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I need a matlab code for two arm archimedian spiral.

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mkcool28

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I am designing a two arm archimedian spiral antenna and i need help in matlab code. In this matlab code i also want to include the specification of antenna like how many turns and how much wide etc. Can anybody please help me. Thanks in advance.
 

thylacine1975

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'morning mkcool28 - while it's not exactly what you're after, I created a MATLAB script some time ago to draw a *conical* spiral antenna in 3D. It might provide a starting point...



Code Python - [expand]
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% drawSpiral.m   JW 21 March 2011
%
% Plots the conical logarithmic spiral antenna corresponding to the set of
% characteristic antenna parameters.
 
alpha  = 50;   % [degrees] Conductor wrap angle
delta  = 76;   % [degrees] Width of conductor around a circular plane parallel to the base
theta0 = 7.5;  % [degrees] Half cone apex angle
minD   = 12;   % [mm] Minimum antenna diameter
maxD   = 100;  % [mm] Maximum antenna diameter
Hs     = 332;  % [mm] Vertical height of spiral 
 
fGap   = 1;    % [mm] Gap at feedpoint of antenna
 
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
% Convert angles to radians
alpha  = alpha*pi/180; 
theta0 = theta0*pi/180;
 
Hc = Hs + Hs*minD/(maxD-minD);        % Effective height of conical form
rho0 = sqrt((minD/2)^2 + (Hc-Hs)^2);  % Initial radius
b = sin(theta0)/tan(alpha);           % Spiral expansion factor
phiMax = tan(alpha)*log(maxD/minD)/sin(theta0); % Total rotation angle
 
figure;
hold on;
axis equal;
 
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% First spiral arm
 
for phi = 0:(phiMax*180/pi)            % Upper side of spiral
    
    rho = rho0*exp(b*pi*phi/180);
    planeR = rho * sin(theta0);
    xPos = planeR*cos(phi*pi/180);
    yPos = planeR*sin(phi*pi/180);
    zPos = cos(theta0)*(rho0-rho);
    
    plot3(xPos, yPos, zPos);
end
 
for phi = 0:delta                      % Inside top edge of spiral
    
    planeR = minD/2;
    xPos = planeR*cos(phi*pi/180);
    yPos = planeR*sin(phi*pi/180);
    zPos = 0;
    
    plot3(xPos, yPos, zPos);
end
 
for phi = delta:(delta+phiMax*180/pi)  % Lower side of spiral
    
    rho = rho0*exp(b*pi*(phi-delta)/180);
    planeR = rho * sin(theta0);
    xPos = planeR*cos(phi*pi/180);
    yPos = planeR*sin(phi*pi/180);
    zPos = cos(theta0)*(rho0-rho);
    
    plot3(xPos, yPos, zPos);
end
 
for phi = (phiMax*180/pi):(delta+phiMax*180/pi) % Outside bottom edge of spiral
    
    planeR = maxD/2;
    xPos = planeR*cos(phi*pi/180);
    yPos = planeR*sin(phi*pi/180);
    zPos = -Hs;
    
    plot3(xPos, yPos, zPos);
end
 
% Define tapered feed
 
feed1 = [minD/2 0 0; ... 
         fGap 0 0; ...
         fGap*cos(delta*pi/180) fGap*sin(delta*pi/180) 0; ...
         minD/2*cos(delta*pi/180) minD/2*sin(delta*pi/180) 0];
 
plot3(feed1(:,1), feed1(:,2), feed1(:,3));
     
 
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Second spiral arm
 
for phi = 180:(180+phiMax*180/pi)            % Upper side of spiral
    
    rho = rho0*exp(b*(pi*phi/180-pi));
    planeR = rho * sin(theta0);
    xPos = planeR*cos(phi*pi/180);
    yPos = planeR*sin(phi*pi/180);
    zPos = cos(theta0)*(rho0-rho);
    
    plot3(xPos, yPos, zPos, 'r');
end
 
for phi = 180:(delta+180)                    % Inside top edge of spiral
    
    planeR = minD/2;
    xPos = planeR*cos(phi*pi/180);
    yPos = planeR*sin(phi*pi/180);
    zPos = 0;
    
    plot3(xPos, yPos, zPos, 'r');
end
 
for phi = (180+delta):(delta+180+phiMax*180/pi)  % Lower side of spiral
    
    rho = rho0*exp(b*(pi*(phi-delta)/180-pi));
    planeR = rho * sin(theta0);
    xPos = planeR*cos(phi*pi/180);
    yPos = planeR*sin(phi*pi/180);
    zPos = cos(theta0)*(rho0-rho);
    
    plot3(xPos, yPos, zPos, 'r');
end
 
for phi = (180+phiMax*180/pi):(delta+180+phiMax*180/pi) % Outside bottom edge of spiral
    
    planeR = maxD/2;
    xPos = planeR*cos(phi*pi/180);
    yPos = planeR*sin(phi*pi/180);
    zPos = -Hs;
    
    plot3(xPos, yPos, zPos, 'r');
end
 
% Define tapered feed
 
plot3(-feed1(:,1), -feed1(:,2), -feed1(:,3), 'r');

 

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