Wideband Wireless Communication Systems Research Articles

A wideband quasi-Yagi antenna using symmetrical slots on the ground plane

ABSTRACT A wideband quasi-Yagi antenna with symmetrical rectangular slots in the ground plane is studied. The feeding structure of the antenna is simplified, consisting of a microstrip transmission line and a short strip. The driver and director arms are designed as half on both sides of the substrate to improve pattern stability. The antenna’s bandwidth is improved by symmetrically adding rectangular slots to the ground. The antenna works between and GHz with a gain that varies between to dBi, a bandwidth of , and an efficiency of more than . The antenna has a very compact size of ( is the wavelength for the lowest operating frequency). The simulation and measurement results are in good agreement. The antenna has highly stable end-fire radiation within its operating frequency and can be used for wideband wireless communication systems.

Gain-Improved Wideband Circularly Polarized Magnetoelectric Dipole Antenna With Parasitic Helix

This communication presents a magnetoelectric (ME) dipole antenna with wideband circularly polarized (CP) and gain-improved performance. Two pairs of perpendicular sub-ME dipoles which are realized by horizontal and vertical patches constitute the original ME dipole. By connecting one pair of sub-ME dipole with metallic strip, CP operation is achieved at lower band firstly. Then, we change the coupling slot from rectangle to cross which leads to the enhancement of impedance and axial-ratio (AR) bandwidth. Furthermore, a helix with different turn radii and uniform turn spacing is introduced to improve the gain in the whole band. Performance of the proposed design is verified by measured results. The fabricated antenna exhibits an -10-dB impedance bandwidth of 3.33-6.75 GHz, corresponding to 67.9%. Besides, the measured 3-dB AR bandwidth and 3-dB gain bandwidth are 3.6-6.25 GHz (53.8%) and 3.4-5.8 GHz (52.2%), respectively. The proposed design could provide promising application values for wideband wireless communication systems.

New Construction of Z-Optimal Type-II Even-Length Quadriphase Z-Complementary Pairs

Type-II Z-complementary pairs (ZCPs) play an important role in suppressing asynchronous interference in a wideband wireless communication system where the minimum interfering-signal delay is large. Based on binary Golay complementary pairs (BGCPs) and interleaving technique, new construction for producing Z-optimal Type-II even-length quadriphase ZCPs (EL-QZCPs) is presented, and the resultant pairs have new lengths in the form of 2 × 2α10β26γ (α, β, γ non-negative integers), which are not included in existing known Type-II EL-QZCPs.

Wideband Reconfigurable Reflectarray Based on Reflector-Backed Second-Order Bandpass Frequency Selective Surface

In this communication, a wideband reconfigurable reflectarray based on reflector-backed active second-order bandpass frequency selective surface (FSS) is presented. The reflector is composed of periodic short-circuited parallel plate waveguide (PPW) and the FSS is composed of stacked non-resonant metallic elements separated by thin dielectric substrates. By integrating microwave varactors in the capacitive layers of FSS, more than 270° continuous phase tunability is achieved within a fractional bandwidth of 14%. A 1-D reflectarray prototype operating at C-band is fabricated and measured. The experimental results show that it can achieve ±55° beam scanning coverage. Symmetric beam steering is observed due to the center-fed configuration. With advantages of low cost and simple structure, the proposed reflectarray can be potentially used in wideband wireless communication and radar systems.

Review on Radio over Fiber Systems for Capacity Enhancement

Radio-over-fiber (RoF) system is one of the latest plans for future wideband wireless communication systems like mobile communications, suburban and residential areas. These are good nominees to build the backbone of the next generation of wireless networks. Besides, the fundamental requirement for next-generation radio optical fiber and mobile communication is the need for more capacity and speed which has a huge scope, that is further required for a better system to attain demands such as Fiber to The Home (FTTH) and 5G. The combination of RoF with spectrally-efficient modulation techniques can accomplish increasing demand for high data rates for mobile users. Currently, analog fronthaul is promoted as an energy-efficient and bandwidth solution that can reach the necessity of the 5G vision for high data rates, low latency, and energy efficiency. Mainly, this paper presents a review that focuses on various techniques which several approaches have been listed to perceive the large-capacity data transmission and describe them including Wavelength Division Multiplexing (WDM), Subcarrier Multiplexing (SCM), Mode Division Multiplexing (MDM), Polarization Division Multiplexing (PDM), Generalized Frequency Division Multiplexing (GFDM), Parallel  Intensity Modulation (PIM)/Phase Modulation (PM) transmitter, and Millimeter-wave (Mm wave) generation techniques. Also, a comparison between them has been done

A compact multiple-input multiple-output antenna with high isolation for wireless applications

This paper presents a high-performance multiple-input multiple-output (MIMO) antenna with a compact size of 42 × 42 mm2. The proposed antenna operates in the frequency range of 3.2–12 GHz for ultra wide band (UWB) wireless communication systems. The proposed MIMO antenna has four identical elements arranged to be orthogonal to each other to achieve a good performance. To achieve high isolation, stubs between the four radiating elements were used. Measured and simulated results were analyzed to obtain the antenna performance in the form of studying radiation pattern, Envelope Correlation Coefficient (ECC), diversity gain, and channel capacity loss. Additionally, simulated peak gain and total efficiency are acquired. Results indicate that the proposed antenna has UWB bandwidth, high isolation higher than 17 dB, and low correlation coefficient; therefore, this antenna is suitable for UWB wireless applications.

Miniaturized Wideband Planar Antenna Using Interembedded Metasurface Structure

One kind of interembedded metasurface (MS) structure is proposed and applied to realize miniaturized wideband MS antennas (MSA). Different from conventional MSA, the proposed interembedded MSs are formed by etching slots on the radiating patch with various sawtooth schemes rather than rectangular gaps. Consequently, the resonance frequency of MSA can be decreased due to introducing those interdigital-like capacitances, while obvious miniaturization can be realized accordingly. By optimizing the parameters of the sawtooth radiating slots, a miniaturized antenna using cross-shaped interembedded MS is proposed, achieving an impedance bandwidth of 35.08% and a high gain of about 8.25 dBi with a compact overall size of 0.66λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ×0.66λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . Moreover, one further miniaturized antenna using modified cross-shaped interembedded MS is also presented, realizing a larger impedance bandwidth of 41.35% and a high gain of about 6.62 dBi with a smaller aperture of 0.48λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ×0.48λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . Compared with conventional MSA, 42% overall size reduction and larger bandwidth can be obtained. The design approach may provide a feasible solution to realize compact MSAs with the unique advantages of large bandwidth, low profile, low cost, and easy fabrication. Due to above good features, the proposed antenna can be a promising candidate for applications in modern wideband wireless communication systems.

Massive MIMO perspective: improved sea lion for optimal antenna selection

The massive MIMO is an advanced technology in the wideband wireless communication system’s future, which provokes extensive attention in both academia and telecommunication industry. Pilot contamination is considered as a fundamental issue in the system of massive MIMO. The designing of wireless systems has the main concern over the system throughput. Though, the environmental protection and energy-saving have concerned as inevitable trends and global demands. Hence, on considering all these consequences, this paper intends to introduce a new improved sea lion optimization algorithm to select the optimal transmit antennas selection by accounting the multi-objective issue that maximizes both the relative energy efficiency and capacity. In fact, the proposed algorithm is the enhanced version of traditional sea lion optimization algorithm, which optimally tunes the count of transmit antennas and determines which antenna to be selected. Finally, the performance of proposed work is compared and proved over other conventional models regarding capacity analysis, relative efficiency analysis, and optimal antenna selection analysis as well.

Dual Pulse Shaping Transmission and Equalization for High-Speed Wideband Wireless Communication Systems

Analog-to-digital and digital-to-analog conversion devices for signals with very large bandwidth are not always available due to technical or cost issues. This limits the realization of very high data-rate digital communication systems. In this paper, we propose a dual pulse shaping (DPS) transmission scheme, which can achieve full Nyquist rate transmission with only a half of the sampling rate for each of the two data streams. Two classes of ideal complementary Nyquist pulses are formulated assuming raised-cosine (RC) pulse shaping. The condition for cross-symbol interference (CSI) free transmission is derived and validated for the proposed pulses. Structures of the DPS transmitter and receiver are described and low-complexity equalization techniques tailored to DPS are proposed. With DPS, a millimeter wave system with commercially available and affordable data conversion devices is exemplified for achieving high-speed low-cost wireless communications. Simulation results with two sets of practical dual spectral shaping pulses are provided. The results verify the effectiveness of the proposed scheme, with comparison to the benchmark conventional Nyquist pulse shaping system.

Fractal-based triangular bandpass filter with a notched band for interference rejection in wideband applications

PurposeThis paper aims to present the design of a novel triangular-shaped wideband microstrip bandpass filter implemented on a low-cost substrate with a notched band for interference rejection.Design/methodology/approachThe conventional dual-stub filter is embedded with simple fractal-based triangular-circular geometries through various iterations to reject wireless local area network (WLAN) signals with a notched band at 5.8 GHz.FindingsThe filter covers a wide frequency band from 3.1 to 8.8 GHz and has a fractional bandwidth of 98 per cent with the lower passband of 57.5 per cent and upper passband of 31.6 per cent separated by a notched band at 5.8 GHz. The proposed wideband prototype bandpass filter is fabricated in FR-4 substrate using PCB technology and the simulation results are validated with measurement results which include insertion loss, return loss and group delay. The fabricated filter has a sharp rejection of 28.3 dB at 5.8 GHz. Measured results show good agreement with simulated responses. The performance of the fractal-based wideband filter is compared with other wideband bandpass filters.Originality/valueIn the proposed work, a fractal-based wideband bandpass filter with a notched band is reported. The conventional dual-stub filter is deployed with triangular-circular geometry to design a wideband filter with a notched band to suppress interference signals at WLAN frequency. The proposed wideband filter exhibits smaller size and better interference rejection compared to other wideband bandpass filter designs implemented on low-cost substrate reported in the literature. The aforementioned wideband filter finds application in wideband wireless communication systems.

Compact and wideband bandpass filters with analysis of the CRLH-TL characteristics based on stepped impedance resonator

In this paper, we have investigated two unique wideband (WB) bandpass filters (BPFs) based on composite right/left-handed (CRLH) structure that have high performance in C-band. The proposed filters have been implemented with stepped-impedance resonator (SIR) section and interdigital capacitors on it with a parallel coupled-shorted stub (CSS). High selectivity, high out-of-band rejection, low loss and two transmission zeroes at the lower and upper passband/stopband edges have been observed. The out-of-band rejection levels in two filters are better than 17 dB and 20 dB at the lower and upper band edges, respectively. In addition, the return loss and insertion loss of the proposed CSS filter are greater than 17 dB and less than 0.7 dB, respectively. Also, the return loss and insertion loss of the proposed spiral CSS (SCSS) filter are greater than 20 dB and less than of 0.5 dB, respectively. The presented structures have been investigated analytically and experimentally in order to verify balance between the results of the full-wave simulation and the equivalent circuit model with the experimental ones. The dimensions of the suggested filters are 21.6 × 3.06 mm2 and 14.6 × 4.2 mm2. The specifications and compact size of the filters make them suitable for wideband wireless communication systems.

A Dual Interference-Canceling Active Quasi-Circulator Achieving 36-dB Isolation Over 6-GHz Bandwidth

Circulator is a key component in full-duplex wireless and radar detection systems. In this letter, a dual interference-canceling active quasi-circulator is proposed to enhance the isolation capability over the range of 1–7 GHz. The circulator is fabricated in the standard 0.18- $\mu \text{m}$ CMOS process occupying 1.03 mm $\times0.55$ mm including the pads. Measurement results demonstrate more than 36-dB isolation from the Tx to the Rx within 6-GHz bandwidth. The designed circulator is a good candidate for duplexers to allow the integrated transmitter and receiver to share a single antenna in the certain short-range wideband wireless communication systems, where noise figure (NF) is not strictly demanded but low cost and high integration are urgently required.

Space-Time Block Coding-Based Beamforming for Beam Squint Compensation

In this paper, the beam squint problem, which causes significant variations in radiated beam gain over frequencies in millimeter wave communication system, is investigated. A constant modulus beamformer design, which is formulated to maximize the expected average beam gain within the bandwidth with limited variation over frequencies within the bandwidth, is proposed. A semidefinite relaxation (SDR) method is developed to solve the optimization problem under the constant modulus constraints. Depending on the eigenvalues of the optimal solution, either direct beamforming or transmit diversity based beamforming is employed for data transmissions. Through numerical results, the proposed transmission scheme can compensate for beam squint effectively and improve system throughput. Overall, a transmission scheme for beam squint compensation in wideband wireless communication systems is provided.

Pilot Design for Sparse Channel Estimation in Orthogonal Frequency Division Multiplexing Systems

Orthogonal Frequency Division Multiplexing (OFDM) is a well-known technique used in modern wide band wireless communication systems. Coherent OFDM systems achieve its advantages over a multipath fading channel, if channel impulse response is estimated precisely at the receiver. Pilot-aided channel estimation in wide band OFDM systems adopts the recently explored compressive sensing technique to decrease the transmission overhead of pilot subcarriers, since it exploits the inherent sparsity of the wireless fading channel. The accuracy of compressive sensing techniques in sparse channel estimation is based on the location of pilots among OFDM subcarriers. A sufficient condition for the optimal pilot selection from Sylow subgroups is derived. A Sylow subgroup does not exist for most practical OFDM systems. Therefore, a deterministic pilot search algorithm is described to select pilot locations based on minimizing coherence, along with minimum variance. Simulation results reveal the effectiveness of the proposed algorithm in terms of bit error rate, compared to the existing solutions.

Wideband printed monopole antenna for application in wireless communication systems

Empirical results of an electrically small printed monopole antenna are described with a fractional bandwidth of 185% (115 MHz to 2.90 GHz) for return-loss better than 10 dB, peak gain and radiation efficiency at 1.45 GHz of 2.35 dBi and 78.8%, respectively. The antenna geometry can be approximated to a back-to-back triangular shaped patch structure that is excited through a common feed-line with a meander-line T-shape divider. The truncated ground-plane includes a central stub located underneath the feed-line. The impedance bandwidth of the antenna is enhanced with the inclusion of meander-line slots in the patch and four double split-ring resonators on the underside of the radiating patches. The antenna radiates approximately omni-directionally to provide coverage over a large part of very high frequency, the whole of ultrahigh frequency, the whole of L-band and some parts of S-band. The antenna has dimensions of 48.32 × 43.72 × 0.8 mm 3 , which is corresponding to the electrical size of 0.235 λ 0 × 0.211 λ 0 × 0.003 λ 0 , where λ 0 is the free-space wavelength at 1.45 GHz. The proposed low-profile low-cost antenna is suitable for application in wideband wireless communications systems.

Nonbinary LDPC-Coded Modulation System in High-Speed Mobile Communications

As a class of capacity-approaching codes, nonbinary low-density parity-check (LDPC) codes have attracted much attention because of noticeable performance. Nonbinary LDPC-coded modulation systems which have excellent performance for high-spectral efficiency transmission are also potential schemes in the future communication system. In this paper, we propose a new construction method of quasi-cyclic nonbinary LDPC codes. Furthermore, a comparative study about the performance of various coded systems over the AWGN channel and the high-mobility channel is performed on turbo codes in LTE communications and LDPC codes in 5G standard. Simulation results show that the nonbinary LDPC-coded modulation system is effective for improving the performance of wideband wireless communication systems with orthogonal frequency division multiplexing in the high-mobility scenario.

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.

New Wideband Notch Antennas for Communication Systems

Wireless communication industry is in rapid growth in the last years. Due to the huge progress in development of communication systems in the last decade development of wideband communication systems is continuous growth. However, development of wideband efficient antennas is one of the major challenges in development of wideband wireless communication systems. Low cost compact antennas are crucial in the development of communication systems. Printed notch antennas and miniaturization techniques are employed to develop efficient compact notch antennas. Fractal technology is used to improve the electrical performance and efficiency of notch antennas. Design tradeoffs, computed and measured results of wideband notch antennas with high efficiency are presented in this paper. All antennas are analyzed by using 3D full-wave software. The paper presents new compact Ultra-Wideband notch antenna 1 GHz to 6 GHz, a wideband notch antenna 2.1 GHz to 7.8 GHz and a 5.8 GHz to 18 GHz fractal notch antenna.

WIDEBAND VERTICAL PLANAR PRINTED UNIDIRECTIONAL ANTENNA

A new wideband vertical planar printed unidirectional antenna is presented. The proposed antenna is composed of a bowtie electric dipole, a loop antenna and a microstrip-to-coplanar stripline balun. All of them are printed in the same plane perpendicular to the ground. The antenna has a wide impedance bandwidth of 88.9% for SWR • 2 from 3.3 to 8.58GHz and a stable gain of 7:3 § 1:5dBi over the operating frequencies. Moreover, stable unidirectional radiation pattern with low back-lobe radiation, low cross polarization and nearly identical E- and H-plane patterns is also demonstrated over the frequency of interest. A prototype is fabricated and measured. The measured results indicate that the antenna is suitable for wideband wireless communication system.

Front-End Narrowband Interference Mitigation for DS-UWB Receiver

Narrow band interference (NBI) suppression is one of major issues for ultra wideband (UWB) wireless communication system operating over huge spectrum occupied by narrow band wireless systems. In this paper, we propose an interference mitigation scheme based on complex-valued adaptive notch filter, which smartly exploits the substantial correlation difference of signals and removes the NBIs in UWB signal with noise by estimating the corresponding central frequencies. To obtain high speed convergence and maintain small signal distortion, a low complexity gradient algorithm for one-order basic adaptive notch filter cell is deduced. Considering that the data rate prior to despreading is extremely high, a novel time-division multiplexing (TDM) parallel approach for eliminating a single NBI is presented, which effectively simplify the hardware design especially in high speed digital signal processing. Based on the one-order basic adaptive notch filter cell, three different implementations including direct forms, linear cascade forms and TDM parallel cascade forms to eliminate multiple NBIs are developed and discussed. Theoretical analysis and simulation results indicate that the proposed scheme possesses the advantages of high convergence speed, small distortion and high stability. Furthermore, the propose scheme utilized as a preprocessing unit prior to despreading can considerably improve the interference tolerance margin of UWB systems, leading to it's suitable for the low complexity direct sequence (DS)-UWB receiver.