This letter presents an ultrawideband multiple-input-multiple-output (MIMO) antenna that covers the WCDMA (1.92-2.17 GHz), WiMAX (2.3, 2.5 GHz), WLAN (2.4 GHz), and UWB (3.1-10.6 GHz) bands for wireless device applications. The proposed antenna consists of a printed folded monopole antenna coupled with a parasitic inverted-L element, with an open stub inserted in the antenna to reject the WLAN (5.15-5.85 GHz) band that interferes with the UWB band. These two antennas are symmetrically arranged on a mobile device substrate. The -10-dB bandwidth of the designed antenna is 1.85-11.9 GHz without the WLAN band 5.15-5.85 GHz. S ₂₁ and the envelope correlation coefficient are lower than -17.2 dB and 0.18 in the operating bands, respectively. The size of the antenna is 55 ×13.5 × mm ² .

An electrically small spherical UHF (911.25 MHz) radio frequency identification (RFID) tag antenna is proposed. A dipole-typed RFID tag antenna is wound into a spherical shape to achieve small size and quasi-isotropic pattern. The overall diameter of the antenna is 25 mm (0.076¿), and the resulting electrical size is a kr of 0.24. A short stub is employed for good conjugate impedance matching with a RFID chip (Z_chip = 14 - j145 ¿). The designed antenna has a -10-dB bandwidth of 7 MHz (0.77%) and the maximum readable distance of 132 cm at 5.2 W EIRP.

By placing inverted-L- and T-shaped parasitic elements at both the radiating apertures of a microstrip patch antenna, a low-profile, compact single-layer multiband microstrip antenna operable in various bands has been developed. These bands include LTE TDD No. 34 (2.0175 GHz), WLAN (2.45 GHz), and WiMAX (3.5 GHz) bands. The antenna has dimensions of 0.26 λ_L ×0.25 λ_L ×0.03 λ_L, where λ_L is the free-space wavelength at 2.0175 GHz, and resonance in the parasitic elements occurs through coupling and perturbations to the microstrip patch. In each band, the measured -10-dB bandwidths cover the required bandwidths at 28 MHz (1.39%), 91 MHz (3.71%), and 255 MHz (7.29%). Within each of the designed bands, a broadside radiation pattern is observed.

A novel array configuration for improving the direction-finding (DF) accuracy of an interferometer DF system is presented. The interferometer DF system that uses a single array configuration provides a high DF accuracy over a wide frequency range. However, the DF accuracy in the low-frequency range for this array configuration is lower than that of the high-frequency range. The use of a different array configuration and spacing according to the frequency range or the extension of the widest baseline in the low-frequency range by the addition of an antenna can be applied to overcome this limitation. With the proposed method, the DF accuracy in the low-frequency band is improved while the DF accuracy in the high-frequency band is maintained. Simulation results for some examples are presented to demonstrate the effectiveness of the proposed array configuration.

A miniaturised dual-band S-shaped RFID tag antenna, which is mountable on a metallic surface, and which can handle UHF bands (Korea band: 908.5–914 MHz, Europe band: 865–868 MHz), is presented. The antenna was designed with a meander and spiral structure, through modifying the microstrip feeding line and ground line, and was miniaturised to a size of 20 mm (width)×33.5 mm (length)×2 mm (height). The maximum read ranges were 1.6 m (Korea band, EIRP of reader: 4 W) and 0.75 m (Europe band, EIRP of reader: 1 W), respectively.