IndexI. IntroductionII. S-matrix and shielding effectivenessIII. Design Procedure Abstract: Frequency selective surface (FSS) is a repeating structure that transmits, reflects or absorbs based on the mode of interest using patches or slots. Patch and slot arrays effectively create band stop and band pass filters. FSSs have potential applications in providing sufficient shielding in desired frequency ranges. The work proposed in this document is to study and analyze the structural requirements of the FSS for protection from GSM band frequencies. People working near mobile towers are exposed to strong EM fields, especially near fields, so they must protect themselves from these fields. The FSS concept is extended to the printing of structures on aerial fabrics, and the same can be worn by the assigned personnel. The paper is mainly based on simulation analysis of fabrics designed using EM software tools. The simulation results are validated using experimental results. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original Essay Keywords: Frequency Selective Surface, Frequency Selective Fabric, Shielding EffectivenessI. IntroductionMobile phone technology has brought about significant changes in the telecom scenario in India. Cell phone technology has undergone tremendous changes over the past decade. Currently, there are more cell phone users and cell phone towers to meet the demand for communication. The number of cell phones and cell towers is increasing day by day without knowing the disadvantages. Cell tower antennas transmit in the frequency range 869 - 894 MHz (CDMA), 935 - 960 MHz (GSM900) and 1810 - 1880 MHz (GSM1800). In addition, 3G, whose base station antenna transmits in the frequency range 2110 – 2170 MHz. Cell towers transmit a power of 20-25 watts, and the cell phone transmits a power of 1-2 watts, cell phone radiation and of cell towers affect and cause serious risks to human health due to electromagnetic field (EMF) Radiation from mobile towers and cell phones. An antenna is designed in such a way that the mobile phone is able to transmit and receive the signal for successful communication up to a few kilometers. Most of the towers are mounted near residential buildings and offices to provide good mobile phone coverage to users. These cell towers transmit radiation 24/7, so people who live or work within 10 meters of the tower will receive a stronger signal than is required for mobile communication. In India, millions of people reside in these high radiation zones. The International Commission on Non-Ionizing Radiation Protection (ICNIRP) studies possible adverse effects on human health resulting from exposure to non-ionizing radiation[1]-[2]. The main purpose of ICNIRP is to disseminate information and advice on potential health risks arising from exposure to non-ionising radiation. According to ICNIRP guidelines, the current limits/levels are detailed in the table below. Microwaves from cell phone towers can interfere with our body's electromagnetic fields, causing alterations in white blood cells in children; childhood leukemia, impaired motor function, headache, dizziness, fatigue, weakness, memory loss, birth defects, cancer and DNA damage, etc.[3]-[5]. Therefore, it wasdeveloped a fabric with filtering properties in a specific frequency band of GSM -1800 is important for human health. GSM-1800 (Global System for Mobile Communications) uses 1810–1880 MHz to receive information from the mobile station to the base transceiver station (downlink). In recent years, various methods have been proposed for the production of electromagnetic shielding fabrics for protection against electromagnetic interference (EMI) waves [6]. In this field, customized, flexible, lightweight and porous conductive fabrics have been developed for EM shielding or functional electronics applications by knife-on-roll coating [7]-[8]. In another study, conductive co-woven knitted and woven fabrics were produced with desirable electromagnetic shielding effectiveness properties. The main purpose of EMI shielding methods is to block electromagnetic radiation, so that the wave cannot pass through the blocking medium. EMI shielding fabrics refers to the production of fabrics from conductive and non-conductive materials using various processing methods. In all the conductive samples described above, these types of fabrics play the role of metal foils for EMI shielding [9]. Therefore, the problem with these fabrics is that they are unable to shield EM waves in a specific frequency band. Therefore, the frequency selective surface (FSS) technique is necessary to prepare a fabric with EM filtering properties in the GSM-1800 frequency band. Frequency Selective Surface (FSS) is a repetitive structure that acts as a filter and has a wide range of applications such as radomes, lenses, RFID, Electromagnetic Interference Protection, medical and military sectors [10]. FSS can also block unwanted mobile signals based on traditional FSS. Frequency selective fabrics are made for filtering properties in the GSM-1800 band[11]-[13]. The FSS structure can be printed on flat fabrics to shield from the GSM frequency band. This fabric is useful for humans to protect themselves from strong radiation fields coming from cell towers.II. S-matrix and shielding effectiveness The S-matrix can play a very important role in filtering problems. The matrix S can be written as the linear relationship between the reflected wave b and the incident wave a and can be derived from the following formula (1)b1=a1S11+a2S12b2=a1S21+a2S22 (1)Here, the matrix S is called the matrix scattering of the two gates and each of the four S parameters has a defined physical meaning. In particular, S21 is the transmission coefficient of port1 when port2 connects the matched load and can be calculated by the formula (2)S21=b2/a1|a2=0 (2)The meaning of S21 is illustrated by the line theory microwave transmission, but in in many cases, the energy loss due to the difference between the EM impedance and the intrinsic impedance of the shielding material is more intuitive for designers to characterize and evaluate the material. According to the Schelkunoff principle, for monolithic conductive materials without holes, the shielding effectiveness can be calculated by the formula (3)SE=SEA+SER+SEM=10log (p1/p2) (3)Where SE represents the shielding effectiveness shielding, which means degree of attenuation of EM wave caused by shielding materials and the unit is dB. SEA stands for absorption loss, SER stands for reflection loss, SEM stands for multiple reflection loss. P1 and P2 receive energy without and with the tested material. In reality, S21 indicates the ratio between the transmitted wave (equivalent to P2) and the total incident wave (equivalent to P1) when the EM wave passes through the medium. Therefore, S21 can be calculated by the formula (4)S21=10log (p2/p1) = -SE (4)As a medium in the EM field, the periodic structure, such as FSS, can be evaluated.