Antenna Array Factor Null Steering

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?

[Honglei Chen]

Is there a particular algorithm you have in mind?

[Zain Shafiq]

I want to use the array factor and simply change the phase of each element in the array factor.

Answer 1

[Albert]

Have a look at this example:

https://es.mathworks.com/help/phased/examples/array-pattern-synthesis.html

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
wd = steervec(getElementPosition(ula)/lambda,thetaad);

% 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)