# Antenna Array Factor Null Steering

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Zain Shafiq on 27 Apr 2020
Answered: Albert on 31 May 2020
Hi,
I am looking to steer the null using the antenna array factor. I can steer the sum already. I have been using the N-element linear array factor.
Could someone help in telling me how to control the position of the null?
##### 2 CommentsShowHide 1 older comment
Zain Shafiq on 28 Apr 2020
I want to use the array factor and simply change the phase of each element in the array factor.

Albert on 31 May 2020
Have a look at this example:
You can choose one direction and compute the steering vectors for each element. In essence, you can compute the steering vectors youself and just do the last part of the code
% steering vector for null direction
wn
% steering vectors for lookout direction
wd
% Compute the response of desired steering at null direction
rn = wn'*wd/(wn'*wn);
% Sidelobe canceler - remove the response at null direction
w = wd-wn*rn;
Full code:
c = 3e8; % signal propagation speed
fc = 1e9; % signal carrier frequency
lambda = c/fc; % wavelength
thetaad = -30:5:30; % look directions
thetaan = 40; % interference direction
ula = phased.ULA(10,lambda/2);
ula.Element.BackBaffled = true;
% Calculate the steering vector for null directions
wn = steervec(getElementPosition(ula)/lambda,thetaan);
% Calculate the steering vectors for lookout directions
% Compute the response of desired steering at null direction
rn = wn'*wd/(wn'*wn);
% Sidelobe canceler - remove the response at null direction
w = wd-wn*rn;
% Plot the pattern
pattern(ula,fc,-180:180,0,'PropagationSpeed',c,'Type','powerdb',...
'CoordinateSystem','rectangular','Weights',w);
hold on; legend off;
plot([40 40],[-100 0],'r--','LineWidth',2)
text(40.5,-5,'\leftarrow Interference Direction','Interpreter','tex',...
'Color','r','FontSize',10)

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