Summary
International Symposium on Antennas and Propagation
2009
Session Number:2B1
Session:
Number:2B1-2
A Small and Low Profile Meander Antenna Using Capacitive Feed Structure
Kazuki Ide, Takeshi Fukusako,
pp.353-356
Publication Date:2009/10/21
Online ISSN:2188-5079
Summary:
Small and low profile antennas with back reflector have been widely studied in recent years, so as to reduce the electrical effects from the backing material when the antenna is installed on IC chips, human body or on any metallic or lossy material [1], [2]. In low profile linear antennas with back conductors [3], [4], the real part of the input impedance becomes zero on most frequencies other than at the parallel resonant frequencies, when the distance between the linear antenna and back conductor is smaller than quarter wavelength. At a parallel resonance frequency, there is a steep transition in the imaginary part of impedance from a very large positive value to a large negative value. Therefore, it is usually difficult for such antennas to operate at the parallel resonance [1], [5]. Using meander line and incorporating capacitances are effective to make electrically small antennas [6], [7] to operate at a serial resonance frequency. But the leakage current existing on the outer conductor of a coaxial cable still causes drastic changes in antenna characteristics [8] when the feed is unbalanced. A small and low profile antenna using a capacitive coupling with the back conductor is presented in [5] so as to operate at a serial frequency using the electrically small and low-profile structure. However, the coupling terminal with small area easily generates the leaky current on the feeding coaxial cable unless a ferrite choke on the cable is used. This paper proposes a novel feed structure using a capacitive feed (C-feed) technique. A metallic feed plate placed in between the back metal (ground plane) and the meander line provides capacitance to the input impedance. The meander line, which is the radiating element, is electromagnetically coupled from the feed plate. The effect of CPW feed and C-feed on the antenna is discussed by simulated and measured results.