MATLAB: Question about sensorsig function of phased array system toolbox

arraydoaphasedPhased Array System Toolboxsensorsigsignal generationtoolbox

Good evening
I am trying to generate some signals for DOA estimation using the sensorsig function. My code is the following:
 az = 0; % Azimuth direction
el = 0;  % Elevation direction
dim = 4; 
fc = 300e6;              % Operating frequency
lambda = physconst('LightSpeed')/fc;
samples =100;
nPower = 0;
rs = rng(30);
sCos = phased.CosineAntennaElement(...
    'FrequencyRange',[200e6 1.2e9]);
xDim = 4; % number of elements in x dimension
yDim = 4; % number of elements in y dimension
linear_dim=dim;
d = lambda/2; % Inter-element spacing
N = linear_dim;
pos_along_x = (0:xDim-1)*d;
pos_along_y = (1:yDim-1)*d;
pos_along_z = (1:N-1)*d*0;
pos = [[pos_along_x ];...
   [zeros(1,xDim)];...
   [ zeros(1,xDim)]]; % Sensors positions
for k=1:yDim-1
    a = [[pos_along_x];...
        repmat(pos_along_y(k),1,xDim);...
        [zeros(1,xDim)]];
    pos = [pos a];
end
my_array = phased.ConformalArray('Element',sCos,'ElementPosition',pos);
my_array.Element.FrequencyRange = [2e8 1.2e9];
ang1 = [az;el];       
signals=[ang1];
rxsig = sensorsig(getElementPosition(my_array),...
   samples,signals,nPower);
sensor = transp(rxsig);
Here i have a signal coming from azimuth 0 and elevation 0, and i also have a rectangular 4×4 array. After i get the samples of the received signals from sensorsig, i plot the signals at the first and second antenna. What i observe is that on one hand the real part of the signal at the first antenna is also the imaginary part of the signal at the second antenna, with an offset.On the other hand, the real part of the signal at the second antenna, is the negative of the real part of the signal at the first antenna. Could someone explain to me why this happens? Here's also a picture of the figures
Thank you in advance

Best Answer

If I understand it correctly, the signal at antenna #2 is essentially the negative of the antenna #1. This is because the first two elements are along x axis. So for a plane wave incoming from azimuth 0 and elevation 0, the wave travels along x axis. The two elements are approximately half wavelength, thus the phase shift between the two signal is given by exp(1i*pi), which is -1. So the signals are just opposite of each other.
Maybe you actually want an array in yz plane instead of xy plane?
HTH
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