System Bandwidth Research Articles

A Design Method of Diffraction Structure Based on Metasurface for High-Resolution Spectroscopy.

In this paper, a design method of diffraction structure based on metasurface is proposed for light splitting and focusing simultaneously. In the method, firstly, the light field calculation model of the proposed structure is established based on Fresnel diffraction and the transmittance function is calculated. Then, the model structural parameter selection mechanism is determined, and the spectrum resolution equation of the structure is derived. Simulation results indicate that the proposed method can offer a broader working bandwidth and enhanced higher resolution compared to off-axis meta-lens. Moreover, this proposed method can be deployed in high-resolution, wide-band ultra-compact spectrometer systems potentially.

An optimization framework for RIS-based energy-efficient multi-cell NOMA systems

Non-orthogonal multiple access (NOMA) is a highly promising multiple access strategy for wideband communication systems due to its high spectral efficiency. However, in multi-cell multi-band systems, interference issues can arise from resource sharing among multiple users, which limits the potential of NOMA. To tackle these issues, in this paper, we study a NOMA system where reconfigurable intelligent surfaces (RIS) are employed across multiple cells with multiple users clusters. Specifically, we propose an optimization framework to maximize the system energy efficiency (EE) through jointly designing the transmission beamformer at each base station, the RIS phase shifts and the corresponding binary selection matrix indicating which elements of the RIS should be used to serve a specific cell. Our optimization framework takes into account the minimum rate requirements of users, the successive interference cancellation (SIC) decoding-based rate constraint, fairness among users as well as the maximum allowed transmission power. The resulting non-convex problem is solved by using an alternating optimization algorithm, wherein semidefinite programming (SDP), successive convex approximation (SCA), and penalty-based difference-of-convex (DC) programming are used to reach a solution. Simulation results show that the proposed system outperforms conventional orthogonal access in terms of EE performance, the achievable rate, and power consumption. Also, the results revealed the critical transmission power level for NOMA beyond which the EE starts decaying. Moreover, the proposed NOMA system shows a limited EE performance compared to the conventional orthogonal access as the number of clusters exceeds a certain limit.

Transmitter Space Shift Keying With Maximum- Ratio Combining and Receiver Spatial Modulation With Maximum-Ratio Transmission in Downlink Cellular Systems

The author investigates the performance of transmitter space shift keying (TSSK) with maximum-ratio combining (MRC) and receiver spatial modulation (RSM) with maximum-ratio transmission (MRT) in an unbalanced number of antennas at the transmitter and receiver. The author shows that RSM-MRT exhibits a superior performance under the same data rate, transmit power, and bandwidth in downlink cellular network systems where the number of transmit antennas at the base station is much larger than the number of receiver antennas at the mobile station. The author identifies a figure of metric as fading parameters and finds their probability density function (PDF) and cumulative distribution function (CDF). The performance gap between TSSK-MRC and RSM-MRT expands as the number of antennas increases while maintaining the same ratio of the number of antennas at the transmitter and receiver for a chosen modulation.

Demonstration of a Real-Time UWOC System Using a Bandwidth Limited LED Based on Hardware and Software Equalization

In this work, we propose and experimentally demon-strate a real-time and cost-efficient underwater wireless optical communication (UWOC) system based on field programmable gate arrays (FPGAs) for practical application. A three-stage cascaded T-bridge equalizer (TCBE) is designed to enlarge 3 dB bandwidth of the light-emitting diode (LED). Also, a digital waveform shaping filter (DWSF) is proposed to assist the TCBE circuit by shortening the rise and fall time of the received waveform and adjusting equalization parameters to flexibly satisfy diverse communication scenarios. The 3 dB bandwidth of UWOC system is extended from 2.5 MHz to 44 MHz via TCBE. With the proposed scheme, a data rate of at least 50 Mbps with a bit error rate (BER) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathbf{8} \times \mathbf{1}\mathbf{0}^{{\bf - 5}}$</tex-math></inline-formula> without forward error correction (FEC) code can be guaranteed over an underwater channel of 1 m. On the basis of TCBE, the DWSF is capable of further reducing the BER by 15%, 22%, 26%, 28%, 95%, and 98% for the data rates of 10 Mbps, 20 Mbps, 30 Mbps, 40 Mbps, 45 Mbps, and 50 Mbps, respectively. The results show that the method can remarkably improve the performance of UWOC system, especially when data rates are greater than 40 Mbps.

Design of Vivaldi array antenna with low sidelobe for Monopulse tracking application

The article will present the array antenna system for Monopulse tracking application. The Antenna includes 3 parts: monopulse comparator, unequal power divider, and antenna array. The monopulse comparator and unequal power divider are designed by microstrip line on PCB. Antenna array consists of 244 Vivaldi elements. Conducted simulation of the antenna system and obtained the following results: The bandwidth of the antenna system is greater than 10% with Voltage Standing Wave Ratio smaller than 1.6 (VSWR ≤1.6); Realized gain of the sum beam (radiation pattern) at the central frequency reaches 26.2 dBi; Sidelobe level of sum beam is less than -20dB in the whole frequency range; The peak and null of two difference beams are smaller than 20dB. With the results obtained, the Antenna Monopulse system is mentioned as completely suitable for use for tracking applications and arrangement in narrow space locations with compact size.

Design of displacement detection system for differential inductance sensor

To improve the resolution of displacement detection of the differential inductance sensor and meet the requirement of real-time, that is, high output bandwidth of displacement detection system, a displacement detection system of differential inductance sensor was designed based on the Zynq-7020 platform. The PL terminal (FPGA) of Zynq 7020 is used to generate the sensor excitation signal, collect the sensor probe displacement signal, digital phase-lock amplification and demodulation of the sensor, and transmit the original shift signal and the displacement signal after demodulation at the PS terminal (ARM). The measurement error can be reduced by using the band-pass filter to pretreat the signal before the digital phase-locked amplifier. According to the experimental results, the resolution of the demodulated displacement signal can reach more than 0.0028%FS, and the nonlinear error can reach 0.0278%FS after smooth approximation fitting.

Analysis of MIMO methods for 5G and subsequent technologies: advantages and disadvantages

Formulation of the problem. The global bandwidth shortage in the wireless communications sector has prompted the study and research of wireless access technology, known as mass Multiple Input/output (MIMO) technology. Mass MIMO is one of the key technologies for next-generation networks, which combines antennas in both the transmitter and receiver to provide high spectral and energy efficiency using relatively simple processing. Gaining a better understanding of the massive MIMO system to overcome the fundamental challenges of this technology is vital for the successful deployment of 5G and higher networks to implement various intelligent sensor system applications. Thus, in this paper, fully digital, analog and hybrid structures are analyzed and the method of multilevel massive MIMO transmission is described in detail. Purpose. Analysis of the main technologies needed to meet the demand for data transmission expected for 5G and 6G networks, with the allocation of transmission methods necessary for the mass implementation of MIMO. Practical significance. Evaluation of the MIMO system bandwidth, hardware and computational complexity, as well as energy efficiency, it is shown that massive MIMO circuits can rely on asymptotic linear independence when designing signal processing, given the large number of antennas used. Classical MIMO methods are not able to meet the technical requirements, so hybrid architectures use a combination of analog and digital areas to use the spatial resolution provided by a large number of antenna elements, but at the same time the number of energy-consuming and expensive radio frequency circuits remains within reasonable limits, and computational complexity is controlled. It becomes clear that there is no single structure/algorithm that would provide the best compromise between complexity and performance in all possible scenarios, rather, there is a need to adapt them to the characteristics of the application and channel when designing the system. As for optimizing the energy efficiency of the RF power supply, this is achievable using solutions such as multilayer massive MIMO.

Time-sharing orbit jump and energy harvesting in nonlinear piezoelectric energy harvesters using a synchronous switch circuit

Nonlinearity has enabled energy harvesting to advance toward higher power output and broader bandwidth in monostable, bistable, and multistable systems. However, operating in the preferable high-energy orbit (HEO) rather than the low-energy orbit (LEO) for making such advancement has restricted their applications. Based on a monostable nonlinear system, this paper proposes a self-contained solution for time-sharing orbit jump and energy harvesting. The joint dynamics of an electromechanical assembly consisting of a nonlinear energy harvester and a switched-mode piezoelectric interface circuit for high-capability energy harvesting is studied. The proposed solution is carried out by utilizing a cutting-edge switched-mode bidirectional energy conversion circuit (BECC), which enables time-sharing dual functions of energy harvesting and vibration exciting. A theoretical model is established based on impedance analysis and multiple time scales method to analyze the stability, frequency response, and phase evolution of the autonomous and nonautonomous nonlinear energy harvesting systems. In particular, the detailed dynamics for the orbit jumps with the vibration exciting mode of BECC are studied. Experiments are performed to validate the full-hysteresis-range orbit jumps with the monostable nonlinear energy harvester. The harvested power after orbit jumps yields a nine-fold increase, compensating for the energy consumption under vibration exciting mode quickly. The proposed solution also refrains the system from extra mechanical or electrical energy sources for orbit jumps, which leads to the first self-contained solution for simultaneous energy harvesting and orbit jump in nonlinear piezoelectric energy harvesting. This work enhances the practical utility of nonlinear energy harvesting technologies toward engineering applications.

Design and development of half impulse radiating antenna based ultra wide band system

Abstract An ultra wide band system utilizing Half Impulse Radiating Antenna topology has been designed and developed. A compact Marx generator and a solid dielectric pulse forming line fed the antenna. Based on pulse parameters, frequency range of 250 MHz–1250 MHz is chosen for antenna design. Analytical equations and CST Microwave Studio are used for design and analysis of the Antenna and ultra wide band system. Maximum electric field of 11 kV/m at 20 m distance from source has been measured using half-transverse electromagnetic horn type sensor. This paper discusses both time domain and frequency domain results for the designed UWB system. A good agreement between the simulated and the measured power pattern has been demonstrated in this paper.

Configuring reconfigurable intelligent surfaces using a practical codebook approach

It is proven that the scattering, reflection, and refraction properties of electromagnetic signals can be adapted and managed by using reconfigurable intelligent surfaces (RISs). In this paper, we have investigated the performance of a single-input-single-output (SISO) wideband system in terms of achievable data rate by optimizing the phases of RIS elements and performing a fair power allocation for each subcarrier over the entire bandwidth. A new beamforming codebook is developed from which the maximizing signal-to-noise (SNR) configuration is selected. The channel state information (CSI) along with the selected maximizing SNR configuration is then used by the proposed power algorithm to obtain the optimal configuration of the RIS. To validate our proposed method, it is compared with state-of-the-art semidefinite relaxation (SDR) scheme in terms of performance, complexity and run-time consumption. Our method shows dramatically lower computational complexity than the SDR method and achieves an order of 2.5 increase in the achievable data rate with an optimized RIS compared with an un-configured surface.

A novel radial network for feeding concentric ring antenna arrays

This paper presents a novel radial network for feeding concentric ring antenna arrays. The proposed feeding network consists of a radial network of 1 input to 20 outputs. Two stages are required for this planar radial network: a radial power divider of 1 to 5 and a cascade Wilkinson power divider of 1 to 4 to generate 20 outputs that feed to a concentric rings antenna array. The proposed radial network provides a feeding network having balance in magnitude and phase to be applied in antenna systems based on a concentric rings array geometry. The paper provides as an interesting contribution the full antenna system considering the proposed radial feeding network (1 to 20) and the concentric rings antenna array. Full wave electromagnetic simulations and experimental measurements are implemented to verify the performance of matching, bandwidth and radiation pattern of the full system taking the mutual coupling into account.

Design of MEMS gyroscope interface ASIC with on-chip temperature compensation

Zero bias and scale factor are important overall performance indicators for micromechanical gyroscopes and are commonly used to describe the temperature stability of MEMS gyroscope. This article presents a mode-matched MEMS gyroscope interface Application Specific Integrated Circuit (ASIC) with on-chip temperature compensation, which improves the temperature adaptability of the gyroscope by means of temperature compensation. By establishing a mathematical model between the equivalent integration constant of the driving loop and the temperature, the relationship between the phase margin of driving loop and temperature is analyzed. The effect of sense loop control parameters on the bandwidth of the gyroscope system is investigated, and the influence law between bandwidth and loop gain of the sense circuit is verified. A temperature compensation method based on an on-chip virtual temperature sensor is presented, and the design principle with an on-chip temperature compensation interface ASIC is described. The experimental results show that the standard deviation of scale factor in the temperature range of −40 to 60 °C is reduced to 11.2% of that before compensation, and the standard deviation of the zero bias is reduced to 2.5%. The zero bias instability of the gyroscope is reduced from 4.6 to 1.9°/h of that before compensation.

Suppressed Noise Enhancement Equalization Combined With Nonlinear-MLSE Techniques for Bandwidth-Limitation IM/DD System

Bandwidth limitation introduced inter-symbol interference (ISI) is the major impediment for high baud rate intensity modulation and direct detection (IM/DD) system with commercial devices. Least mean square (LMS) criterion based feedforward equalizer (FFE) is the most common method to eliminate ISI in single-carrier system. However, there is a tradeoff between the residual ISI and enhanced noise when the system bandwidth is severely limited. Although a post filter (PF) followed by maximum likelihood sequence estimation (MLSE) can suppress the enhanced noise effectively, the residual ISI left by post-FFE will degrade the system performance as the subsequent MLSE only handles ISI introduced by PF. In this paper, an adaptive partial response equalization realized by a channel-shortening filter (CSF) is investigated, which is combined with MLSE. As the target of CSF is a partial response signal with desired low-pass feature, the noise will not be enhanced in this scheme. And the residual ISI with determined response can be fully solved by MLSE. The performance of CSF based MLSE (CSF-MLSE) is evaluated and compared to PF based MLSE (PF-MLSE) in 60/70/75Gbaud four-level pulse amplitude modulation (PAM-4) system with 10-dB bandwidth of 16.2GHz. The experimental results show that CSF-MLSE has a better capability of ISI elimination compared to PF-MLSE. The bit error rate (BER) can be reduced from 7.4×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> to 4×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> and from 3×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> to 1×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> for 70Gbaud and 75Gbaud in optical back-to-back (OBTB) transmission. To further compensate the system nonlinear impairments, several nonlinear MLSE (NL-MLSE) techniques assisted by look-up table (LUT) or Volterra filter are proposed and investigated in this paper. The BER of 75Gbuad PAM-4 can be below 3×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> after using NL-MLSE schemes.

Reduced spatiotemporal bandwidth of motion stabilized event-based imaging sensors: experimental demonstration.

This work investigates event-based sensor (EBS) imaging system's read-out bandwidth performance under linear motion, with and without hardware stabilization techniques. We implement three image stabilization methods using hardware rotation to cancel the sensor platform's linear motion and recapture lost EBS performance. We successfully demonstrated the methods, showing a bandwidth reduction of over an order of magnitude in two scenes, 10 scene variations, and five EBS velocities. This work demonstrates the benefits of stabilization with EBS to reduce bandwidth requirements versus unstabilized EBS systems.

Rate optimization using low complex methods with reconfigurable intelligent surfaces

With the help of a developing technology called reconfigurable intelligent surfaces (RISs), it is possible to modify the propagation environment and boost the data rates of wireless communication networks. In this article, we optimized the phases of the RIS elements and performed a fair power allocation for each subcarrier over the full bandwidth in a single-input-single-output (SISO) wideband system where the user and the access point (AP) are provided with a single antenna. The data rate or its equivalent channel power is maximized by proposing different low-complex algorithms. The strongest tap maximization (STM) and power methods are compared with the semidefinite relaxation (SDR) method in terms of computational complexity and data rate performance. Runtime and complexity analysis of the suggested methods are computed and compared to reveal the actual time consumption and the required number of operations for each method. Simulation results show that with an optimized RIS, the sum rate is 2.5 times higher than with an unconfigured surface, demonstrating the RIS's tremendous advantages even in complex configurations. The data rate performance of the SDR method is higher than the power method and less than the STM method but with higher computational complexity, more than 6 million complex operations, and 50 ​min of runtime calculations compared with the other STM and power optimization methods.

Single-shot spatial frequency modulation for imaging.

Spatial frequency modulation for imaging (SPIFI) has traditionally employed a time-varying spatial modulation of the excitation beam. Here, for the first time to our knowledge, we introduce single-shot SPIFI, where the spatial frequency modulation is imposed across the entire spatial bandwidth of the optical system simultaneously enabling single-shot operation.

Distributional Spectrum Series (DSS) with Beamforming in 5G Communication System

The transmission channel choice and other relevant characteristics affect the communication system's bandwidth loss and signal strength. This causes energy loss during transmission since the channel bandwidth is being used up so heavily. This may be avoided by carefully choosing the channels in the spectrum to allot the bandwidth in accordance with the consumption limit. In this study, the optimum energy reduction-based 5G communication system aids in improving the channel bandwidth selection in accordance with the prediction of the ideal antenna directionality. The Distributional Spectrum Series (DSS) and the beamforming method may be used to accomplish this. This kind of optimum antenna selection analyzes the signal spectrum and optimizes the energy based on the beamforming parameters by using directionality prediction from the Direction of Arrival (DOA). The testing results and comparative graphs demonstrate the performance of the proposed 5G communication system through parameters of Energy (Joule), Blocking Probability (BP), throughput (bps), and other relevant factors.

Simultaneously Transmitting and Reflecting Surface (STARS) for Terahertz Communications

A simultaneously transmitting and reflecting surface (STARS) aided terahertz (THz) communication system is proposed. A novel power consumption model is proposed that depends on the type and resolution of the STARS elements. The spectral efficiency (SE) and energy efficiency (EE) are maximized in both narrowband and wideband THz systems by jointly optimizing the hybrid beamforming at the base station (BS) and the passive beamforming at the STARS. 1) For narrowband systems, independent phase-shift STARSs are investigated first. The resulting complex joint optimization problem is decoupled into a series of subproblems using penalty dual decomposition. Low-complexity element- wise algorithms are proposed to optimize the analog beamforming at the BS and the passive beamforming at the STARS. The proposed algorithm is then extended to the case of coupled phase-shift STARS. 2) For wideband systems, the spatial wideband effect at the BS and STARS leads to significant performance degradation due to the beam split issue. To address this, true time delayers (TTDs) are introduced into the conventional hybrid beamforming structure for facilitating wideband beamforming. An iterative algorithm based on the quasi-Newton method is proposed to design the coefficients of the TTDs. Finally, our numerical results confirm the superiority of the STARS over the conventional reconfigurable intelligent surface (RIS). It is also revealed that i) there is only a slight performance loss in terms of SE and EE caused by coupled phase shifts of the STARS in both narrowband and wideband systems, and ii) the conventional hybrid beamforming achieves comparable SE performance and much higher EE performance compared with the full-digital beamforming in narrowband systems but not in wideband systems, where the TTD-based hybrid beamforming is required for mitigating wideband beam split.

A New Alternating Predictive Observer Approach for Higher Bandwidth Control of Dual-Rate Dynamic Systems

Dual-rate dynamic systems consisting of a sensor with a relatively slow sampling rate and a controller/actuator with a fast updating rate widely exist in control systems. The control bandwidth of these dual-rate dynamic systems is severely restricted by the slow sampling rate of the sensors, resulting in various issues like sluggish dynamics of the closed-loop systems, poor robustness performance. A novel alternating predictive observer (APO) is proposed to significantly enhance the control bandwidth of a generic dual-rate dynamic systems. Specifically, at each fast controller/actuator updating period, we will first implement the prediction step by using the system model to predict the system output, generating a so-called virtual measurement, when there is no output measurement during the slow sampling period. Subsequently, the observation step is carried out by exploiting this virtual measurement as informative update. An APO-based output feedback controller with a fast updating rate is developed and rigorous stability of the closed-loop system is established. The superiority of the proposed method is demonstrated by applying it to control a permanent magnet synchronous motor system.

A Comprehensive Noise Model for Wideband and High Frame Rate Electrical Impedance Tomography Systems

Clinical applications call for comprehensive performances of electrical impedance tomography (EIT) system, including sufficient signal-to-noise ratio (SNR), high frame-per-second (Fps), and wide bandwidth. In this article, thorough analyses of switching noise in an EIT system are presented. The energy of switching noise is split into two parts: spurs and extra quantization noise of analog-to-digital converter (ADC). Based on the characteristics of switching noise, a comprehensive noise model of EIT systems with digital matched filter, is proposed. The impacts of switching noise, frame rate, and bandwidth of an EIT system are considered in the noise model. Simulation and experiment conducted in a laboratory-built EIT system are employed to validate the noise model. Test results show that the EIT system can obtain an average SNR greater than 94dB with a frame rate of 31Fps and a bandwidth of 2MHz, and an average SNR greater than 90dB with a frame rate of 31 Fps and a bandwidth of 10MHz, under the guidance of the proposed model. Overall, this work provides a novel and comprehensive noise model by including the impacts of switching noise, frame rate, and bandwidth, which can serve as a guide to improve the comprehensive performance of an EIT system for clinical applications.