Microstrip-line-fed elliptical wide-slot antenna with similar parasitic patch for multiband applications

Abstract

This study presents two design improvements over conventional microstrip antenna in terms of multiband operation, gain and cross-polarisation (XP) level. The first design (Type-I) consists of a microstrip line on one side and an elliptical slot (ES) on the other side of the substrate. The second design (Type-II) consists of a parasitic elliptical patch inside the ES in addition to the first design. A theoretical analysis using an equivalent circuit model is performed for both antenna designs for estimating the dimensions of each part of the proposed structures. It is found that the size of the wide ES determines the lower operating frequency, whereas coupling between the parasitic patch and microstrip line decides the multiband operation. Experimental results show that the Type-I antenna resonates in three frequency bands at 2.49, 3.7, and 9.76 GHz with peak gain and XP level of 8.66 and 44.43 dB, respectively. With proper selection of the dimensions of the parasitic patch, the Type-II antenna generates five frequency bands at 1.87, 6.42, 10.76, 12.67, and 13.66 GHz. An exceptionally high gain of 16.79 dB with an XP level of 36.15 dB is reported in Type-II antenna. The theoretical and simulation results show a good agreement with the measured results.