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In this paper, an integrated low-profile low radar cross section (RCS) circularly polarized (CP) antenna array based on multi-functional modes generation method is proposed, which can realize good in-band radiation performance and wide out-of-band RCS reduction characteristics on the same layer without additional subassembly except resistors. By embedding a resistor in the center of a metallic strip, the half and one and a half wavelength resonant modes are changed into the absorption modes; while the one wavelength resonant mode is excited as the radiation mode when offset feeding at an appropriate location. Furthermore, the CP radiation performance is achieved with four bent and center-rotating-symmetric metallic strip and the sequentially rotated feeding network. The simulation results show that the designed integrated antenna array generates the same left-hand CP radiation performance as the array without embedding resistors, and the monostatic RCS of the array is significantly reduced in the lower and upper bands, with an average reduction value of 10 dB. Prototypes of the designed antenna array with 4×4 elements are fabricated and measured to validate the simulation results.

The supersonic mode in hypersonic flows is studied numerically. The radiation characteristics of this mode in a Ma=6 flat-plate boundary layer with cooled walls are focused on. The linear stability...

Recent experiments have demonstrated remarkable mode-selective reactivities by coupling molecular vibrations with a quantized radiation field inside an optical cavity. The fundamental mechanism behind such effects, on the other hand, remains elusive. In this work, we provide a theoretical explanation of the basic principle of how cavity frequency can be tuned to achieve mode-selective reactivities. We find that the dynamics of the radiation mode leads to a cavity frequency-dependent dynamical caging effect of a reaction coordinate, resulting in suppression of the rate constant. In the presence of competitive reactions, it is possible to preferentially cage a reaction coordinate when the barrier frequencies of competing reactions are different, resulting in a selective slow down of a given reaction. Our theoretical results illustrate the cavity-induced mode-selective chemistry through polaritonic vibrational strong couplings, revealing the fundamental mechanism for changing chemical selectivities through cavity quantum electrodynamics.

In this communication, based upon a squeezed-state trial wave function, we have performed a simple variational study of the spectral collapse in the anisotropic two-photon Rabi model. Our analysis indicates that the light-matter interaction and the spin-flipping (together with the anisotropy) effectively constitute two competing impacts upon the radiation mode. Whilst the former tries to decrease the radiation mode frequency, the latter may counteract or reinforce it. The light-matter interaction appears to dominate the frequency modulation as its coupling strengths go beyond the critical values, leading to the emergence of the spectral collapse. However, at the critical couplings the dominance of the light-matter interaction is not complete, and incomplete spectral collapse appears. Accordingly, at the critical couplings the eigenenergy spectrum comprises both a set of discrete energy levels and a continuous energy spectrum. The discrete eigenenergy spectrum can be derived via a simple one-to-one mapping to the bound state problem of a particle of variable effective mass in a finite potential well, and the number of bound states available is determined by the energy difference between the two atomic levels. Each of these eigenenergies has a twofold degeneracy corresponding to the spin degree of freedom.

Refereed/Peer-reviewed Nonreciprocity in optical fibers are opening new avenues for fields such as quantum computing and quantum photonics. In this study we explore the chiral properties of the radiation modes of optical fibers and show that whispering gallery mode resonances, as part of radiation modes, carry specific transverse spin angular momenta. The transverse spin angular momentum is different for forward and backward propagating radiation modes, hence indicating spin–momentum locking. As a result of spin–momentum locking, a nonreciprocity in the emission coupling of an atomic transition with a specific spin into the forward and backward propagating modes is observed. Modeling an atomic transition by a classical dipole that rotates clockwise or anticlockwise, we optimize the position of the dipole within the optical fiber to achieve maximum nonreciprocity between the coupling of the dipole emission into the forward or backward propagating mode. subwavelength waveguides. We find near-perfect nonreciprocity in both radiation and guided modes and further outline the fiber diameter and dipole position to achieve this state. This study not only shows the rich physics of fiber radiation modes within the context of light–matter interaction but also complements previous studies of nonreciprocity in

Research has shown that using acoustic radiation modes combined with surface velocity measurements provide an accurate method of measuring the radiated sound power from vibrating plates. This paper investigates the extension of this method to acoustically radiating cylindrical structures. The mathematical formulations of the radiation resistance matrix and the accompanying acoustic radiation modes of a baffled cylinder are developed. Computational sound power calculations using the vibration-based radiation mode (VBRM) method and the boundary element method are then compared and shown to have good agreement. Experimental surface velocity measurements of a cylinder are taken using a scanning laser Doppler vibrometer and the VBRM method is used to calculate sound power. The results are compared to sound power measurements taken using ISO 3741.

A circularly polarised (CP) monopulse waveguide antenna array for Ka-band wireless communication is proposed. The antenna structure can be divided into six layers from top to bottom, including radiating layer, aperture layer, cavity layer, aperture layer, feeding layer and monopulse comparator. The upper radiating layer allows two transmission modes of the transverse electric (TE) wave and the transverse magnetic (TM) wave to pass through. The 90° phase difference can be obtained by adjusting the horizontal and vertical angles of the horn radiator, which realises the CP radiation pattern. Besides, the 0° or180° phase difference produced by the monopulse comparator enables the antenna to obtain a monopulse radiation mode. In order to obtain the low sidelobe characteristics, the coupling parameters of the coupling layer are weighted by the Taylor distribution. The overall size of the antenna is 194 × 25 × 31 mm3. The slot waveguide antenna is fabricated and measured to validate the proposed design. The measured results show that the monopulse system can achieve an impedance bandwidth of 3.7% (34.5–35.8 GHz) in the Ka-band at the centre frequency of 35 GHz. The sum-pattern maximum gain and radiation efficiency are 23.3 dBic and 75% at 35 GHz, and the gain of the whole bandwidth is >20 dBic. The axial ratio and the sidelobe level is less than 1.2 and −28 dB, respectively. The difference-pattern amplitude imbalance is

This article presents the results of the numerical and experimental study of a Ka -band Cherenkov oscillator with the average diameter of the slow wave structure (SWS) ${D}= {2.4}\lambda $ , where $\lambda $ is the wavelength. The operating point on TM01 is set close to the $\pi $ -point to enhance the electric field in SWS. Meanwhile, by optimizing the structural parameters, the influence of TM02 on the mixed output mode is minimized. Then in the optimized structure with a straight output waveguide, the proportion of TM01 in the mixed output mode reaches as high as 97%, achieving the target of mode selection. The experimental researches are carried out with a high-current SINUS881 accelerator. A solenoid magnet provides the guiding magnetic field of 0.9T. In the range of voltages 552–585 kV and currents of 7.3–7.85 kA, the generation of 7–10 ns pulse at the frequency 29.93–29.96 GHz and 277–312 MW output power was realized. The radiation mode is investigated by the neon lamp luminescence and the radiation pattern of power density in far-field, which both verified that the output mode is mainly composed of TM01, demonstrating the practicability of the proposed method in solving the mode competition problem.

A novel analytical method has been proposed to compute radiation mode RCS of phased arrays. The array RCS is computed by tracing the path of an impinging EM signal as it travels through the array system. The scattered field contribution from each component of array and its feed network is expressed in terms of the reflection and transmission coefficients. The individual contributions are then coherently superimposed to arrive at total array RCS. The proposed method can be used to obtain the radiation mode RCS of any conventional phased array or low profile patch array with high impedance surface (HIS)-based substrate or superstrate. Results are shown for dipole array with parallel feed network, corporate-fed patch array with conventional metallic ground plane and HIS-based hybrid ground plane. This approach is applicable for estimation and control of radiation mode RCS of any type of phased array.

—The properties of the aberrational pattern resulting from the self-action of the light radiation mode TEM01 in liquid-crystal systems are studied. It is found that the interference of light rays corresponding to two peaks of intensity and nonlinear phase shift leads to the formation of a system of fringes in the Fraunhofer region; their angular period is controlled by the distance between peaks. These fringes fill the entire aberrational pattern (concentric ring pattern) or only its part, depending on the type of the profile of the light-induced phase shift. The possibilities of using the properties of the aberrational pattern in the TEM01 mode for studying the light-induced reorientation of the nematic liquid crystal director are shown.

The substrate-integrated coaxial line (SICL) is a potential transmission line due to its good characteristics of high efficiency, nondispersive, and single operational mode. A tapered slot SICL balun is proposed, which can realize the impedance transformation from the microstrip line to the coplanar strip line (CPS). At the same time, the proposed balun can transform the quasi-TEM mode of the microstrip line to the TEM mode of CPS. A printed dipole radiator is designed and is fed by the proposed SICL balun to achieve the impedance matching. The dual-polarized radiation mode is realized by employing two orthogonal printed dipoles. For each polarization radiator, the CPS is bended to avoided the occlusion of two polarization ports and realize the direct assembling of two orthogonal printed circuits. What is more, the assembling method is advantageous to improve the port isolation degree and decrease the cross polarization level. To improve the ratio of front to back (F/B) of the radiation pattern, a cylindrical metal cavity is adopted. According to the results of simulation and experiments, the VSWR of each port is lower than 2, the isolation degree between two polarization ports is higher than 20 dB, and the cross polarization level at the boresight is lower than −20 dB at the operational frequency. The patterns of two ports are almost symmetric, and high radiation efficiency is obtained. The experimental results of the principle prototype verify the design schemes of the balun and the dual-polarized antenna. The proposed dual-polarized antenna fed by the tapered slot SICL balun is suitable for the airborne radar application.

The resolution of the microwave radar coincidence imaging (MRCI) can break the diffraction limit, which has been validated by experiments. However, there is still no theoretical analysis. In this article, the resolution of the MRCI is theoretically analyzed using the orthogonal subspace projection algorithm based on the space spanned by the discrete reference radiation mode. First, a target location estimate (TLE) method using the data from the nonfocusing radar array of the MRCI system is proposed to estimate the target position assisted by the equivalent detection method. The estimation precision of the TLE method is approximately equal to the 3-dB beamwidth of the coherent transmitting radar array with the same aperture; hence, the imaging plane can be obtained. Then, the equivalent internal noise (generated by the error of the target distance estimation, i.e., the location of the imaging plane) is theoretically analyzed. Finally, the imaging resolution threshold of the MRCI system is theoretically analyzed. The relationship between the resolution threshold and the factors (such as the deployment of the transmitting radar array, the distance between the target and the radar array, and the signal-to-noise ratio of the imaging system) is summarized. The proposed estimation method and the analyses of the MRCI system are validated through a set of simulations and experiments.

In this paper, a rectangular dielectric resonator antenna (RDRA) based on substrate integrated suspended line platform (SISL) is proposed for millimeter-wave applications. The dielectric resonator is embedded in the air cavity and fixed by the substrate 3. The cone feed line of the RDRA is presented in this design to excite the TEx1Δ1 (1 < Δ < 2) radiation mode. By using the SISL structure, the loss is reduced and a high gain is realized. Compared to the traditional DRA fed by microstrip line and coupling slot, the proposed design presents merits of low substrate lost, self-packaging and high efficiency. Simulated results show that the proposed RDRA obtained 10 dB impedance bandwidth of 11.41 % from 24.95 to 27.97 GHz. At 26.03 GHz, the simulated gain is 6.58 dBi.

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.

In case of multiple failure scenario, such as LOCA with ECCS failure, the decay heat continues to raise the reactor core temperature, eventually leading to the core voiding. In such scenario the convective heat transfer becomes poor and the majority of the heat transfer from fuel bundle takes place by radiation mode. During this abnormal working condition, if the channel pressure is less than 1 MPa, the PT sags and come in contact with the CT. This results in high rate of heat transfer from contact location to moderator. The present paper aims to capture the temperature profile over a simulated nuclear channel during such scenario at a steady state temperature of 600 °C (Centre pin) at two different configurations of PT i.e. PT concentric with CT and PT contact with CT. The results showed that the bottom nodes of all the components (Fuel bundle, PT and CT) of the simulated channel was greatly influenced by the PT/CT contact. Moreover, higher temperature were observed at top nodes of the PT and outer pins of the fuel bundle. However, no significant variation in temperatures were obtained in fuel bundle and CT in concentric condition. Keywords: LOCA, ECCS, Fuel bundle, PT, CT, Moderator

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.

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.

A dual circularly polarised (CP) omnidirectional antenna is proposed. The antenna consists of an in-phase current loop, a printed dipole and a feed network. The in-phase current loop formed by zero-phase-shift line is placed orthogonally to the printed dipole to produce E φ and E θ components in the far-field of antenna radiation. By adjusting the amplitude and phase of E θ and E φ , good CP characteristics can be formed. A simple and feasible 3 dB coupler can realise the switching between the left-hand CP (LHCP) and right-hand CP (RHCP) without additional complex feed structure. Furthermore, the structure of the parallel strip line to the microstrip can effectively eliminate the unbalanced current of the coaxial cable. Finally, the optimised antenna was processed and measured. The measured results show that the impedance bandwidth (| S 11

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.

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.

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.

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.

In this communication, based upon a squeezed-state trial wave function, we have performed a simple variational study of the spectral collapse of the two-photon Rabi model. Our analysis indicates that the light-matter interaction and the spin-flipping effectively constitute two competing impacts upon the radiation mode. Whilst the former tries to decrease the radiation mode frequency, the latter may counteract or reinforce it, contingent upon the state of the atomic system. The light–matter interaction appears to dominate the frequency modulation as its coupling strength goes beyond the critical value, leading to the emergence of the spectral collapse. However, at the critical coupling the dominance of the light–matter interaction is not complete, and incomplete spectral collapse appears. The extent of incomplete spectral collapse is found to depend upon the energy difference between the two atomic levels as well.

We investigate bottom-emitting organic light-emitting diodes (B-OLEDs) integrated with metasurface (MS) to analyze the effect of the structural parameters on the output performance. The performance of the MS-integrated B-OLED (MIB-OLED) is evaluated by out-coupling efficiency (OCE) and reflection of the ambient light, while attention is paid mainly to dielectric capping and metal structure of MS that may influence excitation of surface plasmon (SP). The results suggest that layer thicknesses affect the performance by as much as 10% for the OCE and up to 32% for reflectance. The OCE is in general weakly affected by the structural parameters of MS. In contrast, the reflectance characteristics are found to be dominated by localized SP that is largely determined by the length and the width of a unit slot of MS. An optimization factor introduced to evaluate the performance based on out-coupling power to the radiation mode and reflectance of MIB-OLEDs confirms that integration with MS improves performance by 16% over conventional planar structure. In particular, MIB-OLED is found to enhance OCE by 51% with Lambertian-like pattern. Enhanced performance is experimentally confirmed. The findings provide insights on how to optimize the MS structure to produce MIB-OLEDs with enhanced out-coupled power and contrast ratio.

Recent experiments have demonstrated remarkable mode-selective reactivities by coupling molecular vibrations with vacuum fluctuations inside an optical cavity. The fundamental mechanism behind such effects, on the other hand, remains elusive. In this work, we theoretically demonstrate the basic principle of how cavity photon frequency can be tuned to achieve mode-selective reactivities. We find that the non-Markovian nature of the radiation mode leads to a cavity frequency-dependent dynamical caging effect of a reaction coordinate, resulting in a suppression of the rate constant. In the presence of multiple competitive reactions, it is possible to preferentially cage a reaction coordinate when the barrier frequencies for competing reaction paths are different. Our theoretical results illustrate the cavity-induced mode-selective chemistry through polaritonic vibrational-strong couplings, revealing the fundamental mechanism for changing chemical selectivities through cavity quantum electrodynamics.