The emission from a monopole over circular ground plane applied TEM mode via coaxial transmission line is simulated with Electro Magnetica v.1.5.0..
The key features of this model are:
- TEM mode stimulation in coaxial transmission line,
- Signal separation of input/output signals for S parameter calculation
- Attenuator algorithm (ABC) outgoing from coaxial transmission line.
EM v.1.5.0 is now added these features.
A monopole antenna is taken as a demonstration in this case.
The antenna is directed into z-axis (Green axis), the circular ground plane is aligned on x-axis (Red) and y-axis (Yellow). You can not see the antenna rod hidden with z-axis, the rod is the centre pin of the coaxial transmission line and the length of the rod is 0.1 meter.
The port of TEM mode is specified by the red opaque circle in the 3D view (right figure). The EM simulator calculates the mode and field distribution and apply the TEM mode in the transmission line and the outgoing field also calculated and attenuate to evaluate S11 parameter precisely.
To evaluate S parameters "voltage" should be defined. We adopt the generalized voltage introduced by Gwarek. Our case described here, the mode is TEM so we can define the conventional voltage but we adopt the generalized voltage for future applications.
The above movie shows the time variation of the isosurface of the power of the electric field applied an impulsive Gaussian signal of TEM mode. You can see the signal is applied in the input port and conducted to the monopole antenna, radiated, and attenuate the reflected signal in the coaxial transmission line.
The left-bottom figure shows S11 obtained by the EM. The length of the rod of the monopole antenna is 0.1meter so it indicates λ/4=0.75Ghz, 3λ/4 = 2.25GHz. The right figures shows the RCS in z-x plane
 coaxial_antenna_2.em3 | [Description file for EM] | 2 kB |
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