Regarding the radar configuration

[yyuan-luo]

Hi Xiangyu,

I have some questions regarding the radar configuration. I tried to set my own AWR1843 radar to the same configuration you used. However, I had some problems when doing this.

My radar configuration

Questions

Tx1 with Tx2 or Tx1 with Tx3?

There are in total 3 Tx on AWR1843. In your project, you applied TDM on the Tx on the left and the one on the right. Between them, the distance is 4d. However, in mmWave Studio, I am not sure what is the correlation between the 3 Tx in the mmWave Studio and the 3 Tx actually on the radar board. It would be very nice if you could point it out to me.

The frame periodicity

radar_configs = {
    "startFreqConst_GHz": 77.0,
    "bandwidth_GHz": 0.67,
    "chirpDuration_usec": 60.0,     # single chirp per antenna
    "freqSlopeConst_MHz_usec": 21.0,  # slope: MHz/us
    "numAdcSamples": 128,   # samples
    "digOutSampleRate": 4000.0,     # sampling rate: Ksps
    "numLoops": 255,     # chirp loops
    "framePeriodicity_msec": 33.33333,  # frame rate 30 fps
}

In your configuration, the frame periodicity is 33.3333ms. I tried to use the same configuration except the chirpDuraiton_usec which I don't know how to set. In the end, the mmWave Studio reminds me that the minimum requirement for frame periodicity is 81.6ms. Could you please go through my configuration as provided above to provide some possible explanation for this?

Thanks in advance!

[yyuan-luo]

By playing the idle time and Ramp End Time, I can set the frame periodicity to 33.3333 ms. Could you please share your setting to the idle time and Ramp End Time? Thanks.

[yyuan-luo]

I think I have calculated both time based on the bandWidth and chirpDuration. BandWidth = Frequency Slope * Ramp End Time. So, the Ramp End Time is around 32.66us. However, when I set it to 32.66us, there is this error saying that Ramp duration is not enough to capture 128 samples at 4000 ksps. But 32.66* 4,000,000 = 130.64, which means it should be able to sample 128 times in one chirp.

[Xiangyu-Gao]

Tx1 with Tx2 or Tx1 with Tx3? I do not remember the details since it has been a long time ago. You may want to refer to the TI reference doc for checking the name correspondence. The frame periodicity The Ramp End Time should be longer than the exact value, 32.66us, you calculated to leave some room. The idle time can be very small

[yyuan-luo]

Thanks for the reply. Now, I get it. The bandwidth here refers actually to the frequency change in ADC sampling Time. Based on your configuration, ADC sampling time = 128 / 400k= 32us, hence the bandwidth = 32 x 21Mhz / 1000 = 0.67GHz. I thought that the bandwidth means the value showed in mmWave Studio, which equals slope x ramp end time. Now, it is clear.