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Microstrip antennas are used in
applications where size, weight, cost and ease of installation are
required. These antennas are low-profile and conformable to both planar
and non-planar surfaces. Antenna characteristics are also dependent of
dielectric parameters. Antenna arrays are used in order to achieve
higher gain. The larger number of antenna elements, the better gain of
antenna array is achieved. Antenna arrays are more demanding for EM
simulation than single element antennas due to their electrical size.
A model of a microstrip patch array is simulated in WIPL-D Pro (Fig. 1).
Analyzed microstrip array consists of 144 elements. A single element is
shown in Fig. 2. The feeding lines are also modeled. This antennas
intended application is in anti-collision radars.
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Figure 1. Quarter of microstrip
patch array |
Figure 2. Element of microstrip
array |
We will focus on only one parameter to
illustrate the electrical size of the array:
• length of quarter model of antenna (AntQLen)
The width of entire the array is approximately four times less than
length.
WIPL-D Simulation
In WIPL-D Pro antenna arrays can be designed using convenient built in
features. One can use Copy and Move manipulations to build just the
basic array element and then easily extend it into an array. Also,
(Anti-) Symmetry feature can be used to diminish memory requirements and
simulation time, so in this case only a quarter of given antenna is
needed (Fig. 1). Metallic parts are considered to be perfectly
conducting.
Operating frequency is 24.2 GHz, which means that free space wavelength
is 12.4 mm. Dielectric parameters are:
•
•
For parameters given in Tab. 1, we will calculate gain. The array is
about 18 λ by 4.5 λ at this operating frequency. Computer used for these
calculations has two Intel® Core™2 Quad CPUs (8 cores in total) and 24
GB of RAM.
Radiation pattern in 3D is shown in Fig. 3 and its phi cut, where phi=0,
is shown in Fig. 4. Please note that the theta angle is measured with
respect to the xOy plane. Number of unknowns, memory requirements, and
simulation time are given in Tab. 2.
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Figure 3. Radiation pattern with
antenna array |
Figure 4. Radiation pattern,
phi-cut |
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Table 1. Parameter of analysis
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Table 2. Analysis characteristics
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Model |
No. of unknowns (memory [GB]) |
Time @ 24.2 GHz [min] |
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quarter |
23705 (4.5) |
20.2 |
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Conclusion
We saw that usage of WIPL-D Pro advanced features such as Symmetry and
Copy/Move enables easy modeling of structure and simulation using only a
quarter of structure, which is very important for simulation of complex
or electrically large structures. This paper demonstrates that WIPL-D
Pro is successfully used in simulation of large printed arrays, taking
into account all the couplings between arrays elements. The model is
simulated completely realistically (finite size), whereas many other
competitor tools would require approximating this array as infinite
(applying periodic boundary conditions) or simulating it
element-by-element (neglecting coupling between elements).
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