Microstrip Line Impedance Matching Using ENZ Metamaterials, Design, and Application

The idea of this paper is to extend the tunneling effect of epsilon-near-zero (ENZ) narrow channel for matching two microstrip lines with different impedance characteristics. The main advantage of this method is the possibility to design a channel with subwavelength electrical size and obtain similar matching condition when compared with a conventional lambda/4-transformer. The bandwidth of the structure is directly related to the bandwidth of the ENZ metamaterials. The suggested matching circuit is comprised of a metallic wall and an ENZ narrow channel. To realize the ENZ channel, a rectangular waveguide which operates in TE10 mode is designed and implemented using a substrate integrated waveguide (SIW) technology. A set of vias are also needed for emulating the metallic wall to reduce the ENZ channel cross section. The proposed structure for different impedance values of 50, 100, and 150 Omega was designed, simulated, fabricated, and tested. Moreover, as an important application of a matching network, a microstrip patch antenna has been matched over the desired frequency band. The simulation results based on CST microwave studio have a good agreement with measurements. It is shown that the bandwidth of the circuit is 8%-15%.