Difference between revisions of "Application Note 5: Simulating The Performance Of Installed Antennas On Vehicular Platforms Using EM.Tempo"
Kazem Sabet (Talk | contribs) (→Examining the Radiation Pattern of an Isolated Patch Antenna) |
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[[EM.Cube]] provides a number of wizards for quick construction of patch antennas with different feed mechanisms: a probe feed, an edge-connected microstrip feed with or without a recess, and a slot-coupled open-ended microstrip feed. For this project, we consider a probe-fed square patch antenna with the following specifications: | [[EM.Cube]] provides a number of wizards for quick construction of patch antennas with different feed mechanisms: a probe feed, an edge-connected microstrip feed with or without a recess, and a slot-coupled open-ended microstrip feed. For this project, we consider a probe-fed square patch antenna with the following specifications: | ||
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! scope="col"| Parameter Name | ! scope="col"| Parameter Name | ||
! scope="col"| Value | ! scope="col"| Value | ||
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|- | |- | ||
| Substrate Height (h) | | Substrate Height (h) | ||
| 1.5mm | | 1.5mm | ||
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|- | |- | ||
| Substrate Relative Permittivity (ε<sub>r</sub>) | | Substrate Relative Permittivity (ε<sub>r</sub>) | ||
| 2.2 | | 2.2 | ||
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|- | |- | ||
| Patch Length | | Patch Length | ||
− | | | + | | 88.20mm |
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|- | |- | ||
| Feed Offset (from Center) | | Feed Offset (from Center) | ||
− | | | + | | 35.28mm |
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|- | |- | ||
− | | | + | | Substrate Size |
− | | | + | | 150mm |
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|} | |} | ||
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+ | <table> | ||
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+ | <td> | ||
+ | [[Image:Patch wizard raw.png|thumb|left|480px| The geometry setup for a rectangular microstrip patch antenna on a finite-sized substrate in EM.Tempo.]] | ||
+ | </td> | ||
+ | </tr> | ||
+ | </table> | ||
Revision as of 21:49, 18 October 2016
Contents
Introduction
In this application note, we demonstrate how to use EM.Tempo to compute and analyze the radiation pattern of a patch antenna installed on a vehicular platform. Specifically, the CAD model of a Volkswagen Golf automobile is first imported to EM.Cube. Then, a microstrip patch antenna with a finite-sized substrate is placed at different locations of the automobile's chassis.
Examining the Radiation Pattern of an Isolated Patch Antenna
EM.Cube provides a number of wizards for quick construction of patch antennas with different feed mechanisms: a probe feed, an edge-connected microstrip feed with or without a recess, and a slot-coupled open-ended microstrip feed. For this project, we consider a probe-fed square patch antenna with the following specifications:
Parameter Name | Value |
---|---|
Substrate Height (h) | 1.5mm |
Substrate Relative Permittivity (εr) | 2.2 |
Patch Length | 88.20mm |
Feed Offset (from Center) | 35.28mm |
Substrate Size | 150mm |
Computational Environment
The Mirage III CAD model has an approximate length of 15m, a wingspan of 8m, and an approximate height of 4.5m. Expressed in free-space wavelengths at 850 MHz, the approximate dimensions of the aircraft model are 42.5 λ0 x 22.66 λ0 x 12.75 λ0. Thus, for the purposes of EM.Tempo, we need to solve a region of about 12,279 cubic wavelengths. For problems of this size, a very large CPU memory is needed, and a high-performance, multi-core CPU is desirable to reduce the simulation time.
Amazon Web Services allows one to acquire high-performance compute instances on demand, and pay on a per-use basis. To be able to log into an Amazon instance via Remote Desktop Protocol (RDP), the EM.Cube license must allow terminal services. For the purpose of this project, we used a c4.4xlarge instance running Windows Server 2012. This instance has 30 GB of RAM memory, and 16 virtual CPU cores. The CPU for this instance is an Intel Xeon E5-2666 v3 (Haswell) processor.
Patch on Roof
Materials used in car model:
Material | Relevant Components
of Golf Model |
εr | σ |
---|---|---|---|
PEC | car body | 1 | ∞ |
Glass | car windows | 6.5 | 0.005 |
Plastic | head-light covers, brake-light covers,
license plate mounts |
2.2 | 0.0 |
Rubber | tires | 2.9 | 0.005 |
Aluminum | wheel-rims | 1 | 3800000 |
Cement | road | 1.9 | 0.0 |
Simulation Information:
Mesh size: 220 million cells
Farfield Resolution: 2.5 degrees
Simulation Time: 4 hours, 45 minutes
Typical Performance : 320 MCells/s
Power Threshold: -40 dB
Thread Factor: 8
The thread factor setting essentially tells the FDTD engine how many CPU threads to use during EM.Tempo's time-marching loop. For a given system, some experimentation may be needed to determine the best number of threads to use. In many cases, using half of the available hardware concurrency works well. This comes from the fact that many modern processors often have two cores per memory port. In other words, for many problems, the FDTD solver cannot load and store data from CPU memory quickly enough to use all the available threads or hardware concurrency. The extra threads remain idle waiting for the data, and a performance hit is incurred due to the increased thread context switching. EM.Cube will attempt use a version of the FDTD engine optimized for use with Intel's AVX instruction set, which provides a significant performance boost. If AVX is unavailable, a less optimal version of the engine will be used alternatively.
By default, EM.Tempo's mesher tries to place grid points at the corners of each graphic object's bounding box, and also at any internal boundaries the object may have. For models with a large number of complex objects, this can drive the typical mesh cell size toward the Absolute Minimum Grid Spacing, and result in a much finer mesh than is required. Since the VW Golf model has around 2000 graphic objects, we will turn off these options.
Patch on Hood
Simulation Information:
Mesh size: 230 million cells
Farfield Resolution: 2.5 degrees
Simulation Time: 5 hours, 25 minutes
Typical Performance : 320 MCells/s
Power Threshold: -40 dB
Thread Factor: 8