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2.1 KiB
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54 行
2.1 KiB
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Numerical comparisons
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This section presents comparisons of models using different numerical modelling techniques.
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FDTD/MoM
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========
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The Finite-Difference Time-Domain (FDTD) method from gprMax is compared with the Method of Moments (MoM) from the `MATLAB antenna toolbox <http://uk.mathworks.com/products/antenna/>`_.
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Bowtie antenna in free space
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----------------------------
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This example considers the input impedance of a planar bowtie antenna in free space. The length and height of the bowtie are 100mm, giving a flare angle of :math:`90^\circ`.
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FDTD model
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^^^^^^^^^^
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:download:`antenna_bowtie_fs.in <../../tests/other_codes/vs_MoM_MATLAB/antenna_bowtie_fs/antenna_bowtie_fs.in>`
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.. literalinclude:: ../../tests/other_codes/vs_MoM_MATLAB/antenna_bowtie_fs/antenna_bowtie_fs.in
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:language: none
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:linenos:
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A Gaussian waveform with a centre frequency of 1.5GHz was used to excite the antenna, which was fed by a transmission line with a characteristic impedance of 50 Ohms.
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The module ``plot_antenna_params`` from the ``tools`` subpackage was used to calculate and plot the input impedance from the FDTD model.
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MoM model
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^^^^^^^^^
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The bowtie antenna was created using the antenna toolbox in MATLAB, and the ``bowtieTriangular`` class.
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.. code-block:: matlab
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bowtie = bowtieTriangular('Length', 0.1)
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zin = impedance(bowtie, 33.33e6:33.33e6:6e9)
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Results
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-------
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:numref:`antenna_bowtie_fs_ant_params` shows the input impedance (resistive and reactive) for the FDTD (gprMax) and MoM (MATLAB) models. The frequency resolution for the FFT used in both models was :math:`\Delta f = 33.33~MHz`.
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.. _antenna_bowtie_fs_ant_params:
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.. figure:: ../../tests/other_codes/vs_MoM_MATLAB/antenna_bowtie_fs/antenna_bowtie_fs_ant_params.png
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:width: 600 px
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Input impedance (resistive and reactive) of a bowtie antenna in free space using FDTD (gprMax) and MoM (MATLAB) models.
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The results from the FDTD and MoM modelling techniques are in very good agreement. The biggest mismatch occurs in the resistive part of the input impedance at frequencies above 3GHz.
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