Determination of accurate modal fields is one of the most crucial issues to understand the proper behavior of circular sector microstrip antennas (CSMAs) to achieve the best performance. In this article, dominant and higher order modal characteristics have been rigorously studied which germinate an improved, accurate, and efficient computer-aided design (CAD) formulation to estimate the resonant frequency of CSMA with and without air gap between substrate and ground plane. The proposed formulation can address the wide variety of issues (such as substrate height, substrate permittivity, air gap height, higher order modes, etc.). The computed results were validated against the results obtained from high-frequency structure simulator (HFSS) and our own experiments, while they have been also justified through the results obtained from the available literature.
K E Y W O R D Santenna parameters, circular sector, microstrip antenna, resonant frequency
| I NT ROD UCTI ONIN the modern era of microwave communications, the design and analysis of miniaturized and multifunctional antennas of different geometries continue to be the focus of state-ofthe-art research. In this scenario, microstrip patch antennas (MPAs) are extremely useful and are the obvious choice of the designers because of their light weight, small size, and excellent compatibility with monolithic microwave integrated circuits. The most common geometries of MPAs, such as rectangular and circular, have been extensively studied, analyzed, and implemented for at least the last three decades. In fact, a significant number of analyses 1-6 and applications [7][8][9][10][11][12] of common MPA geometries have been reported during the last two decades. However, in various practical wireless applications, radiators should be conformally mounted onto the previously existing structures, where space limitation is a crucial problem. In such applications, a circular sector microstrip antenna (CSMA) is highly advantageous because it requires less space than a conventional patch antenna of common geometries. Approximately 30% and 35% patch area reductions can be achieved with a CSMA using 608 and 908 sector angles, respectively, compared with a conventional circular MPA. Therefore, an accurate analysis of CSMA is a priority in the present scenario of printed antenna research. In this context, we have found a limited number of analyses, [13][14][15][16][17] in which the computation of the accurate resonant frequency of CSMA with arbitrary sector angles has been dealt with. The formulation of the resonant frequency of a CSMA based on the cavity model was first reported in ref. 13. The electric field beneath the patch and the eigen functions of those antennas were also presented in ref. 13. In ref. 14, a generalized transmission line modeling was used for computing the resonant frequency of a CSMA. However, the effect of fringing fields, which should be considered for the accurate estimation of the resonant frequency of a CSMA, was not included in refs. 13 and 14.Int J...