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In this article, a compact broadband circularly polarized (CP) antenna with non-planar reflector is presented. In this antenna, two fan-shaped cross-dipoles as the primary radiator and a stepped ground as a reflector are proposed to generate a broadband CP radiation. Besides, four L-shaped patches are introduced to effectively extend the bandwidth (BW) and extract a gain improvement together with the stepped ground. The measured -10 dB impedance BW is 132.08 % (1.36-6.65 GHz) and 3 dB axial ratio (AR) BW is 128.6% (1.39-6.4 GHz), closely with the simulated AR BW 136.73% (1.18-6.28 GHz), showing the proposed antenna features a wider bandwidth, comparing with other broadband CP antennas using similar structures. Due to the compact structure, the overall size of the proposed antenna is only 0.27λl×0.27λl©0.12λl (where λl is the free-space wavelength at 1.36 GHz). The proposed antenna has a wide application scope, such as the wireless network and satellite telecommunications.

A flexible dual-band antenna with a metamaterial structure (MS) is presented. Polyimide substance, which makes the antenna thin and bendable, is used as the substrate for the antenna. When the MS is placed between the antenna and the human’s forearm, the antenna gain is increased by 9.3 and 5.37 dB, and the radiation efficiency is increased by 48.4% and 35.7%, at 2.45 and 5.8 GHz, respectively. In addition, the specific absorption rate is decreased by more than 70%, considering the limitations imposed by Federal Communications Commission and the regulation of International Commission on Non-Ionizing Radiation Protection (ICNIRP) for the frequencies cited above. The fabricated prototype of the antenna with the integrated MS was investigated by placing it on different places of human body, as also on different human bodies. The obtained results show that the proposed antenna is safe and suitable for use, in terms of the ICNIRP standards of World Health Organization.

A wearable antenna based on the metal watch strap is proposed. A prototype of a TISSOT classic watch is used for the demonstration. The width of the strap has only a little impact on the radiation patterns. However, the variations of the feeding location would dramatically influence the resonance frequency and the matching performance. The shapes and the graphic patterns of the wristband have contributions on the reflection coefficients as well as the radiation patterns. A fractional bandwidth of 77.8% could be obtained when feeding to the right of the dial at 2.46 GHz, which falls into the ISM (industrial, scientific, and medical) band. The main lobe is fairly wide in both $E$ - and $H$ -planes, which would enable the strap antenna to have a good adaptation for the various postures of the arm. The measurement results show good agreement with that of the simulations, which indicates it a potential option for the applications of wearable systems.

An improved element pattern reconstruction method is introduced to calibrate the mutual coupling effect of antenna arrays, and its applications in wide-angle direction-of-arrival estimation are presented. In this method, direction-of-arrival estimations and a calibration matrix are achieved by alternate iteration. The improved method can achieve a more accurate calibration matrix and direction-of-arrivals with less calculation time and iterations than the joint estimation methods for direction-of-arrivals and calibration matrix. Additionally, the angle ranges of direction-of-arrival estimations can be widened by this method for practical antenna arrays. The validity was verified by some numerical examples with a microstrip antenna array.

This paper presents a coplanar waveguide (CPW)-fed slot antenna consisting of a slotted ground and a parasitically coupled split ring for multiband operation. In the design, the use of both the loaded split ring to rectangle wide slot and embedded L-slots into the ground is found an effective skill for exciting multiresonant modes as well as miniaturizing the slot antenna. The numerical and experimental results show that the optimal antenna has triple operating bands below – 10-dB reflection coefficients magnitude |S 11|) centered at 2.4/3.5/5.8 GHz covering the required bandwidths of various wireless communication standards. In addition, stable monopole-like radiation patterns and acceptable antenna gains are achieved across the operating bands.

A novel compact triple-band slot antenna is proposed for WLAN/WiMAX applications. With the use of three L-shaped slots and an open-ended slot on the ground plane, three resonant modes centered at 2.4/3.5/5.8 GHz are excited. These modes cover the standards of 3.5 GHz WiMAX and 2.4/5.8 GHz WLAN, three useful frequency bands for present wireless communication systems. The proposed antenna fed by L-shaped microstrip line has a small overall dimension of16×30 mm2. The numerical and experimental results show that acceptable radiation characteristic is obtained over the operating bands.

This paper analyzes the suitability of several important parameters which would influence on the signal combining efficiency in antenna arraying techniques. We establish a simulation model in Matlab Simulink environment. The numerical results demonstrate the relationship between the combining loss and each parameter clearly.