AWR6843AOPEVM: Is the AWR6843AOPEVM board capable of doing RCS measurements with a single tone?

Hi Ethan,

Thank you for reaching out, I looped in our DCA1000 expert and will answer your question sometime next week.

Best,

Vignesh K.

HI, Ethan:

We can not support you to perform RCS measurement?  It is easy to perform relative RCS measurement between different targets.  But it is hard to perform absolute RCS measurement.

Best,

Zigang

How would you perform relative RCS measurement's using a single tone? Can you use the raw IQ data and take the magnitude of the real and imaginary components?

No, I would use FMCW chirp and apply range FFT and Doppler FFT to the received signal.   Then find the peak power that comes from the target.    If you have other target placed at the same location, then apply the exact same chirp and apply the exact post processing. Then the power ratio is the relative RCS between the two targets.   Please note that the targets should be treated as point target in this measurement.  

Best,

Zigang

Thank you for the suggestion, I agree that will give me a relative measure between the two targets. What are the units of the raw IQ data? Can you point me to documentation to better understand the IQ data?

the FS (full scale) is ADC's maximum power. The maximum ADC swing is +-1 V (2Vp-p) and the FullSwing would be 10 dBm (0dBFS).

Assume you use 16 bit ADC raw data, +-2^15 code value would be +-1V.

Best,

Zigang

Please find the related discussion on this topic.

https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/1254696/iwr1843boost-calculation-of-rcs/4751328?tisearch=e2e-sitesearch&keymatch=RCS%2520computation# 

Best,

Zigang

Hi, I had a follow up question, we talked about finding the peak power that comes from the target when applying range FFT, what exactly is this peak power in reference to? The background power level I measure with no target in the vicinity is around 60dB, which is very high. How is this power determined?

Hi, Ethan:

Usually if you looked at the range FFT, the peak from the target should be quite obvious.   You can also look at the range-Doppler output and combine non-coherently across the antenna (range-Doppler heatmap) to further improve SNR.   

I assume this test is done in the anechoic chamber.  Which means the test environment is very clean, your signal power from the neighboring range bins should be low.   The target is a point target that not moving during your test.  

Please send over your setup picture, and the ADC data plot and range FFT, and range-doppler heatmap to help me analyze. 

Best,

Zigang

Yes, the measurements are being done in an anechoic chamber. Here is the range FFT, where our target is placed at 1.4m. My first question is what the large (90dB) peak at 0.1 m is, this is present in all measurements. If the bandwidth of the chirp is decreased these peak decreases which suggest to me some mutual coupling between elements. 

Secondly this graph is produced with the plotresponse() function, my question is how is the "power" determined? What is this "power" a measure of? 

Thank you for your help.

Ethan

Hi, Ethan:

Yes, the close in peak comes from the TX coupling. You can adjust the HPF corner frequency to adjust it.

I am not familiar with plotresponse, is it coming from TI? 

Best,

Zigang