I. Introduction
Wireless communication today is a very large and important market affecting our lives in many ways. The number of wireless standards is increasing for every year and higher data rates are requested by even more users than before. To make this possible a numerous number of different standards and technologies are used. Recently, integrated waveguide filter (IWF) have attracted the attention of many researchers due to low cost, lightweight and efficient high frequency characteristics [1]–[3]. IWF is the printed circuit realization of a waveguide. The IWF is a like waveguide structure implemented by employing arrays of CRLH-TL that perform the electric and magnetic parallel metal plate side walls as conventional rectangular waveguide side walls. Reference [4] has been discussed the transition from ordinary transmission line concepts to waveguide theories. It has been considered by the development of a waveguide from a two- wire transmission line. At the junction with the line, the insulators must present a very high impedance to ground for proper operation of the line. A low impedance insulator would obviously short-circuit the line to ground, and this is what happens at very high frequencies. Ordinary insulators display the characteristics of the dielectric of a capacitor formed by the wire and ground. As the frequency increases, the overall impedance decreases. A better high-frequency insulator is a quarter-wave section of transmission line shorted at one end. The impedance of a shorted quarter-wave section is very high at the open-end junction with the two-wire transmission line. This type of insulator is known as a metallic insulator and may be placed anywhere along a two wire line. As more insulators are added, each section makes contact with the next, and a rectangular waveguide is formed. The energy is then conducted within the hollow waveguide instead of along the two-wire transmission line [4]–[7]. Metamaterials are a special class of structured materials. In nature, the permittivity and the permeability of all the materials are positive. The material with positive permittivity and permeability are referred as right-handed materials (RHMs). But the negative and can be achieved in some artificial materials, which are referred to as left handed materials (LHMs). The metamaterial is usually used to refer the artificial material. Electromagnetic metamaterials are artificially structured composite materials that can be engineered to have desired electromagnetic properties, while having other advantageous material properties. The CRLH are the metamaterials with both of the RH and the LH properties [8]–[13]. In this paper, the main goal of this paper is to develop low cost, realizable and reliable band rejection IWF design using CRLH-TL array structure. The CRLH-TL array structure has been introduced for number of fingers, pair of fingers. The analysis and investigation are done by the HFSS simulator [14] based on the finite element method (FEM). The good agreement between the theoretical expectation and the simulation results is observed. Finally, the application of the proposed CRLH-TL array was examined in IWF design structure. The proposed CRLH-IWF design structure has been fabricated and the measured S-parameters of the proposed structure can be analyzed with Agilent FieldFox network analyzer, N9918A, to demonstrate the performance as a band rejection waveguide filter.