This Matlab project demonstrates the technique of the usage of a image of a planar antenna to generate a feasible antenna version and its next analysis for port, surface and subject characteristics. The Image Segmenter app might be used to carry out segmentation on the image of an RFID tag, and the resulting barriers can be used to installation the antenna version in Antenna Toolbox™. An initial impedance evaluation could be achieved over a frequency range to understand the port traits of the antenna. After determining the resonance frequency, the cutting-edge and far-discipline pattern might be calculated and plotted.
Image Segmentation Using Image Segmenter App
Choose Foreground and Background
Using the app, import this antenna and choose the graph reduce choice at the toolstrip. Pick the foreground and historical past regions on the photo. For this case, the foreground location is the metallized regions of the RFID tag and the background is the coloured location.
Export Code and Boundary
The shade based segmentation system yields the masks of the antenna photograph. Use the export alternative on the app, to acquire a function and the boundary information that may then be utilized in a script for in addition processing (consisting of this one).
Analyzing the Heuristic Solution
We begin by performing an impedance analysis to determine the port characteristics of the antenna over a coarsely sampled frequency range. To do so, use the impedance function with a pair of inputs, namely the antenna and the frequency. The RFID tag is expected to operate in the UHF band, between 800 and 900 MHz. The analysis frequency range will extend slightly beyond 900 MHz. Any analysis will result in an automatic meshing of the geometry at the highest frequency chosen in the range. This mesh is then passed into the solver, which identifies the feed location and the corresponding feeding edge to apply a 1V excitation. The interaction matrix between the RWG basis functions (pairs of triangles) is calculated and the unknowns in the form of the currents on the surface are solved for.
f_coarse = linspace(0.8e9,0.95e9,21);
figure
impedance(p, f_coarse)
2D RFID Antenna Design
Designing Short Range Rader system
Calculate Boundaries in Cartesian Space
For performing complete-wave evaluation in this shape the subsequent step is to transform the pixel area illustration of the boundary to a cartesian area representation. To try this we extract the maximum and minimum pixel indices in the x, y dimensions and scale it based totally on average tag dimensions in phrases of its duration and width.
//Code
B = bwboundaries(BWf);
xmax = max(B{1}(:,1));
xmin = min(B{1}(:,1));
ymax = max(B{1}(:,2));
ymin = min(B{1}(:,2));
% Scale per pixel based on tag dimensions
L = 18.61e-3;
W = 72.27e-3;
LperColpixel = L/(xmax-xmin);
WperRowpixel = W/(ymax-ymin);
Bp = B;
for i = 1:length(Bp)
Bp{i} = [Bp{i}(:,1).LperColpixel Bp{i}(:,2).WperRowpixel zeros(size(Bp{i},1),1)];
end
p = cell2mat(Bp);
x = p(:,1);
y = p(:,2);
figure
plot(x,y,’*’)
grid on
axis equal
xlabel(‘x (m)’)
ylabel(‘y (m)’)
title(‘Boundary points’)
Reduce Boundary Points
The boundary has 28000 points, and this can result in a very big mesh length. Down sample this boundary through a thing of 39. The down sample thing become selected because it nevertheless represented the boundary details correctly primarily based on a simple visual inspection.
D = 39;
xD = x(1:D:end);
yD = y(1:D:end);
BpD{1} = Bp{1}(1:D:end,:);
figure
hold on
plot(xD,yD,’r*’)
shg
grid on
axis equal
Designing 3D drawing for analyzing the electrical behavior
Creating the Antenna Feed
The feed area of the tag nevertheless has a few sharp artifacts within the boundary. This have to be wiped clean up previous to defining the feed. We use a boolean subtract operation to cast off this artifact.
sf1 = antenna.Rectangle(‘Length’, 5e-3, ‘Width’, 2e-3, …
‘Center’, [0.019 0.0392]);
c.Boundary = [BpD(1) {getShapeVertices(sf1)}];
c.Operation = ‘P1-P2’;
figure
show(c)
view(0,90)
Port Analysis – Impedance Behavior vs. Frequency
Determine the port traits of this antenna with the aid of executing an impedance evaluation over a rough sampled frequency range. The tag is predicted to operate inside the UHF band, among 800 – 900 MHz. Our frequency variety will enlarge barely beyond 900 MHz.
Field Analysis – Pattern at Center Frequency
RFID tags typically have an omnidirectional far-field pattern in one plane. Visualize the far-field radiation pattern of the tag.
figure
pattern(c,854e6)
Conclusion
A procedure for identifying the antenna boundary from a picture, conversion into a geometric model of the antenna and its subsequent full-wave analysis has been precise in this case. These steps are graphically depicted as proven: