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S-Parameter Analysis for Balanced and Unbalanced Modes Corresponding Dissipated Power of a Small Antenna
Takashi YANAGI Yasuhiro NISHIOKA Toru FUKASAWA Naofumi YONEDA Hiroaki MIYASHITA
IEICE TRANSACTIONS on Communications
Publication Date: 2020/07/01
Online ISSN: 1745-1345
Type of Manuscript: PAPER
Category: Antennas and Propagation
balanced mode, unbalanced mode, S-parameter, self-balancing, measurement,
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In this paper, an analysis method for calculating balanced and unbalanced modes of a small antenna is summarized. Modal condactances which relate dissipated power of the antenna are directly obtained from standard S-parameters that we can measure by a 2-port network analyzer. We demonstrate the validity and effectiveness of the proposed method by simulation and measurement for a dipole antenna with unbalaned feed. The ratio of unbalanced-mode power to the total power (unbalanced-mode power ratio) calculated by the proposed method agrees precisely with that yielded by the conventional method using measured radiation patterns. Furthermore, we analyze a small loop antenna with unbalanced feed by the proposed method and show that the self-balancing characteristic appears when the loop is set in resonant state by loading capacitances or the whole length of the loop is less than 1/20th the wavelength.