IWR6843ISK: Why is the azimuth 3rd-FFT peak index reused for elevation in AoA (IWR6843ISK)?

Dear TI Support Team,

I’m analyzing the Long Range People Detection project on IWR6843ISK and have a question about the 3rd-FFT AoA processing on the DSP path.

Code context
In static inline uint32_t AoAProcDSP_angleEstimationAzimElev(...), the azimuth 3rd-FFT peak index is detected and stored in maxIdx:

maxIdx = mmwavelib_powerAndMax((int32_t*)&azimuthFftOut[0],
                               DPU_AOAPROCDSP_NUM_ANGLE_BINS,
                               &azimuthMagSqr[0], &maxVal);

This maxIdx is then passed into:

peakAzimIm = (float) azimuthFftOut[maxIdx].imag;
peakAzimRe = (float) azimuthFftOut[maxIdx].real;
peakElevIm = (float) res->elevationFftOut[maxIdx].imag;
peakElevRe = (float) res->elevationFftOut[maxIdx].real;

Question
Could you clarify why an independent elevation peak search is not performed, and why the azimuth peak index (maxIdx) is reused for elevationFftOut as well?

• Is this driven mainly by latency/throughput constraints (HWA/EDMA budget), array-resolution asymmetry (better SNR/resolution in azimuth), or an algorithmic separability assumption (e.g., az/el steering vector factorization)?

Best regards,
Jaehoon Kim