Broadband Communication Systems Research Articles

Design of a Reconfigurable Band-notched Wideband Antenna using EBG Structures

A compact WLAN band-notched reconfigurable wideband antenna using two mushroom-like electromagnetic band-gap (EBG) structures is proposed in this paper. It is designed based on a dual wideband microstrip feed patch antenna with operating frequency bands of 2.2-3.7 GHz and 4.8-6 GHz. One of the EBG cells is positioned alongside the feed line, while the other EBG cell is laid on the back of the substrate. The patch or ground of the two EBG units are fed with a stronger current through a ground slot and a parasitic stub respectively, and the connections between the EBG structures and the antenna are controlled by loading a PIN diode with two 56 pF DC blocking capacitors. The advantage of this proposed design is that the antenna and the EBG unit can be designed independently. The proposed antenna has an overall size of 35×46×1.6 mm3. When testing the S11 of the antenna, the influence of the bias circuit on the antenna is also considered. The measured results show that the proposed antenna can generate two notched bands of 2.3-2.49 GHz and 5.11-5.51 GHz of WLAN, and the realized gain in the notch bands can be reduced to -2.65 dBi and -4.55 dBi, respectively, demonstrating its anti-interference characteristics, and can be applied in band notch broadband communication systems or anti-interference communication equipments such as unmanned aerial vehicles and radars.

A Low-Cost High-Throughput C-Band Communication System for CubeSats

This paper presents the physical layer of a proprietary broadband communication system for CubeSats. The system operates in the C band (5.8 GHz), delivering at least 10 Mbps of the net user throughput. Operation at low elevation angles (and therefore low SNRs) and high Doppler shifts is made possible thanks to a sophisticated synchronization subsystem. The system can be adapted to propagation conditions experienced during a given visibility window by changing the signal bandwidth and coding rate. It is implemented using Software Defined Radio (SDR) technology. The system will be used in two missions that are scheduled for 2023 and 2024 and are planned in cooperation with the National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute” and SatRev S.A.

Broadband linear frequency modulation signal compression based on a spectral Talbot effect.

Broadband linear frequency modulation (LFM) signals with a long duration are widely used in radar and broadband communication systems. The LFM signals are compressed to a Fourier-transform-limited pulse train after matched filtering, which effectively improves the signal-to-noise ratio (SNR) of detection. Quadratic phase response is the key component of matched filtering, which can be achieved by phase filters or dispersion elements. Suffering from the limited resolution of phase filters and complex equivalent large dispersion structures, pulse compression of broadband LFM signals with a long duration remains an open challenge. In this paper, LFM signal compression based on the spectral Talbot effect is proposed and experimentally demonstrated, where ultra-large equivalent dispersion (around 1.7 × 109 ps/nm) is realized by a simple optical filter ring. Experimentally, the LFM signal with a bandwidth of 12 GHz and a duration of 163 µs is compressed into a Fourier-transform-limited pulse train, which improves the SNR by 24 dB. Moreover, the proposed method also measures the delay difference between two LFM signals, ranging from 0 to 110 ns.

Steganographic method of acoustic information protection in critical applications systems

The subject of the study is the process of protecting acoustic information in critical computer systems to ensure the required level of system security. The purpose of the article is to study the method of protecting acoustic information in critical computer systems by means of masking to ensure the impossibility of unauthorized access to the system. The paper outlines the following tasks: to analyze the software and hardware masking of speech; to study the masking of speech messages in order to introduce unrecognizability; to consider the features of speech message compression; to investigate methods of covert transmission of acoustic information. The results of the work, which were obtained using mathematical methods of information transformation in computer systems, are potentially possible methods of masking speech messages to ensure the impossibility of unauthorized access to the system. The analysis of the functioning of the proposed methods made it possible to formulate specific conclusions. The research has shown that the use of direct expansion of the spectrum of discrete signals for steganographic purposes helps to covertly embed information messages in still images. The task of extracting a message on the receiving side of a steganography system is equivalent to the task of detecting information from a mixture of a useful signal and an interference in a broadband communication system. The research revealed certain disadvantages of steganographic systems with an expanded spectrum of discrete signals: the probability of correct extraction of embedded data depends on the amount of distortion introduced, which depends on the provided bandwidth of the steganographic channel. Further research is desirable to analyze the possible use of methods for synthesizing large ensembles of quasi-orthogonal discrete signals with improved ensemble, structural, and correlation properties to ensure higher security of acoustic channels in computer systems for critical applications.

Performance of 5G NR-polar QAM-OFDM in nonlinear distortion plus Non-Gaussian noise over Rayleigh fading channel

The polar code readily provides rate adaptation, reaching Shannon’s capacity at low encoding and decoding complexity. It has entered the 5G New Radio (5G-NR) as a result of these alluring features to improve the bit error rate (BER) performance in Gaussian noise. In challenging environments for modern broadband communication systems, the amplitude and phase distortion caused by nonlinear distortion (NLD) of high-power amplifiers (HPAs), non-Gaussian noise or impulsive noise (IN), and multipath fading channels (H) play a significant role in BER degradation in an orthogonal frequency-division multiplexing (OFDM) system. Therefore, to improve the BER degradation of the conventional NR-polar QAM-OFDM system over such environments, different novel closed-form expressions of combined NLD-HPA and IN distributions and the log-likelihood ratios (Ls) at the OFDM demodulator output with and without Rayleigh fading channel have been derived. In addition, the novel derived closed-form BER expressions validate the derived distributions using Monte-Carlo simulation in the downlink (DL) and uplink (UL) scenarios. This system demonstrates a significant performance improvement and achieves a coding gain of 28 dB and 25.5 dB compared to the traditional coded OFDM system, which achieved only 10 dB in the case of IBO = 4 dB over the Rayleigh fading channel.

Design of Ternary Convolutional Code using Reconfigurable Architecture

The need for trustworthy and efficient digital data transmission and storage systems has increased in recent years. The demand to handle and store digital information has grown in the business sector, the military, and the government as a direct result of the widespread availability of high-speed, large-scale data networks. This requirement must be met in order for the design of these systems to keep up with the rapid pace set by communication and computer technologies. When trying to overcome the variable degradation in real time, one of the most important factors to consider is the dependability of the broadband communication channel. Therefore, the use of convolutional codes and other channel-coding strategies is an essential component of any broadband communication system. DSL, WLAN, and 3G standards all require different configurations of convolutional coding, each of which must achieve a specific level of coding performance despite operating at a unique data rate (constraint length and code rate) Therefore, from the perspective of channel-coding techniques, hardware implementations for the development of an encoder are essential. This encoder should be able to support multiple networks using a reconfigurability approach and should be able to function across a variety of standards. Additionally, flexibility and hardware performance should both be prioritised. This calls for forward error control coding with reconfigurable logic, which provides high-speed, low-power dynamically dedicated hardware architectures under a number of speed/power performance constraints at different time intervals that can function within a variety of channel conditions. The ternary computation system has a number of benefits, the most notable of which are the availability of a high data rate, improved spectral efficiency, enhanced coverage, and lower latency. As a result, there is a growing demand for ternary-based systems that use convolutional encoders as a result of developments in technology

Research on Relay Network Method of Aerial Platform

As a regional wireless communication means, a wireless broadband communication system mainly provides communication services for mountainous areas with imperfect infrastructure construction. When the system provides communication services in mountainous areas, the vehicle-mounted base stations encounter obstacles to block communication, which causes the problem of non-cascade communication. In this paper, an improved genetic algorithm based on the adaptive change of crossover and mutation probability is proposed to formulate the air platform relay network planning scheme. The simulation results show that the crossover and mutation probabilities of the adaptive improved genetic algorithm change with the iteration of the algorithm, which improves the search ability of the algorithm and prevents it from falling into the local optimal solution.

Anchor-Aided Channel Estimation for RIS-Assisted Multiuser Broadband Communications

Due to the passive nature of reconfigurable intelligent surface (RIS) and a large number of users, it is very challenging to estimate the cascaded base station (BS)-RIS-user channel directly, especially for multiuser broadband communication systems. In this letter, we propose a novel two-phase method to estimate multiuser broadband cascaded channels with the assistance of two anchor nodes. Specifically, in the first phase, the cascaded channel from the two anchors to the BS and that between two anchors are estimated to acquire the BS-RIS channel state information (CSI) with sign ambiguities. It is accomplished based on cyclic-prefixed single-carrier transmission and phase configuration at the RIS, which creates multiple cyclic delayed versions of transmitted signals for isolating all broadband channel taps. In the second phase, the RIS-user channel and subsequently the cascaded BS-RIS-user channel are estimated in the frequency domain using the knowledge of the partial BS-RIS CSI. Simulation results verify the superiority of the proposed scheme over the state-of-the-art methods in terms of estimation overhead, normalized mean-squared error and bit error rate.

Physical Layer Security for Visible Light Communication in Reflected Indoor Environments With Inter-Symbol Interference

Visible light communication (VLC) is a promising technology for next-generation indoor wireless broadband communication systems. Physical layer security (PLS) is one proposed method to ensure data security for VLC in public areas. However, most PLS studies in the literature neglect the reflections in the VLC channel and do not consider inter-symbol interference (ISI). This paper investigates the ISI effects on the secrecy rate in multiple-input single-output VLC systems where the reflections are not neglected for the cases of perfect and imperfect knowledge of the eavesdropper’s channel state information. We aim to compensate for the ISI effects by designing zero-forcing (ZF) and artificial noise (AN) beamformers. In addition, we formulate optimization problems to maximize the secrecy rate resulting in non-convex and NP-hard problems. Thus, we utilize the particle swarm optimization algorithm for solutions and also convert non-convex optimization problems into easily solvable linear problems. Furthermore, robust ZF and AN beamformers for the worst-case scenario are considered for the cases of ISI and no ISI. The results reveal that ISI severely degrades the secrecy rate; however, well-designed beamformers can reverse the ISI effects.

NEW BARKER’s COMPOSITE CODES AS MODULATION SIGNALS IN BROADBAND COMMUNICATION SYSTEMS

Background. Currently noise-like signals (NLS) are widely used and provide high level of jamming immunity and security in broadband communication systems (BСS) when transmitting confidential information in an open radio channel, especially in emergencies. Increasing the efficiency of the NLS is possible when using more advanced code structures.
 Objective. The purpose of this research is to study new Barker’s composite codes as modulation signals in broadband communication systems.
 Method. Simulation modeling based on MatLab software package and analytical calculation methods are used.
 Results. Modeling in the MatLab software package showed the possibility for using new Barker’s composite codes as modulation signals in direct spread spectrum systems but efficiency depends on code words length as well as type synchronization signal.
 Conclusions. Analysis of research results shows that the new Barker composite codes 21a, 33a, 49, 77a, 121 can be effectively used as modulation code words in broadband systems with direct spectrum expansion.

Correlation Between the Electromagnetic Properties of Building Materials and Wireless Signal Penetration Loss

Though, largely ignored, the building penetration loss (BPL), is a critical consideration during network planning and design of wireless broadband communication systems, especially, disaster communication networks. Different experimental works have established that BPL varies with different building materials. In this work, we aimed at determining the relationship (if any) between the BPL and the electromagnetic (EM) properties (permittivity/permeability) of such materials. We derived the correlation model between the BPL and the two EM properties of permeability and permittivity. An experimental measurement campaign was conducted in seven different sites to determine the BPL of different building materials. Using the measurement data and the derived BPL-permittivity and permeability correlation model, the correlation values for the different building materials were obtained. The results showed multiple correlation values ranging from 0.85 to 0.9. These highly positive correlation values imply that BPL correlates positively with the EM properties. With the result of this work, design engineers of wireless networks, especially, disaster communication systems, can estimate BPL in situations where measurement values are not available.

OFDM and MIMO wireless communication performance measurement using enhanced selective mapping based partial transmit sequences

The great spectral efficiency to mitigate multipath fading of OFDM (orthogonal frequency division multiplexing) made more accepted for broadband communication systems with some drawbacks such as high PAPR (Peak-to-Average Power Ratio), ISI (Inter-Symbol Interference) and ICI (Interiv Carrier Interference). High PAPR forces the operations of the HPA amplifier to work beyond its linear region causing in-band distortion as well as out-band noise and are overcome by using an amplifier with a large dynamic range. In this method, OFDM symbols are partitioned into multiple disjoint sub-blocks which are independently rotated in phase by optimum phase weighting factors. The resultant OFDM signal has less PAPR when compared to that of original OFDM signal in wireless communication. To minimize computational complexity, a modified PTS technique is proposed to enhance PAPR reduction and power amplifier efficiency in OFDM and MIMO (multiple inputs, multiple outputs)-OFDM methods through Selective Mapping based PTS (SMPTS) method combined with PAPR reduction methods.

A Manifold Regularization Approach for Low Sampling Rate Digital Predistortion With Band-Limited Feedback

Digital predistortion (DPD) is an effective linearization technique for RF power amplifiers (PAs), but conventional full sampling (FS) DPD systems use ADCs with three to five times signal bandwidth, and high-speed ADCs are expensive and power-hungry. In this article, we develop a novel band-limited DPD for reducing feedback sampling rate and acquisition bandwidth based on a general framework for semisupervised learning called manifold regularization (MR), which utilizes the geometry of unlabeled data to construct regularization terms for mitigating the overfitting problem. Considering the properties of DPD, we design a basis MR term and introduce it into the classical MR to obtain the extended MR (ExMR) method. To validate the proposed ExMR DPD method, experiments were conducted on two different RF PAs operating at 2.4 and 39 GHz, respectively. The test results demonstrate that the proposed ExMR DPD can linearize the RF PA with a 40-MHz acquisition bandwidth at 100-MHz input. The proposed method significantly reduces the cost and power consumption of the DPD system in comparison with the conventional FS DPD method, which provides a promising solution for broadband communication systems.

Planar Microstrip Patch Antenna Arrays with Semi-elliptical Slotted Patch and ground Structure for 5G Broadband Communication Systems

Planar Microstrip Patch Antenna Arrays with Semi-elliptical Slotted Patch and ground Structure for 5G Broadband Communication Systems

Stealth radome with an ultra-broad transparent window and a high selectivity transition band.

Stealth radome (SR), especially with an ultra-broad and nearly transparent window between two absorption bands, plays a crucial role in stealth techniques, antenna radomes, and so on. However, current devices have the defects of narrow transmission bands, high insertion loss, and wide transition bands between the transmission and absorption bands, which are unfavorable for the stealth of broadband radar and communication systems. In this paper, a novel SR with an ultra-broad and high-efficiency inter-absorption band transparent window is proposed by combining broadband resonance lumped circuits with a multi-layer cascaded frequency-selective surface (FSS). The equivalent circuit model (ECM) and transmission line method (TLM) are provided and analyzed as a guideline for the SR design. The SR consists of a resistive lossy layer loaded with wide passband lumped circuits and two stacked lossless FSS layers to collectively achieve the high selectivity and ultra-broad transmission band. Simulated results indicate that the proposed SR exhibits an ultra-broad passband from 8.2 to 11.2 GHz (31%) with transmission amplitude more than 0.85 and two 90% absorption bands over 6.8-7.8 GHz and 12-13 GHz, and the transition bands at both sides are only 0.4 GHz and 0.8 GHz, respectively. Our findings can stimulate the promising applications of SR in broadband stealth devices with integrated ultra-broad communication capability or in other electromagnetic (EM) compatibility facilities.

An Ultrawideband GaAs MMIC Microstrip Directional Coupler With High Directivity and Very Flat Coupling

By introducing an adaptive lumped bridged-T amplitude equalizer into the microstrip directional coupler, this article realizes a 2.2 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times1.3$ </tex-math></inline-formula> mm ultrawideband GaAs monolithic microwave integrated circuit (MMIC) directional coupler with high directivity and very flat coupling by using the GaAs integrated passive device (IPD) process. The experimental results show that the proposed directional coupler exhibits more comprehensive radio frequency (RF) performance than the reported directional couplers due to the use of an adaptive bridged-T amplitude equalizer. In the ultrawide working frequency range from 2 to 20 GHz, the insertion loss of the coupler is less than 1.5 dB, the return loss is better than −20 dB, the coupling flatness is within ±0.3 dB, the isolation is higher than 40 dB, and the directivity is more than 20 dB, which are basically consistent with theoretical predictions. The microstrip directional coupler using the adaptive bridged-T amplitude equalizer shows great potential in the high-performance broadband communication system.

Low-Noise Phase-sensitive Parametric Amplifiers Based on Integrated Silicon-Nitride-Waveguides for Optical Signal Processing

Low-noise optical amplification has been a long-lasting research topic in various fields including communication, metrology and quantum optics. Here we report optical signal processing at different wavelengths enabled by a low-noise optical phase-sensitive amplifier (PSA) using a single compact integrated silicon nitride photonic waveguide. For 10 Gbit/s non-return-to-zero optical signals with central wavelengths tuned in the telecommunication band, the waveguide-based PSA exhibits a gain of more than 10 dB and a noise figure of about 1.2 dB when the coupling losses are neglected. For a bit-error-rate level of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−9</sup> , penalties of less than 0.8 dB for all channels are observed after the signals propagating through the chip-based PSA, which may be due to the distortions in the few-mode waveguide. These experimental results generally agree with theoretical prediction and indicate that silicon-nitride-based PSAs are promising for the next generation of broadband optical signal processing and communication systems.

High-Frequency Vacuum Electron Devices

Vacuum electron devices at frequencies of millimeter waves and terahertz play highly important roles in the modern high-data rate and broadband communication system, high-resolution detection and imaging, medical diagnostics, magnetically confined nuclear fusion, etc [...]

Study of interference resistance of autocorrelative receiving methods in broadband communication systems

Modern broadband communication systems are not able to completely eliminate the effects of interference characteristic of various communication channels, namely interference caused by the multipath nature of signal propagation and concentrated interference which reduce the reliability of information transmission. Although the picture is qualitatively clear, the variety of interference and the specificity of the impact of some of them on broadband communication systems do not allow one to quantitatively take into account the impact of all interference at the same time. Therefore, there is a need to study the issue of increasing immunity to various reception methods. This article is devoted to the study of methods of increasing immunity to interference in broadband communication systems with fluctuating interference using autocorrelation methods of reception. The probability of errors in a multi-position system with orthogonal signals at incoherent reception with incoherent accumulation is investigated. Probabilities of errors during autocorrelation reception of signals with single phase-difference modulation are analyzed. The article defines that the immunity of intercorrelation methods of reception does not depend on the base of the signal, and the immunity of autocorrelation methods depends on the base and at the same energy is lower in the signal with a larger base (larger number of elements). The results of the work characterize the interference immunity of multi-position systems with different reception methods and the dependence of the immunity of a group of autocorrelation reception methods on the number of elements N or the FT base of the composite signal. According to the results of the work, the composite signals from the FRM in all reception methods provide a gain in energy twice as compared to the systems with orthogonal signals.

Power line communication: A review on couplers and channel characterization

&lt;abstract&gt; &lt;p&gt;Powerline communication is gaining momentum with the rise of the smart grid, the Internet of Things as part of the 4th industrial revolution and associated applications such as transportation and energy efficiency. Coupling and channel characterization are essential parts of a power-line communication system. Therefore, understanding these components allows performance evaluation and prediction of the system. This paper presents an entire review of couplers and channel characterization modeling techniques used in narrow and broadband power-line communication systems. Types and applications of different couplers are presented; a review of different power-line communication channel modeling techniques and the fundamentals allows a clear understanding of factors influencing or affecting the signal propagation through the channel. The purpose of this review is to guide researchers and system designers looking for literature resources on couplers and channel characterization for power-line communication applications.&lt;/p&gt; &lt;/abstract&gt;