AWR6843: Questions about the configurations in the vital sign demo

Hi Tian,

First, which vital signs demo are you working with? If you haven't evaluated already, our latest demo with the most advanced vital signs detection algorithm is vital signs plus people tracking. 

1. How do we calculate or get the IF signal sampling rate 2MHz as well as calculate the chirp duration 50us?

This guide gives an introduction to calculating radar parameters such as max IF bandwidth. The time spend chirping, also known as ADC sampling time, can be estimated as the number of samples / sampling rate. These are set by the profilecfg in the .cfg file which comes with the lab. All these parameters are tunable. 

2. What's the purpose here to send two chirps? Meanwhile, could we configure the duration of each chirp and the time gap between these two chirps (not the gap between the frames)?

By configuring the profilecfg command the parameters of the chirp, including idle time and adc start time seen in the figure below, can be configured. The modifiable configurations are detailed in our SDK user's guide on page 19 which can be be found at C:\<sdk download location>\mmwave_sdk_03_05_00_04\docs

Thanks,

Angie

Hello Angie,

Thank you for the answers! I'm currently studying the vital signs demo in the industrial toolbox w/o the people tracking as an entry point. I'll definitely check the latest demo after completing understand the basic vital sign demo.

For the answers, I still have few further questions.

Angie Mitchell said:

This guide gives an introduction to calculating radar parameters such as max IF bandwidth.

(1) According to the demo config, the ADC sampling frequency is 4MHz and the number of ADC samples is 200. We can calculate the chirp duration time, which is 200/4M = 50 us. Could you please help me confirm if the ADC sampling frequency is the IF signal frequency here? The linked guide seems to calculate the max range using the max IF bandwidth and the chirp slope.  

Angie Mitchell said:

The modifiable configurations are detailed in our SDK user's guide on page 19 which can be be found at C:\<sdk download location>\mmwave_sdk_03_05_00_04\docs

(2) Yes, I did check that document. I think there are two key configuration commands for chirps including <profileCfg> and <frameCfg>. From your answer to the question (1), I can configure the chirp duration using  number of samples / sampling rate. But I'm still not sure about the description "Each frame is configured to have 2 chirps. However only the 1st Chirp in the frame is used for processing" in Vital Sign 68xx User guide. 

I assumes that I can configure the number of chirps in a frame by setting <number of loops> in <frameCfg>, which is 2 in the demo. Thus, according to the attached figure, there should be two chirp cycles in each frame. My question is if there will be any gap between those two chirp cycles in one frame? 

Thank you very much!

Tian

Hello Tian,

Great! The vitals + people tracking demo builds on the vitals demo you are using. If you are interested in that lab or have questions about the source code please let us know.

(1) According to the demo config, the ADC sampling frequency is 4MHz and the number of ADC samples is 200. We can calculate the chirp duration time, which is 200/4M = 50 us. Could you please help me confirm if the ADC sampling frequency is the IF signal frequency here? The linked guide seems to calculate the max range using the max IF bandwidth and the chirp slope.  

The max IF signal frequency used in these equations is approximated at .9*ADC Sampling Frequency in complex 1x sampling mode. This value is then used to estimate max range. This method is explained in the paragraph after the max range equation. 

(2) Yes, I did check that document. I think there are two key configuration commands for chirps including <profileCfg> and <frameCfg>. From your answer to the question (1), I can configure the chirp duration using  number of samples / sampling rate. But I'm still not sure about the description "Each frame is configured to have 2 chirps. However only the 1st Chirp in the frame is used for processing" in Vital Sign 68xx User guide. 

I assumes that I can configure the number of chirps in a frame by setting <number of loops> in <frameCfg>, which is 2 in the demo. Thus, according to the attached figure, there should be two chirp cycles in each frame. My question is if there will be any gap between those two chirp cycles in one frame? 

I believe the only gap between these two chirps in one frame can be configured by modifying the Idle Time <idleTime in profileCfg> and the ADC Valid Start Time <adcStartTime in profileCfg>. Since <numLoops in frameCfg> is set to 2 there will be 2 chirps per antenna. Then the rest of the frame time is used for processing and waiting for the next frame to start. 

For further information, below are some approximations of the statics of this demo determined by using the equations from the documents linked. Now this is an ideal case approximation which is mean to give an idea of what the scene parameters may look like with this config. 

Thank you,

Angie

Hello Angie,

Thank you very much! Just one last question, nay I know if the ADC sampling frequency is the IF signal frequency? 

Sincerely,

Tian

Thank you!