Adaptive Frequency Sampling (AFS)
- Adaptive Frequency Sampling (AFS)
FEKO uses rational fitting functions to model and interpolate the parameters of interest, for example the input impedance, S-parameters, currents, far- and near-fields, etc. The adaptive frequency sampling (AFS) technique automatically selects the sample points, enabling fast and accurate solutions without any prior knowledge of the parameter of interest. The response is sampled more densely where needed, for example at resonances, to ensure that important details are included. This will result in run-time savings over discrete frequency sampling.
Shielded Box with slot and
monopole antenna inside.
The excitation is a plane wave propagating in the negative z-direction, polarised in the y-direction, with amplitude 1V/m. The current induced in the base of the monopole antenna is computed from 10 MHz to 1.5 GHz. To accurately capture the sharp resonance behaviour of the current over the entire band, a discrete frequency sweep required 1500 points. In contrast, AFS only required 39 sample points.
AFS requires only 39 frequency sampling points to model
the behaviour over the whole band.
The structure has both a normal mode monopole resonance and a high-Q transmission line mode resonance. AFS uses only 9 adaptive frequency samples to produce very accurate results for the input admittance over the entire frequency band (Virga et. al. ).
Example 2: Only 9 AFS samples are used to determine the input admittance of a forked monopole.  Kathleen L. Virga and Yahya Rahmat-Samii, "Efficient Wide-Band Evaluation of Mobile Communications Antennas Using [Z] or [Y] Matrix Interpolation with the Method of Moments", IEEE Trans. on Antennas and Propagation, vol. 47, no. 1, pp. 65-76, Jan 1999.
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