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A novel textile antenna is proposed to produce an omnidirectional radiation pattern. It can be integrated with clothes as a wristband due to its cylindrical conformal design. The antenna has a resonant cavity fabricated from conductive fabric and filled with cotton fabric. Three edges of the cavity are short-circuited with conductive threads and coupled-fed by a patch coupler fabricated with flexible printed circuit (FPC). Theoretical analysis shows that the proposed antenna is equivalent to a magnetic current loop, which produces a dipole-like radiation pattern when its radius is less than 0.4 wavelengths. Simulated results show that the antenna produces a low specific absorption rate (SAR) when it is loaded on human tissues. Measured results show a bandwidth from 2.36 GHz to 2.52 GHz with an omnidirectional radiation pattern. The peak gain varies between 0.6 dBi and -0.6 dBi within the bandwidth. The small thickness and simple structure of the proposed antenna make it a good candidate for wearable applications.

In this paper, a gain-enhanced patch antenna with a periodic microstrip rampart line is proposed. The periodic microstrip rampart line can modify the effective dielectric constant of the dielectric plate, and help to improve the gain of the traditional microstrip patch antenna. Based on the antenna design principle, a formula for calculating the gain-enhanced frequency point is proposed. A proposed high gain microstrip antenna is designed, fabricated and tested. The experimental results demonstrate that the gain of the proposed antenna reaches 10.0 dBi, which is 2.55 dB or 79.9% higher than that of the traditional patch antenna at the same operating frequency of 5.8 GHz. The measured and simulated results show a high consistency.

The alternating direction implicit parabolic equation (ADI-PE) method and the Crank–Nicolson parabolic equation (CN-PE) method have been widely used for solving the 3D parabolic equation (3D-PE) in radio wave propagation. The ADI-PE method is more computationally efficient than the CN-PE method. The accuracy of the ADI-PE method is improved by the higher-order Mitchell–Fairweather (MF)-ADI method. This paper presents an iterative high-accuracy (IHA)-ADI method for the 3D parabolic equation. A derivation of the proposed method is presented. The convergence and stability of the proposed method are estimated. Several numerical examples are considered to illustrate the advantages of the proposed method. The results of error analysis and a comparative study show that the proposed method is unconditionally stable and computationally efficient. The proposed method is more numerically accurate than the MF-ADI method.

A periodic microstrip leaky wave antenna (MLWA) constructed of non-uniform aspect ratios microstrip patch periods is presented in this communication. Effective equations and simulations for the relevant antennas are used to obtain the propagation constants of the proposed antenna and design it. However, due to the presence of an open stop-band (OSB) in the broadside direction, double-side parallel-strip lines are then introduced in the antenna design. Truncating and interlacing the unit cells are developed to make them become impedance matched structures with the elimination of the OSB and the improvement of the radiation patterns. As a result, a new antenna configuration is created, and a prototype of the antenna is fabricated and measured. Continuous main beam scanning is observed from back-firing to end-firing with the operating frequency band of 4.8-18 GHz. Excellent agreements between the predicted and measured results are obtained. The measured peak gain of the prototype is 14 dBi, and the gain exceeds 6 dBi over the frequency band.

A multi-frequency patch antenna with double-sided parallel-strip line (DSPSL) periodic offset structure is proposed. The designed antenna consists of a simple rectangular patch as well as an embedded one-dimensional DSPSL periodic offset structure, which is employed to replace the traditional rectangular microstrip patch antenna. The periodic DSPSL structure is characterized leaky wave structure. After the periodic DSPSL structure is embedded, the resonance frequency of rectangular patch is offset, and the leaky wave characteristics can determine the number and position of new operating frequencies. As an application, a tri-band antenna is manufactured and these three operating frequencies can be calculated by the derived formulas studied in this communication. Experiment results suggest that the antenna can work at 4.28, 4.78, and 6.42 GHz, respectively. The results of simulated, measured and calculated show high consistency.

An approximate circuit model to analyze microstrip rampart line in open-stopband (OSB) suppressing is presented. The proposed antenna consists of periodically orthogonally bending microstrip transmission line, and the widths of two transversal lines are adjusted to match the input impedance of the unit cell to the characteristic impedance of the transmission line. The approximate circuit model is presented to analyze the behavior of the PLWA. The prototype antenna shows a seamless frequency scanning from 3.7 to 6.8 GHz with a scanning range of 118° from the backward to forward quadrant. The simulation and measured results have demonstrated that the OSB is successfully suppressed in the improved case.

A novel reconfigurable microstrip magnetic dipole antenna with switchable conical beams is proposed for aerial drone applications. The proposed antenna consists of three sub-cavities that are separated by two groups of shorting posts. To reconfigure the resonant cavities, a number of p-i-n diodes are connected to the shorting posts and are used as RF switches. The antenna is capable of resonating in three different operating states. The theoretical analysis shows that the three resonant modes produce conical beams with different elevation angles. The reconfigurable microstrip magnetic dipole antenna yields an overlapping bandwidth from 2.39 to 2.49 GHz for WLAN 2.4-GHz application and produces switchable conical beams for different operating states. The peak gain is 3.9, 4.0, and 4.3 dBi, respectively, when the elevation angle is 90°, 66°, and 54°. The conical beams have omnidirectional radiation patterns in the azimuth plane for the elevation angles. The proposed antenna shows promise for improving the transmission of aerial drones operating at varying altitudes.

A periodic fixed-frequency staggered line leaky wave antenna (LWA) with wide-range beam scanning capacity is proposed in this paper. The reconfigurable antenna is based on a periodic staggered line LWA. The dispersion and Bloch characteristics of the periodic antenna is analyzed by the Macro Cell Method (MCM). The open-stop band (OSB) of the antenna can be suppressed effectively using the relationship between widths of oblique feeding lines and stubs. The reconfigurable characteristic is achieved by switches and microstrip lines between the edge gaps of each unit cell. A “supercell” is established by combining several reconfigurable unit cells, and the state is controlled by connecting or disconnecting the edge gaps of each unit cell using switches. Fixed-frequency beam-scanning capacity is implemented due to different propagation constants in different supercell states. The prototyped reconfigurable antenna can scan the beam between 130° and 54° at 4.5 GHz.

A novel dual-band printed end-fired antenna with double-sided parallel-strip line (DSPSL) feeding is presented. The DSPSL acts in wideband transition using balanced transmission. Two different modes of the parasitic patches allow the antenna to work in different bands. The printed antenna is designed as a quasi-Yagi structure to achieve directivity in the lower band, and the parallel rectangular patches serve as the parasitic director. These patches act as radiation patches with end-fire direction characteristics in the upper band. The measured bandwidths were 18.3% for the lower frequency band (2.28–2.74 GHz) and 12.6% for the upper frequency band (5.46–6.2 GHz).

A new center-fed circular patch antenna with two coupled annular rings is presented. When the two annular rings are coupled properly, a wide band from 5.45 GHz to 7.16 GHz is achieved with a monopole-like radiation pattern. Measured results show that the antenna with a low profile of 0.027 wavelengths (at 5.45 GHz) has a bandwidth of 27.1% and a measured maximum gain of 6 dBi. The radiation pattern is omnidirectional and remains relatively stable within the operating band.

A multi-band monopole antenna with the improved inverted-trapezoidal coplanar waveguide (CPW) feeding is presented. The antenna has a simple planar structure, and occupies an area of 15 mm × 50 mm. The proposed antenna consists of an improved inverted-trapezoidal CPW-fed patch, and a series of monopole strips with different length. This monopole antenna utilizes the advantages of the CPW feeding to simplify the structure of the antenna into a single metallic level and achieve high antenna gain. The improved inverted-trapezoidal CPW-fed patch and a meander shorting strip lead to a better impedance matching result and multi-band operation. The experimental results of the proposed antenna are shown and discussed. The antenna generates two wide bands centered at about 900 and 2200 MHz to cover the GSM850/GSM900/DCS/PCS/UMTS/LTE2300/2500 bands and the 2.4 GHz WLAN operation. Meanwhile the antenna covers the 4 G bands of China Telecom (2370–2390 MHz/2635–2655 MHz), China Unicom (2300–2320 MHz/2555–2575 MHz) and China Mobile (1880–1900 MHz/2320–2370 MHz/2575–2635 MHz), too.

A novel dual-frequency broadband design of a stacked microstrip monopolar patch antenna is proposed for WLAN applications. The antenna is composed of a via-loaded ring on the bottom layer and a circular patch on the top layer, both of which are coupled-fed by a circular coupler. A broad lower band is generated by converging the TM01 and TM02 modes of the via-loaded ring, and a broad upper band is yielded by coupling the TM03 mode of the via-loaded ring and the TM02 mode of the circular patch. Measured results show that the proposed antenna provides a broad lower band from 2.28 to 2.55 GHz and a broad upper band from 5.15 to 5.9 GHz with a low profile of 6 mm. Monopole-like radiation patterns are obtained in the dual bands with peak gains in the lower and upper bands of about 5 and 6 dBi, respectively. [ABSTRACT FROM PUBLISHER]