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Examples:
Helix antenna over circular ground plane
Simulation of an axial mode helix antenna over a circular ground plane. The helix is fed at its base by a straight wire with a voltage source operating at 100 MHz. The ground plane is 1 wavelength in diameter. The helix input parameters are:
Helix input data:
Geometrical Properties:
Start point: (477, 0, 300) mm
Radius: 477 mm
Pitch: 692 mm
Number of turns: 8
Orientation: Theta = 0º, Phi = 0º
Rotation angle around helix axis: 0º
Cross-section: Circular: radius = 5 mm
Electrical Properties:
Segment length / lambda: 0.1
Number of segments: 80
Resistivity: 0 Ohm/m
Number of sources: 0
Output data:
Input impedance: 240+ j 74.7 Ohm
Radiated Power: 1.9 mW
Maximum power density: 1.63 mW/m² (normalized to 1 m)
Average power density: 0.15 mW/m² (normalized to 1 m)
Directivity: 10.3 dB
Current Along The Helix
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3D Radiation Pattern
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2D Field Pattern
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Antenna with grid reflector
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Simulation of an antenna with a low-windload grid reflector. The reflector size is about 2 x 1 meters and it has the shape of a parabolic cylinder. The operating frequency is 350 MHz. The total number of unknown currents is 220.
Output data:
Input impedance: 39.6 + j 16.2 Ohm
Radiated Power: 10.9 mW
Maximum power density: 9.06 mW/m² (normalized to 1 m)
Average power density: 0.866 mW/m² (normalized to 1 m)
Directivity: 10.2 dB
3D Radiation Pattern
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2D Field Pattern - Polar
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2D Field Pattern - Rectangular
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Characteristic impedance of a transmission line
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The line is 500 mm long and is located at 40 mm over a PEC ground plane. The
cross-section of the line is circular with 2 mm in radius. The line is excited
with an 1 V voltage generator. The simulation is performed at 100 MHz and the
conductor is divided into 9 segments. The line is first short-circuited and
its input impedance is obtained; next the input impedance of the open-circuited
line is computed.
The relation for the characteristic impedance of a line above a ground plane
is given by:
where a is the cross-section radius and h is the height above the ground plane.
On the other hand, the input impedances obtained in the simulation are:
Zin (short-circuited line) = j 503 Ohm
Zin (open-circuited line) = -j 107 Ohm
The characteristic impedance is then given by:
As can be seen from these results, the agreement is quite good.
Crosstalk between two parallel
lines
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The lines are 160 mm long and are terminated to a common ground plane. They are flat and 2 mm wide. The height over the ground plane is 2 mm. One of the lines is excited with an 1 V voltage source and the other ends of both lines are terminated with 1 KOhm resistors. The current through the Rc resistor is plotted vs. frequency. Each line has 6 segments.
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RLC circuit
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An RLC circuit with R = 10 Ohm, L = 20 mH and C = 2 uF is simulated by a circular
loop with 6 cm in diameter and fed by an 1 V voltage source. The loop is divided
into 7 segments and the computation is performed at the frequencies 600, 610,
..., 1000 Hz.
Resonance is obtained at the frequency:
that can be verified in the following "current vs. frequency" plot:
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