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AWR1642: questions about MMWave Demo Visualizer User's Guide

monica
Intellectual 340 points
Part Number: AWR1642

Hi,

  After reding the  MMWave Demo Visualizer User's Guide and Programming Chirp Parameters in TI Radar Devices, I have some questions as below:

1. I thing the slope of chirp = sweep bandwidth / ramp end time and the sampling rate = samples per chirp / ramp end time according to the above documents, is my understanding correct?

2. I found the CLI command details of 2.7.4 and 2.7.5 on the  MMWave Demo Visualizer User's Guide are the same, does this mean that the rang resolution or  max distance alone cannot determine certain CLI command, which can only be determined when both rang resolution and  max distanc are determined ?

3. On the 2.8.2 of  MMWave Demo Visualizer User's Guide, I can't understand that why max range can defines  the frequency slope constant? Because acording the Programming Chirp Parameters in TI Radar Devices, the max Range = (IF_max*c)/(2S), and  the IF_max is also dependent on the ADC sampling frequency  used, so I think the max range can only determines the value of (IF_max/S) . Can you help me solve my problem?

Best Regards ,

Monica

  • 0
    TI__Mastermind 30405 points

    Hi Monica,

    Please find the responses below:

    1. Your understanding is correct. However note that the total ramp time also includes the ADC start time and excess ramping time (typically 1us) at the end of the ramp so the total sweep bandwidth is given by the following formula

    total_sweep_bandwidth = ramp_slope * (adc_valid_start_time+number_of_samples_per_chirp/sampling_frequency+excess_ramping_time);

    2. This is correct for the profileCfg command which defines the ramp parameters. The ramp parameters are determined based on max range, range resolution and velocity as well. Max range alone cannot define the complete ramp configuration since Range resolution determines the total sweep bandwidth. Range resolution is a function of sweep bandwidth and is given by Rres = c/2B where c is the speed of light and B is the sweep bandwidth. So you need to know the range resolution to determine the total bandwidth and hence ramp end time and ramp slope.

    3. For a given sweep bandwidth, slower ramps provide higher maximum range while faster ramps  (i.e. higher slope) provide higher maximum velocity so maximum distance affects ramp slope.

    I would recommend you to go through the videos provided in mmWave Training Series to understand the fundamentals behind FMCW radar operation. These videos are an excellent resource for understanding the theory behind FMCW (and mmWave) radar technology and how the scene parameters e.g. max. range affect the chirp parameters. 

    I would also recommend looking at the mmWave Sensing Estimator tool which automatically generates the chirp parameters based on scene requirements.

    Thanks

    -Nitin