Figure 3-2 and Figure 3-3 compare the antenna geometries of xWR6843AOP ES1.0 and xWR6843AOP ES2.0.

Figure 3-2 xWR6843AoP ES1.0 Antenna Geometry and Resulting MIMO Virtual Antenna Array

Figure 3-3 xWR6843AoP ES2.0 Antenna Geometry and Resulting MIMO Virtual Antenna Array

The key antenna updates in xWR6843AOP ES2, as shown above are:

• RX Antennas: RX1 and RX2 are swapped on xWR6843AOP ES2. Similarly RX3 and RX4 are swapped
• TX Antennas: TX2 and TX3 are swapped on xWR6843AOP ES2.
• Line Feed: The RX line feeds on xWR6843AOP ES2 are same as on ES1 i.e. RX1 and RX2 are fed from opposite ends, which results in a 180° phase difference between RX1 and RX2. Similarly, RX3 and RX4 are out of phase by 180°. To compensate for the opposite line feeds, a 180° phase inversion needs to be applied in software processing for the corresponding virtual channels as shown in Figure 3-3.

MMWAVE-SDK 3.2.0.6 and MMWAVE-SDK 3.4 include the AoA2dProc DPU which performs Angle of Arrival processing for the xWR6843 AoP antenna array using the Hardware Accelerator. The AoA2dProc DPU (Datapath Processing Unit) is used in the xWR64xx AoP mmw demo for angle of arrival processing.

To understand the AoA updates needed for xWR6843AOP ES2, it is recommended to understand the antenna geometry concept defined in AoA2dProc DPU.

1. Navigate to C:\ti\mmwave_sdk_03_04_xx_xx\docs and and open the file mmwave_sdk_module_documentation.html in a browser.
2. Click on the AoA using 2D FFT method link as highlighted in the picture below:
   Figure 3-4 AoA2dProc HTML Documentation
3. Scroll down to the section named Antenna Geometry Definition, which explains how the generic antenna geometry structure is defined and used by the HWA AoA2dProc DPU code. The antenna geometry for a specific antenna (for example, xWR6843AoP ES2.0) is defined in the corresponding C structure in mmwave_sdk_03_04_xx_xx\packages\ti\board\antenna_geometry.c.

The image below shows the antenna geometry structure update for xWR6843AoP ES2.0 as compared to xWR6843AoP ES1.0 in MMWAVE-SDK 3.2.0.6.
Code Snapshot: see Section 5.13

The antenna geometry structure is passed to the Object Detection DPC during initialization in mmwave_sdk_03_04_xx_xx\packages\ti\demo\xwr64xx\mmw\main.c
Code Snapshot: see Section 5.14

RX Channel Phase Compensation: To compensate for the opposite line feeds as shown in Section 5.12, a 180° phase inversion is applied to the corresponding RX channels (including virtual channels) using the compRangeBiasAndRxChanPhase CLI command available in the mmw demo.

Figure 3-5, from the MMWAVE-SDK user's guide, explains the structure of this command.

Figure 3-5 RX Channel Phase Compensation: CompRangeBiasAndRxChanPhase CLI Command

To understand the CompRangeBiasAndRxChanPhase values configured in the example AoP profile configuration provided in MMWAVE-SDK, see Section 5.15.