AWR2544LOPEVM: Discrepancy in Maximal Range Calculation Using IF Factors in mmWave Radar

Shlomi Shvartzman

Prodigy 180 points

Part Number: AWR2544LOPEVM

Tool/software:

Hi,

I have encountered an issue with the maximal range calculation.

As I understand, the calculation should be:

IF_max_MHz = IF_factor * fs_MHz
if mode == 2:  # real
    IF_max_MHz = IF_max_MHz / 2 
IF_max_MHz = min(IF_max_MHz, IF_BW_MHz)
max_range = IF_max_MHz * c_ms / (2 * slope_MHz_usec) * 1e-6

For every chip, IF_factor is set to 0.9, and IF_BW_MHz is 20 for the 2544 chip.

I designed a chirp with fs_MHz = 45 and slope_MHz_usec = 98 and calculated max_range according to the above code is 30.59 meters (mode=2 for real ADC data).

However, after opening the captured file with mmWaveStudio 3.1.3.1, I found that the max range in all graphs is 34.34 meters. This result seems correct if IF_factor is set to 1 and the 4th line is ignored, i.e., setting IF_max_MHz = fs_MHz / 2 in the code without considering the IF maximum supported bandwidth. This discrepancy also affects the range resolution calculation.

Can you please help me understand the mistake?

Thanks,

Shlomi

over 1 year ago

0 Aydin Kiasat over 1 year ago

TI__Expert 5461 points

Hi shlomi,

The formula is correct. I confirmed with the team that studio does not take 0.9 into account and as you mentioned with 1, it would be correct. What is shown in the studio is just a graph, however the calculation is correct.

Regards,

Aydin

0 Shlomi Shvartzman over 1 year ago in reply to Aydin Kiasat

Prodigy 180 points

Hi Aydin,

Thanks for your confirmation.

I want to clarify one more point regarding range resolution.

The formula for range resolution is:

```python
unambiguous_range = fs_MHz * c_ms / (2 * slope_MHz_usec) * 1e-6
range_res_m = unambiguous_range / N_samples
```

where `N_samples` is the number of ADC samples.

I want to emphasize the distinction between `unambiguous_range` and `max_range` as calculated above. For `unambiguous_range`, I use `fs_MHz`, while for `max_range`, I use `min(IF_factor * fs_MHz, IF_BW_MHz)` instead. I want to confirm that the latter is used just for plotting, and the former is the correct value for range resolution.

Thanks,

Shlomi

+1 Aydin Kiasat over 1 year ago in reply to Shlomi Shvartzman

TI__Expert 5461 points

Hi Shlomi,

That's correct in max range, will be limited by the maximum IF bandwidth, so the formula is correct. The formula you have calculating the range resolution should also get the same result as C/2B once the unit conversions are correctly applied.

Regards,

Aydin

0 Shlomi Shvartzman over 1 year ago in reply to Aydin Kiasat

Prodigy 180 points

Thank you Aydin!

0 Aydin Kiasat over 1 year ago in reply to Shlomi Shvartzman

TI__Expert 5461 points

You're very welcome.

Regards,

Aydin

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AWR2544LOPEVM: Discrepancy in Maximal Range Calculation Using IF Factors in mmWave Radar