Design and Performance Analysis of Microstrip Array Antenna

This paper describes the design of difierent microstrip array antennas. Series- feed, corporate-feed and their combination that makes series-corporate feed and full-corporate feed antennas are analyzed and simulated. These antennas are designed on a thin substrate for the application of conformal microstrip array antenna. In all cases we get return losses below than i15dB at resonance frequency. The gain of these antennas are simulated and found adequate results also sidelobe label is maintained 11.0dB or lower than main lobe. One of these simulated antennas is implemented for performance tests. Operating frequency of these antennas are 2.45GHz, 1.88GHz, so these antennas are suitable for L-band and S-band application. 1. INTRODUCTION Microwave equipments require low proflle and light-weight to assure reliability, an antenna with these characteristics is essentially required and a microstrip antenna satisfles such requirement. The key features of a microstrip antenna are relative ease of construction, light weight, low cost and either conformability to the mounting surface or, at least, an extremely thin protrusion from the surface. Microstrip arrays are limited in that they tend to radiate e-ciently only over a narrow band of frequencies and they can not operate at the high power levels of waveguide, coaxial line, or even stripline (1). In various communications and radar systems microstrip antenna is greatly desired. Microstrip antennas are very versatile and are used, among other things, to synthesize a required pattern that cannot be achieved with a single element. In addition, they are used to scan the beam of an antenna system, increase the directivity, and perform various other functions which would be di-cult with any one single element. The elements can be fed by a single line or by multiple lines in a feed network arrangement. The flrst is referred to as a series-feed network while the second is referred to as a corporate-feed network (2). This paper presents the characteristic of microstrip array antennas, series-feed, corporate feed and their combination. There performance comparisons are also given for better understanding. Substrate selection and element spacing for grating lobe minimization are also given. For microstrip antennas, the dielectric constants are usually in the range of 2:2 • "r • 12. Dielectric constants in the lower end of the range can give us better e-ciency, large bandwidth, loosely bound electric fleld for radiation into space, but at the expense of large element size. In microwave circuit that requires tightly bound flelds to minimize undesired radiation and coupling, and lead to smaller element size. In some application we need small size antennas, substrate with high dielectric constant is a better choice in this application. High dielectric constants have greater losses so they are less e-cient and have relatively small bandwidth (2). In our design, we consider all these things. Simulated antennas can be easily fabricated on FR-4 ("r = 4:4), RT/duroid 5880 ("r = 2:2) or high dielectric constant of ("r = 10:2, R03010) substrate. Recessed microstrip line feeding techniques is used as this gives a good impedance matching at inputs of the radiating elements. 2. MICROSTRIP SERIES-FEED ARRAY ANTENNA