Browsing by Subject "Input impedance"

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Open Access
Analysis of input impedance and mutual coupling of microstrip antennas on multilayered circular cylinders using closed-form green's function representations
(Institute of Electrical and Electronics Engineers Inc., 2014) Karan, S.; Erturk, V. B.
Closed-form Green's function (CFGF) representations for cylindrically stratified media are developed and used in conjunction with a Galerkin method of moments (MoM) in the space domain for the analysis of microstrip antennas on multilayered circular cylinders. An attachment mode is used in the MoM solution procedure to accurately model the feeding of probe-fed microstrip antennas. The developed CFGF representations are modified in the source region (where two current modes can partially or fully overlap with each other during the MoM procedure) so that singularities can be treated analytically and hence, the proposed CFGF representations can be safely used in this region. Furthermore, accurate CFGF representations for the probe-related components (necessary for probe type excitations including the attachment mode) are obtained when the radial distance between the source and field points is electrically small or zero. Numerical results in the form of input impedance of various microstrip antennas and the mutual coupling between two antennas are presented showing good agreement when compared to the available published results as well as the results obtained from CST Microwave Studio.
Open Access
Hybrid model for probe-fed rectangular microstrip antennas with shorting pins
(IEEE, 2000) Mutlu, Selma; Aksun, M. İrşadi
For a probe-fed microstrip antenna, it is quite common to employ the cavity model to find the field distribution under the patch and other electrical properties. Therefore, a multiport analysis technique based on the cavity model is usually employed to predict the input impedance of a probe-fed microstrip antenna with shorting pins. However, this approach does not provide any information about the field distribution under the patch with the shorting pins, which is usually used to calculate the radiation properties of the patch antenna. In this study, shorting pins are considered as current sources with unknown amplitudes, and the field distribution under the patch is obtained as a linear superposition of the contributions from each source via cavity model. Then, the unknown current densities over the shorting pins are determined by implementing the boundary condition of the tangential electric field on the pins. This is a hybrid approach because the field distribution is calculated from the cavity model, and the current densities over the shorting pins are obtained from the point matching of the resulting field distributions over the shorting conductors. The input impedance results found from this approach agree extremely well with those obtained from the multiport analysis, which shows that the proposed approach predicts both the input impedance and the field distribution under the patch. In addition, since the feeding probe is also made of PEC, the electric field under the patch should satisfy the boundary condition on this conductor as well. In the application of the cavity model, this is always ignored, with the assumption that the source probe is too thin to affect the field distribution under the patch significantly. In this study, the boundary condition of the electric field is implemented over the source, and its effect on the field distribution, in turn on the resonant frequency, is demonstrated.