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AWR1843: MIMO & Beam-forming

Sam Ref
Expert 1610 points
Part Number: AWR1843

Hello,

  1. The document “Design Guide: TIDEP-01021 Beamsteering for Corner Radar Reference Design” refers us to the document “Programming Chirp Parameters in TI Radar Devices”. The 1st document states, in Page 6, that angular resolution will be improved by a factor of 3. The 2nd document also clearly states (in Equations 7 & 8) that using MIMO system will result in virtual antennas which will improve resolution by a factor of 3. If we employ three Tx Antennas (instead of 1). A gentleman from Texas Instruments by the name of "Cesar" in correspondence with us says it is a factor of 2 (not 3).  Does MIMO improve angular resolution by a factor or 2 or 3? Or does that factor depend on the mechanical configuration of the Tx antennas? If so which mechanical configuration results in a factor of 2 and which mechanical configuration results in factor of 3?
  2. If our system has 3 Tx antennas and 4 Rx antennas and we employ beam-steering with a steering step of ~5 degrees à we should be able to distinguish two Objects one at an angle of 45 degrees and the other at an angle of 50 degrees (for example). This is because (as you said before in answering Q6 of our previous communication) at each of these angles we obtain the maximum possible resolution for the case of 1Tx antenna and 4 * Rx Antennas. That is, we eliminate the factor of 1/cos (40) in case of beam-steering. This is effectively angular resolution of ~5 degrees. At the same time if we employ MIMO and we end with 12 virtual Rx antennas then the resolution is 15 degrees, and at angle of 40 degrees we have to apply the factor of 1/cos(40) to obtain the effective resolution. In other words, it might harder to distinguish objects that are 5 degree apart in that MIMO case. In third words, we might be able to distinguish more objects (that are arranged in an angular direction) when we employ beam-forming and subsequently beam-steering. We accept that in between the steered angles the resolution might be really bad if compared with the case of MIMO and virtual antennas. Correct?

Regards

Sam