall be doubled. For example, According to your original design, 3.125M correponds to decimation 32, which took the symbol rate to be 3.125M and only one sample per symbol. Unfortunately, this is not correct according to Nyquist sampling theory and inconsistent with the demodulation subVI. I changed it to 3.125M correponding to decimation 16, so the actual sample rate is 6.25MHz to be consistent with the demodulation subVI and Nyquist theory.
2. In the demodulation subVI , there is a bug in the find threshold VI. Once the threshold to arbitrate 0 and 1 is found, the output valid signal shall not be toggled.
My questions :
1. For cascading the 5640 to 5610 upconverter, I used the upconverter only mode VI , it worked, I just wondered if there is a way to turn on the RF carrier wave all the time even when no signal is generated by NI 5640 because in my application I need this feature.
2. About the NI-tuner for cascading   the 5600 downconverter: I looked at the two available examples in the ni Tuner directory, should I just use the getting started VI and then connect the output of 5600 to the AI port of 5640? I also find that in another example,  it uses NI scope. But I guess it doesn't apply to my case because there is no digitizer now(it is 5640 instead).
So any suggestions?
帖子被xy_se在05-29-2008 01:28 PM时编辑过了

Answer 1

Hi Airian,
To set your Tx IQ rate:
1. Get the complex output waveform from MT after QAM modulation.
2. Get the dt component of this waveform. Set 1/dt as the IQ rate using ni5640R Configuration Generation.VI. But 5640R does not support all IQ rate. Hence find using the ni5640R Get Actual IQ Rate.vi to get the closest supported/ coerced IQ rate.
3. Using the new IQ rate, use MTs IQ resample to resample the modulated waveform to the new IQ rate.
4. Now write this waveform into the 5640R using ni5640R Write Waveform.vi.
On the Rx side,
1. Set the IQ rate to the newly obtained IQ rate.
2. Resample the acquired waveform to the original IQ rate.
3, Now perform the demodulation.
If you notice, in the examples of MT with RFSG, the write waveform VI actually performs resample internally and then writes the waveforms into RFSG's memory. But 5640R does not resample.
The OOK transceiver that we have developed is an example to show how the FPGA of the 5640R can be programmed using LabVIEW FPGA.
You can find the FPGA based IP that the team has developed at ni.com/ipnet.
Cheers!
--Vinay