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With the widespread use of unmanned aerial vehicles (UAVs) in life, the real-time recognition of UAVs has become an important issue. The authors of this paper mainly studied the application of the random forest (RF) algorithm in the outdoor real-time recognition of UAVs. Mel-Frequency Cepstral Coefficient (MFCC) features were extracted from sound signals firstly, and then the RF method was combined with weighted voting to obtain the improved random forest (IRF) method to identify UAV sounds and environmental sounds. An experimental analysis was conducted. The modeling time of the IRF method increased by 9.52% compared with the RF method, and the recognition rate of the IRF method decreased with the increase of the distance from the microphone; however, the recognition rate of the IRF method was always higher than that of the RF method, and the recognition rate of the IRF method for the mixed samples was always higher than 90%. When the distance was 10 m, the IRF method still had a recognition rate of 91.29%. The experimental results verify the effectiveness of the IRF method for the outdoor real-time recognition of UAVs and its practical application feasibility.

Breakdown in the atmosphere is a significant issue limiting the transmission of high-power microwave (HPM). The formed plasma not only shield the incident wave, but also reflect HPM to the source after electron density multiplies. A volume- averaged global model is employed to study the characteristics of the repetitive HPM breakdown in the atmosphere. The susceptibility is analyzed considering the external atmosphere environment. Different repetitive HPM parameters is combined to investigate the cumulative effect on the breakdown phenomena. The simulation results show that a critical point exists, indicating the most sensitive height for breakdown. Among the HPM parameters, the pulse width has the greatest impact on the pulse number, and the HPM frequency has the least impact on the pulse number.

This paper addresses an Integrated Circuit Immunity Model-Conducted Immunity (ICIM-CI) of the embedded controller area network (CAN) controller in microcontroller to the conducted disturbances. The procedure is based on a gray-box approach to predict the behavior of a disturbed circuit. The parameters are estimated from time and frequency domain measurements, allowing accurate and efficient reproduction of nonlinear device switching behaviors. The immunity of the CAN controller is measured with the direct RF power injection method. The obtained model is successfully implemented to predict both the functional signals and the RF noise immunity at component level.

The scattering properties and regularity of high power microwave propagation on the jungle-ground are analyzed with finite difference time domain (FDTD) method. The scattering properties at different incident angles are obtained, and the relationship between jungle scattering coefficient and grazing angle are comparatively analyzed with analytic and numerical methods. The theoretical analysis and numerical computation indicate that the scattering coefficient curve has a Brewster angle. Larger electrical parameters of topography lead to smaller Brewster angle. When the grazing angle is less than the Brewster angle, the scattering coefficient decreases with the grazing angle increasing; when the grazing angle is greater than the Brewster angle, the scattering coefficient increases with the

The existence of seed electrons is the precondition of air breakdown induced by high power microwave (HPM). Seed electrons are usually assumed to exist in background atmosphere when simulating the air breakdown triggered by HPM. However, this assumption may lead to some large errors especially in lower atmosphere where the number of electrons is very small. We establish a physical model of seed electron production from O- detachment collision with air molecules using the Monte Carlo method. A three-dimensional Monte Carlo program is developed to simulate this process. The average energies of O- and the average generation time of seed electrons under different electric intensities, frequencies, air pressures and breakdown volumes are obtained through simulation. The simulations show that the average generation time of seed electrons becomes longer with the increase of air pressure or the HPM frequency. The average seed electron generation time becomes shorter with the increase of electric intensity or breakdown volume. Finally, we simulate the processes of O- detachment collision with air molecules under the same experimental conditions. The comparative results show that the seed electron generation from O- detachment can explain the experimental results when the HPM frequency is low, while at higher frequencies, the average seed electron generation time becomes so long that it cannot correspond to the experimental value. Therefore some other mechanisms should be considered in the higher frequency case.

At present research on HPM non-linear propagation mainly focuses on air-breakdown. It is not enough to design the whole HPM system. Theoretical research on HPM should combine with the actual HPM antenna. Three different types of near-field region propagation model of typical plane antenna for HPM are presented in this paper.

In this paper, we have utilized the set of recently five years meteorologic profiles sounding made in five representative areas along the coast of southeast China and applied mode of subsection to calculate statistically refractive index. Based on former work, analysis on oceanic and terrestrial domino effect of atmosphere refractive has been carried through using graph coming from statistic data, and standard deviation has also been obtained by least mean square (LMS).

This paper presents an effective method to analyze electromagnetic interfering-electromagnetic topology. It emphasizes on the basic concept of electromagnetic topology and the approximate approach in system analysis. After that, we introduce the application of it in the analysis of HPM effects on the system. Lastly, we use electromagnetic topology to analyze a simple system as an example.

In this paper, theoretical research on the air breakdown threshold of high power microwave pulse propagating in atmosphere is derived approximately. Some new views are presented about the existed questions of air breakdown.

Considering the series effects of high power microwave such as thermal fast electrons effect, collision frequency effect and ionization frequency effect, a unified high power microwave (HPM) propagation model is presented in this paper. A unified air-breakdown model for single-pulse HPM is discussed in detail and the breakdown threshold is determined. It is found that the frequency of plasma induced by high power microwave is greater than previous value. The threshold of air breakdown increases with altitude increasing under the same condition. When the threshold reaches a minimum, a reverse trend will appear. And the minimum value will be obtained in an area of 30-60 km. The typical phenomenon waveform and threshold are gained in the experiment of air breakdown in microwave darkroom. And a well uniform distribution of the air breakdown threshold is shown theoretically and experimentally.