Compact broadband microstrip antennas have recently received much attention due to the increasing demand for extremely small antennas covering a wide operation bandwidth for many radar and satellite communication applications. This paper reports a method to enhance the impedance bandwidth of a rectangular microstrip antenna by suitably modifying its geometry in the form of plus shape. The experimental results show that there is an improvement of 12.27% impedance bandwidth, when compared to conventional microstrip antenna. Further, after incorporating the optimum slot in the ground plane, the impedance bandwidth increases to 29.4%. This impedance bandwidth becomes 39.5% when two-element array is constructed. This enhancement is achieved at X-band frequency without much change in the radiation pattern. The wideband operation of the proposed antennas may find applications in modern communication systems.

With the saturation of low-frequency bands, the operating frequencies of many modern communication frequency bands have been raised. The planar microstrip antennas have become attractive elements in such communication systems and hence considerable amount of research work has been carried out in the last decades for the design and development of microstrip antennas.

Microstrip antennas have received much attention due to their attractive features such as low profile, low cost and ease of integration and fabrication. They have also been found suitable in satellite communication, radars, missiles, high-speed space vehicles and other strategic defense equipments, due to compatibility with planer solid-state devices. One of the major disadvantages of microstrip antenna is narrow impedance bandwidth of nearly 1 to 2%. Several research efforts have gone towards the development of creative designs and techniques for improving the impedance bandwidth of microstrip antennas. So, along with other developments, widening the bandwidth of microstrip antennas has been a major issue in the development of the same. In the recent years, many designs utilized reactive loading technique (Legay and Shafai, 1997; and Gao et al., 2001) to obtain dual-band structures with a low frequency ratio and attempted to merge two resonant modes together to form a single impedance bandwidth (Chen and Lin, 2001).

In this paper, a simple technique is used to enhance the impedance bandwidth of rectangular microstrip antenna by suitably modifying its geometry in the form of plus shape. This antenna is named Modified Rectangular Microstrip Antenna (MRMSA). Since loading the slot is effective in enhancing the impedance bandwidth of antenna (Liu et al., 2007), the optimum slot is designed and placed on the ground plane of MRMSA to enhance its impedance bandwidth. This antenna is termed Slotted Groundplane Modified Rectangular Microstrip Antenna (SGMRMSA). Further, by using SGMRMSA, the two-element array is constructed. This antenna is named Two-element Slotted Groundplane Modified Rectangular Microstrip Antenna (TSGMRMSA).

Electrical and Electronics Engineering Journal, Satellite Communication Applications, Microstrip Antennas, Modified Rectangular Microstrip Antenna, MRMSA, Vector Network Analyzer, Science and Technology, Strategic Defense Equipments, Microstrip Line Feeding, Pyramidal Horn Antenna.