A Study on a Artificial Transmission Line with Second Harmonic Suppression and its Application to Six-port Modulator

• Main Authors: Chi-hui Lai, 賴季暉
• Other Authors: Tzyh-ghuang Ma
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/02886327443898670521

碩士 === 國立臺灣科技大學 === 電機工程系 === 97 === A novel slow-wave artificial transmission line with approximate elliptic function lowpass response is proposed in this thesis. The proposed artificial transmission line is capable of synthesizing microstrip lines with a variety of characteristic impedances and electrical lengths. Additional harmonic suppression capability is introduced to the artificial lines as well. The design concept, circuit geometry, equivalent lumped model and the simulated and measured results are carefully investigated and discussed. Miniaturized Wilkinson power divider, quadrature hybrid and rat-race coupler are developed by utilizing the proposed artificial transmission line. The components reveal significant size reduction percentages as compared with conventional designs. In addition, the quadrature hybrid also demonstrates excellent signal suppression ability at the second harmonic frequency. The circuit performances are tabulated and compared with the conventional ones. By utilizing the newly developed miniaturized Wilkinson power divider and quadrature hybrid, three miniaturized six-port junctions with compact size and second harmonic suppression characteristic are designed. Meanwhile, a miniaturized reflection type modulator, composed of the developed six-port junction and the cold-mode field effect transistors (FETs), is also implemented in this thesis. The modulator is experimentally demonstrated with QPSK modulation of a data rate up to 8 Mbps. The measured root mean square (RMS) error vector magnitudes (EVMs) are ranged around 4.2 %.