AWRL6432: presence and motion demo BPM decode Via HWA FFT

Ken Zhang

Expert 3395 points

Part Number: AWRL6432

Hi Experts

In SDK 5.1.0.3, Rangeprochwa.c, we are using HWA FFT engine to perform BPM decoding.

I understand the first bin of 2-point FFT represent for the sum value of sample 1 and sample 2 as the thread mentions.

AWR2944: High end corner radar demo: SUM RX via HWA FFT - Sensors forum - Sensors - TI E2E support forums

Does the second bin represent for the differ value between sample 1 and sample2? Is it FFT nature or it is special mechanism of BPM decoding in our HWA?

Thanks

Ken

over 2 years ago

0 Kevin Ortiz over 2 years ago

TI__Expert 3525 points

Hi Ken,

Let me take a look into this. I will update by end of week!

Best Regards,

Kevin

0 zigang Yang over 2 years ago

TI__Mastermind 39955 points

Hi, Ken:

When you do BPM decoding,

Chirp1 represent TX1 + TX2

Chirp2 represent TX1 - TX2

When you add Chirp1 and Chirp2, you will get TX1

when you subtracting chirp1 from chirp2, you will get TX2.

And TX1 and TX2 represent different visual antenna. Instead of different range bins. And the above operation will be applied to every range bins.

Best,

Zigang

0 Ken Zhang over 2 years ago in reply to zigang Yang

TI__Expert 3395 points

Hi Zigang

Thanks for your kind help!

understood BPM decoding, but still not clear how decoding is implemented by performing FFT

Ken

+1 zigang Yang over 2 years ago in reply to Ken Zhang

TI__Mastermind 39955 points

HI, Ken:

For implementation detail, please go through C:\ti\MMWAVE_L_SDK_05_01_00_04\docs\MotionPresenceDetectionDemo_documentation.pdf, section 7.1.

And you can google on 2-point FFT, and find something similar to the link below. You can see how BPM decode is similar to 2-point FFT.

www.researchgate.net/.../the-butterfly-of-a-2-point-DFT_fig1_299513316

Please let me know if this is helpful.

Best,

Zigang