Transmission Phase Research Articles

An impedance matching section based on composite right/left‐handed transmission line model in viewpoint of phase shift and noise figure

AbstractIn this paper, a genetic‐based synthesis approach for an impedance matching section based on a composite right‐/left‐handed (CRLH) transmission line model called CRLH transmission line impedance matching section (CRLHTLIMS) in viewpoint of transmission phase shift and noise figure is newly presented. To find the unknown values of right‐/left‐handed inductances and capacitances of a CRLHTLIMS, a type of global optimization algorithm called continuous parameter genetic algorithm is used. The length, transmission phase shift, and noise figure of the CRLHTLIMS are computed by using simple equations. Different examples for a uniform CRLHTLIMS are given. According to the results, this approach is an easy and effective way for the synthesis of transmission line impedance matching sections in viewpoint of transmission phase shift and noise figure.

Perspective on quantitative phase imaging to improve precision cancer medicine.

Quantitative phase imaging (QPI) offers a label-free approach to non-invasively characterize cellular processes by exploiting their refractive index based intrinsic contrast. QPI captures this contrast by translating refractive index associated phase shifts into intensity-based quantifiable data with nanoscale sensitivity. It holds significant potential for advancing precision cancer medicine by providing quantitative characterization of the biophysical properties of cells and tissue in their natural states. This perspective aims to discuss the potential of QPI to increase our understanding of cancer development and its response to therapeutics. It also explores new developments in QPI methods towards advancing personalized cancer therapy and early detection. We begin by detailing the technical advancements of QPI, examining its implementations across transmission and reflection geometries and phase retrieval methods, both interferometric and non-interferometric. The focus then shifts to QPI's applications in cancer research, including dynamic cell mass imaging for drug response assessment, cancer risk stratification, and in-vivo tissue imaging. QPI has emerged as a crucial tool in precision cancer medicine, offering insights into tumor biology and treatment efficacy. Its sensitivity to detecting nanoscale changes holds promise for enhancing cancer diagnostics, risk assessment, and prognostication. The future of QPI is envisioned in its integration with artificial intelligence, morpho-dynamics, and spatial biology, broadening its impact in cancer research. QPI presents significant potential in advancing precision cancer medicine and redefining our approach to cancer diagnosis, monitoring, and treatment. Future directions include harnessing high-throughput dynamic imaging, 3D QPI for realistic tumor models, and combining artificial intelligence with multi-omics data to extend QPI's capabilities. As a result, QPI stands at the forefront of cancer research and clinical application in cancer care.

A Collaborative Control Method of Transmission Amplitude and Phase for Transmitarray Antenna Design

In this paper, a collaborative control method of transmission amplitude and phase for transmitarray antenna (TA) design is proposed. In this proposed method, one of the most popular hypersurface fitting models, Gaussian stochastic process (GP) model, is utilized to construct an accurate surrogate model. Following this implementation, a mapping relationship between structural parameters of TA unit cell and its transmission amplitude and phase is established. The most advantage of this method is its applicability for general TA designs because it is much difficult to control the amplitude and phase of unit cell independently through adjusting separate structural parameters. To verify the high efficiency of the proposed method, three TA antennas with different scanning angles are designed to obtain high sidelobe suppression level. Measured results show that the proposed collaborative control method of amplitude and phase is much promising for high sidelobe suppression level in TA designs.

Dual-wavelength terahertz two-dimensional phase gratings based on all dielectric metasurfaces

Efficient and accurate phase gratings hold immense significance in the realization of large format heterodyne array receivers at terahertz frequencies. Metallic phase gratings have made substantial advancements in terms of operating wavelength and the number of diffraction beams. Like most other diffractive optical devices, metallic phase gratings are primarily optimized to operate at one specific wavelength. Metasurfaces compositing arrays of subwavelength nanostructures have been demonstrated with various optical functions, by freely modifying the polarization, phase, and amplitude of light. In this study, we present an approach to create a multi-wavelength phase grating compositing segments that incorporate multiple nanostructures. The resulting transmission phase grating not only exhibits uniform diffraction beams (2 × 2) but also achieves the same diffraction angles at both 1.31 and 2.7 THz. The measured total power efficiency of the diffraction beam pattern is 53.2% for 1.31 THz and 42.4% for 2.7 THz. These devices can be applied in terahertz astronomical observations and fluorescence microscopy applications, where multi-wavelength operation is necessary.

Gain and mode purity filtering dual polarized OAM beam generation using cavity waveguide-based 3D transmitarray

A 3D transmitarray (TA) is proposed to generate dual-polarized orbital angular momentum (OAM) beams with gain and mode purity filtering responses. The TA units are realized by square cavity filters with the same passband and different orders and inner widths, resulting in different coupling cavity numbers. The evanescent modes in the coupling cavities will greatly decrease the propagation constant, thus generating a large phase variation. The square structure of the cavity filter makes it able to support dual-polarized wave propagation with the same phase delay and insert loss. Based on these transmission characteristics, eight different TA units are designed to realize a 3-bit phase gradient within the passband of 25.4–26.7 GHz. It should be emphasized that the dispersed transmission phase and magnitude of the eight TA units in the stopbands will deteriorate the purity of the OAM beam. Therefore, the gain and mode purity filtering responses can be realized simultaneously. In order to verify the performance of the proposed OAM TA design, a TA prototype with the mode number l = −1 is fabricated by 3D printing technology. The TA can realize the maximum gain of 25.9 dB in the passband, and the rejection level is below −15.0 dB within the main beam direction. The purities of dual-polarized OAM beams are over 0.5 in the passband, and the cross-polarization is below −16.5 dB. The advantages of the OAM TA, including gain-filtering and mode purity-filtering responses, dual-polarization, and high efficiency make it a promising solution for millimeter-wave OAM sensing and communication applications.

Dual-polarized bidirectional beam-steering array with beam-scanning capability in full-space

This paper presents a dual-polarized bidirectional electronically reconfigurable beam-steering array (DBSA) for the first time, which integrates the beam-scanning capabilities of both dual-polarized reconfigurable transmitarray and dual-polarized reconfigurable reflectarray. First, a novel phase and direction reconfigurable dual-polarized element is proposed. Four PIN diodes are soldered onto the symmetric transmitting patches to tune the 1-bit transmission phase, while two PIN diodes are soldered onto the reflecting patches to tune the 1-bit reflection phase. By controlling the states of the PIN diodes, the DBSA element can achieve 1-bit reconfigurable phase in both transmission and reflection modes. Second, based on the proposed element, a 100-element DBSA prototype is fabricated and measured. At dual-polarization, the angles of the scanned beams can reach 45∘ and 222∘ in forward- and backward-spaces. Therefore, the proposed novel method opens a new avenue to designing a dual-polarized electronically reconfigurable spatially fed array antenna with full-space beam-scanning capabilities, and the proposed design is suitable for dual-polarized bidirectional wireless communication applications.

Tunable VO2 metasurface for reflective terahertz linear and circular polarization wavefront manipulation at two frequencies independently

In this work, a tunable VO2 metasurface (MS) is proposed and numerically demonstrated in the terahertz (THz) region, which can independently manipulate reflected linearly polarized (LP) and circularly polarized (CP) wavefronts at two frequencies independently. The unit-cell of the proposed VO2 MS consists of a metallic circular ring (CR) structure, rectangular-shaped-patch (RSP) and circular-double-split-ring (CDSR) structure VO2 adhered on a dielectric substrate by a bottom metallic ground plane. The proposed MS structure enables the reflected cross-polarization conversion of LP waves at lower frequencies (fL = 1.34 THz) and CP waves at higher frequencies (fH = 2.53 THz), respectively. By changing the external temperature, the conductivity of the VO2 RSP and CDSR structures can be adjusted dynamically. By varying the conductivity of the VO2, the proposed MS can achieve a reflected LP conversion with efficiency from 0% to 98.86% at lower frequency of 1.34 THz and the reflected CP conversion with efficiency from 0% to 81.86% at higher frequency of 2.53 THz. Moreover, the corresponding modulation depths of this MS are as high as 98.86% and 81.86% at two different frequencies, respectively. Moreover, a 2π phase shift can be realized by the transmission phase and geometric phase principles at lower and higher frequencies, respectively. Finally, two VO2 MSs have been constructed to achieve the reflection deflection for both CP and LP waves, and reflective CP focusing and LP vortex beam generation, respectively. These findings are favorable for expanding the range of temperature-controlled VO2 MS for wavefront manipulation, thereby opening up new possibilities for the development of advanced, tunable, and multifunctional THz devices that can handle both LP and CP waves.

A Broadband Transmitarray Antenna Using a Metasurface-Based Element for Millimeter-Wave Applications.

In this manuscript, a broadband transmitarray antenna (TA) using a metasurface-based element is presented for millimeter-wave communication applications. The metasurface-based TA element adopts a receiver-transmitter configuration: metasurfaces are applied as the receiver and transmitter, and slot-coupled differentially fed striplines are used as the phase compensation. The designed TA element achieves good transmission performance with a more than 360° transmission phase shift range and less than 1-dB transmission insertion loss within a wide frequency range. To verify the proposed TA, a prototype is fabricated based on the conventional printed circuit board (PCB) process, and a pyramid horn is designed as the source. The measured results show that the proposed TA with the differential feed network presents a 1-dB gain bandwidth of 26.2% from 23.5 to 30.5 GHz and a peak gain of 24.5 dBi. The designed TA is a promising alternative for millimeter-wave communications applications because of its high gain, broad bandwidth, low costs, and convenient integration with other circuits.

Learning curves for itinerant nurses to master the operation skill of Ti-robot-assisted spinal surgery equipment by CUSUM analysis: A pilot study.

This study aimed to investigate the minimum number of operations required for itinerant nurses in the operating room to master the skills needed to operate the Ti-robot-assisted spinal surgery equipment. Additionally, we aimed to provide a corresponding basis for the development of qualification admission criteria and skill training for nurses who cooperate with this type of surgery. Nine operating room itinerant nurses independently performed Ti-robot equipment simulations using a spine model as a tool, with 16 operations per trainee. Four evaluation indices were recorded: time spent on equipment preparation and line connections, time spent on image acquisition and transmission, time spent on surgical spine screw placement planning, and time spent on robot arm operation. Individual and general learning curves were plotted using cumulative sum analysis. The number of cases in which the slope of the individual learning curves began to decrease was 3-11 cases, and the number of cases in which the slope of the general learning curve began to decrease was 8 cases. The numbers of cases in which the learning curves began to decrease in the four phases were the 5th, 8th, 11th, and 3rd cases. Itinerant nurses required at least eight cases to master the equipment operation skills of Ti-robot-assisted spinal surgery. Among the four phases, the image acquisition and transmission phases and the surgical spine screw placement planning phase were the most difficult and must be emphasized in future training.

A non-invasive technique for monitoring supply voltage variation to single phase induction motor using doppler UWB radar signal analysis

The induction motors (IMs) are important components of various industries. The condition of IMs monitored continuously using contact and non-contact methods continuously. The contact methods are expensive, complex and difficult to implement. This paper proposes a non-contact method of fault identification in the single-phase induction motor operating in different conditions by analyzing doppler ultra-wide band (UWB) radar signal. The UWB radar generates a high frequency signal, which is transmitted on to the Induction motor form transmitter and software phase locked loop (SPLL) condition received signal from the receiver. The PLL implements as low pass filter, receives reflected signal from an induction motor along with high frequency noise. The received signal filtered to remove the high frequency noise and filtered output is analyzed to identify the different faults such as over voltage faults and under voltage faults when the motor is running with high, medium and low speed. The proposed non-invasive method has advantages compared to other such as the sensor’s sensitivity will not affect with motor temperature and accuracy will not change with position of the sensor and presence of other machines.

A versatile design method applied to reconfigurable metasurfaces

This paper introduces a versatile design method for reconfigurable metasurfaces based on the Pancharatnam–Berry phase theory. Unlike traditional reconfigurable metasurfaces that require designing independent surfaces for specific applications, leading to a significant time investment for designers to learn and create, this study proposes a foundational, invariant metasurface. By selectively metallizing holes or inserting metal cylinders, it achieves nine available functionalities. Regardless of the chosen operating function, the metasurface demonstrates high efficiency at 8.2 GHz, with amplitude loss less than 1 dB. Additionally, when operating in phase modulation mode, the design provides a 360° phase adjustment range and a 30° phase step. A prototype containing 31×31 units (425.6×425.6mm2) has been fabricated and tested under function 7 (TM and RHCP transmission phase modulation). Measurement results confirm the metasurface’s capability for polarization conversion and phase modulation at the frequency of 8.2 GHz.

Pattern-reconfigurable integrated array antenna based on a coding metasurface.

An electrically tunable pattern-reconfigurable integrated array antenna based on a 1-bit digital coding metasurface is proposed in this paper. The array antenna consists of 8 × 8 unit cells which is divided into the radiation antenna and the phase control metasurface. The rectangular microstrip patch antenna is used as the radiation source. The phase control metasurface includes three stacked layers of square slot units loaded with varactor diodes and a biasing circuit layer. The metasurface regulates the transmission phase of the quasi-plane wave generated by the radiation antenna. The pattern reconfigurability is achieved by switching coding sequences of the metasurface which can be regulated by the capacitance of varactor diodes. The measured results show the design has the capability of pencil-beam radiation, beam deflection, and multi-beam radiation at 5 GHz. The proposed array antenna preserves the coding metasurface without requiring the additional horn antenna. This highly integrated design is more concise and reduces the profile height. This article offers what we believe is a new method for the design of high integration, multi-unit, and electrically tunable reconfigurable array antenna.

Smart plant disease net: Adaptive Dense Hybrid Convolution network with attention mechanism for IoT-based plant disease detection by improved optimization approach

ABSTRACT Plant diseases are rising nowadays. Plant diseases lead to high economic losses. Internet of Things (IoT) technology has found its application in various sectors. This led to the introduction of smart farming, in which IoT has been utilized to help identify the exact spot of the diseased affected region on the leaf from the vast farmland in a well-organized and automated manner. Thus, the main focus of this task is the introduction of a novel plant disease detection model that relies on IoT technology. The collected images are given to the Image Transmission phase. Here, the encryption task is performed by employing the Advanced Encryption Standard (AES) and also the decrypted plant images are fed to the pre-processing stage. The Mask Regions with Convolutional Neural Networks (R-CNN) are used to segment the pre-processed images. Then, the segmented images are given to the detection phase in which the Adaptive Dense Hybrid Convolution Network with Attention Mechanism (ADHCN-AM) approach is utilized to perform the detection of plant disease. From the ADHCN-AM, the final detected plant disease outcomes are obtained. Throughout the entire validation, the offered model shows 95% enhancement in terms of MCC showcasing its effectiveness over the existing approaches.

Suitability analysis of optical filters for enhancing performance parameters in a QPSK CO-OFDM modulation system

Abstract Optical filtering affects the fiber impairments in a fiber optic transmission system and its overall efficiency. The fiber impairments like attenuation, dispersion, and nonlinearities are challenges to overcome. The optical orthogonal frequency division multiplexing (O-OFDM) modulation is among the techniques to overcome these challenges. This paper uses O-OFDM with coherent transmission (denoted as CO-OFDM) and quadrature phase shift keying (QPSK) for modulating subcarriers. It is denoted as QPSK CO-OFDM modulation. This QPSK CO-OFDM (denoted here as QC) modulation system is further modified by introducing different optical filters in its fiber optic link. Different variants of QC are created by using optical filters in its fiber link. For example, the QC_BL is the variant having an optical Bessel filter in its fiber link. Performances of each variant have been evaluated and compared in terms of BER. This comparison allows us to select a suitable filter for a particular parameter, such as dispersion, fiber length, input power, etc. The QC variant having no filter is denoted as QC_WF and is taken as a reference for comparison.

Optimization of Intelligent-Reflecting-Surface-Enabled Covert Communication in Multi-Sensor Systems

This study investigates covert communication in multi-sensor systems employing Intelligent Reflecting Surfaces (IRSs). Different from previous works, we focus on optimizing transmission amplitudes and phase angles for a 2-BPSK codebook in the presence of asymmetric noise over complex Gaussian channels. We adopt KL divergence as a covertness constraint and mutual information as a metric for transmission rate. We employ Taylor series expansion to approximate KL divergence and mutual information. Leveraging these approximations, we derive optimal phase angles through a proposed gradient descent algorithm. The numerical simulations validate the effectiveness and precision of our Taylor approximation method. Through validation in different scenarios, our algorithm demonstrates robust convergence, deriving all optimal phase angles. Comparing initial phase angles from prior works to those obtained via our algorithm, we observe a higher covert transmission rate.

High-efficiency terahertz wavefront manipulation based on optimized catenary metasurface

Catenary optics, as a new development object in the field of subwavelength optics, has been paid close attention and studied by scientists since it was proposed. As a two-dimensional planar structure, metasurface can realize the free control of electromagnetic wave in space. Traditional metasurface structures are often designed with discrete unit structures, which process is complicated and prone to error. In this paper, we introduce the catenary structure and use the principle of continuous geometric phase and the all-dielectric material silicon to design and optimize the catenary structure at 2 THz frequency, thereby realizing efficient transmission functional metasurfaces such as abnormal deflectors and focusing lenses that can generate Bessel beams. By optimizing the unit of catenary structure, the generation of parasitic transmission phase can be effectively avoided, and the working efficiency of the metasurfaces can be effectively improved. It is believed that the design in our work may pave the way for wavefront manipulation of high-performance terahertz waves and has potential for broadband terahertz devices.

Toddlers do not preferentially transmit generalizable information to others.

Children actively and selectively transmit information to others based on the type of information and the context during learning. Four- to 7-year-old children preferentially transmit generalizable information in teaching-like contexts. Although 2-year-old children are able to distinguish between generalizable and non-generalizable information, it is not known whether they likewise transmit generalizable information selectively. We designed a behavioral study to address this question. Two-year-old children were presented with three novel boxes, identical except for their color. In each box, one of two equally salient actions led to a generalizable outcome (e.g., playing a [different] tune in each box), whereas the other led to a non-generalizable outcome (e.g., turning on a light, vibrating the box, or making a noise). In the discovery phase, children had a chance to discover the functions of each box presented one-by-one. Then, in the exploration phase, they were given the opportunity to independently explore all three boxes presented together. Finally, in the transmission phase, an ignorant recipient entered the room and asked the child to show them how these toys work. We measured whether children preferentially transmitted either generalizable or non-generalizable information when they were asked to demonstrate the function of the toys to a naïve adult. We found that children did not display any preference for transmitting generalizable information. These findings are discussed with respect to toddlers' selectivity in transmitting information but also the development of sensitivity to information generalizability. RESEARCH HIGHLIGHT: Young children transmit information to others and do so with some degree of selectivity to a variety of factors. Generalizability is an important factor affecting information transmission, and older children tend to associate generalizable information with teaching-like interactions. We tested whether toddlers selectively transmitted it to others over non-generalizable information. We found that toddlers do not show a preference to transmit generalizable over non-generalizable information.

Use of telemedicine to tackle health problems in South Asia during the COVID-19 era and beyond: a systematic review

Introduction: Telemedicine (TM) and teleconsultation services flourished during coronavirus disease 2019 (COVID-19) transmission to avoid COVID-19 infection and physical contact. Many physicians switched to the virtual treatment mode and nearly all types of health disciplines were covered. Through this systematic review, the authors tried to explore the strengths and weaknesses of TM, identify the barriers to adopting TM by population, and explain the limitations of this healthcare delivery model. Methods and results: In this systematic review, 28 studies were included (>53% high-quality studies) as eligible, where nearly 75% (n=21) of the studies were from India, and the remaining 25% (n=7) were from Pakistan, Bangladesh, Sri Lanka, and Nepal. Advice related to cancer, autoimmune diseases, and neurological diseases were the most common among the health disciplines in which TM was used. A peak in teleconsultation was observed during the high transmission phase of COVID-19, although major queries were associated with existing health complications and comorbidities. Conclusion: Other than a few concerns regarding connectivity, privacy, and diagnosis, TM was in fact affordable, timesaving, feasible, and accurate, which ensured a highly satisfying experience among the participants (>80%).

Combined Displacement and Angle Sensor with Ultra-High Compactness Based on Self-Imaging Effect of Optical Microgratings

In this paper, an ultracompact combined sensor for displacement and angle-synchronous measurement is proposed based on the self-imaging effect of optical microgratings. Using a two-grating structure, linear and angular displacement can be measured by detecting the change of phase and amplitude of the optical transmission, respectively, within one single structure in the meantime. The optically transmitted properties of the two-grating structure are investigated in both theory and simulation. Simulated results indicate that optical transmission changes in a sinusoidal relationship to the input linear displacement. Meanwhile, the amplitude of the curve decreases with an input pitch angle, indicating the ability for synchronous measurement within one single compact structure. The synchronous measurement of the linear displacement and the angle is also demonstrated experimentally. The results show a resolution down to 4 nm for linear displacement measurement and a maximum sensitivity of 0.26 mV/arcsec within a range of ±1° for angle measurement. Benefiting from a simple common-path structure without using optical components, including reflectors and polarizers, the sensor shows ultra-high compactness for multiple-degrees-of-freedom measuring, indicating the great potential for this sensor in fields such as integrated mechanical positioning and semiconductor fabrication.

Optimization of Covert Communication in Multi-Sensor Asymmetric Noise Systems

This work investigates wireless covert communication in a multi-sensor asymmetric noise scenario. We adopt KL (Kullback–Leibler) divergence as the covertness constraint metric and mutual information as the transmission rate metric. To accurately approximate KL divergence and mutual information in covert communication, we employ the Taylor series expansion technique. Analytical expressions for KL divergence and mutual information in covert communication are derived, and we optimize the amplitude gain and phase angles based on these analytical expressions. Our findings underscore the importance of phase angle selection in covert communication within asymmetric noise systems. We propose an effective method for optimizing the transmission amplitude gain and phase angles in scenarios with asymmetric noise. Numerical results validate the effectiveness and superiority of our proposed method.