AWR1642BOOST: DopplerCompensation in the virtual antennas.

Part Number:AWR1642BOOST

Hi, in Dss_data_path.c (c:\ti\mmwave_automotive_toolbox_2_1_2\labs\lab0002_short_range_radar\src\dss)

void MmwDemo_addDopplerCompensation(int32_t dopplerIdx,
                                    int32_t numDopplerBins,
                                    uint32_t *azimuthModCoefs,
                                    uint32_t *azimuthModCoefsHalfBin,
                                    int64_t *azimuthIn,
                                    uint32_t numAnt)

It says that 

 * Function Name       :    MmwDemo_DopplerCompensation
 *
 * \par
 * <b>Description</b>  : Compensation of Doppler phase shift in the virtual antennas,
 *                       (corresponding to second Tx antenna chirps). Symbols
 *                       corresponding to virtual antennas, are rotated by half
 *                       of the Doppler phase shift measured by Doppler FFT.
 *                       The phase shift read from the table using half of the
 *                       object Doppler index  value. If the Doppler index is
 *                       odd, an extra half of the bin phase shift is added.

It is true that signal received when the second Tx antenna is working should be shifted by half of the Doppler phase shift measured by Doppler FFT.

However, I feel that “If the Doppler index is odd, an extra half of the bin phase shift is added" makes no sense, and I cannot figure it out.

Could our algorism engineer give us a detailed explanation?

    /* Add half bin rotation if Doppler index was odd */
    if (dopplerIdx & 0x1)
    {
        expDoppComp = _cmpyr1(expDoppComp, *azimuthModCoefsHalfBin);
    }

Thanks a lot.