Abstract
This paper addresses the issues of low bandwidth, gain, and efficiency of miniaturized microwave antennas by proposing a novel wideband dual-frequency coplanar waveguide antenna design based on a simplified composite right/left-handed (SCRLH) transmission line structure with Hilbert curve loading. The multifrequency characteristics of the SCRLH transmission line structure are evaluated theoretically, and the antenna parameters promoting bandwidth broadening under zeroth-order resonance (ZOR) and first-order resonance (FOR) mode operation are evaluated. The bandwidth broadening in the ZOR and FOR modes is accordingly revealed to be independent of the antenna length, and the structure therefore facilitates wideband operation under miniaturization. Finally, the dual-frequency ZOR and FOR mode antenna design with center frequencies of f0 = 1.865 GHz and f1 = 2.835 GHz is validated via simulation, and the performance of a compact prototype antenna is evaluated experimentally. The −10 dB return loss bandwidths at f0 and f1 are 187 MHz (from 1.773 GHz to 1.96 GHz) and 368 MHz (from 3.002 GHz to 3.37 GHz), and the corresponding relative bandwidths are 10.1% and 11.5%, respectively. The experimentally measured peak gains and radiation efficiencies at f0 are 1.54 dB and 81.3%, respectively, and those at f1 are 1.71 dB and 74.2%, respectively.
Highlights
Wireless communication systems have been increasingly subjected to the parallel development trends of miniaturization and integration in both military and civilian applications [1]
Excellent multifrequency antenna performance has been achieved by antennas based on composite right/left-handed (CRLH) transmission lines owing to their unique dispersion controllability and the capability of controlling their negative, zeroth, and positive-order resonance frequencies
Narieda et al [5] proposed a coplanar waveguide (CPW) dual-frequency antenna design based on a one-dimensional CRLH transmission line structure using the zeroth-order resonance (ZOR) mode and the positive firstorder resonance (FOR) mode
Summary
Wireless communication systems have been increasingly subjected to the parallel development trends of miniaturization and integration in both military and civilian applications [1] This is problematic when integrating antennas with miniaturized wireless communication devices because they invariably degrade the performance of the antenna, such as by narrowing the bandwidth and deteriorating the directivity pattern. Gummalla et al [6] proposed a three-frequency antenna based on a two-dimensional CRLH transmission line using the ZOR, positive FOR, and positive second-order resonance modes. While these past studies have both achieved multifrequency antenna performance, the antenna designs suffered from unacceptably narrow bandwidths
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