Title :
A Directivity-Enhanced Directional Coupler Using Epsilon Negative Transmission Line
Author :
Pourzadi, Aref ; Attari, Amir Reza ; Majedi, Mohammad Saeed
Author_Institution :
Commun. & Comput. Res. Center, Ferdowsi Univ. of Mashhad, Mashhad, Iran
Abstract :
In this paper, a high directivity parallel coupled line coupler using the ε negative (ENG) transmission line is proposed. With the aid of even- and odd-mode analysis, it is shown that by using ENG transmission lines in a parallel coupled line coupler, the even- and odd-mode phase velocities can become equal at a desired frequency. Hence, the directivity of a coupler can be infinite theoretically. The coupler circuit model and closed-form relations for lumped elements of this model are presented. In addition, a design procedure for microstrip implementation of this coupler is proposed. Based on the proposed procedure, a 10-dB ENG directional coupler is designed at 2 GHz and validated by full-wave simulations. This coupler is fabricated and measurement results are presented. Experimental results show maximum directivity of nearly 40 dB at 1.95 GHz.
Keywords :
UHF couplers; coupled transmission lines; microstrip lines; ε negative transmission line; ENG transmission line; closed-form relations; coupler circuit model; directivity-enhanced directional coupler; epsilon negative transmission line; even-mode analysis; even-mode phase velocities; frequency 1.95 GHz; frequency 2 GHz; full-wave simulations; high directivity parallel coupled line coupler; lumped elements; microstrip implementation; odd-mode analysis; odd-mode phase velocities; Directional couplers; Equivalent circuits; Integrated circuit modeling; Mathematical model; Microstrip; Power transmission lines; $varepsilon$ negative transmission line; Directional coupler; directivity; even/odd modes; metamaterial;
Journal_Title :
Microwave Theory and Techniques, IEEE Transactions on
DOI :
10.1109/TMTT.2012.2216283
