Mixer-Duplexer-Antenna Leaky-Wave System Based on Periodic Space-Time Modulation

We present a mixer-duplexer-antenna leaky-wave system based on periodic space-time modulation. This system operates as a full transceiver, where the upconversion and downconversion mixing operations are accomplished via space-time transitions, the duplexing operation is induced by the nonreciprocal nature of the structure, and the radiation operation is provided by the leaky-wave nature of the wave. A rigorous electromagnetic solution is derived for the dispersion relation and field distributions. The system is implemented in the form of a spatio-temporally modulated microstrip leaky-wave structure incorporating an array of sub-wavelengthly spaced varactors modulated by a harmonic wave. In addition to the overall mixer-duplexer-antenna operation, frequency beam scanning at fixed input frequency is demonstrated as one of the interesting features of the system. A prototype is realized and demonstrated by full-wave and experimental results

Dynamic Modulation Yields One-Way Beam Splitting

This article demonstrates the realization of an extraordinary beam splitter based on nonreciprocal and synchronized photonic transitions in obliquely illuminated space-time-modulated (STM) slabs which impart the coherent temporal frequency and spatial frequency shifts. As a consequence of such unusual photonic transitions, a one-way beam splitting and amplification is exhibited by the STM slab. Beam splitting is a vital operation for various optical and photonic systems, ranging from quantum computation to fluorescence spectroscopy and microscopy. Despite the beam splitting is conceptually a simple operation, the performance characteristics of beam splitters significantly influence the repeatability and accuracy of the entire optical system. As of today, there has been no approach exhibiting a nonreciprocal beam splitting accompanied with transmission gain and an arbitrary splitting angle. Here, we show that oblique illumination of a periodic and semi-coherent dynamically-modulated slab results in coherent photonic transitions between the incident light beam and its counterpart space-time harmonic (STH). Such photonic transitions introduce a unidirectional synchronization and momentum exchange between two STHs with same temporal frequencies, but opposite spatial frequencies. Such a beam splitting technique offers high isolation, transmission gain and zero beam tilting, and is expected to drastically decrease the resource and isolation requirements in optical and photonic systems. In addition to the analytical solution, we provide a closed-form solution for the electromagnetic fields in STM structures, and accordingly, investigate the properties of the wave isolation and amplification in subluminal, superluminal and luminal ST modulations

Space-Time Medium Functions as a Perfect Antenna-Mixer-Amplifier Transceiver

We show that a space-time-varying medium can function as a front-end transceiver, i.e., an antenna-mixer-amplifier. Such a unique functionality is endowed by space-time surface waves associated with complex space-time wave vectors in a subluminal space-time medium. The proposed structure introduces pure frequency up- and down-conversions and with very weak undesired time harmonics. In contrast to other recently proposed space-time mixers, a large frequency up-/down conversion ratio, associated with gain is achievable. Furthermore, as the structure does not operate based on progressive energy transition between the space-time modulation and the incident wave, it possesses a subwavelength thickness (metasurface). Such a multi-functional, highly efficient and compact medium is expected to find various applications in modern wireless telecommunication systems

Nonreciprocal Electromagnetic Scattering from a Periodically Space-Time Modulated Slab and Application to a Quasisonic Isolator

Scattering of obliquely incident electromagnetic waves from periodically space-time modulated slabs is investigated. It is shown that such structures operate as nonreciprocal harmonic generators and spatial-frequency filters. For oblique incidences, low-frequency harmonics are filtered out in the form of surface waves, while high-frequency harmonics are transmitted as space waves. In the quasisonic regime, where the velocity of the space-time modulation is close to the velocity of the electromagnetic waves in the background medium, the incident wave is strongly coupled to space-time harmonics in the forward direction, while in the backward direction it exhibits low coupling to other harmonics. This nonreciprocity is leveraged for the realization of an electromagnetic isolator in the quasisonic regime and is experimentally demonstrated at microwave frequencies

Enhanced Bandwidth and Diversity in Real-Time Analog Signal Processing (R-ASP) using Nonuniform C-section Phasers

We show that a continuously nonuniform coupled line C-section phaser, as the limiting case of the step discontinuous coupled-line multisection commensurate and non-commensurate phasers, provides enhanced bandwidth and diversity in real-time analog signal processing (R-ASP). The phenomenology of the component is explained in comparison with the step-discontinuous using multiple-reflection theory and a simple synthesis procedure is provided. The bandwidth enhancement results from the suppression of spurious group delay harmonics or quasi-harmonics, while the diversity enhancement results from the greater level of freedom provided by the continuous nature of the nonuniform profile of the phaser. These statements are supported by theoretical and experimental results

Assessment of Falls on a Medical-Telemetry Unit

Purpose: The purpose of this quality improvement project is to implement a falls intervention to improve falls on the Medical-Telemetry unit. Background: Between 700,000 and 1,000,000 falls occur in hospitals every year. Furthermore, approximately 30-35% of these falls result in injury and 11,000 falls result in death (Health Research & Educational Trust, 2016). Falls harm patients, families, and providers. They are also a high cost, as many insurance companies will not reimburse care when a fall occurs. As a hospital organization, it is important to ensure funds are going to the appropriate places. Currently the metropolitan hospital had an increase of 5 falls from 2016 fiscal year to 2017 fiscal year. Through data itemization it appears the current protocol and procedures is not meeting the need to decrease and diminish falls

A Needs Assessment Survey of Southern California Pest Management Professionals

Pest Management Professionals were surveyed in training workshops/meetings in Southern California between 2015 and 2017 to understand their needs, challenges, and view of integrated pest management. The most encountered pests by pest control technicians were ants, cockroaches, rodents, spiders, termites, and bed bugs. The most challenging pest groups to control were bed bugs, cockroaches, ants, and rodents. The main challenges that professionals faced in doing their work were regulations, followed by managing pests, and customer-related problems. Most participants had a favorable view of IPM. However, they faced several challenges in implementing IPM, among which customer-related issues were the most common

Knowledge and Attitude of Preschool Children Parents Towards Professional Topical Fluoride Therapy

Purpose: Since various factors such as parents' attitudes and knowledge can affect the use of fluoride, this study aims to assess the relationship between children's parents' attitudes and knowledge towards preventive caries methods with their children's caries experience. Materials and Methods: In this cross-sectional study, 110 parents of preschool children in Ahvaz were randomly selected. Using a questionnaire, parents' knowledge and attitude about fluoride therapy were evaluated, and their children's teeth were examined for dmft. Data were analyzed by Mann-Whitney and Kruskal-Wallis tests. Results: The mean of parents' knowledge about caries prevention methods was 2.22 ±3.23 of 9, and the knowledge of 68% was poor, 21% moderate, and 11% was good. The mean of parents' attitude about caries prevention techniques was 9.5 ±2.05 of 14, and the attitude of 0% was poor,60% moderate, and 40% was good. There was no significant relationship between parents' knowledge with gender, age, education, source of information, and dmft. There was a direct relationship between knowledge and the experience of professional topical fluoride (PTF). There was no significant relationship between the attitudes of parents with gender, the history of PTF, and the source of information. There was a direct, significant relationship between parents' attitude and their educational level, age, and child's dmft. Children's experience of PTF was 18.6%. Conclusion: Parents' knowledge and attitude towards fluoride roles in the prevention of dental caries were low. So, assigning programs to increase parents' knowledge and, subsequently, using caries prevention techniques is suggested

Programmable Nonreciprocal Metaprism

Optical prisms are made of glass and map temporal frequencies into spatial frequencies by decomposing incident white light into its constituent colors and refract them into different directions. Conventional prisms suffer from their volumetric bulky and heavy structure and their material parameters are dictated by the Lorentz reciprocity theorem. Considering various applications of prisms in wave engineering and their growing applications in the invisible spectrum and antenna applications, there is a demand for compact apparatuses that are capable of providing prism functionality in a reconfigurable manner, with a nonreciprocal/reciprocal response. Here, we propose a nonreciprocal metasurface-based prism constituted of an array of phase- and amplitude-gradient frequency-dependent spatially variant radiating super-cells. In conventional optical prisms, nonreciprocal devices and metamaterials, the spatial decomposition and nonreciprocity functions are fixed and noneditable. Here, we present a programmable metasurface integrated with amplifiers to realize controllable nonreciprocal spatial decomposition, where each frequency component of the incident polychromatic wave can be transmitted under an arbitrary and programmable angle of transmission with a desired transmission gain. Such a polychromatic metasurface prism is constituted of frequency-dependent spatially variant transistor-based phase shifters and amplifiers for the spatial decomposition of the wave components. Interesting features include three-dimensional prism functionality with programmable angles of refraction, power amplification, and directive and diverse radiation beams. Furthermore, the metasurface prism can be digitally controlled via a field-programmable gate array (FPGA), making the metasurface a suitable solution for radars, holography applications, and wireless telecommunication systems

Pure and Linear Frequency Converter Temporal Metasurface

Metasurfaces are ultrathin structures which are constituted by an array of subwavelength scatterers with designable scattering responses. They have opened up unprecedented exciting opportunities for extraordinary wave engineering processes. On the other hand, frequency converters have drawn wide attention due to their vital applications in telecommunication systems, health care devices, radio astronomy, military radars and biological sensing systems. Here, we show that a spurious-free and linear frequency converter metasurface can be realized by leveraging unique properties of engineered transmissive temporal supercells. Such a metasurface is formed by time-modulated supercells; themselves are composed of temporal and static patch resonators and phase shifters. This represents the first frequency converter metasurface possessing large frequency conversion ratio with controllable frequency bands and transmission magnitude. In contrast to conventional nonlinear mixers, the proposed temporal frequency converter offers a linear response. In addition, by taking advantage of the proposed surface-interconnector-phaser-surface (SIPS) architecture, a spurious-free and linear frequency conversion is achievable, where all undesired mixing products are strongly suppressed. The proposed metasurface may be digitally controlled and programmed through a field programmable gate array. This makes the spurious-free and linear frequency converter metasurface a prominent solution for wireless and satellite telecommunication systems, as well as invisibility cloaks and radars. This study opens a way to realize more complicated and enhanced-efficiency spectrum-changing metasurface