Due to their inherent versatility and wideband frequency response, spiral slot antennas have a variety of applications for different microwave frequency bands. For example, these antennas are used for wireless communication, sensing, positioning, and tracking. To optimize the design of spiral slot antennas, engineers can use electromagnetics analysis to accurately calculate characteristics such as S-parameters and far-field patterns.
The Benefits of Spiral Slot Antennas
Spiral slot antennas have several advantages, including:
The slot object is a rectangular slot antenna on a ground plane. Toggle Main Navigation. このリンクは、Web ブラウザーでは動作しません。MATLAB コマンド ウィンドウに以下を入力すると、このコマンドを実行できます。. The slot object is a rectangular slot antenna on a ground plane. The default slot has its first resonance at 130 MHz.
- Nearly perfect circularly polarized radiation
- A wideband frequency response
- The ability to maintain a consistent radiation pattern and impedance over a large bandwidth
In addition, the design of spiral slot antennas allows them to be conformally mounted on a variety of objects. This is useful in, for example, the defense industry, where spiral slot antennas can be mounted on military automobiles and aircraft and used for communication and surveillance purposes. Foxwoods online casino promo codes.
Example of a spiral antenna. Image by Bin im Garten — Own work. Licensed under CC BY-SA 3.0, via Wikimedia Commons.
While there are multiple types of spiral antennas, one of the most common is the Archimedean spiral antenna. Here, we discuss modeling this antenna with the COMSOL Multiphysics® software and add-on RF Module.
Evaluating the Design of a Spiral Slot Antenna with COMSOL Multiphysics®
Let’s start by examining the geometry of the spiral slot antenna, which consists of a two-arm Archimedean spiral slot. We use parametric curves to create the spiral pattern on a single-sided metal substrate. The parametric curves provide the freedom to draw an arbitrary line shape by using a mathematical formulation. The substrate is a perfect electric conductor (PEC) with a very high conductivity and negligible losses on the surface. At the center of the spiral slot is a lumped port, which is used to excite the antenna.
Spiral slot antenna geometry (left) and mesh (right).
The antenna and substrate are surrounded by an air region and perfectly matched layer (PML), the latter of which is depicted in gray in the left image above. The physics-controlled mesh, which is shown in the right image above, is generated by default. Here, the maximum mesh size is set to 0.2 wavelengths, which is based on the maximum frequency defined in a Frequency Domain study step. The mesh is also automatically scaled by material properties such as the permittivity and permeability inside the dielectric substrate. The PML is swept with five elements along the radial direction.
Examining the Results of the Electromagnetics Simulation
The first plot looks at the electric field norm at the antenna’s top surface. This plot shows more intense electric fields along the slot than over the rest of the antenna surface, confirming that the fields are well confined to the slotted substrate.
Next, we examine a plot of the calculated S-parameters. From the results, we determine that over the studied frequency range, S11 is around -10 dB.
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The log-scaled electric field norm on the xy-plane (left) and an S-parameter plot (right).
To perform a far-field analysis, we first create a 2D polar plot. This plot enables us to visualize the bidirectional radiation patterns of the antenna at different frequencies. We see that the shape of the radiation pattern remains similar for different frequencies.
Polar plot on the yz-plane.
Finally, we examine the bidirectional far-field radiation pattern in 3D at a frequency of interest (3 GHz in this case). The results suggest that the direction of maximum radiation is along the z-axis. In addition, we see a symmetric pattern in the far field.
The 3D far-field radiation pattern of the antenna at 3 GHz (left) along with the antenna (right).
Next Steps
To get started with modeling spiral slot antennas, click the button below. Doing so will take you to the Application Gallery, where you can log into your COMSOL Access account and download the MPH-file and step-by-step instructions for the example.
Learn More About Modeling Antennas
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TAGS
Slot length, specified as a scalar in meters.
Example: 'Length',2
Data Types: double
Slot width, specified a scalar in meters.
Example: 'Width',0.02
Data Types: double
SlotCenter
— Slot antenna center
[0 0 0]
(default) | three-element vector in Cartesian coordinates
Slot antenna center, specified as a three-element vector in Cartesian coordinates.
Example: 'SlotCenter',[8 0 0]
Data Types: double
GroundPlaneLength
— Ground plane length
1.5000 (default) | scalar
Ground plane length, specified as a scalar in meters. By default, the length is measured along the x-axis.
Free Matlab Codes
Example: 'GroundPlaneLength',3
Data Types: double
GroundPlaneWidth
— Ground plane width
1.5000 (default) | scalar
Ground plane width, specified as a scalar in meters. By default, the width is measured along the y-axis.
Example: 'GroundPlaneWidth',4
Data Types: double
FeedOffset
— Distance from center along x-axis
0 (default) | scalar
Distance from center along x-axis, specified as a scalar in meters. Offset from slot center is measured along the length.
Example: 'FeedOffset',3
Data Types: double
Load
— Lumped elements
[1x1 LumpedElement] (default) | lumped element object handle
Lumped elements added to the antenna feed, specified as a lumped element object handle. For more information, see lumpedElement
.
Example: 'Load',lumpedelement
. lumpedelement
is the object handle for the load created using lumpedElement
.
Matlab Antenna Array
Example: s.Load = lumpedElement('Impedance',75)
Tilt
— Tilt angle of antenna
0
(default) | scalar | vector
Tilt angle of the antenna, specified as a scalar or vector with each element unit in degrees. For more information, see Rotate Antennas and Arrays.
Example: 'Tilt',90
Example: 'Tilt',[90 90]
,'TiltAxis',[0 1 0;0 1 1]
tilts the antenna at 90 degree about two axes, defined by vectors.
Data Types: double
TiltAxis
— Tilt axis of antenna
[1 0 0]
(default) | three-element vector of Cartesian coordinates | two three-element vectors of Cartesian coordinates | 'X'
| 'Y'
| 'Z'
Tilt axis of the antenna, specified as:
Three-element vectors of Cartesian coordinates in meters. In this case, each vector starts at the origin and lies along the specified points on the X-, Y-, and Z-axes.
Two points in space, each specified as three-element vectors of Cartesian coordinates. In this case, the antenna rotates around the line joining the two points in space.
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A string input describing simple rotations around one of the principal axes, 'X', 'Y', or 'Z'.
For more information, see Rotate Antennas and Arrays.
Example: 'TiltAxis',[0 1 0]
Example: 'TiltAxis',[0 0 0;0 1 0]
Example: ant.TiltAxis = 'Z'