The statistic models for evaluating the fading term caused by the incoherent scatter in clear and rainy environments are derived, which are critical for establishing the multiple-input ...multiple-output (MIMO) channel model at Ka band. The channel model of Ka-band single-polarization MIMO satellite-earth link is established, which comprehensively takes into account the propagation and scattering effects induced by those environments. Based on the channel model, the bit error rate (BER) performances in clear and rainy environments are investigated taking an assumed 2 × 2 satellite-earth link at 30 GHz in circular polarization as an example. During the investigation, the M-ary Phase Shift Keying (M-PSK) modulation modes with different M and the space-time codes of Space-Time Block Code (STBC), Space-Time Trellis Code (STTC) and Vertical Bell Laboratories Layered Space-Time (VBLAST) are considered. It is also discussed that the BER varies with propagation environment parameters, equivalent isotropically radiated power (EIRP), ground receiving antenna gain and elevation angle. The channel model given in this paper is also valid for the single-polarization MIMO satellite-earth link at other frequencies above 10 GHz.
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The concept of a perfect electromagnetic conductor (PEMC) material, which is a class of a magneto-electric metamaterial, has been recently examined in the context of the optical ...radiation force theory J. Quant. Spectr. Rad. Transfer, 233 (2019) 21–28; ibid 256 (2020) 107280, with particular emphasis on the rotary polarization effect and the contribution of the cross-polarized waves to the transfer of linear momentum, assuming an illumination of linearly-polarized plane progressive waves. The present investigation shows that additional cross-interference factors, which cannot be ignored, contribute to the time-averaged optical radiation force exerted on an absorptive electromagnetic conductor (AEMC) sphere when the incident field becomes circularly-polarized. Moreover, the analysis is extended to investigate the co-polarized, cross-polarized and cross-interference components of the time-averaged optical spin radiation torque. The multipole series expansion method in spherical coordinates is utilized to derive exact mathematical partial-wave series for the co-polarized, cross-polarized and cross-interference components of the radiation force and torque based on the integration of Maxwell’s radiation stress tensor and its moment over a spherical surface of large radius enclosing the sphere suspended in a lossless medium of wave propagation. Numerical results for the radiation force and spin torque efficiencies and their corresponding co-polarized, cross-polarized and cross-interference components illustrate the analysis with emphasis on the size parameter of the sphere ka, its electromagnetic admittance M as well as its imaginary part amounting to absorption. The computations are of importance from the standpoint of the fundamentals of the linear and angular momenta of circularly-polarized electromagnetic waves transferred to an AEMC and related applications in optical tweezers and particle manipulation of objects exhibiting circular dichroism.
In this article, we study the optical force exerted on nanorods. In recent years, the capture of micro-nanoparticles has been a frontier topic in optics. A Photonic Jet (PJ) is an emerging ...subwavelength beam with excellent application prospects. This paper studies the optical force exerted by photonic jets generated by a plane wave illuminating a Generalized Luneburg Lens (GLLs) on nanorods. In the framework of the dipole approximation, the optical force on the nanorods is studied. The electric field of the photonic jet is calculated by the open-source software package DDSCAT developed based on the Discrete Dipole Approximation (DDA). In this paper, the effects of the nanorods' orientation and dielectric constant on the transverse force
and longitudinal force
are analyzed. Numerical results show that the maximum value of the positive force and the negative force are equal and appear alternately at the position of the photonic jet. Therefore, to capture anisotropic nanoscale-geometries (nanorods), it is necessary to adjust the position of GLLs continuously. It is worth emphasizing that manipulations with nanorods will make it possible to create new materials at the nanoscale.
The selection of the type of the structured beam is great importance in the study of optical and first-order rainbow scattering by a particle. The Airy light-sheet is a specific type of ...limited-diffracting beam (in 2D), which has been used in investigations related to radiation forces and torque. Equally important and of practical significance is the study of the electromagnetic/optical resonance and first-order rainbow scattering by a dielectric sphere. The purpose of this paper is to calculate the electromagnetic resonance scattering, energy efficiencies and far-field scattered intensity of a lossless homogeneous dielectric spherical particle of arbitrary size, illuminated by a linearly-polarized non-diffracting electromagnetic Airy light-sheet. A rigorous parametric study is undertaken here to investigate the effect of varying the light-sheet parameters γ, kw0, and its polarization state as well as the size parameter ka of the lossless dielectric sphere on the scattering efficiencies and intensity. The analysis is extended to examine the first-order rainbow scattering phenomenon in the context of Airy light-sheets with different polarizations. Numerical results show that kw0, γ, ka and the state of polarization affect the amplitude and scattering directivity patterns of the efficiencies and intensity. Rainbow scattering arises along the polar scattering angle θ=143°, and is minimally influenced by the different values of the parameters kw0, γ, polarization, and ka. The results are of some practical significance in optical resonance scattering and related applications in optical tweezers, super-resolution imaging, particle characterization, and the measurement of temperature, velocity and size of a liquid jet to name a few applications.
The radio waves commonly used in terrestrial wireless communication are severely absorbed by the conductive seawater. However, the low-frequency magnetic fields can penetrate a much farther distance ...in seawater to realize wireless communication by magnetic induction (MI). An electromagnetic coil is generally used as a magnetic field generator, but it will consume excessive power when generating a strong magnetic field to achieve long-range communication. Instead, this study investigated the use of a motor-driven rotating permanent magnet as a mechanical transmitter for undersea MI communication. The frequency-dependent power consumption and the power-efficient operating frequency range of the mechanical transmitter were analyzed. To establish the undersea MI communication channel model, we derived exact analytic expressions for the fields generated by a rotating permanent magnet in seawater and explored the path loss of the undersea MI channel. A prototype mechanical transmitter using a cylindrical rare-earth magnet (Nd-Fe-B) with a diameter of 4 cm and a length of 15 cm driven by a servo motor was created, which consumes only about 2.74% of the power of the equivalent coil at 30 Hz. The surface-to-undersea MI communication using this prototype mechanical transmitter was demonstrated at a distance of 10 m.
This paper presents a novel signal modulation method to efficiently improve the data transmission capability of the mechanical antenna based on rotating dipoles. Such mechanical antennas were shown ...to be orders of magnitude more efficient than conventional antennas in the extremely low frequency (ELF, 3-3000 Hz) band. However, the signal modulation is constrained by inertia because this mechanical antenna relies on mechanical motion rather than on electromagnetic wave resonance. When using the existing signal modulation methods designed for circuit systems, the performance of the mechanical antenna is limited. Therefore, we presented an inertial compatible modulation method for the mechanical antenna called chirp-rate shift keying (CSK). In CSK modulation, the transmitted data are directly related to the driving torque, which can change instantly regardless of inertia. The orthogonal modulation methods of CSK were also established to achieve optimal detection. To demonstrate the feasibility of CSK modulation, we conducted a wireless communication experiment that used a rotary magnet-based mechanical antenna as the transmitter. The experimental results indicated that CSK modulation requires less torque and can achieve a higher reliable communication rate at the same bit error rate (BER) level compared to conventional frequency-shift keying (FSK) modulation.
In this communication, we propose a method of designing shared-aperture antennas based on excitations of both even- and odd-mode spoof surface plasmon polaritons (SSPPs). The antenna consists of a ...feeding monopole and a tapered SSPPs structure, both of which are placed vertically on a metallic ground. Due to tilted electric vectors of the monopole in near fields, both even- and odd-mode SSPPs can be excited. Standing waves of even-mode SSPPs on the SSPPs structure will enable broadside or tilted radiation, while traveling waves of odd-mode SSPPs on the tapered end will enable endfire radiation. Therefore, such an antenna configuration can achieve broadside, tilted, and endfire radiations. As an example, a shared-aperture antenna operating in <inline-formula> <tex-math notation="LaTeX">C/X </tex-math></inline-formula>/ Ku -bands was designed, fabricated, and measured. Both the simulated and measured results verify that the antenna can achieve broadside radiation in 4.68-4.83 GHz, tilted radiation in 8.51-8.82 GHz, and endfire radiation in 11.00-17.38 GHz, with peak gains about 2.7, 3.5, and 6.8 dB, respectively. The antenna itself can work in multiple bands with customized radiation patterns, without using several antenna radiators and complex feeding network. This communication provides an effective method of designing shared-aperture antennas in future lightweight and multifunctional wireless communication systems.
A physics-inspired hybrid method for extrapolating the conducting target's radar cross section (RCS) versus frequency is presented. Inspired by physical optics, we propose using the nonlinear least ...squares method to capture the global trend of the conducting target's RCS and using Gaussian process regression to automatically extrapolate the remaining local fluctuations. Experiments based on simulated and measured data are carried out to verify the proposed method. This method achieves a maximum root-mean-square error of only 0.444 dBsm on the simulated data of an electrically large aircraft model, and 0.065 dBsm on the measured data of a combinatorial model. These results fully demonstrate its high extrapolation accuracy.
In this paper, we propose the design of antennas with low radar cross section (RCS) based on dispersion engineering of spoof surface plasmon polaritons (SSPPs). The antenna consists of a feeding ...monopole and SSPPs guiding structure placed vertically on a metal ground. By comprehensively engineering the weak and strong dispersion regimes of the SSPPs structure, the cutoff frequency of SSPPs can be made close to the upper operating frequency of the feeding monopole. In this way, the SSPPs structure serves as a high-efficiency radiator in the operating band and as a broadband absorber out of band, leading to low RCS out of band. As an example, a C -band antenna with low RCS in the X -band was designed, simulated, and measured. Both the simulation and experiment results show that the antenna can radiate in the C -band, with average gain 6 dB and fractional bandwidth 28%. In order to evaluate the RCS reduction performances, a <inline-formula> <tex-math notation="LaTeX">5\times 5 </tex-math></inline-formula> antenna array was fabricated and the mono-static RCS was measured. The measured results show that the mono-static RCS is reduced by more than 10 dB in the whole X -band (8.0-12.5 GHz), with a maximal reduction above 30 dB. The design method provides an effective alternative to low-RCS antennas.
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