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IWR6843ISK: txPhaseShifter values

Prodigy 70 points

Replies: 1

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Part Number: IWR6843ISK

Hi,

this might be an easy question, but I'm having trouble interpreting the phase shifter values in the profileCfg command.
In the document from the long range people detection lab there is an example for an command with -15, 0, 15 and 30 degree angle.
When converting the decimal number for the 15 degrees angle to binary I end up with the phase shifts calculated from the formula on page 1: [0 (17*5.625=)95.625 (33*5.625=)185.625].
Though, in the -15 degrees example the two's complement of 17 and 33 is used. But how does my program know when to interpret the numbers as the two's complement and when not to? Because I would have interpreted the numbers as [0 (47*5.625=)264,375 (31*5.625=)174,375] - not building the two's complement.
Also the 30 degree example doesn't make sense to me at all. Converting the decimal to binary: 00000001 00000000 10000000 00000000. For example, wouldn't that mean that two of the antennas phase shifts where zero? The way I understood it 30 degree shift would convert to: 00000000 11111111 10000000 00000000 to represent a phase shift of 180 and 360 degrees in the two antennas.
could you please correct me, so that I can adjust my beam correctly.
Thanks so much in advance.

Best wishes.

  • Hi, 

    please use this matlab script for phaseShifter generation.  We are in the effort to update that document to include this script.

    theta_desired = -15;

    m_ind = [0 1 2];   % antenna distance in unit of lambda  

    phaseInc = 5.625; % step size for the phase shifter

        

    phaseTX_rad = 2*pi*(m_ind*sind(theta_desired));

    phaseTX_deg = (phaseTX_rad)*180/pi;

    phaseTX_deg_wrap = wrapTo360(phaseTX_deg);

    phaseShifter = round(phaseTX_deg_wrap/phaseInc) * [ 0, 2^8, 2^16].' * 4