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AWR1642: What is the SRR_demo object data output grid size

Ashish Roy
Intellectual 475 points
Part Number: AWR1642

Have a couple of questions regarding the SRR demo object output:

1) What is the grid size (number of range bins and azimuth bins) of the SRR objects those are available in the TLV. In the TLV only the detected objects, clusters and tracked output  locations are provided.

    I understand that the grid size (in range) is determined by the range fft size, that can be scaled properly using the formula (fs/N)*k  where fs is beat (ADC) sampling frequency, N is the range FFT size and k =1:N is the range FFT output sample index. Similarly, the grid size (along azimuth angle direction) is determined by the FFT size that can be scaled using the formula asin(2*kmax/M) where asin is inverse sin, M is azimuth fft size, kmax=1:M is the azimuth fft output bin index. 

where are the range and azimuth FFT sizes been declared in dss_data_path.c ?

2) Will the grid sizes for SRR and USRR subframes be different. How is a TLV  frame for SRR demo populated. Is it alternating between SRR and USRR or the USRR subframe data (till 20 m) is superposed or combined with that of SRR subframe (assuming it to be till 80 m).

  • 0
    TI__Guru*** 138349 points

    Hi,

    You can check the function call to compute the range fft at line 1466 "DSP_fft16x16()" and for angle fft at line 4157 "DSP_fft32x32". This will provide you the size of the fft.

    The number of range bins and angle bins can be different for SRR and USRR subframes

    The TLVs are specific to each sub-frame SRR and USRR

    thank you

    Cesar

  • 0 in reply to Cesar
    Intellectual 475 points

    Thanks for the reply Cesar.

    But my doubt about the frame's representation is not yet clear. For any given frame in the TLV do I get a combination of USRR subframe (till 20 m) and the SRR subframe catering to the longer 20 to 80 m range or is it the other way that for any given frame either SRR or USRR data (detected objects, clusters, tracked O/P ) will be available in the TLV.

  • 0 in reply to Ashish Roy
    TI__Guru*** 138349 points

    Hi,

    It helps to conceptually consider each subframe type as an "independent" frame. There is no combination of detected data in the TLV

    It is the second way you describe

    Frame #1 - SRR Data

    Frame #2 - USRR Data

    Frame #3 - SRR Data

    Frame #4 - USRR Data

    This is easy to see if you take a look at the way the matlab gui receives the data

    in file "read_serial_port_and_plot_object_location.m"

           % Display
            % 1. Detected objects
            if sfIdx == 1

    THIS IS THE SRR frame
                if (detObj.numObj > 0) && load_point_cloud_srr
                    set(guiMonitor.detectedObjectsPlotHndA, 'Xdata', detObj.x, 'Ydata', detObj.y);
                    set(guiMonitor.detectedObjectsRngDopPlotHndA, 'Xdata', detObj.range, 'Ydata', detObj.doppler);
                else
                    set(guiMonitor.detectedObjectsPlotHndA, 'Xdata', inf, 'Ydata', inf);
                    set(guiMonitor.detectedObjectsRngDopPlotHndA, 'Xdata', inf, 'Ydata', inf);
                end
            else

    THIS IS THE USRR FRAME
                if (detObj.numObj > 0) && load_point_cloud_usrr
                    set(guiMonitor.detectedObjectsPlotHndB, 'Xdata', detObj.x, 'Ydata', detObj.y);
                    set(guiMonitor.detectedObjectsRngDopPlotHndB, 'Xdata', detObj.range, 'Ydata', detObj.doppler);
                else
                    set(guiMonitor.detectedObjectsPlotHndB, 'Xdata', inf, 'Ydata', inf);
                    set(guiMonitor.detectedObjectsRngDopPlotHndB, 'Xdata', inf, 'Ydata', inf);
                end
            end

  • 0 in reply to Cesar
    Intellectual 475 points

    Thanks again for the reply Cesar.

    In fact the  sfIdx = Header.subframeNumber+1, contains the information about the subframe (SRR or USRR in alternate subframes) type from which the data is populated on the scatterplot that you have also pointed out in the above reply.

    So what I perceive is that in every frame data the subframe data is populated (one after the other alternately). This confusion arises as in the SRR demo-userguide the frame structure is a combination of SRR (slow and fast chirps) and USRR (for MIMO mode) subframes.