Showing papers on "Radiation mode published in 2019"

High Gain and High-Efficiency Millimeter-Wave Antenna Based on Spoof Surface Plasmon Polaritons

Abstract: Planar spoof surface plasmonic polaritons (SPPs) have attracted much attention due to the features of the subwavelength confinement and low transmission loss. The latter feature is highly desired in millimeter wave (mm-wave) and terahertz band. In this communication, a novel method is proposed to convert bounded spoof SPPs mode to radiation mode. An equivalent radiating aperture is formed by gradually decreasing the grooves of an odd-mode plasmonic structure. The mechanism of SPPs wave radiating out through the aperture is clarified by referring to a horn antenna. Furthermore, a spoof SPPs traveling-wave antenna prototype is designed and measured to validate the concept. Measured results show that the antenna has a high gain (~15 dB) and high radiating efficiency (~90%) at the mm-wave frequency. The measured narrow beamwidth in endfire direction indicates that it can be used to construct switched-beam arrays for 5G applications.

One-dimensional photonic crystal for Bloch surface waves and radiation modes-based sensing

Abstract: We report on a one-dimensional photonic crystal (1DPhC) represented by a multilayer structure used for a surface plasmon-like sensing based on Bloch surface waves and radiation modes employing a structure comprising a glass substrate and four bilayers of TiO 2/SiO 2 with a termination layer of TiO 2. We model the reflectance responses in the Kretschmann configuration with a coupling prism made of BK7 glass and express the reflectances for both (s and p) polarizations in the spectral domain for various angles of incidence to show that a sharp dip associated with the Bloch surface wave (BSW) excitation is obtained in p polarization when an external medium (analyte) is air. For s-polarized wave BSW is not excited and a shallow dip associated with the guided mode excitation is obtained for a liquid analyte (water). For decreasing angle of incidence, the dip depth is substantially increased, and resonance thus obtained is comparable in magnitude with resonance commonly exhibited by SPR-based sensors. In addition, we revealed that the resonances in s-polarization are obtained for other analytes. The surface plasmon-like sensing concept was verified experimentally in the Kretschmann configuration for the guided mode transformed into the radiation mode with a negative and constant sensitivity of −169 nm/RIU, and a detection limit of 5.9 ×10−5 RIU.

Ultra-low Loss with Single Mode Polymer-Based Photonic Crystal Fiber for THz Waveguide

Abstract: Abstract In this article, a low loss circular photonic crystal fiber (C-PCF) has been suggested as Terahertz (THz) waveguide. Both the core and cladding vicinity of the suggested PCF are constituted by circular-shaped air holes. The optical properties such as effective material loss, effective area, core power fraction and V-parameter have numerically been probed by utilizing full vectorial finite element method (FEM) with perfectly matched layers (FMLs) boundary condition. The reported PCF reveals low absorption loss and large effective area of 0.04 cm−1 and 2.80×10−07 m2 respectively at 1 THz operating frequency. In addition, the core power fraction of the fiber is about 50.83 % at the same activation frequency. The V-parameter shows that the proposed PCF acts as a single mode over 0.70 to 1.15 THz frequency. So, the reported PCF offers the best performance in long distance communication applications.

Wideband Millimeter-Wave Antenna With Low Cross Polarization Based on Spoof Surface Plasmon Polaritons

Abstract: A novel wideband millimeter-wave antenna with low cross polarization based on spoof surface plasmon polaritons (SPPs) is proposed in this letter. Periodic metallic grooves operate as an SPP transmission line with high electromagnetic field confinement. The concept of dielectric tapered rod antenna is employed to design an SPP rod antenna with linear-tapered groove depth, converting the confined energy to radiation mode. Meanwhile, the tapered structure only affects the $E_{z}$ component on the transverse plane, and thus it can achieve low cross polarization. This prototype is fabricated by three-dimensional printing technique and surface metallization process. The radiating length of the linear-tapered SPP antenna is 29.2 mm, and the measured | S 11| is below −15.6 dB from 50 to 75 GHz. Experimental results show that the linear-tapered antenna can achieve an average gain of 14.95 dBi with ±1.45 dBi variation and better than −25.6 dB cross-polarization level for E -plane radiation.

Circularly Polarized RFID Tag Antenna Design for Metallic Poles Using Characteristic Mode Analysis

Abstract: This letter presents a novel circularly polarized ultra-high frequency radio frequency identification (902–928 MHz) tag antenna design for metallic poles using characteristic mode analysis (CMA). The traditional tags are usually mounted on the surface of the pole, which is a vulnerable position for tag mounting since it can be easily broken or anyone can easily remove the tag from the pole surface, whereas the proposed tag is placed on the chassis of the metallic pole with the metallic pole cut through the center of the tag. According to the CMA, the conical radiating mode will not be so effective in our application because it will provide the main beam in an upward direction, which made this tag difficult to read from the side direction. Therefore, the proposed tag exploits the broadside radiating mode as the optimal radiation mode to meet the application requirements such as main beam direction at 45° to provide long read range. Moreover, a Wilkinson power divider is used to provide equal power with a 90° phase difference to form the circularly polarized radiation. Furthermore, the proposed tag provides a read range of more than 7 m with and without the metallic pole in the center of the tag. The simulated and measured results show that the proposed tag design is a suitable candidate for tagging metallic poles such as traffic signal, guide boards, and street light poles, which is vital for the Internet-of-Things applications.

Design of Wideband and High-Gain Slotline Antenna Using Multi-Mode Radiator

Abstract: In this paper, a novel wideband slotline antenna with high gain characteristic is presented by using a multi-mode radiator under the circumstance of the optimized ground plane. The proposed antenna is analyzed from a traditional slot antenna with one full-wavelength radiation mode. Subsequently, two pairs of slot stubs are symmetrically loaded along the arms of the initial antenna near the nulls of the magnetic current of the full-wavelength radiation mode. By suitably choosing the lengths of the loaded stubs, extra two radiation modes can be introduced and merged with the full-wavelength one, resulting in a wide impedance bandwidth with three resonances. Finally, the size of the ground plane and locations of stubs are investigated to suppress the sidelobes and ensure high gain within the impedance bandwidth. For validation, a prototype antenna is fabricated and its electrical performances are measured. The experimental results show that the operating fractional bandwidth (FBW) of the proposed antenna can be effectively increased to 40.8% while keeping the inherent narrow slot structure. Besides, the measured average peak gain and its corresponding ripple within the impedance bandwidth are 6.2 dBi and 1.1 dB, respectively, and the radiation patterns are maintained constant. Compared with the reported works, the proposed design can allow a slotline antenna to achieve high gain and constant radiation patterns in a wide bandwidth simultaneously.

Mode conversion and orbital angular momentum transfer among multiple modes by helical gratings

Abstract: The coupling feature of helical gratings (HGs) has been studied on flexible conversion between two orbital angular momentum (OAM) modes by both the transverse and longitudinal modulation of HGs. Apart from one to one OAM exchange, HGs can achieve OAM transfer among multiple modes, provided both the helix and phase matching conditions are well satisfied for successive coupling. It is contributed from the fold number of modulation fringes of HGs and the difference multiplication of propagation constants between two of the successive modes. Based on the coupled mode theory, we investigate the mode conversion and OAM transfer among three modes using a 3 fold HGs in a ring core fiber, and numerically simulate it by transmission matrix. Our work about the multiple modes transferring can be regarded as an extension of mode coupling for optical gratings, and might flourish the mode conversion, as well as OAM manipulation in optics fields.

Numerical and Experimental Characterization of Radiation Mode of 45° Tilted Fiber Grating

Abstract: In this paper, we have numerically and experimentally investigated the radiation mode of 45° tilted fiber grating (45° TFG). By introducing the axial distributions into the volume current method, we have established a three-dimensional theoretical model to analyze spatial distributions of the radiation mode of 45° TFG, and measured the radiation mode spatial distributions in experiment. Both numerical and experimental results show that the radiation mode of 45° TFG exhibits an exponential reduction along the fiber axial direction, and a quasi-Gaussian profile along the radial direction of fiber. Additionally, we have also measured the detailed polarization-dependent azimuthal intensity distributions of radiation modes of both s- and p-polarized core modes. The degree of polarization of radiation mode is around 99.886%, which is independent of the length and the polarization extinction ratio of the grating. Moreover, for the first time, we have experimentally observed a very weak p-polarized component existing in the radiation mode, which has matched well with the simulation results.

Compact linear polarization spectrometer based on radiation mode shaped in-fiber diffraction grating.

Abstract: We propose a compact linear polarization spectrometer based on the in-fiber polarization-dependent diffraction grating. The beam profile of radiated light of the grating is shaped to be a Gaussian profile to improve the performance of the spectrometer, where the size of the focused light spot is reduced from 44 um to 33 um with the shaped radiation mode of the grating. Based on the experimental results, the proposed spectrometer can achieve 0.05 nm resolution and 115 nm wavelength responding range from 1495 nm to 1610 nm. To verify the performance of the proposed fiber spectrometer, we measure the transmission spectra of an excessively tilted fiber grating, which has a pair of orthogonal polarization transmission spectra. Compared with the traditional measuring method, the proposed fiber spectrometer integrates the polarizing and spectral analyzing functions in the measuring system and achieves the polarization-sensitive spectral analysis, which shows good wavelength consistency and perfect polarization characteristics.

“Shutdown” of the Proton Exchange Channel Waveguide in the Phase Modulator under the Influence of the Pyroelectric Effect

Abstract: It is shown that the termination of the channeling of the fundamental radiation mode in the waveguide can be observed upon heating of an optical integrated circuit based on proton exchange channel waveguides formed in a lithium niobate single crystal. This process is reversible, but restoration of waveguide performance takes tens of minutes. The effect of the waveguide disappearance is observed upon rapid heating (5 K/min) from a low temperature (minus 40 °C). This effect can lead to a temporary failure of navigation systems using fiber optic gyroscopes with modulators based on a lithium niobate crystal.

Wide-Angle Frequency Scanning Leaky Wave Antenna Loaded CSRR Patch Based on SSPP Transmission Line

Abstract: A novel composite left-and-right-composite-handed leaky wave antenna is proposed based on Spoof Surface Plasmon Polaritons slow-wave transmission line at microwave band in this paper. Wide-angle frequency scanning of the antenna is achieved by combining the slow-wave dispersion characteristics of Spoof Surface Plasmon Polaritons and the left-and-right-composite-handed characteristics of the complementary split ring resonator structure. The simulated and experimental results show that, with the increase of frequency, the radiation mode of the antenna gradually changed from slow-wave mode to fast-wave radiation mode, and the pattern changed continuously. The scanning region of the main beams proposed covers 110° in =0° plane when the frequency increases from 8GHz to 15GHz, and the gain of the antenna kept between 7dBi and 10.4dBi.

Second harmonic generation by crossed surface plasma waves over a metallic surface

Abstract: Excitation of second harmonic radiation by nonlinear mixing of two surface plasma waves (SPWs), propagating at an angle to each other over an air–metal interface, is investigated. The SPWs exert a ponderomotive force on electrons, driving a nonlinear surface current and producing the second harmonic. Depending upon the angle between the SPWs and the electron density of metals, the excited radiation could be a radiation mode or a surface mode. The latter requires a surface ripple for phase matching. The efficiency of radiative second harmonic increases with the free electron density of the metal. It is sensitive to the angle between the interacting SPWs. The surface mode second harmonic is relatively more efficient.

Wideband Patch Antenna With Ground Radiation Mode and Patch Radiation Mode

Abstract: In this paper, patch antenna structures are studied to simultaneously excite the ground radiation mode and patch radiation mode. Based on the analysis of characteristic current distribution on the ground plane of patch antenna, an exciting method of the ground radiation mode is proposed. Then a dual-mode patch antenna of patch radiation and ground radiation is designed, which can achieve a wideband radiation using two modes resonating at two adjacent frequencies. To improve the radiation efficiency of the ground mode, the electric field distribution of the dual-mode antenna is investigated in detail and the electric field models for two modes are constructed. It is suggested that the additional notches introduced on the ground plane can enhance the resonance component of the ground mode. By this way, the modified patch antenna presents better radiation efficiency over the operating band. The measurement results show that the relative bandwidth of the patch antenna prototype with the notches is about 16.2%, defined by the reflection coefficient less than -10 dB. The proposed dual-mode antennas have the inherent characteristics of weak directivity, for that the antenna application scenarios also are indicated.

A Reconfigurable Circular-Ring Patch Antenna with Pattern and Polarization Diversities

Abstract: A reconfigurable circular-ring patch antenna with pattern and polarization diversities is proposed. The reconfigurable antenna has a simple two-layer structure with three PIN diodes mounted on it. The circular-ring patch is printed on the upper layer. An open-ended microstrip stub is introduced on the lower layer with the purpose of impedance matching. By switching on/off states of the PIN diodes, the antenna can be reconfigured to have conical radiation or broadside radiation. Besides, the antenna achieves vertical polarization (VP) for conical radiation mode and provides two orthogonal linear polarization for broadside radiation mode. The overlapped impedance bandwidth for the three modes is 2.35-2.64 GHz. The antenna shows the advantages of simple structure, easy fabrication and low cost, suitable to be used in wireless communication systems.

"Shutdown" of the Proton Exchange Channel Waveguide in the Phase Modulator under the Influence of the Pyroelectric Effect

Abstract: It is shown that the termination of the channeling of the fundamental radiation mode in the waveguide can be observed upon heating of an optical integrated circuit based on proton exchange channel waveguides formed in a lithium niobate single crystal. This process is reversible, but restoration of waveguide performance takes tens of minutes. The effect of the waveguide disappearance is observed upon rapid heating (5 K/min) from a low temperature (minus 40 °C). This effect can lead to a temporary failure of navigation systems using fiber optic gyroscopes with modulators based on a lithium niobate crystal.

Broadband Optimization of a High Power UHF Band Cylindrical Sleeve Dipole Antenna

Abstract: The sleeve dipole radiator [1] has been used in various configurations to extend the impedance bandwidth of the classical dipole antenna by using a transmission radiation mode along with the fundamental dipole radiation mode. The dual mode resonances generate a two null return loss response. The cylindrical sleeve dipole and balun variation has over eight interactive design variables that are less intuitive compared with simpler dipole designs but provide extensive optimization opportunities. The design and bandwidth optimization of a new high power UHF sleeve dipole used in a new four element prime focus phased array feed is investigated

Entropy and Temperature of Electromagnetic Radiation

Abstract: Electromagnetic (EM) radiation is both wave and heat. Waves are characterized by spectral distribution, spatial distribution, time coherence, spatial coherence, energy flux, and polarization. Heat, namely energy transferred from a hot body to a cold one, is characterized by its energy and entropy, and the ratio between them is the temperature. Here we calculate the entropy and temperature of a single radiation mode from the wave properties of the radiation. Using the Heisenberg uncertainty principle and Planck law, we calculate, from the optical properties of the radiation, the number of modes and their occupation number. Then we calculate the entropy and temperature of a single-mode EM radiation. It is shown that the entropy of a single-mode varies from zero for low occupation number, namely in the quantum limit to one Boltzmann constant for high occupation number, namely in the classical limit. The temperature varies from zero Kelvin in the quantum limit to infinity at high energies in the classical limit. This analysis is consistent with Fourier optics and statistical mechanics namely: Stephan-Boltzmann Law, Wein Law, Zipf law, IT File’s entropy, and the canonical distribution.

High Gain and Wideband Leaky Wave Holograms using Gap Waveguide Surface Wave Launchers

Abstract: In this paper a low loss, high gain and frequency scannable leaky wave holographic antenna is designed for operation in the frequency band 58 to 70 GHz. The antenna is realized based on the one-dimensional holography theory in the microwave frequency range. The antenna is composed of two basic sections: 1 - A surface wave launcher for the generation of TM 0 mode surface wave, and 2 - A one-dimensional hologram for the transformation of surface wave to radiation mode at a desire direction. For the avoidance of losses and dielectric dispersion, unit cells made of metallic bed of pins are used for the realization of holographic surface. The hologram is designed to generate a beam at the angle of 30 degrees relative to the normal at the frequency of 62 GHz. The gap waveguide technology is used for the realization of surface wave launcher. The designed antenna is scannable from 26 to 45 degrees in elevation. In the pass-band the gain of antenna is better than 26:5 dB and its total efficiency is more than 90%.

An array antenna electrical performance analysis method based on an array element characteristic mode

Abstract: The invention discloses an array antenna electrical performance analysis method based on an array element characteristic mode. The array antenna electrical performance analysis method comprises the steps of determining an array element radiation mode; calculating a mode excitation coefficient of the array element in an array environment; calculating an array antenna far-field directional diagram;and solving network parameters of the array antenna excitation port. According to the method, the mutual coupling effect between the array elements is strictly considered, and the electrical performance of the array antenna can be accurately analyzed. The method provided by the invention can be used for revealing the mutual coupling effect essence between array elements, and has important engineering significance for the analysis and design of the array antenna.

Estimation and Control of Total Array RCS of Microstrip Patch Array with Hybrid HIS-based Ground Plane

Abstract: For a radiating structure such as a patch array placed on an aerospace platform, the radiation mode RCS plays a significant role when compared to the structural mode RCS. It is due to the fact that the structural RCS of a patch array is computed when the antenna impedance is perfectly matched to the feed structure. To achieve a perfectly matched state is practically not possible. The corporate feed structure in the antenna array itself contributes to most of the mismatches. It has been corroborated that a high impedance surface (HIS) plays an important role in controlling the structural RCS of an antenna. The challenge remains to compute the radiation mode RCS of the antenna array. The combination of JC element and square patch arranged in a chessboard configuration is able to provide RCS reduction based on the principle of phase cancellation. However, this configuration can only provide narrow-band RCS reduction.

Liquid crystal optical waveguide and laser radar

Abstract: The invention discloses a liquid crystal optical waveguide and laser radar. The liquid crystal optical waveguide comprises a liquid crystal assembly, a waveguide core, a cladding layer and a first conductive film. When the first conductive film is not connected with a first electrode, the waveguide core is in a mode guiding mode, and therefore, when the laser beams enter the waveguide core, the laser beams can carry out total reflection propagation in the waveguide core. Due to the fact that the first conductive film is arranged on one side of the liquid crystal assembly, when the first conductive film is connected with the first electrode, the liquid crystal assembly is in an electric field, so that the liquid crystal molecules can be re-ordered under the action of the electric field, andthe refractive index of the liquid crystal assembly is changed, and at the moment, the waveguide core is in a radiation mode state. When the laser beams are emitted into the waveguide core, the laserbeams can be refracted into the liquid crystal assembly, and the original laser beams can be deflected under the action of the liquid crystal molecules, so that the laser beams can be emitted at different angles, and therefore, the laser beams can complete scanning of the plane direction of the vertical waveguide core.

Miniaturized multi-branch optical waveguide chip with high-polarization extinction ratio

Abstract: The invention discloses a miniaturized multi-branch optical waveguide chip with a high-polarization extinction ratio. The thickness of the chip is d, d is more than dmin, and dmin is the value of thechip thickness when a minimum incident angle deltawmin of a TM mode reaching the output optical fiber through the reflecting of the chip bottom surface center is equal to an aperture angle theta0 of the output optical fiber; and/or the chip comprises a groove arranged on a chip surface, thereby effectively preventing the TM radiation mode parallel to the chip surface from coupling to the output optical fiber. The polarization extinction ratio of the chip is effectively improved, the problem that the polarization extinction of the waveguide chip is reduced along with the increasing of the chipsize is solved, and an application demand on the waveguide chip in the high-precision optical fiber gyroscope is extended.

Non-Gaussian bosonic channels in the Tavis–Cummings model

Abstract: The time evolution of two-level atoms interacting with a single-mode radiation field through the Tavis–Cummings Hamiltonian is studied from the perspective of channel action on the radiation mode. The operator sum representation for the channel in the situation of one atom interacting in resonance with the radiation mode, and two atoms interacting in resonance with the radiation mode, is obtained in the Fock basis. The notions of entanglement breaking, extremality, non-classicality and non-Gaussianity are explored using the obtained operator sum representation. It is shown that the respective channels are not entanglement breaking, are extremal and can generate both non-classicality and non-Gaussianity.

High power millimeter waves generated by an overmoded relativistic Cherenkov-type oscillator

Abstract: An overmoded relativistic Cherenkov-type high power millimeter wave generator operating in Ka-band has been investigated. The associated particle-in-cell (PIC) simulation and experimental results are presented in this paper. The relativistic electron beam with a peak current of 9.9 kA was generated by a pulsed power accelerator launched at a voltage of 605 kV. The relativistic electron beam was guided by an axial magnetic field of about 1 T and transported through the overmoded slow-wave structure. Typically in experiments, the millimeter wave power radiated in the far field was about 630 MW with a frequency of 32.1 GHz and a pulse width of about 10 ns. The radiation mode was well controlled to be quasi-TM 01 mode.

A Novel Triple-Mode Wideband Slotline Antenna

Abstract: In this paper, a novel triple-mode planar wideband sloltine antenna is presented. The proposed antenna starts from a traditional slot one, which only has a radiation mode and suffers from intrinsic narrow bandwidth. To deal with this problem, two pairs of short-ended slots are symmetrically etched along the traditional slot one near the maximum electrical field of its full-wave radiation mode. After suitably choosing the locations and parameters of the short-ended slots, extra two radiation modes can be introduced and merged with the full-wave one, resulting in a wideband characteristic with three resonances. To validate this, a triple-mode prototype is designed and experimentally measured. The experimental results agree well with the theoretical analysis and simulated ones verifying a simple designing approach of wideband slotline antennas with three radiation modes.

Holoscopic, optical coherence tomography

Abstract: A method for holoscopic, optical coherence tomography for an object, wherein the method includes providing source radiation and splitting the source radiation into illumination radiation and reference radiation, illuminating an illumination field on the object with illumination radiation, said illumination field having an areal extent transverse to the direction of incidence, collecting illumination radiation scattered back from the object as measurement radiation, separating the measurement radiation collected from the object from the illumination radiation, and overlaying the measurement radiation with reference radiation and detecting an interference signal of the overlaid radiations with at least one areal detector with a two-dimensional extent, wherein the object in the illumination field is simultaneously illuminated by more than one spatial radiation mode, wherein the radiation modes of the illumination in the illumination field are spatially and temporally coherent with one another but have a fixed phase difference from one another.

Tri-polarized vehicle-mounted antenna applied to 5G-V2X Internet of Vehicles communication system

Abstract: The invention provides a tri-polarized vehicle-mounted antenna applied to a 5G-V2X Internet of Vehicles communication system. The tri-polarized vehicle-mounted antenna comprises a circular dielectricplate, a square dielectric plate, a feed structure and eight groups of inverted L-shaped units, the circular dielectric plate is arranged below the square dielectric plate, and an omnidirectional radiation unit is arranged in the middle of the circular dielectric plate and is responsible for 5.85-5.925 GHz direct connection communication frequency bands; the square dielectric plate is located above the omnidirectional radiation unit of the circular dielectric plate. The center of the square dielectric plate and the center of the circular dielectric plate are located on the same vertical centerline, the area of the square dielectric plate is smaller than that of the circular dielectric plate, and a directional radiation unit is arranged on the square dielectric plate and is responsible fordirectional radiation of a wide coverage surface in 3.30-3.60 GHz and 4.80-5.00 GHz frequency bands. The antenna has the characteristics of triple polarization, low cross polarization, high port isolation, directional radiation mode wide beam and omnidirectional radiation mode low out-of-roundness, realizes relatively high gain on an azimuth angle plane, and meets 5G-V2X requirements.

Optimization and Experiments of Refractive Index Sensing Based on Radiation Mode Couplings

Abstract: Based on the analytical analysis of the complex coupled-mode equations for long-period fiber gratings, coupling states are defined to reveal the relationship between design parameters and transmission characteristics. Thus the design parameters of the gratings can be determined by selecting the coupling state corresponding to ideal transmission characteristics for sensing applications. In this way, gratings are designed for refractive index sensing, and the optimization scheme based on the coupling state is verified by the sensitivity enhancement in the experimental results.

Theoretical analysis and experimental demonstration of the radiation mode distribution of 45° TFG

Abstract: In this paper, we have theoretically analyzed and experimentally demonstrated the spatial distribution of the radiation mode of 45° tilted fiber grating (TFG). The simulation results have shown the intensity distribution of the radiation mode along the fiber axis exhibited an exponential reduction. In experiment, we have observed the radiation mode pattern of a 5-mm long 45°TFG. The captured profiles along the radial direction and axial direction were in good agreement with the simulated results of the model.