SPECTRAL FEATURES OF A SINGLE TYPE III BURST OBSERVED BY PSP ON 04.06.2020

In this paper, an efficient numerical approach is proposed for analyzing the scattering from PEC objects above a lossy half space over wide angular and frequency band. One of the principal tools for the analysis of scattering from targets located in half-space is the method of moments (MoM) and the half-space multilevel fast multipole algorithm (MLFMA). Since the surface current and the scattered field are functions of the incidence angle and frequency, it will cost lots of time for analysis of monostatic scattering over a wide frequency band. To reduce the computation time, an efficient numerical approach is proposed in this paper. The mixed potential integral equation (MPIE) for a general PEC object located above a lossy half space is first presented by using half space Green's functions. Then, the half-space MLFMA is utilized for the efficient matrix multiplication. An adaptive cross approximation (ACA) based method is used for fast analysis of the scattered field with multiple incident angles. Compared with solving linear equations at each angle repeatedly, the ACA method is able to greatly reduce the computation time. The geometric theory of diffraction (GTD) model based interpolation method is utilized for fast analysis of the scattered field over wide frequency band. By utilizing the GTD model parameters, the scattered field over a wide frequency band can be calculated approximately by MoM solutions at very fewer frequency sampling points. This means that plenty of time can be saved comparing with modeling at each frequency sampling points. Numerical examples are presented and analyzed to demonstrate the valid and efficiency of the proposed approach.

By testing and analyzing the input-output characteristics of the piezoelectric macro fiber composite (MFC) actuator within a wide frequency band containing its natural frequency, it is found that a mechanical force with hysteretic characteristics is generated when subjected to a driving voltage, resulting in the clockwise deflection of the hysteretic curve in lower frequency band and counterclockwise deflection, flipping near the natural frequency, and approximate linearization after exceeding the natural frequency of the hysteretic curve in higher broad frequency band. In order to accurately simulate the output displacement of piezoelectric MFC actuators within a wide frequency band containing its natural frequency, an electro-mechanical dynamics (EMD) model, which combines the modified Prandt-Ishlinskii (MPI) model with the dynamic mechanical model in series, is established. Among them, the MPI model is composed of the weighted summation of bidirectional delay non-parallel play operators to describe the asymmetric hysteresis in the lower frequency band, and the dynamic mechanical model is composed of the creep model and the Euler-Bernoulli beam theory model in series to describe the creep and structural dynamics in a wide frequency band. Numerical simulations and analysis are performed and the experimental setup is established to verify the established EMD model. The research results show that the established EMD model can accurately predict the input-output characteristics of the piezoelectric MFC actuator within a wide frequency band with the maximum error of 5.73 μm, the maximum root mean square error of 3.67 μm, and the maximum root mean square error rate of 3.22%. In addition, the MPI model can accurately simulate the hysteresis of the piezoelectric MFC actuator in the lower frequency band. The works presented in this paper will lay a foundation for high-precision application of the piezoelectric MFC actuators within a wide frequency band.

The increase in the number of radio electronic devices leads to the intensive development of RF spectrum management equipment, the functions of which include radio spectrum overview in a wide frequency range, signal detection and evaluation of its parameters. Analysis of signals in a wide instantaneous frequency band (from a few gigahertz up to tens of gigahertz) increases the probability of signal detection and recognition, as well as the speed of taking response actions. However, there are no effective mechanisms for flexible rejection of powerful interfering signals, which, due to the exclusion of frequency scanning, inevitably fall into a wide frequency band. A Sub‐Nyquist multichannel receiver allows for software-defined rejection of the required frequencies. However, there is no scientific and method for configuring receiver parameters to solve this problem. The purpose of this work is to develop a method for configuring receiver parameters when rejecting an interfering signal and to evaluate the effectiveness of this approach. As a result of the conducted research, expressions are obtained for configuring receiver parameters when rejecting an interfering signal. Recommendations for choosing receiver parameters are substantiated. The applicability limits of the software rejection method are presented. One can observe that with a simultaneous increase in the rejection bandwidth and an insignificant frequency shift of the channel frequency response dips relative to each other, their repetition period in the operating frequency range is eliminated. It is shown that when suppressing an interference signal with a frequency band of 80 MHz by 35 dB using this method, the probability of missing a useful signal does not exceed 2.5%. The developed method for configuring receiver parameters can be used at the design stage of RF spectrum management equipment to assess the feasibility and effectiveness of applying technical solutions that reduce the power of an interference signal. Further author’s research is aimed at optimizing the calculation of sampling frequencies; studying the probabilities of suppressing various signal types when using the software rejection method; studying the possibility of rejecting several signals using this method; analyzing the possibility of flexible adjustment of sampling frequencies to ensure interference rejection in a changing signal-interference environment.

We review the studies of gyrotron-type microwave devices whose electrodynamic system has the form of an oversized metal waveguide with a helically corrugated internal surface. For certain parameters, such a corrugation changes radically the waveguide dispersion ensuring an almost constant group velocity of the eigenmode for a small (close to zero) longitudinal wave number in a wide frequency band. The use of “helical” waveguides along with electron optical systems which form near-axis electron beams makes it possible to create high-efficiency amplifiers based on gyro-traveling-wave tubes (gyro-TWTs) with a wide instantaneous frequency band of amplification and gyro-backward-wave oscillators (gyro-BWOs) with continuous wideband tuning of the oscillation frequency. The studied devices are superior to the well-studied microwave sources of this type (gyroklystrons and gyrotrons) in frequency band, by more than an order of magnitude, and are not inferior to them in efficiency even for a wide spread of electron velocities.

Fixed-frequency beam scanning leaky-wave antennas (LWAs) that can scan their main beam over a specific frequency band are highly desired for future wireless communication systems. A composite right-/left-handed (CRLH) LWA is developed in this article that facilitates fixed-frequency continuous beam scanning over a wide operational frequency band. A variation of a simple single-layer nonreconfigurable frequency-based continuous beam scanning CRLH LWA is considered first. Its dispersion properties are approximately investigated using an equivalent circuit model. It is reported how two groups of varactor diodes can be incorporated into its basic circuit model to electronically control its dispersion behavior. An optimized reconfigurable CRLH LWA with practical dc biasing lines is then realized from this nonreconfigurable design. Fixed-frequency continuous beam scanning, from backward to forward directions through broadside, is reported over a wide operational frequency band. Simulations predict that the antenna can operate from 4.75 to 5.25 GHz with the main beam being continuously scannable at each frequency point. A prototype was fabricated, assembled, and tested. The measured results confirm its simulated performance characteristics.

Spectral properties of a single type III burst in the wide frequency band from 10 to 70 MHz are studied in detail. It is shown that electrons corresponding to different levels of type III emission move with different velocities. Moreover, these electron velocities decrease from the maximum value, which corresponds to the 0.1 level of the maximum type III flux at its front, to the minimum value, corresponding to the 0.1 level of the maximum type III flux at its back. The velocity of electrons corresponding to the maximum type III flux was approximately 0.31 c. This value equals 0.6 of maximum velocity, and, namely, it was predicted by the gas dynamic theory of electron propagation through the coronal plasma. In addition, we adduce arguments that the type III radio emission is the harmonic emission. In supposition that type III electrons move through the Newkirk coronal plasma, we find electron velocities for every level of the type III burst. The duration dependence on frequency obtained from the observations is close to Elgaroy–Lingstad dependence. We discuss the contribution of electron velocity dispersion to the type III burst duration. In addition, we derived type III flux dependence on frequency in the frequency bands of 10–33 MHz and 33–62 MHz.

In this paper, a wideband, miniaturized, and high gain double-slot Vivaldi antenna is proposed. First, a corner cutting technique is adopted to broaden the frequency band. Second, a pair of defected ground slots is added to the edges of the antenna to extend the low-end frequency limitation from 2.27 to 1.15 GHz, which provides a great design freedom. Third, a novel unit cell of an index-near-zero metasurface is proposed in our design. The unit cell is a two-stub-loaded split-ring resonator, which has a compact size, a wide frequency band, and a good reflection coefficient. The gain of the double-slot Vivaldi antenna is improved over a wide frequency band by the inclusion of the index-near-zero metasurface in the aperture, without changing the overall dimensions or compromising the whole frequency band performance of the antenna. Finally, to verify the design method, an ultra-wideband double-slot Vivaldi antenna with defected ground slots and metasurface was fabricated and measured. The circuit has an overall size of $0.76\,\,\lambda \text{g}\,\,\times0.41\,\,\lambda \text{g}\,\,\times 0.005\,\,\lambda \text{g}$ . The modified antenna exhibits a measured gain of 0.7–14 dBi over the frequency band of 1.13–12 GHz.

This paper presents a method based on the support vector regression (SVR) model and grey wolf optimizer (GWO) algorithm to efficiently predict the monostatic radar cross-section (mono-RCS) of complex objects over a wide angular range and frequency band. Using only a small-size of the mono-RCS data as the training set to construct the SVR model, the proposed method can predict accurate mono-RCS of complex objects under arbitrary incident angle over the entire three-dimensional space. In addition, the wideband prediction capability of the method is significantly enhanced by incorporating the meta-heuristic algorithm GWO. Numerical experiments verify the efficiency and accuracy of the proposed SVR-GWO model over a wide frequency band.

In this article, we propose a new model order-reduction method for compact modeling of interconnect circuits over wide frequency band using a novel complex-valued adaptive sampling and error estimation scheme. We address the outstanding error control problems in the existing sampling-based reduction framework over a frequency band. Our new method, WBMOR , explicitly and efficiently computes the exact residual errors to guide the sampling process. We show by sampling along the imaginary axis and performing a new complex-valued reduction that the reduced model will match exactly with the original model at the sample points. Additionally, we show in theory that the proposed method can achieve the error bound over a given frequency range. In practice, the new algorithm can help designers choose the best order of the reduced model for the given frequency range and error bound via the adaptive sampling scheme. In addition, WBMOR can perform wideband accurate reductions of interconnect circuits for analog and RF applications where model accuracy needs to be maintained over a wide frequency range. We compare several sampling schemes such as Monte Carlo, logarithmic, recently proposed resampling, and ARMS methods. Experimental results on a number of RLC circuits show that WBMOR is much more efficient than all the other sampling methods, including the recently proposed resampling and ARMS schemes with the same reduction orders. Compared with the traditional real-valued sampling methods, the complex-valued sampling method is more accurate for the same computational cost.

Based on that triangle monopole antenna has wide frequency band, this paper proposes a novel composite triangle monopole antenna, which is composed of three similar triangle metal plates. Through the electromagnetic simulation software CST Microwave Studioreg, we obtain its characteristics under the condition that its ground-plate is infinite perfect conductor. The simulation results show that the composite triangle monopole antenna not only has wide impedance frequency band, but also takes up smaller space comparing with triangle rnonopole antenna. On the above foundation, we construct composite triangle dipole antenna with two symmetrical composite triangle monopoles without ground-plate and simulate its impedance characteristic, the simulation results further prove that the composite triangle dipoles antenna has stable input impedance between 0.15 GHz and 2.0 GHz (resistance = 150 Omega, reactance = 0 Omega) and has wide frequency band.

A class of planar antenna which offers better performance over broad band of frequencies that fits itself in wide range of applications are in need of research. The license free band from 3.1 GHz to 10.6 GHz that do not cause interference to narrowband signals is chosen as operating range of frequencies for the chosen Vivaldi antenna. The novelty of the proposed work consists in the remodeling of a mathematical equations for elliptic antenna structure and the study of the Vivaldi antenna operating over the frequency range between 2.63 GHz to 14.58 GHz that lies in Super High Frequency (SHF) bands – S, C and X bands. The designed antenna is fabricated and its radiation characteristics are studied and analyzed. Purpose. Analysis of the designed antenna on the basis of an elliptical curve mathematical model will allow the antenna to operate over wide band of frequencies thus extending its applications over the areas of application in the areas of satellite communication, military, weather radar, surface ship radar. Methods. The antenna is being designed using HFSS software and fabricated antenna is being tested at anechoic chamber. Results. A mathematical model of a structure of Vivaldi antenna was developed and studied. The performance measures of designed antenna such as return loss, gain, VSWR and radiation pattern are simulated and analyzed. The antenna is being fabricated and tested using vector network analyzer and anechoic chamber. Practical value. The analysis of designed antenna over wide band of frequencies is demonstrated. The further research directions of the designed antenna can be extended for the subsequent implementation of the results in suitable applications.

Classical absorber for vibration suppression of a continuous structure is constructed as a spring-mass oscillator, which only provides coupling force to suppress the vibration of primary structure. In this study, absorber beam is introduced and coupled on the continuous primary beam with magnetic interaction. Thus, the magnetic interaction and coupling bending moment affect the responses of primary beam. Based on the model of the system and Galerkin truncation, the natural frequencies for different magnetic parameters are obtained, which demonstrates that the fundamental frequency can be reduced to zero and the vibration of primary beam can be suppressed in a wide frequency band. Considering the vibration suppression on frequency band, we propose two criteria to evaluate the vibration suppression effect: one is the width of band for vibration suppression and the other is the width for vibration absorption. The two criteria not only show the vibration reduction effect but also correspond to different vibration suppression mechanism. Due to the advantages of zero fundamental frequency induced by the proposed magnetic interaction coupling and wide vibration suppression frequency band, utilizing absorber beam in vibration suppression of continuous structure has potential applications for flexible aim in the fields of manufacturing and aerospace.

Many (>100) packets of pseudo-random signals transmitted during the TREX04 experiments are analyzed in this paper to deduce the narrowband signal envelope amplitude statistics over a wide band (15–19kHz) of frequencies. The envelope amplitude statistics are found to be non-Rayleigh-type with a long-tail distribution at high amplitudes. Long-term and short-term fading statistics are deduced from the data, exhibiting near lognormal and Rayleigh distributions, respectively. The combined distribution is closely approximated by a K-distribution, which fits the measured amplitude distributions well over a wide band of frequencies.

For the study of microwave chemistry, it is necessary to develop a reactor with small-size and wide operating frequency band. This paper presents a novel microwave coaxial reactor. Its main part is a coaxial cavity, and the input end is a coaxial port filled with PTFE, and the other end is a short circuit terminal. Two orifices which are designed as cut-off waveguides for microwave are attached to the cavity as passageway of sample solutions, so the reactor can treat the samples continuously. The distributions of electromagnetic field and temperature of this novel microwave coaxial reactor used for heating edible vegetable oil at 915 MHz and 2450 MHz are simulated with finite-element method multi-fields coupling analysis. It is easy to find out that this novel microwave coaxial reactor could work properly over a wide frequency band. Also, the operating frequency could be chosen over a wide frequency band to get the optimal reaction effect to meet the requirements of experiments.

For matching transformed impedances, various methods are known in the literature that are used reactive, dissipative, and combined circuits. The operation of such circuits is possible either in a wide frequency band, but in the same standard paths, or in a narrow frequency band when matching impedances that differ from each other by a high transformation ratio. Unfortunately, with the help of known methods, it is impossible to matching impedances with a high transformation ratio and simultaneously to operating of the circuit in a wide frequency band. For a reflectionless high-pass filter, the task is to investigate the possibilities of expanding its operating frequencies band when matching impedances have high transformation ratio. For a typical reflectionless high-pass filter, the reflection coefficients of its two equivalent circuits operating in even and odd excitation modes are determined. They are used to find the frequency transmission coefficients for this device, as well as the transfer functions of the complex frequency. It is established that such device has a narrow band of operating frequencies when matching impedances have a high transformation ratio. Possible ways to expand the frequency band by introducing additional electromagnetic coupling to this device are considered. An absorbing filter-transformer with an additional electromagnetic coupling is investigated. The relations for calculating its main elements of the scheme are obtained. It is established that electromagnetic coupling in this device extends the operating frequencies band. Thus, when the magnetic coupling coefficient k tends to 1, this band can be expanded 1 1k2  times. The obtained theo- retical conclusions are fully confirmed by experimental results. The performed studies of reflectionless high-pass filter-transformer confirm the possibility of expanding the operating frequency band when matching impedances have high transformation. The proposed filter-transformer is recommended for use in the design of input matching circuits in power amplifiers using modern GaN transistors, for which broadband reflectionless matching is a necessary condition for eliminating parasitic excitations at low frequencies.