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IWR1443BOOST: Radarstudio Data format: Complex2x versus Complex1x

Karl Nordin
Prodigy 160 points
Part Number: IWR1443BOOST
Other Parts Discussed in Thread: IWR1443

Hello,

As described in the complex baseband in the link: http://www.ti.com/lit/wp/spyy007/spyy007.pdf , the difference between the the complex1x and complex2x in maximum distance as I see it should be equal
when using the same IF-bandwidth, but according to the postproc in radarstudio this is not the case.

Can you explain how the maximum detectable distance doubles with complex1x i comparison with complex2x without having a twice as large IF-bandwidth or is there something I have misunderstood.

Best Regards

Karl Nordin

  • 0
    TI__Expert 4720 points

    Hi Karl, 

    Attached is an explanation. I had to insert it as a pdf to keep the formatting un-corrupted.  Let me know if you have any questions.When the ADC is configured as.pdf

     Regards,
    Anil

  • 0 in reply to Anil Mani
    Prodigy 160 points

    Hello, Anil

    Thank you for your answer.

    I think i figured out how it works. What I incorrectly meant was that the bandwidth is the region that contains the signals of interest e.g. the region 0 - fs/2 when using a positive sloped ramp.

    What i was confused about is that it was possible to create a IF-frequency for the IWR1443 that was higher than 18.75 MHz IF-bandwidth since the 0-fs in complex1x mode would mean 0 - 37.5 MHz bandwidth, but the max fs with complex1x is 18.75 MHz which means that the IF are the same for the region with the signal of interests.

    There is some confusion when I did some testing with changing Complex1x and Complex2x, I noted that it seems that the range resolution was incorrectly calculated when using Complex1x.

    According to the range resolution formula mentioned in the training videos the range resolution is calculated by c0/(2*Bandwidth)

    which in the data in the picture below is 0.4079 m when using the formula. Something seems to be wrong.

    Best Regards

    Karl 

  • 0 in reply to Karl Nordin
    TI__Expert 4720 points
    Hi Karl,

    The 'range resolution' presented in the GUI is intended to be the 'bin resolution' of the FFT plot and is computed using the matlab code shown below. Could you check if you plug in the numbers corresponding to your experiment, whether the measurements add up? It should be correct for the complex1X measurements.

    % Modify the inputs as per your configuration
    sampling_rate_Hz = 5e6;
    num_adc_samples = 256;
    fftSize1D = 512; % modify as next power of 2 of the num_adc_samples
    lightSpeed = 3e8;
    ramp_slope_Hz = 36e12;

    adc_sampling_time = num_adc_samples/sampling_rate_Hz;
    oversampling_effect = num_adc_samples/fftSize1D;
    bandwidth = adc_sampling_time*ramp_slope_Hz; % over sampling changes the 'bin resolution', but the true resolution is still c/2B.
    range_resolution = oversampling_effect*lightSpeed/(2*bandwidth);

    Regards,
    Anil
  • 0 in reply to Anil Mani
    Prodigy 160 points

    Hello Anil,

    I will check it out further next week to see if it could match up, otherwise I think the initial question has been answered.

    Best Regards
    Karl