Browsing by Author "Mutlu, Selma"
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Item Open Access Hybrid model for probe-fed rectangular microstrip antennas with shorting pins(IEEE, 2000) Mutlu, Selma; Aksun, M. İrşadiFor 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.Item Open Access Hybrid model for probe-fed rectangular microstrip antennas with shorting strips(2001) Mutlu, SelmaIn the dual frequency operation of microstrip antennas, shorting strips are used to adjust the ratio of frequencies. A multi-port analysis is usually employed to predict the input impedance and resonant frequency of probe-fed microstrip antennas with shorting strips. However, this approach does not provide any information about the field distribution under the patch. In this thesis, a hybrid model, using both the cavity model and point matching, is developed to calculate the field distribution under the patch with shorting pins and strips. In addition, this model also accounts for the conducting nature of the feed and shorting strips, with the help of the point-matching algorithm. Then, to verify the model, the theoretical results obtained from the hybrid method are compared to the experimental results and good agreement is observed. Finally, a genetic algorithm is developed for optimizing the position and width of the shorting strips to achieve desired frequency ratio and input impedances in dual-band operations.