Multi band microwave circuits with metamaterial effects

• Main Author: Mohan, Manoj Prabhakar
• Other Authors: Arokiaswami Alphones
• Format: Theses and Dissertations
• Language: English
• Published: 2019
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Antennas, wave guides, microwaves, radar, radio
• Online Access: https://hdl.handle.net/10356/89477; http://hdl.handle.net/10220/48372
• Institution: Nanyang Technological University

In this thesis, multi band components are realized by exploiting the electromagnetic metamaterial effects. At first, single negative material (a type of electromagnetic metamaterial) design is discussed. Substrate integrated waveguide (SIW) is usually visualized as planar implementation of conventional metallic waveguide, but it can also be visualized as negative permittivity or epsilon negative (ENG) transmission line. The unit cell of epsilon negative TL is similar to CRLH TL except the former do not have series capacitor in the unit cell. The phase constant obtained using both the theories (waveguide and negative epsilon) are compared. The effective epsilon found out using unit cell parameters and wave guide theory are compared with the simulation. SIW resonator is designed and its resonant frequencies using waveguide and epsilon negative theory are compared with the measured resonant frequencies. A triple band antenna is designed using open circuited SIW. The antenna is designed by including two slots to have three bands at 3.3 GHz, 4 GHz and 4.9 GHz. The first band is formed by merging two resonant modes. So, the first band has higher bandwidth. The second and third bands are from single resonant modes. The 10dB impedance bandwidth of antenna in the three bands are 1.49% (3.3 GHz band), 0.72% (4 GHz band) and 0.56% (4.9 GHz band). The measured realized gains of the antenna are 5.81 dBi (3.3 GHz), 4 dBi (4 GHz) and 2.43 dBi (4.9 GHz). After seeing the single negative material design, next double negative material design is focused. The double negative material considered here is Double periodic CRLH (DPCRLH) TL. DPCRLH unit cell is formed by concatenating two different CRLH unit cells. Two symmetric unit cells of DPCRLH TL are proposed. The DPCRLH symmetric unit cells are analysed using ABCD matrix. The dispersion diagram of DPCRLH has two left and two right handed regions. The important frequency points in the dispersion diagram are analysed. The closing condition of attenuation gap at \beta d=0 in the dispersion diagram is derived. A DPCRLH symmetric unit cell is designed and fabricated with closing condition of attenuation gap at \beta d=0 at 3.39 GHz. The measured results are compared with the simulated results. The DPCRLH symmetric unit cell is converted to resonator by open circuiting the ends. The open circuited resonator has five resonant points which is confirmed by simulation and measurement. The measured resonant points are at around 1.574 GHz, 2.05 GHz, 3.24 GHz, 6 GHz, and 9 GHz. The last three resonant points are selected to design a triple band filter at 3.6 GHz, 6 GHz and 9 GHz. The filter has different fractional bandwidths on all three bands. The order of the filter is three and it is designed using coupling coefficient and external quality factor. The filter is designed and fabricated with microstrip as host line. In order to avoid via holes, coplanar waveguide (CPW) is chosen as host line to create DPCRLH structure in the next design. A DPCRLH symmetric unit cell is designed in CPW and its characteristics are analysed. The measured and simulated results of the DPCRLH unit cell are compared. The open circuited resonator is formed from DPCRLH unit cell. As in the previous case it has five resonant points. The simulated resonant points are at 1.5494 GHz, 2.1968 GHz, 3.5072 GHz, 5.0438 GHz and 6.089 GHz. The relation between the quality factor at resonant points and DPCRLH unit cell parameters is discussed. A triple band antenna is designed using last three resonant points at 3.66 GHz, 5.095 GHz and 6.1188 GHz and fabricated. The 10dB measured impedance bandwidth at the three bands are 1.67%, 11.08%, and 2%. The measured Co-polarization realized gain of the antenna in the three bands are 2.1 dBi (3.66 GHz), 3.19 dBi (5.0119 GHz) and 2.24 dBi (6.1188 GHz).