Modern Wireless Communication Systems Research Articles

A New Class of Highly-Miniaturized Reconfigurable UWB Filters for Multi-Band Multi-Standard Transceiver Architectures

Modern wireless communication systems typically employ multiple frequency bands for several standards. A new class of miniaturized ring filters with tuning capability is introduced for this purpose. The proposed filter structure is based on a single multi-mode resonator with variable section impedances in microstrip technology. The bandwidth of the filter can be significantly extended to cover the whole ultra wideband (UWB) frequency range with high adjustability. Moreover, a tunable bandnotch is introduced within the filter response, which can be arbitrarily placed according to the required application. Varactor and PIN diodes are also utilized to facilitate a high tuning capability throughout the different filter characteristics with respect to bandwidth, center frequency, and bandnotch frequency. Based on the symmetry of the filter, even-odd mode analysis is applied to investigate the different filter design characteristics. In addition, a comprehensive transmission line model is investigated within this paper which showed excellent agreements with full-wave simulations and measurements. The implemented UWB filter is investigated with respect to its frequency-domain characteristics and group delay response. The realized filter has a fractional bandwidth of more than 119% with a low group delay. All measured results are in a very good agreement with analysis and simulations. The overall filter dimensions, including housing, do not exceed 25 mm $\times 25$ mm.

Self‐adapting conformal phased array antennas for complex changing surfaces

ABSTRACTConformal antennas placed on complex surfaces are gaining more attention as a method to increase coverage of modern wireless communication systems. These antennas are capable of adapting to surfaces that change shape in time thus raising the issue of keeping the radiation pattern undistorted when the array is deformed. In this work the projection method is exploited to solve this problem and to fabricate two new self‐adapting conformal array antennas: a 1 × 4 and a 1 × 6 arrays that bend according to an S‐shaped and a Z‐shaped surface respectively. These two conformal arrays consist of microstrip patch antennas distanced from each other, a reconfigurable sensor circuit used to measure the curvature of the conformal surfaces and voltage controlled phase‐shifters through which phase‐compensation is implemented to autonomously recover the radiation pattern as the surfaces on which the arrays are placed change shape. Throughout this paper analytical computations, full‐wave numerical simulations and measurements are compared and shown to agree. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:393–399, 2017

Adaptive Beamforming in TDD-Based Mobile Communication Systems: State of the Art and 5G Research Directions

Adaptive beamforming has been attracting considerable attention from both academia and industry for decades. It has already played an important role in modern wireless communication systems. This article provides an overview of adaptive beamforming and its application in cellular systems including the fundamental principle and schemes. This article points out that TD-SCDMA 3G spins off the commercial scale of adaptive beamforming in cellular networks. Beamforming-based spatial multiplexing is a breakthrough in adaptive beamforming and the symbolic technology of TD-LTE 4G. The standardization of adaptive beamforming in 3GPP LTE networks is summarized. To evaluate adaptive beamforming techniques, system simulation and field test results from commercial TD-LTE 4G networks are presented and associated with gains achieved through adaptive beamforming in different scenarios. Finally, future research areas of massive beamforming in 5G are envisioned.

Introduction to the Issue on Signal Processing for Exploiting Interference Toward Energy Efficient and Secure Wireless Communications

INTERFERENCE has been the central focus for meeting the ever increasing requirements on quality of service in modern and future wireless communication systems, and has long been considered as a deleterious factor that limits the system capacity. In conventional communications systems, the design objective is to allow users to share a medium with minimum or no interference. Thus, great efforts are made to avoid, mitigate, and cancel interference. For instance, to support multiple users, orthogonal access methods in time, frequency, code well as spatial domains have been used in different generations of cellular systems. In future-generation heterogeneous cellular networks, due to the increasing number of uncoordinated lowpower nodes such as femtocells to improve the coverage and pacity, interferences need to be mitigated in multiple domains, rendering their management a challenge. Interference mitigation/avoidance techniques provide convenient mechanisms allow multiple users to share the wireless medium. However, they lead to inefficient use of wireless resources.

A novel single feed frequency and polarization reconfigurable microstrip patch antenna

In this paper, a novel single feed frequency and polarization reconfigurable microstrip patch antenna is presented. This antenna mainly comprises of a corner truncated square patch with a rectangular ring slot, eight PIN diodes and six conductive pads. Four PIN diodes are placed symmetrically in the rectangular ring slot to bridge the gap and to switch the frequency between WLAN bands resonating at 5.2GHz and 5.8GHz. Four PIN diodes connect the corner truncated square patch to parasitic triangular conductors. PIN diodes are used to switch the polarization between linear, right hand circular and left hand circular at each frequency. When compared to conventional patch, the proposed design provides a size reduction of 12% at 5.2GHz, and 30% at 5.8GHz. The simulated reflection coefficient and radiation patterns are presented and compared with the experimental data. This antenna finds applications for modern wireless communication system.

OFDM symbol detection integrated with channel multipath gains estimation for doubly-selective fading channels

Orthogonal Frequency Division Multiplexing (OFDM) is a technique for wideband transmission that is commonly used in modern wireless communication systems because of its good performance over frequency selective channels. However OFDM systems are sensitive to channel time variations resulting in Inter-Carrier Interference (ICI), that without suitable detection methods can degrade performance significantly. Channel State Information (CSI) is essential to various OFDM detection schemes, and its acquisition is a critical factor over time varying channels. This work considers a Kalman filter channel multipath gains estimation technique for time varying environments, integrated with a novel detection scheme for OFDM based on a Sphere Decoding (SD) algorithm derived to exploit the banded structure of the channel matrix. This combined scheme employs decision–feedback from the SD requiring only a low pilot symbol density, and hence improves bandwidth efficiency. Three techniques for integrating the Kalman filter operating in decision–feedback mode, with SD data detection that produces these decisions, are considered in this paper. When compared with other competing schemes, this integrated symbol detection and channel multipath gains estimation approach for OFDM provides performance advantages over time varying channels. Furthermore, it is shown that for moderate Doppler shifts the degradation that carrier phase noise induces in this scheme is small.

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.

Interview

Dr Jianpeng Wang, from the Nanjing University of Science and Technology in China, talks about the work reported in their Letter ‘Compact microstrip balun diplexer using stub-loaded dual-mode resonators’, page 1994. Dr Jianpeng Wang As is well known, dual-band operation is frequently demanded in transceiver modules of modern wireless microwave communication systems. Rather than arranging two separated frequency-selective radio frequency (RF) circuits in the systems, many researchers choose an independent device, i.e., the diplexer, to support such systems. This is a useful component for reducing the overall size of RF transceiver applications. Microstrip diplexers are a three-port passive devices, which have the capability to split common input signals into two individual output streams operating in different frequency bands with high port-to-port isolation. The involved stub-loaded resonators in our design are the typical form of the dual-mode resonator. Their resonant properties have been characterised by using the even-odd mode analysis method. Through this method, we can examine how, by properly adjusting the length of the loaded stub, the even-mode resonant frequency of the dual-mode resonator can be tuned, while keeping the odd-mode resonant frequency almost unchanged. In this context, two resonant frequencies generated by the employed stub-loaded resonator can be flexibly controlled to realise a dual-mode response, which will substantially decrease the size of the balun diplexer, making it preferable to single mode resonators. In general, the utilised resonators play an important role in the implementation of compact balun diplexers with a certain bandwidth and two transmission poles in each operating band. What makes our work unique is the implementation of a typical multi-function integrated component, which effectively simplifies the circuit design, and reduces the overall size of radio frequency (RF) transceiver front-end systems. During the design phase, each balun filter channel in the diplexer can be independently controlled without effecting others, thus showing greater flexibility. Furthermore, no additional T-junction or matching networks are demanded at the common input port in our balun diplexer design. In our Electronics Letters paper, we introduced a new microstrip unbalanced-to-balanced (balun) diplexer, which utilises the stub-loaded dual-mode resonators. The proposed diplexer consists primarily of two balun filter channels. Meanwhile, these two balun filter channels are directly connected through a common open-circuited half-wavelength transmission line without any additional matching network. This unique property will reduce the overall size compared with other diplexer circuits using T-junction for the purpose of impedance matching. By adopting this method, we can create a compact, high performance balun diplexer with a remarkably simple structure. These changes are meaningful for RF engineers who design multi-function embedded unbalanced-to-balanced feeding networks in modern dual-band wireless communication systems. The presented design concept is a worthy guideline for the implementation of multi-function embedded passive components. In short, compared with the current approaches, it is more desirable to develop multi-function embedded components based on the viewpoints of explicit operation principles, simple structures, and high performances. In this way, these components can really facilitate and simplify RF transceiver front-end systems. It is our belief that components or systems using these techniques will prove more valuable to the engineering community.

U‐shape broadband monopole antenna with modified ground plane

ABSTRACTIn this article an U‐shape broadband monopole antenna with rectangular slots loaded ground plane has been designed and analysis. The proposed antenna covers the frequency band of (1.55–8.55 GHz) with multiresonating frequency at 1.65, 2.9, and 7.95 GHz. The effect of movement of radiating patch on the dielectric substrate and the effect of slots on the ground plane are studied. The maximum impedance bandwidth of 138% (simulated) and 142% (measured) with maximum peak gain 3.59 dBi (simulated) and 4 dBi (measured) are obtained. It is very much useful in modern wireless communication systems as an electronics device. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2544–2547, 2016

A compact novel microwave liquid crystal tunable band-pass filter

In this paper, a nematic liquid crystal is used to design a compact tunable band-pass filter at microwave band. The structure and the principles of tunable filters with nematic liquid crystals are analyzed. According to simulation results of the transmission property, it shows that the proposed liquid crystal tunable filter keeps the many advantages of the conventional tunable filter and has better passband performance. The simulated and measured reaults show that the proposed tunable filter has additional advantages of being continuously tunable, miniaturizable, and having low processing costs and low tuning voltage. Therefore, it has shown greater potentials for modern wireless communication systems.

IRadiation Induced SET Impact on DG-FINFET based LC-VCO Design

In wireless communication system, the supply voltage should be as low as possible to increase operation time of the system. This shows how importance the low-power circuits are in this field. Recently, there has been considerable interest in the use of Fin type Field Effect Transistor (FinFET) technology to implement RF components such as low-noise amplifiers (LNAs), mixers, and voltage-controlled oscillators (VCOs). VCOs are critical building blocks in modern wireless communication system which is mainly used in Phase Locked Loop. This work describes designing and simulation of Double Gate (DG) FinFET based Inductor (L) and Capacitor (C) tank VCO and the radiation effect of single event transient (SET) on the topology. The LC VCO topology is implemented with 30 nm DG-FinFET technology with 1V as DC power supply voltage which oscillates at 32.61 GHz frequency, results the VCO draws 64.97 μA current and an average power consumption of 64.97 μW. The measured phase noise of the topology is -120.54dBc/Hz at 1 GHz offset frequency and Figure of Merit (FOM) is - 162.68 dBc/Hz at 1 GHz offset frequency.

Effects of radio- and microwaves emitted by wireless communication devices on the functions of the nervous system selected elements

Nervous system is the most "electric" system in the human body. The research of the effects of electromagnetic fields (EMFs) of different frequencies on its functioning have been carried out for years. This paper presents the results of the scientific literature review on the EMF influence on the functioning of the human nervous system with a particular emphasis on the recent studies of the modern wireless communication and data transmission systems. In the majority of the analyzed areas the published research results do not show EMF effects on the nervous system, except for the influence of GSM telephony signal on resting EEG and EEG during patients' sleep and the influence of radiofrequency EMF on the cardiovascular regulation. In other analyzed areas (EMF impact on sleep, the evoked potentials and cognitive processes), there are no consistent results supporting any influence of electromagnetic fields. Neurophysiological studies of the effect of radio- and microwaves on the brain functions in humans are still considered inconclusive. This is among others due to, different exposure conditions, a large number of variables tested, deficiencies in repeatability of research and statistical uncertainties. However, methodological guidelines are already available giving a chance of unifying research that definitely needs to be continued in order to identify biophysical mechanisms of interaction between EMFs and the nervous system. One of the EMF research aspects, on which more and more attention is paid, are inter-individual differences. Med Pr 2016;67(3):411-421.

Frequency reconfigurable self‐adapting conformal array for changing surfaces

Conformal antennas placed on complex surfaces are receiving more attention as a method to increase the coverage of modern wireless communication systems. Furthermore, frequency reconfigurable antennas are being used in the development of multi-band multi-radio wireless platforms to simplify designs. In this study, theoretical development and a new 1 × 4 frequency reconfigurable self-adapting conformal antenna array that can be attached to changing conformal surfaces is presented. This conformal array consists of four reconfigurable microstrip patch antenna elements, a reconfigurable sensor circuit used to measure the curvature of the conformal surface and voltage controlled phase shifters. These phase shifters are controlled by the reconfigurable sensing circuit to implement phase-compensation to autonomously recover the pattern in both bands of the reconfigurable 1 × 4 array as the wedge- and cylindrical-shaped surface on which the array is attached upon change in shape. Throughout this study, analytical computations, simulations and measurements are compared and shown to agree.

A Survey on Design and Optimization of Microstrip Patch Antenna

Microstrip patch antenna is among the important elements of modern wireless communication systems and hence its designing and optimization has become an important aspect for improving the overall performance of the system. In this paper microstrip patch antenna geometry has been discussed along with the performance analysis of various papers over which the survey was conducted. The main objective behind writing this paper is to provide researchers with background of microstrip patch antenna geometries and optimization techniques so as to make it easier for researchers to choose the method best suited to their aims. Future scope of the study is also given which will help in further advancements in the optimization of microstrip patch antenna.

Analysis on LUT based digital predistortion using direct learning architecture for linearizing power amplifiers

In modern wireless communication system, power amplifier (PA) is an important component which is expected to be operated at the region of high power efficiency, but in this region, PA is inherently nonlinear. Thus, the linearization of high power efficient PA is necessary. In this paper, direct learning architecture (DLA) and indirect learning architecture (ILA) are firstly compared. It shows that DLA is more robust than ILA. Then a baseband digital predistortion (DPD) method with DLA is proposed for power amplifier linearization based on combined look-up tables (LUT) and memory polynomial (MP) model. The main innovation is that a LUT-based approach is proposed to calculate directly the complex-valued predistorted signal. Moreover, some interpolation techniques are introduced to reduce the LUT size. The proposed DPDs are validated experimentally. Additionally, the influences of some important parameters in experimental setup, such as the number of bits of analog-to-digital converter (ADC) and the instrument bandwidth, are analyzed.

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.

Compact microstrip diplexer using new design of triangular open loop resonator for 4G wireless communication systems

A compact microstrip diplexer for 4G wireless communication systems is proposed in this paper. This diplexer consists of two bandpass filters based on the triangular open loop asymmetric stepped impedance resonator in order to have a small size as well as simple structure. The T-shaped open stub is used for attenuating the undesired modes. Attenuation level for the proposed diplexer is less than 21dB in the range of 0–10GHz owing to using this T-shaped open stub. The center frequency of each filter can easily change in the range of 20MHz through varying the gap length of the resonator without any changes in the whole structure of the diplexer. The result of this is the stability of other parameters like insertion loss, return loss and isolation. This diplexer has a narrow band frequency response that makes it suitable for modern wireless communication systems. Finally, the diplexer is fabricated at 2.30 and 2.55GHz and measurements demonstrate a good agreement between simulated and fabricated diplexer.

Effect of Swastika Slot in Square Fractal Antenna

In the modern wireless communication systems, antennas of multiple bands, smaller size and wider bandwidth are high in demands to meet the requirement of multiple applications. This has initiated the research in new antenna fields; fractal antenna theory is one among them. Its unique properties such as selfsimilarity and space filling lead to multiband and size reduction characteristics. Due to smaller size and multiband characteristics fractal antenna has drawn the attention of researchers. Fractal antennas have more electrical length, improved SWR and impedance in a reduced physical area. The aim of this work is to design an antenna of square shape with swastika slot for multiband characteristics and efficient gain. The proposed fractal antenna has the dimensions of 22mm x 22mm. The antenna is fabricated on FR4epoxy substrate with dielectric constant (r) =4.4 and thickness 1.5676mm, which is easily available in market and cheap, thus making antenna cost effective. The structure has been designed using four swastika shapes in between two square rings on two sides. In this antenna only single iteration with the scaling factor 0.5 has been done to see the effect of iteration on the geometry. The designing and simulation of the antenna has been done using Ansoft HFSS software. The designed antenna resonates at seven different frequencies 4.9GHz, 5.8GHz, 8GHz, 13.8GHz, 22.3GHz, 26GHz and 27.6GHz. The Gains at these frequencies are 5.8099dBi, 1.6628dBi, -2.0782dBi, 3.6563dBi, 4.7219dBi, 5.2740dBi and 7.0985dBi respectively. This antenna can be used in different C and Ku band applications such as satellite and long distance telecommunication.

SNR and BER Analysis for Multiple Antenna System Using OFDM

Initially communication was carried out using analogue signal. Due to its various drawbacks, digital communication was introduced which has so many advantages over analogue communication and soon become very popular. Due to its low cost and easily reachable properties, wireless communication has become popular in communication.In the current scenario of modern wireless communication system, multiple input multiple output (MIMO) technique has emerged as one of the most efficient and significant method. This paper presents an analysis of MIMO system that has been introduced in the wireless communication to increase the diversity and to mitigate the effect of the channel fading phenomenon. In order to provide the transmit diversity, Space Time Block Code (STBC) is used in the Multiple input multiple output system. Effort has been made for deriving the Signal to noise ratio (SNR) and Bit error rate (BER) for different combination of the MIMO wireless communication system. SNR and BER have been computed for different combination of transmit antenna. The results of the simulation suggest that the performance of the MIMO system can be improved by increasing the diversity gain.

A compact dual band short ended metamaterial antenna with extended bandwidth

A compact dual-band CPW–fed metamaterial inspired antenna using Composite Right/Left Handed (CRLH) resonant approach is presented in this article. The antenna is designed such that it can be operated in series resonant mode where resonance behavior is characterized by series LC parameters. Proposed antenna comprises two annular ring resonators connected with the signal patch intended to excite the higher order modes. This results extension of second band from 51.4% (fc = 6.92 GHz) to 69.2% (fc = 7.35 GHz). In addition to that proposed antenna shows compact nature with an electrical size of 0.14 λ0 × 0.21 λ0 × 0.01 λ0 at f0 = 2.18 GHz. The antenna is operating over 2.14–2.23 GHz, 4.81–9.90 GHz with simulated peak gain of 0.66 and 4.44 dB, respectively. Simulated radiation efficiencies of proposed antenna are 69.8 and 94.1% throughout first and second band, respectively. To examine the resonance and radiation characteristics prototype is fabricated and measured. Observed experimental results are in good agreement with those simulated one. These characteristics makes this antenna is a good candidate for modern wireless communication systems such as Bluetooth, WLAN/Wi-Fi band. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:435–441, 2016.