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Horns are widely used antennas since they have
a simple construction, are easy to excite and have a large gain.
They are employed for example as feed elements in satellite tracking
systems or communication dishes and they serve as a standard
antenna for calibration and gain measurements. Since they have
a limited bandwidth, great efforts have been made to enlarge
the operational bandwidth. Ridges on the side flares are introduced
to extend the bandwidth, similar to the ridges in a waveguide
that lower the cut-off frequency. The design of double-ridged
horn antennas reaches back to the late 1950s. Figures 1
and 2 show a 3D view of the horn that we simulated.
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Fig.
1: Tilted front 3D view of the antenna model.
1: Feed
section, 2: Ridge, 3: Wedge, 4: Lower
flare, 5: Upper flare, 6: Copper
strap. |
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Fig.
2: Feeding section of the double-ridged horn
antenna. 1: Ridge,
2: Cavity, 3: Coaxial feed, 4: Source
plane, 5: Port plane. Wedges and other parts
are removed for better visualization. |
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The model is appropriate for the whole operational
frequency band from 1 GHz to 18 GHz, and it consists
of 4 831 165 tetrahedrons. The maximum volume ratio
of large cells to small cells is 125.
The propagation of the electric field is shown
at two different frequencies (ramped sinusoidal excitation) in
the following movies.
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Fig.
3: Magnitude of the electric near-field at
7 GHz. |
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Fig.
4: Magnitude of the electric near-field at 12 GHz. |
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Figures 5 to 8 show a comparison between measured
and simulated far-field patterns at selected frequencies. On
the LHS the E-plane patterns are shown and on the RHS the H-plane
patterns.
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Fig.
5: E-plane (LHS) and H-plane (RHS) radiation
pattern. Comparison between simulation and
measurement at 2 GHz. |
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Fig.
6: E-plane (LHS) and H-plane (RHS) radiation
pattern. Comparison between simulation and
measurement at 4 GHz. |
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Fig.
7: E-plane (LHS) and H-plane (RHS) radiation
pattern. Comparison between simulation and
measurement at 8 GHz. |
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Fig. 8: E-plane
(LHS) and H-plane (RHS) radiation pattern.
Comparison between simulation and measurement
at 12 GHz
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A three dimensional depiction of the logarithmic-scaled
far-field pattern is shown between 1 and 18 GHz in Fig. 9.
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Fig. 9: 3D
radiation pattern (logarithmic scale).
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Figure 10 depicts the simulated maximum
gain of the horn antenna. Also displayed is the measured and
simulated broadside gain. The reflection coefficient S11 is
taken into account in the computation of the antenna gain. A
deformation of the radiation pattern is apparent in the frequency
range of 10 GHz ≤ f ≤ 14
GHz and f ≥ 16 GHz, where the broadside
gain is much lower than the maximum gain. The 3D radiation patterns
in linear scale at five characteristic frequencies are displayed
beside.
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Fig. 10:
Simulated and measured antenna gain. The
3D radiation patterns are plotted in linear
scale.
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For further information refer to journal paper [2].
Please address questions and comments to the group members
or write an email. |
