AWR2944EVM: Combining chirps of several groups for Doppler FFT to increase processing gain

Arie Rudnitsky

Part Number: AWR2944EVM

Tool/software:

Hi,

there is a limitation of 255 loops within Tf. But I can define several configuration groups, then the total number of chirps increases in a frame. For example, I set 6 groups and 64 loops, then the total number of chirps in a frame is 6*64=384.

Currently as I observe in mmWave studio, Doppler FFT is executed on a per group base. This means that each group decreases its post-Doppler noise floor by a processing gain of 10*log10(Nloops).

However, I can care that all of the groups have the same type of configuration, let's say type 0. In other words, in such case all the chirps in the frame are of the same type.

The question is whether there is a way to combine all these chirps together within the Doppler FFT, as practically them are of the same type?

This is crucial for our application because it provides an additional processing gain of a factor of the number of configurations I set.

Arie

2 months ago

0 Samhitha Bobba 2 months ago

TI__Mastermind 20810 points

Hi Arie,

I think you are looking for DDM demo where you have 6 unique chirps and 64 chirp loops. I suggest you to refer to C:/ti/mmwave_mcuplus_sdk_04_07_01_03/mmwave_mcuplus_sdk_04_07_01_03/ti/datapath/dpc/objectdetection/objdethwaDDMA/docs/doxygen/html/index.html to get a detailed understanding of the DDM processing chain. For more detailed information of each DPU i.e Range processing, doppler processing etc., you can navigate to appropriate document page from C:/ti/mmwave_mcuplus_sdk_04_07_01_03/mmwave_mcuplus_sdk_04_07_01_03/docs/mmwave_sdk_module_documentation.html.

Arie Rudnitsky said:
The question is whether there is a way to combine all these chirps together within the Doppler FFT, as practically them are of the same type?

Below is a screenshot showing doppler spectrum in DDMA. Here you see that there are 4 active bands and 2 empty bands. DDMA Demodulation is done to associate each sub-band with the correct TX channel and identify the active bands.

To understand how a detection matrix is created by summing across Tx, you can refer to Doppler DDMA DPU documentation (Use the link shared at the beginning of my response to navigate to the documentation page).

Regards,

Samhitha

0 Arie Rudnitsky 2 months ago in reply to Samhitha Bobba

Intellectual 300 points

Hi Samhitha,

thank you for your answer.

But let me clarify, because I don't understand: when I define different chirp groups, they should be transmitted by different Tx? I was thinking that this feature of groups may be used for a flexibility to define different types of chirps at different groups without any relation to the number of transmitters to use.

Consequently, I was searching for an option to increase the number of chirps in a frame using these chirp groups without actually caring about increasing the number of transmitters.

Please explain.

And please tell me the maximal number of chirps that may be sent in a single frame by a single Tx

0 Samhitha Bobba 2 months ago in reply to Arie Rudnitsky

TI__Mastermind 20810 points

Arie,

We have two processing chains available - TDM and DDM. In DDM processing chain all 4Tx are enabled at-a-time. If you wish to enable only one Tx at a given point of time, you can refer to TDM demo. For a high level understanding of TDM vs DDM, you can refer to (+) [FAQ] What are the benefits and SW migration effort moving to AWR2944 from AWR1642/AWR1843? - Sensors forum - Sensors - TI E2E support forums.

Maximum number for chirp loops that can be configured is 255.

Arie Rudnitsky said:
I was thinking that this feature of groups may be used for a flexibility to define different types of chirps at different groups without any relation to the number of transmitters to use.

You can use TDM demo, configure chirps by enabling one Tx per each chirp. After configuring the unique chirps, you can configure the chirp loops to iterate the unique chirps configured.

For details about valid range of each chirp parameter, you can refer to "C:\ti\mmwave_mcuplus_sdk_04_07_01_03\mmwave_dfp_02_04_18_00\docs\mmWave-Radar-Interface-Control.pdf". You can check section 5.5.3 Sub block 0x0102 – AWR_FRAME_CONF_SET_SB of the document for frame configuration parameters.

Regards,

Samhitha