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Original question:

TIDEP-01021: Radar - MIMO & Beam-steering

TIDEP-01021: AWR1843 Resolution & Tracked Objects

Sam Ref
Expert 1610 points
Part Number: TIDEP-01021
Other Parts Discussed in Thread: AWR1843

Hello,

  • Q01

Radar Distance Resolution ( Dist Res ) = (c /2)*(1/BW)

AWR1843 BW can be as high as 4GHz à DistRes = (300*106)/(2*4*109) ~4cm (“”-P.4).

Therefore, we potentially can distinguish objects that are ~4cm apart in the radial direction. Correct?

  • Q02

Velocity Resolution ( Vel Res )= λ/(2*Tf)

For AWR1843 we use λ ~ 3.8mm (at 77GHz) à Vel Res ~ 0.3m/sec. This means objects that move slower than ~0.3 m/sec cannot be distinguished using AWR1843. Correct?

 

  • Q03

The velocity resolution calculated in Q02 is useful only if motion is in the radial direction (ie when the object is moving towards or away from the radar). If the object is moving in a tangential direction it cannot be distinguished using Doppler effect. Correct?

 

  • Q04

Angular resolution of AWR1843 (when we employ MIMO) is 15 degrees. Correct?

We can use that to distinguish stationary or moving objects. Motion in that case must be in the tangential direction. Correct?

 

  • Q05

Based on Q1 & Q2 above (with the help of 2D FFT), in case of AWR1843, we will probably be able to distinguish large number of objects (using velocity and range) but we will not be able to know their exact angular location. This is because the angular resolution is limited to 15 degrees. Correct?

 

  • Q06

In some applications of AWR1843 (eg SRR USRR) the number of objects that can we can actually detect is 200. This is a memory and processing power limit, not a limit imposed by range resolution or velocity resolution. Correct?

 

  • Q07

In some applications of AWR1843 (eg SRR USRR) the number of objects that can we can actually track is 24. This is a memory and processing power limit, not a limit imposed by range resolution or velocity resolution. Correct?

 

  • Q08

Our practical observation when we used AWR1843 is that we cannot distinguish static objects using that are 4cm (or even 40cm) apart, even in the radial direction. Any explanation?

 

  • Q09

You track an object by finding velocities, angular position and radial distance of all objects in two consecutive frames and correlating these three quantities in the two frames. Correct? In all cases can you please refer us to a document that describes the tracking process.

 

  • Q10

The outcome of any TI radar code/demo is;

  1. Objects. Each is represented using a point (x, y & z) and a velocity (vx, vy & vz). Correct?
  2. Clusters. Each is represented using a point (x, y & z) and a velocity (vx, vy & vz). Correct?
  3. Tracked Objects. Each is represented using a point (x, y & z) and a velocity (vx, vy & vz). Correct?

 

  • Q11

What is the relationship between a cluster and an object? Is the cluster part of an object?

 

  • Q12

These objects, clusters and tracked objects are all detected in the DSP. All FFT2 calculations are done also in the DSP. The cortex MCU just receives these results and we make it available to us or to the GUI. Correct?

 

 Regards

Sameh

  • 0
    TI__Mastermind 31680 points

    Hello Sameh, 

    Please give us some time to answer your queries. We will get back to each of them in our subsequent replies.

    Regards,

    Ishita

  • 0 in reply to Ishita Kochar
    Expert 1610 points

    Hi Ishita,

    Kindly we need urgent replies to our queries as we are work is held.

    Regards

    Sam

  • 0 in reply to Jitendra Gupta
    Expert 1610 points

    Dear Jitendra

    I am sure literature cover any question. In that case we do not need you. We are capable of downloading documents without any consultation with you.  We are here to get direct technical support for products we bought from TI,  not to get literature advice. Your lazy response dismisses the concept of technical support.

    I hope you keep your non-technical advice to yourself and please address our questions. If you want to refer to a document you can specify the page number of that document that addresses our specific question.

    Regards

    Sam

  • 0 in reply to Sam Ref
    TI__Guru 68990 points

    Hello Sam,

    I understand your anger due to the unfulfillment of your expectation. 

    But to avoid any hindrance to customer projects we provide a lot of documentation on mmwave sensor which is a complex technology and requires a lot more understanding & technical support.

    I guess you don't get time to go through those to understand the technicality of this device, so let me provide assistance here from the same literature mentioned above.

    • Q02: The velocity resolution of the radar is inversely proportional to the frame time (page 6), so controlling to frame periodicity you can get better velocity resolution.
    • Q03: in this case you need to include the angle calculation as well along. velocity is relative and measured wrt to the mmwave sensor.
    • Q04: Improving angle resolution requires increasing the number of receive antennas. Each receive antenna has its own receive chain (LNA, mixer,LPF, ADC). In MIMO case you get more virtual antenna so better angular resolution. 
      • eight RX antennas (4 RX x 2 TX) has an angle resolution of about 15º. 
      • Motion for mmwave sensor is tangential as it sees that object moving towards or away.
      https://training.ti.com/sites/default/files/docs/mmwaveSensing-FMCW-offlineviewing_2.pdf  (page 61)
    • Q05:  angular resolution is to distinguish b/w two object. Angular accuracy can be improved by increasing the Rx antenna.https://www.ti.com/lit/an/swra554a/swra554a.pdf 
    • Q06: yes max no. of object detection limited by device memory.
    • Q07: same as Q06
    • Q08: Which demo or applicaiton you are using for this experiment, and what is distance from the sensor for those objects? I recommend try strong objects for experiment (may be corner reflector).
    • Q09: SRR and MRR demo uses tracking algo. Even mmw demo provide gTrack algo which you can refer C:\ti\mmwave_sdk_03_05_00_01\packages\ti\alg\gtrack
    • Q10: outcome format may vary for different application, and even user can define their own outcome format.You can refer mmw demo document for one of object result format file:///C:/ti/mmwave_sdk_03_05_00_01/packages/ti/demo/xwr18xx/mmw/docs/doxygen/html/index.html#output
    • Q11: In SRR/MRR, an object is part of one cluster.
    • Q12: most of signal processing is done at DSP (or in HWA : MRR-AWR1843) and MRR is being used mainly for data transmission purpose in SRR, but user can balance this load by moving some tracking or other high level algo running on MSS.

    Regards,

    Jitendra