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 letter, we propose the design of a frequency scanning antenna (FSA) based on a hybrid mode of a quasi-TEM mode and a spoof surface plasmon polaritons (SSPPs) mode. The two modes are hybridized using a partially grounded comb-shape microstrip (CSM) structure, a combination of conventional microstrip line and the comb-like structure, the former of which supports propagation of quasi-TEM mode while the latter SSPPs mode. The CSM modulated by periodical radiating elements can achieve wide-angle frequency scanning antennas. Since the dispersion curve of the hybrid mode on CSM lies below that of pure microstrip lines, a larger phase shift can be achieved within the same propagation length than for pure microstrip lines. This is favorable for wide-angle scanning in a narrower bandwidth, so as to take up less spectrum resource. Moreover, dispersion of the hybrid mode can be engineered so that linear frequency scanning can be realized approximately. As an example, an X-band FSA was designed, fabricated and measured. The simulated and measured results agree well, and show that the prototype can achieve ±60° scanning in 8.5–12.5 GHz. In particular, the scanning angles within [−40°, +40°] are linearly proportional to frequency in 9.0–12.0 GHz, with an average gain of about 14 dB and a half-power beam-width of 6°. Moreover, due to the usage of radiating elements with smoothly-varying strip-widths, the open stopband is suppressed and there is no degradation for radiation at the broadside. This work provides an alternative method of designing wide-angle FSAs that may find applications in spectral analysis, direction of arrival estimation, etc.

The curved photonic nanojet (CPNJ) produced due to the interaction between a dielectric circular cylinder rotating at a stable angular velocity and a plane wave is investigated. Based on this model, the optical Magnus effect of a dielectric circular cylinder is verified. And the analytical expression of both internal and external electric field are given based on the instantaneous rest-frame theory and the partial-wave series expansion method in cylindrical coordinates. The influence of the size parameter, the relative refractive index, and the rotating dimensionless parameter on the CPNJ are analyzed and discussed in numerical results. The "photonic nanojet curved" effect is highlighted, which can be used to generate the off-axis photonic nanojet (PNJ) controlling particles by adjusting the angular velocity of the dielectric cylinder. The results of this manuscript have promising application prospects in optical tweezers, particle manipulation, and optical trapping. Moreover, it also provides theoretical support for the particle spinning and generation of the off-axis CPNJ.

The mechanism generating the array‐distributed atmospheric refractivity fluctuation by a coherent acoustic source is analyzed. The theoretical model is established, which is used to quantifiably analyze the array structure of the artificial dielectric irregularities. It is qualitatively validated that the array‐distributed artificial dielectric irregularities really exist and that the array structure of the artificial dielectric irregularities and the scattering effect of the artificial dielectric irregularities on a radio wave can be controlled by adjusting and selecting the optimized parameters of the transmitted acoustic wave and the adopted acoustic antenna array. It can be concluded that the array‐distributed artificial dielectric irregularities can be used to purposefully affect radio wave propagation. After radio acoustic sounding system, the idea of this paper is a novel development in the field of the tropospheric atmospheric refractivity artificial abnormality technique and its applications.

The scattering of a radially polarized (rp) Bessel vortex and nonvortex beam by a perfect electromagnetic conductor (PEMC) sphere is studied based on the generalized Lorenz–Mie theory. The electric and magnetic fields of the incident arbitrary-shaped polarized beams are constructed using vector spherical wave functions (VSWFs) and beam shape coefficients. The analytical expression of the scattered field is expanded using VSWFs and scattering coefficients, which are derived by considering PEMC boundary conditions. The expression of the normalized dimensionless far-field scattering intensity (NDFSI) is also defined and derived. The photonic nanojet (PNJ) and the “bottle beam” generated by the interaction between the PEMC sphere and the vortex and nonvortex Bessel beam under rp are emphasized in this paper. Moreover, the intensity and directivity of NDFSI are also considered. It has been found that the generation of the PNJ and the “bottle beam” is determined by the half-cone angle α₀ of the rp Bessel beam and admittance parameter M of the PEMC sphere. Furthermore, the influence of M, α₀, and integer order l of the Bessel beam on the intensity and distribution of NDFSI is also discussed. The findings are important in the research on meta-materials and promising prospects in microwave engineering, antenna engineering, imaging, subwavelength focusing, optical radiation force, and torque.