Applications In Wireless Communication Systems Research Articles

Aperture‐coupling fed high isolation polarization diversity dual‐element MIMO antenna system for WLAN application

ABSTRACTA novel compact aperture‐coupling fed, polarized diversity, high port isolation microstrip MIMO (multiple input and multiple output) antenna with two antenna elements is presented for WLAN application in this letter. The unique metal radiator is shared by the two antenna elements and the dimension of the proposed MIMO antenna is reduced by nearly a half. In addition, a square slot is etched in the shared radiator to shrink the antenna. The dual ports of the proposed antenna are arranged orthogonally to accept the polarized diversity gain and a corner cut, an extra strip in the metal radiator is also the effective structure to improve the ports isolation. The optimized port isolation (S12/S21) is reduced to −50.3 dB at the resonance frequency f0 = 5.74 GHz and the port isolation is lower than −27.3 dB at the desired band from 5.58 GHz to 5.88 GHz. The performance of proposed antenna is good enough for the application in MIMO wireless communication system. The proposed MIMO antenna has been fabricated for the experimental test and the measured results had a good agreement with the simulated. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:1178–1182, 2017

Wideband directional antenna system with different polarizations for wireless communication system

A novel directional antenna system with different polarizations is proposed for wireless communication system application in this paper. The proposed antenna employs modified E-shaped rectangular patch for vertical polarization and crossed dipoles for ±45° slant polarization. The vertically polarized (VP) element is formed by inserting a pair of wide slits at the boundary of rectangular patch with edge folded. The VP element is fed by using an L-probe feed, designed to work at the frequency range of 773–1013MHz for GSM900 and other wireless communication systems such as GSM850 and LTE700 bands. Dual slant polarized (SP) elements are formed with two orthogonally situated dipoles with corner cut and slots on the patch, which yields a wide impedance bandwidth of 55.5% covering the frequency bands for 3G and LTE communication systems. A wideband diplexer is used to connect VP element and +45° SP element, forming a compact structure. Simulated and measured results show that peak gains of 8.0dBi for VP element and 9.5dBi for ±45° SP element, an isolation better than 26dB over the working frequency bands are achieved. The cross-polarization levels in the azimuth plane for triple polarization states are lower than −14dB.

High-Efficiency High-Isolation Dual-Orthogonally Polarized Patch Antennas Using Nonperiodic RAMC Structure

This communication presents dual-orthogonally polarized patch antennas using nonperiodic rectangle artificial magnetic conductor (RAMC) structure, which take the features of high efficiency and high isolation. The artificial ground composed of several nonperiodic RAMC cells is first theoretically analyzed by projecting it onto a cylindrical surface. It is found that the nonperiodic plane can be similarly equivalent to a cylindrical metal reflector for strongly focusing electromagnetic waves to realize an extremely directive antenna with high aperture efficiency. Based on the above analysis, a novel spherically projected nonperiodic RAMC plane is proposed, and two differentially fed dual-polarized patch antennas using the newly proposed plane are well designed accordingly. Both simulated and measured results demonstrate dual-polarized radiations with very high aperture efficiencies of about 90% and low cross-polarization levels of less than -20 dB at each state, as well as high polarization-isolations of over 30 dB. Compared with 3-D physical reflectors, the proposed artificial grounds not only have similar strong reflections for high-efficiency antennas, but also exhibit a low-profile planar structure, which would be more easily integrated with antennas for applications in wireless communication systems.

An Investigation of Resonant Modes in Rectangular Dielectric Resonator Antenna Using Transcendental Equation

This article presents an analysis of resonant modes in a rectangular dielectric resonator antenna and investigates the generation of higher order modes. Mathematical analysis of resonant frequency and transcendental equation using MATLAB has been performed. A prototype model for rectangular DRA has been developed. Resonant frequency of higher modes based on delta (ź) variation (where delta = 0.1---0.9) on Eigen vector has been investigated. The paper demonstrates that the design of a compact size dielectric resonator antenna (DRA) covering wide range of frequency with multiple modes is possible by selecting the value of p less than 1 (p < 1), where p is number of half-wave variations in the z-direction of TEmnp modes. An orthogonal feed has been used to cancel out the undesired modes. Simulations and experimental measurements were carried out to verify the proposed idea. Theoretical, simulated, and experimental results of resonant frequency and gain of the antenna have been compared and are found to be in agreement with each other. The results presented should have useful potential applications in wireless communication systems and satellite applications.

A Wide-Angle and Circularly Polarized Beam-Scanning Antenna Based on Microstrip Spoof Surface Plasmon Polariton Transmission Line

In this letter, a wide-angle beam-scanning antenna with circular polarization (CP) characteristic is proposed. The antenna consists of two layers. Microstrip spoof surface plasmon polariton (SPP) is introduced on the bottom layer as a slow-wave feeding line. A series of circular patches are placed on the top layer as radiating elements. Simulated and measured results indicate that beam-scanning angle of the proposed antenna is improved and CP beam-scanning ability is obtained by introducing perturbation on the radiating elements. In the operating band of 11–15 GHz, measured scanning angle of the fabricated antenna is from –32° to +34°. The antenna axial ratio (AR) is below 3 dB at the corresponding beam direction, and gain is above 12.8 dBi over the whole band. It has potential applications in radar and wireless communication systems for simple structure, low-cost fabrication, wide beam-steering, and CP properties.

A Broadband Dual-Polarized Base Station Antenna With Anti-Interference Capability

A broadband dual-polarized antenna with antiinterference capability is presented in this letter for base station applications. The proposed antenna contains three parts: main radiator, feed structures, and reflector. Specifically, the main radiator has two crossed dipoles to realize ±45° polarizations; two vertical substrates, which have Γ-shaped feeding lines on the front side and rectangle patches on the back side, are placed between the main radiator and reflector for feeding; the reflector placed below is used to get high gain and unidirectional radiation. In addition, C-shaped stubs are arranged next to the feeding lines in order to filter the unwanted frequency band. A prototype of the antenna was fabricated and tested. The measured results show that it has a bandwidth of 52.6% ( $\rm{VSWR ) along with a sharp notch band from 2.27 to 2.53 GHz. Measured isolation of higher than 25.4 dB, half-power beamwidth of around 60° and average gain of 7.57 dBi across the operating band are also obtained. Having the advantages of anti-interference capability, dual polarization, wide bandwidth, high isolation, and good radiation performance, the proposed antenna can find its application in the next-generation wireless communication systems.

Wideband Loop Antenna With Electronically Switchable Circular Polarization

This letter presents a novel printed antenna with wide bandwidth, high gain, and reconfigurable circular polarizations. A loop antenna is printed on both sides of a dielectric substrate: A dual-p-i-n-diode loaded loop is printed on one side, while a dual-gap loaded smaller loop is printed on the other side. By controlling the on–off states of the p-i-n diodes, the polarization of the proposed antenna can be switched electronically to right-hand circular polarization (RHCP) or left-hand circular polarization (LHCP) over a wideband frequency range. A prototype is fabricated and measured to verify the performance of the antenna. The measured results indicate that the antenna achieves an impedance bandwidth of over 30%, and a 3-dB axial-ratio (AR) bandwidth of 12.7% and 14.9% for RHCP and LHCP, respectively. The measured gain is around 8 dBic for the LHCP state and 7 dBic for the RHCP state. Due to the advantages of wide overlapped bandwidth, simple feeding structure, and high gain, this antenna is promising for applications in dual-CP wireless communication systems.

A Novel Broadband Circularly Polarized Monopole Antenna Based on C-Shaped Radiator

The design and implementation of a compact monopole antenna with broadband circular polarization is presented in this letter. The proposed antenna consists of a simple C-shaped patch and a modified ground plane with the overall size of 0.33 λ × 0.37 λ. By properly embedding a slit in the C-shaped patch and improving the ground plane with two triangular stubs, the measured broadband 3-dB axial-ratio bandwidth of 104.7% (2.05–6.55 GHz) is obtained, while the measured impedance bandwidth of 106.3% (2.25–7.35 GHz), defined by –10-dB return loss, is achieved. The performance for different parameters is analyzed. The proposed antenna is a good candidate for the application of various wireless communication systems.

Design and Development of a Conformal Printed sleeve dipole antenna operating in 800MHz to 3000MHz

In this paper, a conformal loaded printed sleeve dipole antenna operating in 800MHz to 3000MHz frequency band is designed and presented with measured results. The wide band characteristics are achieved using sleeve configuration along with capacitive loading. The proposed antenna has VSWR ≤ 3:1 with good radiation efficiency and omni-directionality. The proposed antenna is designed in CST Microwave StudioTM and fabricated using photolithography technique. As the antennas is printed on 10 mils thick RT Duroid 5880TM substrate. The antenna is flexible and can be conformed to given cylindrical shaped platform. The proposed conformal antenna finds wide applications in avionics and wireless communication systems.

Novel improved metamaterial transmission line and its application in wideband leaky-wave antenna with wide beam-scanning angle range and low cross-polarization

In this paper, a novel-improved metamaterial transmission line (MTM TL) is investigated and applied to design periodic leaky-wave antenna (LWA) with wide beam-scanning angle range and low cross-polarization. The improved MTM TL consists of metallic holes and interdigital fingers (which embedded in the main microstrip line). By introducing the metallic holes loaded in the interdigital fingers, the parasitic resonant modes of conventional MTM TL can be eliminated effectively. Considering the continuous phase constants changing from negative to positive values of the improved MTM TL under the balanced condition, a continuous beam-scanning property from backward to forward directions of the resultant periodic LWA can be obtained. For verification, a periodic LWA, which consists of 20 unit cells of the improved MTM TL, is fabricated and measured. The measured and simulated results are in good agreements with each other in all condition. According to the measured results, the fabricated periodic LWA operates from 3.38 to 4.60 GHz with a bandwidth of 30.57%, and achieves a continuous beam-scanning property from backward –65° to forward +71° (including broadside radiation) over the operating frequency band. Moreover, the measured cross-polarization remains at a level of more than 30 dB below the co-polarization across the entire radiation region. The presented LWA should find promising applications in modern wireless communication systems due to these wonderful electromagnetic performances.

A design of triple lines Wilkinson power divider for application in wireless communication systems

In this article, a novel microstrip Wilkinson power divider (WPD) has been analyzed, simulated, and fabricated, using the proposed triple lines (TLs) in place of the common quarter-wavelength transmission-line. The proposed structure has the high ability of selectivity for designing dimensions. In this direction with the use of PSO algorithm, optimized options will be obtained for the electrical lengths of the TLs. The characteristic admittances, with the intention of fabricating a structure with compact dimensions are also obtained. Besides, three coupled lines theory is used to reach a wideband performance. The proposed triple lines Wilkinson power divider (TLWPD) operates from 0.5 to 4.5 GHz with S11 < −10 dB, which include several wireless communication standards such as GSM, GPS, DCS, PCS, UMTS, WLAN, and WiMAX. The overall size of the TLWPD is 23.5 × 8.3 mm2 or 0.23 λg × 0.08 λg. The results of investigations taken in this article show the fact that the TLWPD, in addition to the small structure dimensions will be a wideband WPD.

Far-field characteristics of the square grooved-dielectric lens antenna for the terahertz band.

In order to improve the gain and directionality of a terahertz antenna, a square grooved-dielectric lens antenna based on a Fresnel zone plate is proposed. First, a diagonal horn, which is adopted as the primary feed antenna, is designed. Then, the far-field characteristics of the lens antenna are studied by using Fresnel-Kirchhoff diffraction theory and the paraxial approximation. The effects of the full-wave period, the focus diameter ratio, the subregion, and the dielectric substrate thickness on radiation characteristics are studied. The experimental results show that the proposed lens antenna has axisymmetric radiation patterns. The gain is over 26.1 dB, and the 3 dB main lobe beam width is lower than 5.6° across the operation band. The proposed lens antenna is qualified for applications in terahertz wireless communication systems.

Microwave Photonic Frequency Conversion With High Conversion Efficiency and Elimination of Dispersion-Induced Power Fading

In this paper, a novel microwave photonic mixer based on a single integrated dual-drive dual-parallel Mach–Zehnder modulator (DD-DPMZM) is proposed. One submodulator is used to generate a single sideband (SSB) signal of the local oscillator, whereas the other submodulator is used to generate a double sideband signal of the radio-frequency signal. By adjusting the main dc bias of DD-DPMZM, we can suppress the optical carrier at the output of the DD-DPMZM. Mixed signals can be obtained after a photodiode. The structure features the advantages of high conversion efficiency and the elimination of dispersion-induced power fading. An experiment is carried out to verify the effectiveness of the scheme, and a significant improvement of 15.5 dB in conversion efficiency compared with the conventional photonic mixer is achieved. In addition, it avoids the influence of fiber dispersion. The proposed mixer is promising to find applications in future wideband wireless communication systems.

Design of leaky‐wave antenna with wide beam‐scanning angle and low cross‐polarisation using novel miniaturised composite right/left‐handed transmission line

In this study, a novel periodic leaky-wave antenna (LWA) with wide beam-scanning angle and low cross-polarisation is proposed by using miniaturised composite right/left-handed transmission line (CRLH TL). By introducing the metallic holes loaded in the interdigital lines of the miniaturised CRLH TL, not only the parasitic resonant modes can be eliminated, but also the miniaturisation is realised. Considering the continuous phase constants from negative to positive values of the balanced CRLH TL, a continuous beam-scanning property from backward to forward of the resultant LWA can be obtained. For verification, a periodic LWA, which consists of 20 unit cells of the balanced CRLH TL, is fabricated and measured; the measured and simulated results are in good agreements with each other, indicating that the fabricated LWA operates from 3.90 to 4.90 GHz (a bandwidth of 22.7%), and has a wide continuous beam-scanning capability from backward −61° to forward 67° (including the broadside) within the operating band. Moreover, it also has very low cross-polarisation, which remains at a level of at least 25 dB below the co-polarisation across the entire radiation region. As a result, the presented LWA should find promising applications in modern wireless communication systems and the high-resolution radar system due to these wonderful electromagnetic performances.

Microwave dielectric properties of low-fired Li2MnO3 ceramics co-doped with LiF–TiO2

Li2MnO3 ceramics co-doped with 2wt% LiF and xwt% TiO2 (x=0, 3, 5, 7, 10) were prepared by solid-state reaction for low-temperature co-fired ceramics (LTCC) applications. The sintering temperatures of Li2MnO3 ceramics were successfully lowered to925°C due to the formation of a LiF liquid phase. Their temperature stability was improved by doping with TiO2. A typical Li2MnO3-2wt% LiF-5wt% TiO2 sample with well-densified microstructures displayed optimum dielectric properties (εr=13.8, Q×f= 23,270GHz, τf=1.2ppm/°C). Such sample was compatible with Ag electrodes, which suggests suitability of the developed material for LTCC applications in wireless communication systems.

Bayesian Inference, Stochastic Simulation and Their Applications in Wireless Communication Systems

Bayesian inference has been successfully applied in fields as varied as anti-spam filtering, DNA sequencing, war codebreaking and election forecasting. Founded on the apparently simple Bayes’ theorem, which relates the previous distribution of a parameter with its distribution after evidence is collected, Bayesian tools allow for incorporating all existing knowledge about the phenomenon under study in order to improve parameter estimation. Because of the stochastic nature of the wireless channel, Bayesian inference is particularly well suited to the problem of symbol detection in many modern digital communication systems. When combined with Markov Chain Monte Carlo (MCMC) techniques, Bayesian receivers are capable of achieving minimum Bit Error Rate (BER) while avoiding the prohibitively high computational complexity associated with standard Maximum Likelihood (ML) or Maximum A Posteriori (MAP) estimators. In addition, such receivers are capable of numerically integrating out channel coefficients and noise variance, thus avoiding the need to use sub-optimal estimates of these parameters. This tutorial presents the rudiments of Bayesian statistics and MCMC in general, and discusses their applications in wireless communications in particular. The paper also details the design of Bayesian MCMC receiver in a system employing BPSK and ubject frequency-selective fading and Gaussian noise. Afterwards, recent advances in Bayesian receivers are surveyed for several important practical wireless transmission schemes, including MIMO, CDMA and OFDM. In addition, the paper addresses the application of Bayesian tools in challenging channel conditions — namely, nonlinear, non-Gaussian, underwater and fast fading channels.

Ultrasmall Dual-Band Metamaterial Antennas Based on Asymmetrical Hybrid Resonators

A new type of hybrid resonant circuit model is investigated theoretically and experimentally. The resonant model consists of a right hand (RH) patch part and a composite right and left handed (CRLH) part (RH + CRLH), which determines a compact size and also a convenient frequency modulation characteristic for the proposed antennas. For experimental demonstration, two antennas are fabricated. The former dual-band antenna operating at f-1=3.5 GHz (Wimax) and f+1=5.25 GHz (WLAN) occupies an area of 0.21λ0×0.08λ0, and two dipolar radiation patterns are obtained with comparable gains of about 6.1 and 6.2 dB, respectively. The latter antenna advances in many aspects such as an ultrasmall size of only 0.16λ0×0.08λ0, versatile radiation patterns with a monopolar pattern at f0=2.4 GHz (Bluetooth), and a dipole one at f+1=3.5 GHz (Wimax) and also comparable antenna gains. Circuit parameters are extracted and researched. Excellent performances of the antennas based on hybrid resonators predict promising applications in multifunction wireless communication systems.

Design of a compact dual-band folded-waveguide bandpass filter using multilayer waveguide resonators

A novel compact dual-band bandpass filter based on multilayer folded-waveguide (FWG) structure is presented in this article.In this design, slots are used to realize direct coupling between adjacent resonators and apertures are adopted to implement cross coupling between non-adjacent resonators.A new technique of external quality factor of FWG resonator and coupling coefficients between different resonators are studied using full-wave simulator. In order to demonstrate the proposed technique, a four-pole dual-band bandpass filter is designed, fabricated and measured using vector network analyzer. Measurement results which are well agreed with simulation results are presented. Moreover, four-pole substrate integrated folded waveguide SIFW dual-band bandpass filter, using two layers of slotted folded waveguide resonators, is demonstrated. The proposed filter has a compact size and it is excellent candidate for the application of wireless communication systems. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:780–788, 2015.

Improving microwave antenna gain and bandwidth with phase compensation metasurface

Metasurface, as a planar version of artificial metamaterial, provide an effective way to manipulate electromagnetic wave propagation. Here, we present a transparent metasurface for compensating the out-of-phase radiation from a microstrip patch antenna to improve its radiation gain and bandwidth. Based on the equivalence principle of Huygens’ surface, we propose metasurface composed of both inductive and capacitive resonant elements which could produce high transmission with variable phase characteristics. Such metasurface mounted on a patch antenna can transform the spherical-like phase profile generated from the patch into an in-phase planar one. A prototype antenna has been fabricated and validated the squeezed radiation pattern with suppressed sidelobes as well as enhanced impedance bandwidth due to strong near-field coupling. As operating at around 5.7 GHz, the proposed antenna may have potential application in wireless communication systems especially for point-to-point data transmission. It is believed that the design methodology could also be scaled to other frequency bands such as millimeter or terahertz wave.

Design of Microstrip Triplexer Using Common Dual-Mode Resonator with Multi-Spurious Mode Suppression for Multiband Applications

A triplexer is an important component for channel separation in microwave front-end systems. This paper proposes a triplexers designed with common dual mode resonator sections have been proposed. By exploiting the variable frequency response of the stepped-impedance resonator, resonators can be shared by the three filter channels of the desired triplexer if their fundamental and the first spurious resonant frequency are properly assigned. Triplexer design method for suppressing spurious responses in the stopband by choosing the constitutive resonators with the same fundamental frequency, but staggered higher order resonant frequencies. The design concept is demonstrated by three of third order parallel-coupled bandpass filters. The bandpass filter is composed of three different stepped impedance resonators for which a general design guideline had been provided in order have the same fundamental frequency and different spurious frequencies. The measured results are in good agreement with the simulated predictions, whereby the spurious responses in the upper stopband can be suppressed below-25dB up to 14 GHz, which can be quite useful for multiband and multiservice applications in future wireless communication systems.