Metamaterial and dispersion engineering techniques in microwave circuits applications

This dissertation introduces a novel methodology, referred as dispersion engineering technique, to design antennas and microwave circuits. This technique is based on engineering the dispersion relation of the metamaterial structure to satisfy the circuit requirements. In this dissertation, the basic characteristics and unique features of the metamaterial will be described and discussed. The implementation of the metamaterial using composite right/left-handed transmission line (CRLH-TL) will be demonstrated and analyzed by using transmission line theory. Several microwave antennas and passive circuits will be investigated and built. The performance and the potential of the metamaterial based circuits will be demonstrated.; Several antenna designs including ultra compact antenna, circular polarized antenna and dual-band antenna will be discussed in this dissertation. The proposed antenna designs are all based on the unique features of the CRLH-TL where its propagation constant is inverse proportional to the frequency. Therefore a small guided wavelength can be obtained at lower frequency to provide the necessary lambdag/2 resonant length for the small antenna. The small antenna de signs will demonstrate more than 90% foot print size reduction compared to the conventional patch antenna using the same material. In addition, by managing the equivalent circuit parameters along the orthogonal direction, an anisotropic medium can be created. The compact dual-band antenna can be accordingly developed.; Another important feature of the dispersion engineering technique is that the slope of the dispersion curve and the point where the propagation constant is zero can be easily controlled. Therefore, these properties can be applied to several broadband microwave circuits such as transitions, filters and a coupler. The CRLH-TL is paired with the microstrip delay line where their phase responses are parallel to each other over a wide frequency range. Based on the different applications, the phase difference between the CRLH-TL and the microstrip line will be chosen to satisfy the requirements. The performances shown in the dissertation indicates the bandwidth enhancement of the proposed microwave circuits can be achieved by employing the dispersion engineering technique.