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This work presents a printed monopole antenna with a miniature size and enhanced wideband using characteristic mode analysis (CMA). The printed monopole antenna structure comprises one vertical and one horizontal monopole, and a ground plane with a vertical extension. By connecting the horizontal monopole to the ground plane extension through a via hole, a significant enhancement in bandwidth is achieved in both lower and high bands. A 105% increment in bandwidth is achieved with the via hole compared to without it. The influence of the via hole is analyzed using CMA to provide a physical insight into the design. The proposed antenna is compact with an electrical size of 0.01 λ2, leading to a miniaturized design. [ABSTRACT FROM AUTHOR]

This work presents a bandwidth enhanced high gain rectangular patch antenna operating under two similar spectrally close modes created from a TM50‐like mode in the vicinity of another higher order mode of the patch. The patch is embedded with two wide slots and meandered linkages are used to maintain current continuity. The whole structure is studied using the theory of characteristic modes and the excitation of these higher order modes is controlled to enhance the bandwidth. One of the two similar modes is very weakly excited and does not affect the antenna's performance. The beam tilting at lower frequencies are compensated by properly choosing the capacitors as phase shifter elements on the meander linkages. The antenna size is miniaturized by properly choosing the dimensions of the meander linkages and the resonant length is reduced by λ/2 as compared to that of a conventional TM50 mode supporting patch. The patch size becomes 3.35 × 4.03λ/2 instead of 5 × 5λ/2 (λ is the substrate wavelength). The coaxial probe fed structure exhibits a good performance of impedance bandwidth of 10.5% around the center frequency of 5.7 GHz with a gain variation 10–12 dBi, which appear to be better than other antennas of similar size. [ABSTRACT FROM AUTHOR]

The Theory of Characteristic Modes (TCM) is proposed as a systematic approach to antenna design to achieve the goal of finding the antenna structure with optimum broadband behavior. This theory provides a physical insight to the radiating nature of microstrip patch antennas and reduces the design optimization time. In this work, the resonant behavior of the highly radiating structure of the single U-slot rectangular patch on a single-layer εr = 4.4 substrate is analyzed using TCM. Modal analysis of this single-layer structure with different single feed excitations concludes that VSWR ≤ 2 impedance bandwidth in the order of 96% can be achieved with a single T-probe feed. Experimental results, included here, show VSWR ≤ 2 impedance bandwidth in the order of 71%. [ABSTRACT FROM AUTHOR]

The creation of a magnetic boundary condition into the plane of symmetry in a radiating ground plane of a portable device is proposed to enhance its radiation efficiency and bandwidth. This magnetic boundary condition is achieved by exciting the antenna through symmetrical feeding. A novel antenna consisting of a symmetrical folded dipole is presented in order to exemplify how a broad bandwidth and very good radiation properties can be obtained with the proposed technique. The Theory of Characteristic Modes is used to analyze and compare a folded dipole with the symmetrical folded dipole. This study shows how the magnetic boundary condition favors excitation of antenna modes in a broad bandwidth while avoiding excitation of transmission line modes. Two different prototype antennas, a monopole and a symmetrical folded dipole with an LC-balun, were implemented and measured. The measured -6 dB impedance bandwidth of the monopole extends from 0.95 GHz to 2.15 GHz. In turn, the bandwidth of the symmetrical folded dipole extends from 0.90 GHz to 1.96 GHz. The average of the measured total efficiencies at the aforementioned bandwidth is -1.6 dB for both prototypes. The measured maximum total gain at 0.95 GHz is 2.6 dBi for the monopole and 1.9 dBi for the symmetrical folded dipole. [ABSTRACT FROM AUTHOR]