IWR6843: Question about capon code in 3DPPL

Hi,

In labs\common\src\dpu\capon3d\modules\DoA\CaponBF2D\src\RADARDEMO_aoaEst2DCaponBF_rnEstInv.c you will find below code.

My customer is asking why the code only uses the even chirp 1DFFT data, but not odd chirp info. Would you pls help?

void  RADARDEMO_aoaEst2DCaponBF_covInv()
{
...
/*Rn estimation */
 diagSum         =   0.f;
 for (antIdx = 0; antIdx < nRxAnt; antIdx++)
 {
  input1  = (cplx16_t *) &inputAntSamples[virtAntInd2Proc[antIdx] * nChirps];

  //i = antIdx case -- diagonal elements
  acc   = _ftof2(0.f, 0.f);
  acc1  = _ftof2(0.f, 0.f);
  acc2  = _ftof2(0.f, 0.f);
  acc3  = _ftof2(0.f, 0.f);
  for (chirpIdx = 0; chirpIdx < nChirps; chirpIdx += 8)
  {
   llinput1 = _amem8(&input1[chirpIdx]);
   itemp1  = _hill(llinput1);
   itemp1  = _packhl2(itemp1, _ssub2(0, itemp1));
   lltemp  = _cmpy(_hill(llinput1), itemp1);
   itemp1  = _loll(llinput1);
   itemp1  = _packhl2(itemp1, _ssub2(0, itemp1));
   lltemp  = _dadd(lltemp, _cmpy(_loll(llinput1), itemp1));
   acc   = _daddsp(acc, _dintsp(lltemp));
   llinput1 = _amem8(&input1[chirpIdx + 2]);
   itemp1  = _hill(llinput1);
   itemp1  = _packhl2(itemp1, _ssub2(0, itemp1));
   lltemp  = _cmpy(_hill(llinput1), itemp1);
   itemp1  = _loll(llinput1);
   itemp1  = _packhl2(itemp1, _ssub2(0, itemp1));
   lltemp  = _dadd(lltemp, _cmpy(_loll(llinput1), itemp1));
   acc2  = _daddsp(acc2, _dintsp(lltemp));
   
   llinput1 = _amem8(&input1[chirpIdx + 4]);
   itemp1  = _hill(llinput1);
   itemp1  = _packhl2(itemp1, _ssub2(0, itemp1));
   lltemp  = _cmpy(_hill(llinput1), itemp1);
   itemp1  = _loll(llinput1);
   itemp1  = _packhl2(itemp1, _ssub2(0, itemp1));
   lltemp  = _dadd(lltemp, _cmpy(_loll(llinput1), itemp1));
   acc1  = _daddsp(acc1, _dintsp(lltemp));
   llinput1 = _amem8(&input1[chirpIdx + 6]);
   itemp1  = _hill(llinput1);
   itemp1  = _packhl2(itemp1, _ssub2(0, itemp1));
   lltemp  = _cmpy(_hill(llinput1), itemp1);
   itemp1  = _loll(llinput1);
   itemp1  = _packhl2(itemp1, _ssub2(0, itemp1));
   lltemp  = _dadd(lltemp, _cmpy(_loll(llinput1), itemp1));
   acc3  = _daddsp(acc3, _dintsp(lltemp));
   
  }

Thanks,

Chris