IWR6843AOP: Please inquire about the difference between the chirp configuration and the actual calculated value.

1-1) Our sensing estimator calculates range maximum based on SNR measuring the range maximum at boresight with noise accounted for. The equation you are referring to which results in 32. 03 is an approximation equation for performance in an ideal environment. Learn more in this application note. 

1-2) Other parameters in the configuration impact the maximum range. By modifying the CFAR thresholding values you can improve performance. You can find more tips on modifying parameters in the SDK User's Guide or in the 3D People Counting Detection Layer User's Guide (in the industrial toolbox)

1-3) Maximum distance and maximum unambigous range mean the same thing. However, we have two different equations to approximate these. The equations are both approximation, one ideal and one based on SNR.

1-4) I would encourage you to compare performance between profileCfg 0 60.5 100 25 69 0 0 50 1 256 6000 0 0 30 and a profile config designed with Fs=300ksps and S=14.05 (something like profileCfg 0 60.5 100 25 120 0 0 14.05 1 250 3000 0 0 30). Ultimately the area scanner STANDARD MMWAVE SDK  COMMANDS command was designed using the approximation equation Range_max=(6000k*3*10^8)/(2*50MHz/us)=14.4m in mind. An SNR based approach (as seen in the sensor estimator) may be more robust and be able to perform better. However, it depends on the enviroment.

Thank you,

Angie

Tank you for your reply

First of all

Is the calculation formula 14.4m in the last answer 1-4) a typo?

-> Range_max=(6000k*3*10^8)/(2*50MHz/us)=14.4m 

So, anyway Let me ask again if my understanding is correct.

You said that 'you have two different equations to approximate these. The equations are both approximation, one ideal and one based on SNR.'

I know there are two equations in the radar

1. SNR Based max range equation

In mmWave Sensing Estimator, i can see Detectable Object Range.

Is it right?

2. ideal max range equation

it is not the maximum unambigous range. Is it right?

3. are there two radar equation right?

 If possible, please also provide a maximum unambigous range equation

Thanks

Hello,

Range max is the maximum unambiguous range.

Thank you,

Angie

Hello Angie.

I'm so sorry. 

I've checked all the documentation you're talking about, but I don't understand

So I'll ask one by one.

I used a area_scanner_68xx_AOP.cfg(C:\ti\mmwave_industrial_toolbox_4_11_0\labs\Area_Scanner\chirp_configs)

so you can see the configuration

% ***************************************************************
% Created for Area Scanner v2.0.x
% Frequency:60
% Platform:xWR68xx
% Azimuth Resolution(deg):15 + Elevation
% Range Resolution(m):0.0703
% Maximum unambiguous Range(m):14.4
% Maximum Radial Velocity(m/s):2.45
% Radial velocity resolution(m/s):0.15
% Frame Duration(msec):100
% ***************************************************************

% *****************STANDARD MMWAVE SDK COMMANDS******************
sensorStop
flushCfg
dfeDataOutputMode 1
channelCfg 15 7 0
adcCfg 2 1
adcbufCfg -1 0 1 1 1
profileCfg 0 60.5 100 25 69 0 0 50 1 256 6000 0 0 30

when i used this equation

Fs=6000ksps

S=50MHz/us

so Range_max=(6000k*3*10^8)/(2*50MHz/us)=18m

You said that range max is the maximum unambiguous range.

But, I got the different values from range max(18m) and maximum unambiguous range(14.4m)

Is this right?

Thanks.

Hi Kuk,

I believe what you are missing here is the calculation of IFmax. IFmax is the maximum IF bandwidth supported at your sampling rate. If the sampling rate seen in your equation is 6000ksps then IFmax will have some roll off at either end due to the analog behavior of the signal. This means IFmax needs to be estimated. In our application note that you took the screenshot from it states that IFmax can be estimated by .9*sampling rate. This can be seen in the code for the sensing estimator. 

Range max = max unambiguous range = (.9*6000k*3*10^8)/(2*50MHz/us) = 16.2m

However, if you look at the datasheet .8*sampling rate is used as a worst case estimator. This is the number I try to use when estimating for customers to be as conservative as possible. Therefore I would say that at 6000ksps you can assume:

Range max = max unambiguous range = (.8*6000k*3*10^8)/(2*50MHz/us) = 14.4m

These are both estimations. The best way to get an understanding of device performance is to test. Then by decreasing the frequency slope or increasing the sampling rate you can increase the maximum range of the device. 

Thank you,

Angie Mitchell

I really appreciate to your reply

Now, I understand the phrase which I misunderstood about .9*sampling rate

So, one more question.

Does the adc sampling we calculated through the mmWave Sensing Estimator

is it satisfy the Nyquist frequency?

Thanks

Hi Kuk,

I appreciate your patience, we are working on some internal updates to our sensing estimator which will hopefully make this all clearer.

There is not a particular check for the nyquist frequency in the sensing estimator but by cutting off the edges of the signal (represented by the [.8 or .9]*sampling rate) we remove aliasing.

Thanks,

Angie