Grooved Linear Microstrip Patch Antenna Array

A simple impedance matching technique for inset feed grooved microstrip patch antenna based on the concept of coplanar waveguide feed line has been developed and investigated for a printed antenna at X-Band frequency of 10GHz. The proposed technique has been used in the design of Linear Grooved Microstrip patch antenna array. The characteristics of the antenna are determined in terms of Return loss, VSWR, gain, radiation pattern etc. The measured and simulated results presented are found to be in good agreement. Keywords—Gain, Microstrip patch, return loss, VSWR, Radiation pattern, CPW Feed, Inset feed. INTRODUCTION ICROSTRIP antennas offer attractive features such as low profile, light weight, easy fabrication and so on. But also possess major shortcomings such as narrow impedance bandwidth, low efficiency and gain, which seriously limit the application of the microstrip patch antennas. These limitations are due to impedance mismatch of the feeding circuitry. In order to match the element to the feeding circuitry the simplest matching method involves choosing the feed location where the resonant resistance is equal to feed-line impedance. In most application, the microstrip patch antenna is fed using either coaxial probe feed or inset microstrip line as both are direct contact methods providing high efficiency [1]. The Coaxial feeding method is used mostly for application such as active antennas while microstrip line feeding is used for high gain microstrip arrays. In both cases the position or inset length determines the input impedance. The grooved antenna as shown in Fig.1 is similar to a cavity backed antenna as proposed by saloon [2] which is a form of suspended antenna designed to achieve high bandwidth and gain but the proposed design suffers from complex impedance matching network. In this paper we propose a simple method for designing the inset feed section of grooved microstrip patch antenna array to reduce the mismatch between the patch and feed network using the concept of CPW feed .The design of linear grooved array using the same method has also been presented . Ayesha Aslam a Ms student at the Department of Electrical Engineering, College of Electrical and Mechanical Engineering (CEME ),National University of Science and Technology(NUST),Pakistan(e-mail: [email protected]). DR F A Bhatti is an Associate professor at the Department of Electrical Engineering, College of Electrical and Mechanical Engineering (CEME ),National University of Science and Technology(NUST), Pakistan ( e-mail: [email protected]). Input impedance of the inset fed microstrip patch antenna mainly depends on the inset distance Yo and to some extent on the inset width [3]. In most cases inset gap is set at least the same width as the feed line itself [4]. This method does not ensure that the inset feed section has the same characteristic impedance as the feed line resulting in an impedance mismatch between the feed line and the point where the feed line connects to the microstrip patch antenna In order to overcome the problem of impedance mismatch between the feed line and the inset feed section for grooved microstrip patch a new model has been proposed using the concept of CPW feed line. The model developed as shown in Fig. 1 involves treating the inset feed section of the microstrip patch antenna as CPW (Coplanar Waveguide) feed line choosing the feed location where the resonant resistance is equal to CPW feed-line characteristic impedance. Fig. 1.Inset Feed Grooved Microstrip Patch designed model The feed section is considered as a series combination of Microstrip line and the inset section as CPW feed line both of which are designed to have the same characteristic section the feed line width S is kept the same as the microstrip line width and the Slot width W which is also the inset width Wf is changed to obtain the same characteristic impedance Zo as the Microstrip line as show in Fig.2. Ayesha Aslam, F A Bhatti Grooved Linear Microstrip Patch Antenna Array M World Academy of Science, Engineering and Technology International Journal of Electrical, Computer, Energetic, Electronic and Communication Engineering Vol:4, No:10, 201