ISM Band Patch Microstrip Antennas and Mutually Coupled Patches

Define Parameters

All these microstrip antennas consisting of PCB with 6.6 mm thickness with dielectric constant EpsilionR 4.2, and loss-tangent of 0.02, and square ground plane of 100 mm-by-100 mm, fed by 1.3 mm diameter coaxial probe, are designed to comply with the ISM band (2.4 - 2.5 GHz).

LGp = 100e-3;       % Ground plane length
WGp = 100e-3;       % Ground plane width
h = 6.6e-3;         % Height of the substrate

Define Parameters of Elliptical Patch Antenna

Design a probe feed patchMicrostripElliptical antenna using a dimension of 33.5 mm major axis, 18.8 mm minor axis. The feed is offset by 11.6 mm from the origin along the X-axis.

a = 33.5e-3;        % Major Axis       
b = 18.8e-3;        % Minor Axis
f = 11.6e-3;        % Feed Offset     
d = dielectric(EpsilonR=4.2,LossTangent=0.02);

Create a patchMicrostripElliptical antenna using the defined parameters.

p_Ellipse = patchMicrostripElliptical(MajorAxis=a,MinorAxis=b,...
    Height=h,Substrate=d,GroundPlaneLength=LGp,...
    GroundPlaneWidth=WGp,FeedOffset=[-(a/2-f) 0]);
figure
show(p_Ellipse)

Define Parameters of Circular Patch Antenna

Design a probe feed patchMicrostripCircular antenna using a dimension of 16 mm Radius. The feed is offset by 9.25 mm from the origin along the X-axis.

r = 16e-3;          % Radius  
f1 = 9.25e-3;       % Feed Offset

Create a patchMicrostripCircular antenna using the defined parameters.

p_Circle = patchMicrostripCircular(Radius=r,Height=h,Substrate=d,...
    GroundPlaneLength=LGp,GroundPlaneWidth=WGp,FeedOffset=[-(r-f1) 0]);
figure
show(p_Circle)

Define Parameters of Rectangular Patch Antenna

Design a probe-fed rectangular patchMicrostrip antenna using a dimension of 28.20 mm length, 34.06 mm width. The feed is offset by 5.3 mm from the origin along the X-axis.

rect1 = 28.20e-3;  % length    
rect2 = 34.06e-3;  % width   
f2 = 5.3e-3;       % feedoffset

Create a patchMicrostrip rectangular antenna using the defined parameters.

p_rect = patchMicrostrip(Length=rect1,Width=rect2,Height=h,Substrate=d,...
    GroundPlaneLength=LGp,GroundPlaneWidth=WGp,...
    FeedOffset=[-(rect1/2-f2) 0]);
figure
show(p_rect)

Define Parameters of Triangular Patch Antenna

Design an equilateral patchMicrostripTriangular antenna using a dimension of 37.63 mm side. The feed is offset by 3.8 mm from the origin along the Y-axis.

side = 37.63e-3;    
f_off = 3.8e-3;     
p_triang = patchMicrostripTriangular(Side=side,Height=h,Substrate=d,...
    GroundPlaneLength=LGp,GroundPlaneWidth=WGp,...
    FeedOffset=[0 -side/2+f_off]);  
figure
show(p_triang)

Visualize Reflection Coefficient Magnitude of Patches

Plot the reflection coefficient for these antennas over the band and a reference impedance of 50 ohms. Curves for the reflection coefficient magnitude are shown in the below figure. Manually mesh of patch antennas with different edge lengths.

Visualize Radiation Pattern

The directivity of the antennas are around 6.37 dB for Elliptical patch, 7 dB for circular patch, 7.37 dB for rectangular patch and 6.16 dB for triangular patch.

Mutually Coupling Between Rectangular and Triangular Patches

This section is devoted to the study of cases, focusing on configurations with the lowest mutual couplings. The relative displacement 'd' is fixed as lambda/2, two patches placed side-by-side configuration and the patches positioned in the center of the rectangular 160 mm x 100 mm ground plane with a substrate of FR4.

LGp1 = 160e-3;       % Ground plane length
WGp1 = 100e-3;       % Ground plane width
Ground_plane1 = antenna.Rectangle(Length=LGp1,Width=WGp1); % Ground plane
dis = 0.0612;        % distance between two patches (d = lambda/2)

Create a patchMicrostrip rectangular antenna using the defined parameters.

r_ant = pcbStack(p_rect);
rect_p = r_ant.Layers{1};
rect_p.Center = [-dis/2 0];

Create a patchMicrostripTriangular antenna using the defined parameters.

t_ant = pcbStack(p_triang);
triangle_p = t_ant.Layers{1};
triangle_p = rotateZ(triangle_p,180);
triangle_p = translate(triangle_p,[dis/2, 0, 0]);
patch = rect_p + triangle_p; % adding patches

Define PCB Stack

Use the pcbStack to define the metal and dielectric layers for mutually coupled patch antenna. the top-most layer is a patch layer, the second layer is dielectric layer, and the third layer is the ground plane.

p_mc = pcbStack;
d4 = dielectric(EpsilonR=4.2,Thickness=h,LossTangent=0.02);
p_mc.BoardThickness = d4.Thickness;
p_mc.BoardShape.Length = LGp1;
p_mc.BoardShape.Width = WGp1;
p_mc.Layers = {patch,d4,Ground_plane1};
p_mc.FeedLocations = [-dis/2 -(rect1/2-f2) 1 3; dis/2 -5.3075e-3 1 3];
p_mc.FeedDiameter = 1.3e-3;
figure
show(p_mc)

Radiation Pattern of Mutually Coupled Patches

The side-by-side configuration directivity is 7.4 dB

figure
pattern(p_mc,2.45e9);

Pattern Magnitude

figure
[fm,~,t10] = pattern(p_mc,2.45e9,0,0:360); 
polarpattern(t10,fm);

Reference

[1] Nascimento, D.C., and J.C. Da S. Lacava. “Design of Arrays of Linearly Polarized Patch Antennas on an FR4 Substrate: Design of a Probe-Fed Electrically Equivalent Microstrip Radiator.” IEEE Antennas and Propagation Magazine 57, no. 4 (August 2015): 12–22. https://doi.org/10.1109/MAP.2015.2453916.