AWR1243: Chirp Profile configuration

Hello Santhana,

The System Estimator tool is typically a good indicator of what the device supports in terms of configuration. It makes certain assumption while making calculations which are conservative and make it easier for calculation, however there could some corner cases which put the tool out of bounds and generate errors.

If you have already calculated the chirp parameter values based on the sensing requirements. The please check the Radar Interface API guide to see if the values are supported by the chirp, profile, Frame config of the device.

Radar Interface Guide is available i.

Regarding the specific requiremnts for sensing.  Speed value of 500kmph paired with the high range resolution could exceeds the devices maximum Intermediate Frequency which is 15Mhz and put further.

Looking at the various parameters you have mentioned the ADC start time seems smaller than Ramp time which would make the chirp invalid.

Total chirp time = idle time+ADC start time+ramp time+ramp excess time = 2+3.14+1.71+0 = 6.85us

Please check the Figure 7 in  Programming Chirp Parameters in TI Radar Devices for these terms on timeline on chirp.

Thank you,

Vaibhav

Hi Vaibhav,

Thanks for the information. Three things:

One: Where do I get the Radar Interface API Guide. I think the link is missing in your post.

Second: I wrongly mentioned the ADC sampling time as ramp time. The corrected statement is as below:

Total chirp time = idle time+ADC start time+ADC valid sampling time+ramp excess time = 2+3.14+1.71+0 = 6.85us

Sorry for the silly mistake. I suppose there is not limitation on ADC valid sampling time that it need not be greater than ADC start time??. and my ramp excess time can be zero??

Third: When the AWR1243 supports 37.5MHz, (which I am targeting) would there be any problem with intermediate frequency as 15MHz??

Hello Santhana,
In the Radar Studio tool there is a tab called "Ramp timing calculator" which will provide guidelines for the timing parameters like the idle time, ADC start time , ramp end time etc.
For 90% settling the recommended setting for you r configuration are
idle time = 2 usec , ADC start time = 3.22usec , ramp end time time = 5.07 usec (that would mean you will have to provide a little excess ramp time at the end).

I also noticed that you are looking for 40cm range resolution. In the chirp profile you have provided the "valid" sweep bandwidth would be only 158Mhz since that the time the ADC samples are being taken. So your range resolution would be ~95cms.

You can use the 37.5Mhz sampling rate for the real only mode and this can support an IF frequency of 15Mhz, thats not an issue.

Regards,
Vivek

Hello Santhana,
Also thank you for pointing out the issue with the sensing estimator seen for this scenario, we will work on fixing it.

Regards,
Vivek

Hi Vivek,

Thank you for the information.

I assumed that the bandwidth to be used for range resolution includes the ramp from ADC starting time and ramp excess time. By your explanation it seems that I have to include only the bandwidth during the ADC's valid sampling time. Is that so??

Let us assume that i am not strict with my range resolution. And concerned about the velocity alone. If that's the case, If I can work with 1m resolution, Would I be able to get the velocity max to 500kmph and velocity resolution to 1kmph with AWR1443 device??

Thanks for the help,
Santhana Raj