A Novel Multilayer Multiband Frequency Selective Surface for IMT Advanced 4G Mobile Phone Service and Airborne Radar Systems Şakir Balta Electric Electronics Faculty Istanbul Technical University Istanbul, Turkey sakirbalta@itu.edu.tr Mesut Kartal Electric Electronics Faculty Istanbul Technical University Istanbul, Turkey kartalme@itu.edu.tr Abstract—In this paper, a novel two-layered low profile multiband frequency selective surface (FSS) design was performed. Two independent FR4 dielectric layers were used in the design, with a thickness of 1 mm, a relative dielectric constant of 4.54, and a loss tangent of 0.02. The proposed FSS unit cell consists of a square frame, dodecagonal rings and upright bars. The FSS is designed for preventing harmful effects to human health from electromagnetic waves in the 800, 900, 1800, 2100, 2600 MHz frequency bands, used for IMT Advanced mobile phone and internet access service global system for mobile communication (GSM), is also designed for the Department of Defense (DoD) ground-based, high-powered shipborne and airborne radar systems 3500-3650 MHz frequency bands, which is known as US245 at United States Federal Table and to prevent interference effects in these frequency bands. The proposed FSS has a very compact size with a cell size of 0.17λ and therefore has a low sensitivity to the angle of incident wave. ANSYS high- frequency structure simulator (HFSS) software was used for verification of the design. Keywords—frequency selective surface (FSS), FR4, GSM, IMT Advanced, US245, The Department of Defense (DoD), shipborne and airborne radar systems, ANSYS HFSS I. INTRODUCTION Communication systems differ in order to keep up with the requirements of the age. Meeting this requirement is possible by using different frequencies in general. IMT Advanced is known as a 4th generation (4G) mobile communication system which includes 800, 900, 1800, 2100 and 2600 MHz frequency bands. The use of each newly added frequency band poses a threat to human health in addition to electromagnetic waves in the frequency band previously used. Since there is no system to prevent these frequencies, we are exposed to these waves in our daily lives, at home, at the office, at any time [1]. On the other hand, RF signals penetrating into the building from the outside cause interference and reduce the quality and speed of communication [2]. For such reasons, it is important to prevent certain frequencies without affecting the communication system at the frequencies we want to use [3]. Therefore, in order to prevent unwanted frequencies, it is important to design an efficient frequency selective surface (FSS) structure [4]-[6]. The Department of Defense (DoD) ground-based, high- powered shipborne and airborne radar systems use 3500-3650 MHz frequency bands which is known as US245 at United States Federal Table [7]. It is used for air defense, traffic control and range safety, gun and bomb control, checking the weapon locations. So this frequency band is very critical for the safety of the national defense. Rapid development of modern communication with radar technology, signal transmission capability at X-, Ku- and Ka- bands is of great importance for military and meteorological satellite. Frequency selective surfaces (FSS) can be designed to reflect the different frequency of the electromagnetic (EM) waves, to prevent inter-symbol interference; and thus they are widely used in different applications such as satellite communications, artificial magnetic conductor, high-selective spatial filter, microwave polarization transducer and antennas for large diaphragm of the surfaces of dichroic reflectors and lower reflectors. Recent research in FSS concentrates on areas with miniaturized frequency selective surfaces (MEFSS) [8], the substrate-integrated waveguide [9], active [10] and multi- band [11]. Since the resonance frequencies of the FSS express a wide range of frequencies, they also include frequencies that we use for different purposes in real life. For this reason, it is aimed to minimize interference effects in these frequency bands and to prevent radio frequency waves coming from these frequency bands and to design structural surface material which has good transmission characteristics at other frequencies [12][13]. On the other hand multi-resonant FSS structures that stop 800, 900, 1800, 2100 and 2600 MHz frequency bands have not been investigated yet. In the proposed design, it is aimed that the transmission coefficient (S21) of the material in the extinguishing band is at a minimum of -10dB, the transmission coefficient (S11) of the transmission band is close to 0dB, and also the design is aimed to be very compact and has a low sensitivity to the angle of incident wave. The surfaces with varying frequency characteristics depending on the value of the current or voltage supplied by