Study of electromagnetically coupled microstrip arrays
Zahedi, Mehdi Hamid
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This thesis focuses on study and design of proximity fed arrays which consist of microstrip patch resonators placed near a feedline and coupling takes place through the gap in between. The configuration is capable of supporting standing-wave and traveling-wave excitations. When operating in the resonant mode, either the current or voltage standing-waves can b used as the excitation. Capacitive coupling or fringing electric fields at feedline edge results in creation of potential difference between two patch edges and resonant current on the patch. Capacitive coupling is best suited for vertical polarization (with respect to the feedline current). Horizontal polarization (or co-linear polarization with respect to the feedline current) is induced effectively by current standing-wave (or magnetic fields). Any desired distribution can be established across the array by a proper adjustment of the gap width. A minor modification in gap distribution along the array is also required in order to obtain a better uniform distribution for either standing-wave or traveling-wave excitation since the excitation is of series-fed type. The configuration can provide a dual band arrangement, an arrangement for a band at one side of the feedline or a single band cross-linear array may be arranged. The cross-linear array is suitable mainly for reducing the cross-polarization in a vertically polarized configuration. One effective technique to improve the performance bandwidth is to configure a progressive incremental length added to the resonant length across the array. The single linear array can surely be expanded to planar configuration for enhancement purposes.