Design and Analysis of Diamond-Shaped PCB Antenna for Ultra-Wideband Applications

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This example shows how to create the diamond-shaped ultra-wideband (UWB) antenna described in [1] with a modified ground plane. It analyzes this antenna over an ultra-wide frequency range of 100 MHz to 15 GHz. UWB antennas are in high demand for various applications, such as wireless communications, medical imaging, radar, and indoor positioning. This demand is due to their ability to enable a high data transmission rate and low power consumption.

The planar diamond-shaped monopole antenna structure described in [1] achieves an ultra-wide bandwidth by using its features, such as its small size, ease of fabrication, low power consumption, and easy integration with the RF system. These features make the antenna a suitable candidate for use in compact devices.

In this example, you design the proposed antenna on a 1.6 mm FR4 substrate with a dielectric constant of 4.8 and loss tangent 0.026. This antenna consists of a diamond-shaped radiating patch, a modified feed line, and a semicircular ground plane. You then modify the conventional rectangular monopole antenna with beveled edges to form a diamond-shaped radiating patch.

Create Antenna Model

Define the ground plane length and width, board thickness, substrate, trace widths and lengths in meters.

% Ground plane dimensions
gndL = 32e-3;
gndW = 40e-3;

% Board thickness
h = 1.6e-3;
R_gnd = 15.6e-3;

% Substrate
sub = dielectric(Name="FR4",EpsilonR=4.8,Thickness=h,LossTangent=0.026);

% Trace widths
Wf = 3.1e-3;
Wf1 = 1.2e-3;
W3 = 13e-3;
W2 = 29e-3;
W1 = 22e-3;

% Trace lengths
Lf = 10e-3;
Lf1 = 6e-3;
L3 = 2e-3;
L2 = 11e-3;
L1 = 5e-3;

Create the top-layer diamond-shaped antenna by passing the parameters and vertices to the antenna.Polygon object.

xver = round([-Wf/2 -Wf/2 -Wf1/2 -W3/2 -W2/2 -W1/2 W1/2 W2/2 W3/2 Wf1/2 Wf/2 Wf/2],12);
yver = round( [-gndW/2 -gndW/2+Lf -gndW/2+Lf+Lf1 -gndW/2+Lf+Lf1+L3 -gndW/2+Lf+Lf1+L3+L2 ...
       -gndW/2+Lf+Lf1+L3+L2+L1 -gndW/2+Lf+Lf1+L3+L2+L1 -gndW/2+Lf+Lf1+L3+L2 ...
       -gndW/2+Lf+Lf1+L3 -gndW/2+Lf+Lf1 -gndW/2+Lf -gndW/2],12);
zver = zeros(1,size(yver,2));
ver = [xver',yver',zver'];
UWB_ant = antenna.Polygon(Vertices=ver);

Create the semicircular ground layer.

cir = antenna.Circle(Radius=R_gnd,Center=[0,-gndW/2]);
rec = antenna.Rectangle(Length=gndL+2e-3,Width=R_gnd,Center=[0,-gndW/2-R_gnd/2]);
rec1 = antenna.Rectangle(Length=0.5*R_gnd,Width=0.5*R_gnd,Center=[-gndL/2-(0.5*R_gnd)/2,-gndW/2+(0.5*R_gnd)/2]);
rec2 = antenna.Rectangle(Length=0.5*R_gnd,Width=0.5*R_gnd,Center=[gndL/2+(0.5*R_gnd)/2,-gndW/2+(0.5*R_gnd)/2]);
gnd = cir - (rec + rec1 + rec2);

Generate the UWB antenna model by using the pcbStack object with the assigned ground layer.

ant = pcbStack;
ant.BoardThickness = h;
ant.BoardShape = antenna.Rectangle(Length=gndL,Width=gndW);
ant.Layers = {UWB_ant,sub,gnd};
ant.FeedLocations = [0,-gndW/2,1,3];
ant.FeedDiameter = Wf/2;

View the antenna.

figure 
show(ant)
title("Diamond-Shaped Ultra-Wideband PCB Antenna")

Figure contains an axes object. The axes object with title Diamond-Shaped Ultra-Wideband PCB Antenna, xlabel x (mm), ylabel y (mm) contains 6 objects of type patch, surface. These objects represent PEC, feed, FR4.

Analyze S-parameters and Gain of Antenna

Mesh the structure using manual mesh mode with a maximum edge length of 0.004 m.

figure
mesh(ant,MaxEdgeLength=0.004,MinEdgeLength=0.0015);

Figure contains an axes object and an object of type uicontrol. The axes object with title Metal-Dielectric, xlabel x (m), ylabel y (m) contains 3 objects of type patch, surface. These objects represent PEC, feed.

Use the sparameters function to calculate the $S_{11}$ of the structure in the frequency range of 0.1 GHz to 15 GHz.

spar = sparameters(ant,linspace(0.1e9,15e9,70));
figure
rfplot(spar);

$Figure contains an axes object. The axes object with xlabel Frequency (GHz), ylabel Magnitude (dB) contains an object of type line. This object represents dB(S_{11}).$

The UWB diamond-shaped antenna exhibits a Passband behavior in the frequency range of 2.5 GHz to 13.5 GHz with a $S_{11}$ lower than -10 dB.

Analyze the radiation pattern of the Wideband antenna at 4 GHz, 8 GHz, and 13.5 GHz frequencies that are within the analysis range.

figure
pattern(ant,4e9,Type="gain");

Figure contains 2 axes objects and other objects of type uicontrol. Axes object 1 contains 6 objects of type patch, surface. This object represents FR4. Hidden axes object 2 contains 18 objects of type surface, line, text, patch. This object represents FR4.

figure
pattern(ant,8e9,Type="gain");

figure
pattern(ant,13.5e9,Type="gain");

The proposed antenna exhibits stable radiation characteristics.

Conclusion

The diamond-shaped antenna achieves the enhanced ultra-wide bandwidth, in which the UWB frequency spectrum covers the range from 3.1 GHz to 10.6 GHz, with stable radiation characteristics. Because the proposed antenna has good UWB characteristics and a compact size, it is suitable for wireless communications systems.

Reference

[1] Singhal, Sarthak, Tushar Goel, and Amit Kumar Singh. "Novel diamond shaped UWB monopole antenna." 2013 Annual IEEE India Conference (INDICON) (January 2014): 1-6. https://doi.org/10.1109/INDCON.2013.6726048.