Α Uniform Design of Microstrip Hairpin Line Filter at 7.2 GHz HARALAMBOS P. KOKKALELLIS (1) and EVANGELIA A. KARAGIANNI (2) (1) Department of Informatics and Telecommunications University of Athens, Panepistimiopolis, Ilissia GREECE me06118@di.uoa.gr (2) Hellenic Naval Academy, Sector of Electronics and Telecomunications Hadjikyriakou Avenue, Piraeus 18539 GREECE evka@hna.gr Abstract: - Recently, the design and development of microwave filters have remarkably improved, in order to correspond to the requirements of technology. In this paper, we present the microstrip resonant coupling structures and the characteristics of them. Based on a mathematical algorithm, we designed a microstrip Chebyshev “Hairpin Line” filter at 7.2 GHz, 20 dB rejection at 6.7 GHz and 0.1 dB ripple in the passband and we discuss about the initial conditions and the acceptances of the problem as well as the simulation’s results. Afterwards, a new uniform design of the filter is presented, making a comparison with the previous design. Two of the materials that can be used for the fabrication of these circuits, are suggested. Finally, after fabricating, we will examine the possibility of developing this structure, as extended work, using a combination of transmission lines and split ring resonators as a defected ground plane. Key-Words: - Chebyshev, Coupling, DGPs, Hairpin-Line, Microstrip, Slot Split Ring, Uniform filter design. 1 Introduction Today, in contemporary telecommunications systems, the requirements of circuits as for the safety and the correctness of transmission data are quite high. Concretely, in civil and military telecommunications, the use of microwave filters is necessary. It is well known, that the basic role of a filter is, to separate or to combine frequencies, according to the special purposes of current application. In this paper, we focus on microstrip coupling resonant filters and particularly, on hairpin line filters, because it has been observed that, these filters have special and interesting properties such as low cost of design, smaller structure size than the classic type of filters, great frequency accuracy, etc. Basic purpose of this paper is the presentation of a microstrip Chebyshev hairpin line filter, which has center frequency at 7.2 GHz, 20 dB rejection at 6.7 GHz and 0.1 dB ripple in the pass-band. 2 The resonant coupling structures One simple structure of microstrip resonant coupling circuit with parallel lines is presented in Fig.1 [1] Fig.1 Resonant Coupling Structure of 5 Microstrips 2.1 Description of the structure These circuits consist of transmission lines with electrical length λ/4.The basic elements are open- circuits at the one edge which is possible to convert into short-circuits and vice versa. At the same time, high junctions are created because of the small distance of elements and the influence of the electromagnetic field. In addition, the first and the last line are matching networks into the characteristic impedance of the lines Ζo, as it is often called. Also, it is important to note that basic property of this kind of structure is the high quality factor Q, that is achieved. However, the dielectric loss of the substrate, the restricted conductivity of MATHEMATICAL METHODS AND APPLIED COMPUTING ISSN: 1790-2769 252 ISBN: 978-960-474-124-3