Bandwidth Reduction Research Articles

Fivefold increased power handling in waveguide UTC-PDs using dual-injection shared CPW PD-arrays

This work presents two circuit-based solutions to enhance the power handling capabilities of waveguide-integrated uni-travelling carrier photodetectors (WG-UTC-PDs). Compared to a baseline WG-UTC-PD, these solutions achieve a fivefold increase in photocurrent before thermal breakdown. First, dual-injection improves the optical power distribution within a baseline WG-UTC-PD, raising the photocurrent threshold before thermal breakdown. Second, an array of four optically parallel WG-UTC-PDs, electrically connected to a single coplanar waveguide (CPW) line, further increases the maximum photocurrent by distributing the input optical power across multiple PDs. The design omits a termination resistor, as the arrays do not rely on a traveling wave configuration, maximizing photocurrent without a 50% reduction of bandwidth. Both 4-PD single-injection and dual-injection arrays were designed, fabricated, and characterized. Compared to a baseline UTC-PD, with a maximum photocurrent of 1.8 mA at a 3 dB bandwidth of 55 GHz, the 4-PD single-injection circuit achieved 5.1 mA at 43 GHz. The dual-injection array further increased the photocurrent to 9.2 mA at a bandwidth of 35 GHz. Electrical reflection measurements confirmed the negative effects of CPW losses on RF performance. These power handling improvements enable compact, high-power integrated solutions for microwave photonics.

Cloud IaaS Optimization Using Machine Vision at the IoT Edge and the Grid Sensing Algorithm

Security grids consisting of High-Definition (HD) Internet of Things (IoT) cameras are gaining popularity for organizational perimeter surveillance and security monitoring. Transmitting HD video data to cloud infrastructure requires high bandwidth and more storage space than text, audio, and image data. It becomes more challenging for large-scale organizations with massive security grids to minimize cloud network bandwidth and storage costs. This paper presents an application of Machine Vision at the IoT Edge (Mez) technology in association with a novel Grid Sensing (GRS) algorithm to optimize cloud Infrastructure as a Service (IaaS) resource allocation, leading to cost minimization. Experimental results demonstrated a 31.29% reduction in bandwidth and a 22.43% reduction in storage requirements. The Mez technology offers a network latency feedback module with knobs for transforming video frames to adjust to the latency sensitivity. The association of the GRS algorithm introduces its compatibility in the IoT camera-driven security grid by automatically ranking the existing bandwidth requirements by different IoT nodes. As a result, the proposed system minimizes the entire grid’s throughput, contributing to significant cloud resource optimization.

Compact dual-band enhanced bandwidth 5G mm – wave MIMO dielectric resonator antenna utilizing metallic strips

A compact dual-band Multiple-Input Multiple-Output Dielectric Resonator Antenna with improved bandwidth for 5G mm-wave applications is presented. Two rectangular DRAs mounted on a substrate backed ground plane are excited by microstrip feed through aperture coupling. Notches cut out from center of the DRAs helps to achieve a dual-band response with improved bandwidth by exciting several modes. The isolation between the DRAs is achieved by appropriately positioning metallic strips on walls on of the DRAs. A dual-band response with enhanced bandwidth and mutual coupling reduction. The impedance bandwidth for the proposed design is between 26.5–30 GHz (12.4 %) and 34.2–40 GHz (15.6 %). The maximum isolation achieved in the lower band is 32 dB and above 45 dB in the upper band. The overall size of the design is 1.88λo x 0.94λo x 0.20λo. The design procedure is described, and the role of decoupling strips are explained. A prototype is fabricated and measured to validate the proposed design.

DermCompressNet: integrated CD-ConvNet and discrete cosine transform for dermoscopic images compression

AbstractTelemedicine has a critical role in healthcare by supporting the information exchange between the patients and the physicians as well as between the physicians for consultation. Such technology has urgent requirements for storage reduction and efficient use of the transmission channel bandwidth. Such requirements can be achieved efficiently via developing accurate medical image compression techniques. For accurate diagnosis, lossless compression methods are recommended. However, the tradeoff between the compression ratio (CR) and the preservation of the image quality is still challenging. On the other hand, the advantages of the convolutional neural networks inspired this work to design a novel proposed system for dermoscopic image compression based on the integration of the compression direction-ConvNet (CD-ConvNet) and decompression direction-ConvNet (DD-ConvNet) with discrete cosine transform (DCT) and Huffman coding, called DermCompressNet. To reconstruct a high-quality image at the receiver, the inverse processes using the DD-ConvNet network were followed. The proposed system was evaluated by measuring several image quality metrics, namely the mean square error (MSE), peak signal-to-noise ratio (PSNR), and structural similarity index measure (SSIM), along with compression quality metrics, namely CR, and computational time (CT). The experimental results achieved 34.6 dB, 2.5, 0.85, and 56% of PSNR, MSE, SSIM, and CR, respectively. A comparison studies with the JPEG and state-of-the-art methods proved the superiority of the proposed system, showing23%, 16%, 4.3%, and 1.8% improvements in the PSNR, MSE, SSIM, and CR, respectively, compared to the JPEG.

Circular Microstrip Antennas in 5G: Evaluating Metamaterial Integration

The rapid emergence of Fifth-Generation (5G) technologies necessitate the development of highly efficient antenna systems with compact design that can support Ultra-Wideband (UWB) frequencies. This work presents the design and enhancement of a Circular Microstrip Antenna (CMSA) for 5G UWB applications using metamaterials. The study focuses on the design of CMSA and the integration of a Complementary Split-Ring Resonator (CSRR) into the circular patch of the CMSA. The design is simulated using Computer Simulation Technology (CST) Studio 2023. The system design without metamaterials achieved a gain of 5.28 dBi and a bandwidth of 353.0 MHz. The integration of the CSRR led to an improvement in gain, 5.39 dBi at 3.8 GHz, which is above most of the literature reviewed, although there was a slight reduction in bandwidth to 135.2 MHz. The objectives of achieving a CMSA design with a gain between 5 to 10 dBi while maintaining a compact size were accomplished. Despite the slight reduction in bandwidth observed when integrating the CSRR into the CMSA, the overall results highlight the significant role metamaterials played in enhancing the performance of microstrip antennas for 5G technology applications.

Enhanced damping and bandwidth in roton-like dispersion of a beyond nearest neighbor periodic chain

This paper investigates the intriguing roton-like phenomenon occurring in systems with non-local interactions, wherein a single dispersion curve exhibits positive and negative group velocities. Previous research has predominantly concentrated on investigating the roton dispersion in undamped metamaterials through steady-state vibration and driven wave methodologies. However, exploring transient wave propagation in damped metamaterials, employing a free wave approach to study damping enhancement (metadamping), has received comparatively little attention. Addressing this research gap, the damping of the system is quantified as the rate of decay of transient vibrations. Results show a significant increase in damping and attenuation bandwidth, coinciding with the presence of the roton-like phenomenon. Unlike previous studies on metadamping, the proposed beyond nearest neighbor (BNN) chain simultaneously enhances both damping and reduction in acoustic bandwidth without sacrificing either property. Spatiotemporal domain simulation evidenced the existence of backward propagating wave packets due to a roton-like phenomenon in the specific frequency range.

Automated phase-visibility modulating interferometry

This paper presents the Phase-Visibility Modulating Interferometry (PVMI) method automated by a microcontroller and three servomotors, under inhomogeneous out-of-phase amplitude modulation (OPAM) in the On-Off Modulation (OOM) mode. PVMI is implemented in a triple-aperture common-path interferometer (TACPI), based on a 4f optical imaging system. The high mechanical stability of the TACPI and the properties of the PVMI technique make the present method immune to noise, robust, fast, and convenient for measuring complex amplitude with high resolution and accuracy. PVMI does not preprocess and post-process the experimental irradiances and does not need a phase step shifter or a carrier frequency. Therefore, a calibration is unnecessary, there are no detuning errors, and no bandwidth reduction. The great advantage of automated PVMI is explained and demonstrated experimentally for three translucent objects. The focal length estimation of a lens with a percentual deviation of 0.14 to validate the automated PVMI, and the evaluation of two arbitrary translucent objects with high resolution and accuracy.

Distributed Vibration Sensing Based on a Forward Transmission Polarization-Generated Carrier.

For distributed fiber-optic sensors, slowly varying vibration signals down to 5 mHz are difficult to measure due to low signal-to-noise ratios. We propose and demonstrate a forward transmission-based distributed sensing system, combined with a polarization-generated carrier for detection bandwidth reduction, and cross-correlation for vibration positioning. By applying a higher-frequency carrier signal using a fast polarization controller, the initial phase of the known carrier frequency is monitored and analyzed to demodulate the vibration signal. Only the polarization carrier needs to be analyzed, not the arbitrary-frequency signal, which can lead to hardware issues (reduced detection bandwidth and less noise). The difference in arrival time between the two detection ends obtained through cross-correlation can determine the vibration position. Our experimental results demonstrate a sensitivity of 0.63 mrad/με and a limit of detection (LoD) of 355.6 pε/Hz1/2 at 60 Hz. A lock-in amplifier can be used on the fixed carrier to achieve a minimal LoD. The sensing distance can reach 131.5 km and the positioning accuracy is 725 m (root-mean-square error) while the spatial resolution is 105 m. The tested vibration frequency range is between 0.005 Hz and 160 Hz. A low frequency of 5 mHz for forward transmission-based distributed sensing is highly attractive for seismic monitoring applications.

Assessment of UHF Frequency Range for Failure Classification in Power Transformers.

Ultrahigh-frequency (UHF) sensing is one of the most promising techniques for assessing the quality of power transformer insulation systems due to its capability to identify failures like partial discharges (PDs) by detecting the emitted UHF signals. However, there are still uncertainties regarding the frequency range that should be evaluated in measurements. For example, most publications have stated that UHF emissions range up to 3 GHz. However, a Cigré brochure revealed that the optimal spectrum is between 100 MHz and 1 GHz, and more recently, a study indicated that the optimal frequency range is between 400 MHz and 900 MHz. Since different faults require different maintenance actions, both science and industry have been developing systems that allow for failure-type identification. Hence, it is important to note that bandwidth reduction may impair classification systems, especially those that are frequency-based. This article combines three operational conditions of a power transformer (healthy state, electric arc failure, and partial discharges on bushing) with three different self-organized maps to carry out failure classification: the chromatic technique (CT), principal component analysis (PCA), and the shape analysis clustering technique (SACT). For each case, the frequency content of UHF signals was selected at three frequency bands: the full spectrum, Cigré brochure range, and between 400 MHz and 900 MHz. Therefore, the contributions of this work are to assess how spectrum band limitation may alter failure classification and to evaluate the effectiveness of signal processing methodologies based on the frequency content of UHF signals. Additionally, an advantage of this work is that it does not rely on training as is the case for some machine learning-based methods. The results indicate that the reduced frequency range was not a limiting factor for classifying the state of the operation condition of the power transformer. Therefore, there is the possibility of using lower frequency ranges, such as from 400 MHz to 900 MHz, contributing to the development of less costly data acquisition systems. Additionally, PCA was found to be the most promising technique despite the reduction in frequency band information.

A Placement Method of the 5G Edge Nodes Based on the Hotspot Distribution of Mobile Users

Due to the emergence of various new applications, such as short videos and online games, higher requirements of their computing and storage capacity are demanded of mobile networks. The traditional cloud computing paradigm has the shortcomings of large latency and high bandwidth demand of the core network. Therefore, how to mine the hotspot distribution of these applications and reasonably configure 5G edge nodes to reduce latency and core network bandwidth are facing great challenges. To address these issues, we designed a placement method for the 5G edge nodes based on mobile hotspots. In this method, we first cluster all locations from the user trajectories to obtain the cluster areas. Further, we extract the features, such as the number of users and duration time in all cluster areas, and extract the hotspots from all cluster areas based on the features of each cluster. Then, we introduce the base station’s high load utilization rate and the core network’s bandwidth reduction rate as the optimization parameters to construct the mathematical model of multi-objective optimization. Finally, we formalize the model into a 0–1 integer programming problem and design a greedy algorithm to solve this model. We also complete a series of experiments to evaluate our proposed methods using the GeoLife dataset. The experimental results show that the high load utilization rate can be increased up to 7.69%, and the bandwidth reduction rate of the core network can be improved up to 6.34%.

PRAC: Round-Efficient 3-Party MPC for Dynamic Data Structures

We present Private Random Access Computations (PRAC), a 3-party Secure Multi-Party Computation (MPC) framework to support random-access data structure algorithms for MPC with efficient communication in terms of rounds and bandwidth. PRAC extends the state-of-the-art DORAM Duoram with a new implementation, more flexibility in how the DORAM memory is shared, and support for Incremental and Wide DPFs. We then use these DPF extensions to achieve algorithmic improvements in three novel oblivious data structure protocols for MPC. PRAC exploits the observation that a secure protocol for an algorithm can gain efficiency if the protocol explicitly reveals information leaked by the algorithm inherently. We first present an optimized binary search protocol that reduces the bandwidth from O(lg² n) to O(lg n) for obliviously searching over n items. We then present an oblivious heap protocol with rounds reduced from O(lg n) to O(lg lg n) for insertions, and bandwidth reduced from O(lg² n) to O(lg n) for extractions. Finally, we also present the first oblivious AVL tree protocol for MPC where no party learns the data or the structure of the AVL tree, and can support arbitrary insertions and deletions with O(lg n) rounds and bandwidth. We experimentally evaluate our protocols with realistic network settings for a wide range of memory sizes to demonstrate their efficiency. For instance, we observe our binary search protocol provides >27× and >3× improvements in wall-clock time and bandwidth respectively over other approaches for a memory with 2^26 items; for the same setting our heap's extract-min protocol achieves >31× speedup in wall-clock time and >13× reduction in bandwidth.

High strength induced wide band gap formations in additively manufactured cubic metamaterial

Strength and band gap are the two basic physical features of the cubic metamaterial. How to design band gap characteristics with high strength of structure is the key for the further industrial application in vibration control of the cubic metamaterial. Here a cubic metamaterial is designed by optimal selection of crystal orientation angle to obtain wide band gaps with high strength. The prototype samples were fabricated using advanced additive manufacturing technology to tensile-pressure experiments and sine frequency sweep experiment, thereby demonstrating the validity of the obtained results. Results indicated that the normalized bandwidth of simple cubic (SC) metamaterials is 0.47 and the ultimate strength is 25.99 MPa. The normalized bandwidth is increased by 3.1 times and 47 times higher than that of the metamaterials of face-centered cubic (FCC) and body-centered cubic (BCC). Its ultimate strength is increased by 3.5 times and 6.7 times. The static simulation results revealed that the maximum mises stress values of SC, FCC, and BCC metamaterials were 1.71, 10.49, and 31.40 MPa respectively. The attenuation amplitude of the elastic wave measured by experiment is 80 dB, which is consistent with the simulation results. The bandwidths of cubic metamaterials exhibit a positive correlation with their strength. The variation in crystal orientation angles plays a crucial role in elucidating the underlying mechanism behind the positive correlation between the strength and the band gap. The further buckling analysis of SC metamaterial with high strength and wide bandgap characteristics reveals that the negative Poisson’s ratio structure experiences a reduction in bandwidth and strength as buckling deformation intensifies.

Moiré band renormalization due to lattice mismatch in bilayer graphene

We investigated the band renormalization caused by the compressive-strain-induced lattice mismatch in parallel AA stacked bilayer graphene using two complementary methods: the tight-binding approach and the low-energy continuum theory. While a large mismatch does not alter the low-energy bands, a small one reduces the bandwidth of the low-energy bands along with a decrease in the Fermi velocity. In the tiny-mismatch regime, the low-energy continuum theory reveals that the long-period moiré pattern extensively renormalizes the low-energy bands, resulting in a significant reduction of bandwidth. Meanwhile, the Fermi velocity exhibits an oscillatory behavior and approaches zero at specific mismatches. However, the resulting low-energy bands are not perfectly isolated flat, as seen in twisted bilayer graphene at magic angles. These findings provide a deeper understanding of moiré physics and offer valuable guidance for related experimental studies in creating moiré superlattices using two-dimensional van der Waals heterostructures.

Influence of Fe2O3 on the absorptivity of in situ synthesized solar high-temperature absorbing and storing integrated mullite-based ceramics

Solar energy absorption and storage of integrated ceramic materials is both the absorption of sunlight and storage of sunlight into thermal energy functional materials. In this paper, the effect of Fe2O3 on the solar absorptivity, thermal storage properties, sintering temperature, and physical properties of mullite-based thermal storage ceramics was investigated. The results show that the absorptivity and thermal storage density of the sample AF4 (Bauxite:50 wt%, Clay:50 wt%, Fe2O3:11 wt%) after sintering at 1420 °C are 87.2% and 1116.5 kJ kg−1, respectively; and the unit volume of the AF4 sample can provide the power grid with 918.01 kW h of electricity, save 112.91 kg of coal, and reduce 361.33 kg of CO2 emission. This study systematically elucidated the mechanism of the enhancement of sample absorption caused by Fe3+ doping-induced changes in substrate color, reduction in material forbidden bandwidth, and lattice anharmonic vibration effect, in addition to comprehensively evaluating the feasibility of the optimal AF4 sample for use in solar energy absorbing and storing integrated ceramic materials.

High-Bandwidth Lumped Mach-Zehnder Modulators Based on Thin-Film Lithium Niobate

Recently, lumped Mach-Zehnder Modulators (MZMs) have received renewed attention due to their potential for low power consumption and compact size. However, the practicality of lumped MZMs with conventional lumped electrodes (C−LEs) is limited by their lower electro−optical (EO) bandwidth. The reduction in EO bandwidth results from the inherent trade−off between EO bandwidth and half−wave voltage length product (VπL) within the C−LE architecture. This paper proposes a thin−film lithium niobate (TFLN)−based lumped MZM with capacitively−loaded lumped electrodes (CL−LEs). The purely linear EO effect of the LN eliminates the parasitic capacitance in the doped PN junction and enhances the EO bandwidth. Furthermore, the CL−LE structure can break the limitation between EO bandwidth and VπL inherent in the C−LE design. Simulations show the proposed device achieves a high EO bandwidth of 32.4 GHz and a low VπL of 1.15 V·cm. Due to the reduced capacitance and lower VπL, the power consumption of the device is as low as 0.1 pJ/bit. Simulation results indicate that the open−eye diagrams are achieved at 64 Gb/s for 1.5 mm TFLN lumped MZM, with an ER of 2.97 dB. Consequently, the proposed device architecture substantially enhances the performance of lumped MZMs, showing promise for application in short−reach optical interconnects within data centers.

Improving canopy transpiration model performance by considering concurrent hot and dry conditions

CONTEXTThe Jarvis-Stewart model has commonly been used to estimate transpiration. However, its assumption regarding independent effects from different influencing factors has seldom been explored. OBJECTIVEThe aim is to test whether the Jarvis-Stewart model can well estimate transpiration under concurrent hot and dry conditions with strong environmental interactions. A secondary objective was to test was to propose a new coupling method without the environmental-independence assumption for transpiration estimation. METHODSThis study tested and compared 24 Jarvis-Stewart models composed of various constraint functions to determine the optimal model structure for an orange orchard under concurrent hot and dry conditions. Meanwhile, a new coupling equation that considers interactive environmental effects on transpiration was proposed, and a total of 48 configurations were examined to determine the most effective configuration. A comprehensive comparison was made between the best Jarvis-Stewart model and the best coupling model based on a Bayesian framework. RESULTS AND CONCLUSIONSResults showed that with fewer parameters, the best new coupling model significantly improved model performance compared with the best Jarvis-Stewart model. Specifically, estimation accuracy was slightly improved, with the average mean relative error decreased from 11.79% to 11.06%, and the average coefficient of determination increased from 0.67 to 0.72. More importantly, estimation uncertainty was significantly decreased, with the average uncertainty band width reduction of 42%. Moreover, the new model generated some water use information that was much more consistent with measured data and did not suffer from over-fitting problems as the Jarvis-Stewart model suffered from. Furthermore, the new model did not require additional data or computational cost. SIGNIFICANCEThe results of our study emphasize the necessity for studying environmental interaction effects on plant water consumption, particularly under the possibility of concurrent hot and dry conditions that are likely to occur under future climate conditions.

Effect of air-loading on the performance limits of graphene microphones

As a consequence of their high strength, small thickness, and high flexibility, ultrathin graphene membranes show great potential for pressure and sound sensing applications. This study investigates the performance of multi-layer graphene membranes for microphone applications in the presence of air-loading. Since microphones need a flatband response over the full audible bandwidth, they require a sufficiently high mechanical resonance frequency. Reducing membrane thickness facilitates meeting this bandwidth requirement, and therefore, also allows increasing compliance and sensitivity of the membranes. However, at atmospheric pressure, air-loading effects can increase the effective mass, and thus, reduce the bandwidth of graphene and other 2D material-based microphones. To assess the severity of this performance-limiting effect, we characterize the acoustic response of multi-layer graphene membranes with a thickness of 8 nm in the pressure range from 30 to 1000 mbar, in air and helium environments. A bandwidth reduction by a factor ∼2.8× for membranes with a diameter of 500 μm is observed. These measurements show that air-loading effects, which are usually negligible in conventional microphones, can lead to a substantial bandwidth reduction in ultrathin graphene microphones. With analytical and finite element models, we further analyze the performance limits of graphene microphones in the presence of air-loading effects.

Comparison of bit error rate (BER) in multipath phenomena Rayleigh and Rician using QPSK modulation in Multiple Input Multiple Output (MIMO) systems

In wireless communications, there are Rician and Rayleigh multipath phenomena, which can cause destructive interference caused by a strong dominant component. The objective of the study is to analyze how these multipath phenomena affect the Bit Error Rate (BER), using phase shift keying (QPSK), as well as 5G Multiple Input Multiple Output (MIMO) technology to reduce or not the effect of fading to improve the BER. For the present study, the quantitative method is used to measure BER by comparative simulations of Rician and Rayleigh phenomena using different MIMO antenna configuration schemes using Matlab software. When comparing the multipath Rician and Rayleigh phenomena with QPSK modulation, it was determined that the most efficient channel is the Rician channel, since the BER is lower, performing a 4x4 MIMO antenna configuration. However, this efficiency may change if another type of modulation is used, which implies reducing the bit rate causing a reduction in bandwidth.

Count-Free Single-Photon 3D Imaging with Race Logic.

Single-photon cameras (SPCs) have emerged as a promising new technology for high-resolution 3D imaging. A single-photon 3D camera determines the round-trip time of a laser pulse by precisely capturing the arrival of individual photons at each camera pixel. Constructing photon-timestamp histograms is a fundamental operation for a single-photon 3D camera. However, in-pixel histogram processing is computationally expensive and requires large amount of memory per pixel. Digitizing and transferring photon timestamps to an off-sensor histogramming module is bandwidth and power hungry. Can we estimate distances without explicitly storing photon counts? Yes-here we present an online approach for distance estimation suitable for resource-constrained settings with limited bandwidth, memory and compute. The two key ingredients of our approach are (a) processing photon streams using race logic, which maintains photon data in the time-delay domain, and (b) constructing count-free equi-depth histograms as opposed to conventional equi-width histograms. Equi-depth histograms are a more succinct representation for "peaky" distributions, such as those obtained by an SPC pixel from a laser pulse reflected by a surface. Our approach uses a binner element that converges on the median (or, more generally, to another k-quantile) of a distribution. We cascade multiple binners to form an equi-depth histogrammer that produces multi-bin histograms. Our evaluation shows that this method can provide at least an order of magnitude reduction in bandwidth and power consumption while maintaining similar distance reconstruction accuracy as conventional histogram-based processing methods.

Robust Permittivity Reconstruction With the Transmission and Reflection Method at mm-Wave Frequencies

The permittivity reconstruction with the transmission and reflection method usually requires time-gating to mitigate distorted measurement data. State-of-the-art approaches reduce the available bandwidth as they introduce ringing. Available frequency extension approaches to avoid a bandwidth reduction are not based on a physically meaningful estimate. In this work, we propose a method that takes advantage of the information already given by the measurement to calculate a reasonable frequency extension. The inverse problem of the actual permittivity reconstruction is most commonly approached by the Baker-Jarvis algorithm from the National Institute of Standards and Technology (NIST) which considers the magnitude of one single complex number. It is calculated from the difference between measurement and model of the scattering matrix. In this article, we demonstrate the superiority of matching all four scattering parameters individually instead. This results in particular in a wider range of initial start parameters with proper convergence to the desired solution and more reliable reconstruction results for optimizations with unknown sample thickness. The benefits of the novel reconstruction techniques are demonstrated and evaluated in detail on simulation and measurement data in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V$</tex-math> </inline-formula> band.