How do you define the circular mesh feed point on a cylindrical dipole built from primary shapes?

How do you define the circular mesh feedpoint on a cylindrical dipole built from shapes similar to the "Design And Analyze Spherically Capped Biconical Antenna" example. Want to analyze a tubular dipole with end caps extending over the tubes and cannot define a feed point properly like the standard tubular dipole in the Antenna Toolbox.

The feed point affects the radiation pattern and I am too new to Matlab to fix it. Help?

[Barry]

Here is the code for it:

tubeRadius = 0.0075;

tubeHeight = 0.080;

discRadius = 0.030;

feedHeight1 = 1.0e-3;

feedWidth1 = tubeRadius*2;

feedDia1 = feedWidth1;

freq = linspace(0.7e9,1e9,30);

tube1 = shape.Cylinder(Cap=[0 0],Height=tubeHeight,Radius=tubeRadius);

translate(tube1,[0 0 tubeHeight/2+feedHeight1/2]);

%show(tube1);

%figure;

feed1 = shape.Cylinder(Cap=[0 0],Height=feedHeight1/2,Radius=feedDia1/2, Color= "r");

feed1 = translate(feed1,[0 0 feedHeight1/4]);

%show(feed1);

%figure;

TubeNfeed1 = add(feed1,tube1);

%show(TubeNfeed1);

%figure;

disc1 = shape.Circle(Radius=discRadius);

disc1 =translate(disc1,[0,0,tubeHeight+feedHeight1/2]);

%show(disc1);

capShape1 = add(TubeNfeed1,disc1);

%show(capShape1);

%figure;

capShape1Copy = copy(capShape1);

[~] = rotate(capShape1Copy,180,[0 0 0],[0 1 0]);

antShape1 = add(capShape1,capShape1Copy,RetainShape=false);

show(antShape1);

ant1 = customAntenna(Shape=antShape1);

%[~] = createFeed(_, FeedShape=shape.Cylinder("Radius",feedDia1/2));

feed = createFeed(ant1,[feedDia1/2 feedDia1/2 0],1);

show(ant1)

%figure;

pattern(ant1,868e6)

Answer 1

[Suraj Kumar]

Hi Barry,

From what I gather, you want to set up a circular mesh feed point on a cylindrical dipole antenna constructed from fundamental shapes and ensure proper visualization.

Follow the steps below along with the attached code snippet:

1. Ensure proper translation and positioning of the tube and feed by centering the tube around the origin and placing the feed point correctly at the dipole's center. 

tube1 = shape.Cylinder('Cap', [0 0], 'Height', tubeHeight,  'Radius', tubeRadius);
translate(tube1, [0 0 tubeHeight / 2 + feedHeight1 / 2]);
feed1 = shape.Cylinder('Cap', [0 0], 'Height', feedHeight1 / 2, 'Radius', feedDia1 / 2, 'Color', 'r');
translate(feed1, [0 0 feedHeight1 / 4]);

2. Accurately combine the tube, feed, and disc to form one half of the dipole and then mirror this combination to create the other half.

TubeNfeed1 = add(feed1, tube1);
disc1 = shape.Circle('Radius', discRadius);
translate(disc1, [0 0 tubeHeight + feedHeight1 / 2]);
capShape1 = add(TubeNfeed1, disc1);
capShape1Copy = copy(capShape1);
rotate(capShape1Copy, 180, [0 0 0], [0 1 0]);
% Combine both halves to form the full dipole
antShape1 = add(capShape1, capShape1Copy, 'RetainShape',  false);

3. Next, set the feed point at the dipole's center with the ‘createFeed’ function, and include the show and pattern functions to validate the antenna geometry and its radiation pattern.

ant1 = customAntenna('Shape', antShape1);
% Define the feed point at the center of the dipole
feed = createFeed(ant1, [0 0 0], 1);
show(ant1);
pattern(ant1, 868e6);

Refer to the output provided below for better understanding:

For further details, kindly refer to the documentation links below:

• 'translate' function: https://www.mathworks.com/help/rfpcb/ref/translate.html
• 'createFeed' function: https://www.mathworks.com/help/antenna/ref/customarraymesh.createfeed.html

I hope this works for you!

[Barry]

Thank you very much Suraj, this is truly a learning experience and aiding my understanding a lot.One gets stuck in a simple example if it does not do the expected, and it is difficult to make that transition just reading the manual if it does not cover your understanding of the subject.

Thanks for the time spent helping me, it built a bridge.

[Suraj Kumar]

No problem at all! Glad I could assist.

Answer 2

[Chen Wu]

Hi Suraj

I copied your code (see following), but cannot get your 3D result. I am using 2025a.

Please check

thanks

Chen

tubeRadius = 0.0075;

tubeHeight = 0.080;

discRadius = 0.030;

feedHeight1 = 1.0e-3;

feedWidth1 = tubeRadius*2;

feedDia1 = feedWidth1;

freq = linspace(0.7e9,1e9,30);

tube1 = shape.Cylinder('Cap', [0 0], 'Height', tubeHeight, 'Radius', tubeRadius);

translate(tube1, [0 0 tubeHeight / 2 + feedHeight1 / 2]);

feed1 = shape.Cylinder('Cap', [0 0], 'Height', feedHeight1 / 2, 'Radius', feedDia1 / 2, 'Color', 'r');

translate(feed1, [0 0 feedHeight1 / 4]);

TubeNfeed1 = add(feed1, tube1);

disc1 = shape.Circle('Radius', discRadius);

translate(disc1, [0 0 tubeHeight + feedHeight1 / 2]);

capShape1 = add(TubeNfeed1, disc1);

capShape1Copy = copy(capShape1);

rotate(capShape1Copy, 180, [0 0 0], [0 1 0]);

% Combine both halves to form the full dipole

antShape1 = add(capShape1, capShape1Copy, 'RetainShape', false);

ant1 = customAntenna('Shape', antShape1);

% Define the feed point at the center of the dipole

feed = createFeed(ant1, [0 0 0], 1);

show(ant1);

pattern(ant1, 868e6);