MICROSTRIP PATCH ANTENNA OPERATING AT DUAL RESONANT FREQUENCY WITH PROBE FEEDING FOR WIRELESS APPLICATIONS BISWAJIT GHOSH Assistant Professor, Birbhum Institute of Engineering & Technology, Suri, Birbhum, India ABSTRACT In this paper, a microstrip patch antenna with enhanced bandwidth is presented .It has been shown that by cutting a slot in the radiating patch the antenna resonates at dual frequency of 4.03 GHz and 3.42 GHz. The impedance bandwidth determined from the -9.55 dB return loss is from 4.21 to 3.27 GHz, equivalent to 0.94 GHz or about 25.1% with respect to the centre frequency at 3.74 GHz, and is sufficient to fully cover the desired bands required for wireless applications. KEYWORDS: Microstrip Patch Antenna, Dual Resonant Frequency, Wide Bandwidth, Wireless Application INTRODUCTION The current demand of wireless communication systems and their miniaturization, antenna design[1] becomes more challenging in present days[2][3]. The main reason of microstrip patch antenna to attract wide interest is because of its inherent characteristics such as light weight, low profile, low cost, mechanically robust, simple to manufacture, easy to be integrated with MIC/MMIC and others RF devices [4][5][6]. In spite of its several advantages, microstrip patch antennas suffer from low gain and a narrow impedance band width[6]. TECHNOLOGY It is observed that by cutting a slot inside or along the periphery of the RMSA (Rectangular Microstrip Antenna), various compact configurations are realized[7][8]. If the resonance frequency[9] of the slot and the patch[10] are close to each other then broad bandwidth could be obtained. A very promising configuration that yields broad bandwidth [11] is a RMSA with a U- shaped slot. A resonant U- slot is cut symmetrically around the center of the patch. When a slot is cut inside the patch the resonance frequency of the patch changes slightly in comparison with the resonance frequency of the slot. ANALYSIS OF THE PROPOSED WIDE BANDWIDTH RESPONSE OF THE ANTENNA The geometry of the proposed antenna is given in Figure 1. It consists of a rectangular patch loaded in the centre with a U-shape slot and separated from the ground plane by two PTFE substrate ( r   3.2) having thickness 0.79 mm and an air substrate which is situated between the two PTFE substrates. The thickness of the air substrate is varied in our design. The patch has dimensions 36 mm x 26 mm. Note that the width of the patch is much greater than its length. The patch is fed at the centre b y a 50 Ω coaxial probe. A 2 mm wide U-shaped slot of dimensions 14 mm x 16 mm is cut at the centre of the patch. The ground plane has dimensions 80 mm x 70 mm. The simulation of U-slot RMSA is done for thickness of air substrate ∆=6mm (∆=thickness of the air substrate). International Journal of Electronics and Communication Engineering (IJECE) ISSN 2278-9901 Vol. 2, Issue 2, May 2013, 99-104 © IASET