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VHF antenna miniaturization using external non‐foster matching circuit
Author(s) -
Niang Anna,
de Lustrac André,
Piau GérardPascal,
Sabanowski Guy,
Burokur Shah Nawaz
Publication year - 2017
Publication title -
microwave and optical technology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 76
eISSN - 1098-2760
pISSN - 0895-2477
DOI - 10.1002/mop.30441
Subject(s) - antenna tuner , impedance matching , bandwidth (computing) , miniaturization , reactance , electronic engineering , electrical engineering , electrical impedance , electronic circuit , antenna measurement , broadband , engineering , antenna (radio) , antenna factor , telecommunications , voltage
Electrically small antennas are characterized by large reactance and small radiation resistance. Conventional passive impedance matching is limited by the gain‐bandwidth theory which predicts narrow bandwidth characteristics. Furthermore, Wheeler‐Chu limitation forecast a very narrow band relative to the size of the small antenna and a high quality factor impedance. Non‐Foster circuits can overcome these restrictions and achieve broadband performances by using negative circuit elements. These circuits based on negative impedance converters allow cancelling the antenna's reactance and transforming its frequency‐dependent radiation resistance to a constant value over a broad frequency band. In this article a miniaturized antenna using a non‐Foster impedance matching circuit is presented. This active external matching circuit allows shifting the resonance frequency of an antenna initially designed at 1100–125 MHz while keeping its original dimension of 7 cm and also extending its relative bandwidth from 10% to 104%. An analytical study is used to design the active impedance matching circuit and to implement it. A prototype is fabricated and experimentally tested. Measurements show that non‐Foster circuits can be successfully used to overcome fundamental limitations of electrically small passive antennas in terms of bandwidth even if this gain remains weak. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:986–991, 2017