In this paper, the varactor-loaded openring microstrip antenna is proposed. To overcome the inherent characteristics of narrow bandwidth of the open-ring microstrip antenna, the varactor is positioned on the edge of the ring. The frequency is tuned by controlling the DC voltage connected to the varactor. For the simulation model, instead of the real varactor, the discrete capacitor is used. The return loss (S 11 ) from the simulation shows that the resonant frequency is lowered by increasing the capacitance value. This frequency-tuning technique could be used in the many applications such as the frequencyreconfigurable small antenna.

This letter proposes an open‐ended waveguide antenna with a single split‐ring resonator. In contrast to the waveguide antennas incorporating multiple rings reported in a previous study, which exhibited narrow bandwidth, the proposed antenna uses only one ring to achieve broader bandwidth while keeping the aperture small. A single ring has a relatively low quality factor compared to multiple rings. The simulated and measured fractional bandwidth was 4.13% and 4.03%, respectively, which is much broader than the fractional bandwidth of about 1% demonstrated in a previous study. This simple technique can be used in many applications that require small apertures including near‐field probes and array elements.

In this paper, a small broadband dipole antenna that simultaneously satisfies DCS1800/PCS/WCDMA/WLAN is designed and fabricated. To reduce the size and to improve the bandwidth of planar microstrip dipole antenna, a new symmetric double-ring radiator structure is used. An antenna can be reduced with increasing effective current length of dipole, and can be obtained a wide band impedance characteristic with decreasing reactance component by using a novel symmetrical double-ring structure. The proposed antenna shows broadband characteristic of 1.07GHz(52%) from 1.5GHz to 2.57GHz with VSWR < 2 (≤-10 dB).

This letter describes a dual-band compact monopole antenna with two branches for Wi-Fi applications. The proposed antenna is based on a planar monopole design, and composed of two branches of radiating patches for dual-band operation. The ground size of the antenna matches the ground size of a typical hand-held cellular phone for improved compatibility with mobile phone printed circuit boards. The antenna is designed using a simulator and fabricated with optimized parameters. The fabricated antenna is measured at the lower and higher operating frequencies, and the return loss coefficient, gain, and radiation patterns are determined. 키워드 dual-band antenna, two branches, monopole antenna, Wi-Fi application 이중대역 안테나, 두개 브랜치, 모노폴 안테나, 와이파이 응용

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