IWR6843ISK-ODS: Verification of Rx Gain

Hi Jeonghoon,

We will need a few days to look into this but should have an answer for you sometime this week.

Cheers,

Akash

Hi~

Could you feedback the status or answer for my questions?

If you have any discussion points, please let me know. 

Thank you!

Hi~..

In case of Rx Gain measurement, Radar Chip which is not included DSP & MCU can be verified easily by CW signal.

However, IF signal of single chip can't be measured directly because there are signal processing through the channel.

My question point is how I can get the Rx gain based on the raw data from the IWR6843 to verify sensor module.

Best regards,

Jeonghoon

Hi CHETHAN KUMAR Y.B,

As you mentioned above, I already have tested EVK to estimate IF signal power level(voltage or dBm) from ADC values through the mmwave studio .

We can easily calculate Rx input signal of ODS_EVK from the link budget through the Tx and known RCS reflection to Rx.

And We can estimate IF signal Power(dBm) from the Rx Gain of ODS_EVK (If it's right, the Rx Gain of IWR6843 is 30dB).

However, the estimated signal level is not matched with FFT ADC values of the DCA1000 signal.  (I have calculated fft magnitude based on the ADC values of DCA1000)

Specifically, please let me know missing point to calculate IF magnitude from ADC values.

I listed part of matlab code as following.

ps. What does that mean of 'codes' which is y-axis of time domain display in the mmwave stuido?

fs=10^7;%sampling frequency
N=256; %FFT size
c=3*10^8;
S=16.7*10^6/(10^(-6)); % Chirp Slope=16.7MHz/usec
df=fs/N; % Frequency Resolution
R=c*df/(2*S);
sampleindex=0:N-1;
x=csvread('ADC_raw.csv',0,0);
X=fft(x(sampleindex+1,1),N);%N-Point Complex DFT
a=abs(X(sampleindex+1));

Hi

Raw ADC data to dBFs.pdf

Please see the attached document for information on how to convert 'raw ADC data to dBfs and then to a dBm measurement'. Let me know if you have any questions. 

Regards

Anil

According to the attached file, the correction factor is about 132dB.(= 20log(2^15)+20log(N)-20log(2^0.5)), N=256)

P(dBfs)= Pfft_out -132dB, Pfft_out can be estimated based on the ADC data from the DCA1000. As shown below image, I try to fit the studio results with the calculated one by matlab.

 However, The graph is not perfectly matched with TI's studio results.

Could you guide to me to make the same results?
I really want to know transfer function of matlab.

Thank you for your kind assistance.

 fig1. matlab result fig2. TI Studio

Hello,

   Your figures are not visible in the post, could you please re-post? 

Thanks and regards,

CHETHAN KUMAR Y.B.

Hello CHETHAN KUMAR Y.B.,

There is a problem to upload figure files because of security issue, I think.

Anyway, I'd like to calculate IF Power based on the raw data from DCA1000.

I think the IF power could be estimated by a following fomular.

rpfft = 10.*log10(1000.*(rfft.*conj(rfft))./Z0); %Z0=50 ohm

If there are some mistake, let me know that.

Could you guide to me the process from dBFS calculation to FFT power of IF signal.

Thank you.

Regards

Hi Anil,

It's about 2~3dB. Basically, I have not used windows in my FFT processing.

But mmwave Studio uses a Hann window function by defalut although I have not set that. I can make sure window function in a miscellaneous tab of postprocessing window.
(Please let me know if there is way to control window function in a sensorconfig tab.)

Anyway, my FFT Power (I think it is IF power) results are very similar with dBFS value of postprocessing in the mmwave Studio.

According to the attaced file, dBFS value should be so different with FFT Power.(more than 10dB)

I'm very confused why these results are happened.

Could you explain the reason ?

And Could you tell me how to estimate IF Power?

Please guide to me if there is mistake.

Regards,

Hi Anil,

I have tested again and changed window of FFT processing settings in the miscellaneous tab.

There is no change for the dBFS level whatever I select anything window function.(Hann, no window, etc..)

The TI's dBFs level is very similar with my calculation under 1dB, but not the same.

I'd like to know the reason why dBFs value is similar with my result. and let me know how to estimate the IF Power from the result.

My calculation is something like this.
ADC = rawADC./10^15;
rfft = fft(ADC(:,1:4)./N,N);
rpfft = 10.*log10(1000.*(rfft.*conj(rfft))./Z0);

Regards,

Jeonghoon

Jeonghoon