Methods for increasing the efficiency of shapers powerful microwave radiation in the task of electromagnetic destruction of a group of radio-electronic means.

Methods for increasing the efficiency of electromagnetic field shapers based on powerful microwave generators in case of electromagnetic defeat to a group of radio-electronic means distributed on the earth is surface have been determined. As an indicator of efficiency the radius of the zone of electromagnetic defeat of the most resistant radio-electronic mean was chosen. The limitations of the maximum power of the generator due to the finite energy of the power supply and (or) the electrical strength of the air in the radiating antenna are taken into account. It was found that the main methods to improve the efficiency of the electromagnetic field formers are the choice of the radiation parameters of the generator and the directivity characteristics of the radiating antenna. The optimal modes of operation of a microwave generator with a limited energy the power source have been determined. A comparison is made of the efficiency of shapers with different types of radiating antennas. It is shown that antennas with narrow toroidal radiation patterns are the most preferable for solving the problem under consideration.

Algorithm for determining the design of an unbalanced wave channel antenna with a given direction of maximum radiation in the vertical plane

An integral part of the communication system with unmanned aerial vehicles is the airborne antenna-feeder system. As a rule, a circular pattern is required in the horizontal plane. However, since omnidirectional antennas have a small gain, they switch to schemes of several directional switchable antennas. It is proposed to use an unbalanced antenna for such systems. Unbalanced antennas have limited substrate dimensions. The maximum gain is achieved not towards the horizon, but at some elevation angle. Proposes a design definition algorithm an unbalanced antenna wave channel with a given direction of maximum radiation. For example, a similar antenna is constructed using the algorithm. An antenna for operation in the frequency range of 2,3…2,7 GHz is taken as the initial data. The dimensions of the antenna elements are obtained from numerical experiments using an optimization module in CAD. A study of the directivity characteristics of an unbalanced wave channel of an antenna with a limited substrate and the dependence of the elevation angle of the maximum of the directivity pattern is carried out. The minimum size of the substrate at which the gain in the direction to the horizon stops growing is revealed. The range of values of the elevation angle of the maximum of the amplitude radiation pattern in the vertical plane is determined.

Enhanced Frequency Reconfigurable Antenna for LTE Implementations

The design is focused on fabrication and testing of frequency reconfigurable antenna designed to operate in LTE and Wi-Fi implementations. The reconfigurable mechanism is governed by three PIN diodes and the operating bandwidth (1.38 GHz - 3.24 GHz) is efficiently controlled by diode’s different operating states. The antenna’s working principle is elucidated with the reflection coefficient, VSWR, gain and directivity characteristics. The antenna exhibits a maximum gain of 2.23 dBi and the VSWR of less than 1.5 throughout the bandwidth. The ON and OFF conditions of the diode go well with the desired operation and it does not induce the cross polarization. This work aims to design the simulations which are conceded using ANSYS HFSS full wave EM simulator and the measurements are in accordance with the simulated one.

Printed broadband dipole for phased array antenna

The article discusses ways to increase the operating frequency band of a symmetrical broadband vibrator in printed version for a phased array antenna. The equivalent circuit of such an emitter is described. Various designs of an emitter made on a Rogers RT5880 dielectric substrate with a thickness of t = 1.5 mm and εr = 2.2 and the results of electromagnetic modeling are considered. A wide working band is achieved due to the introduction of a dual-circuit system and a modified geometry of the vibrator arms. Topologies, as well as matching and directivity characteristics of three types of antennas are given. The developed antenna is intended for use in broadband systems both as a separate independent antenna and as a radiator for digital phased antenna arrays. The CST Microwave studio environment was used to simulate the emitter.

SOME FEATURES OF ULTRASONIC TESTING OF CAST IRON OBJECTS WITH FLAKE AND GLOBULAR GRAPHITE USING NORMAL LINEAR PROBES WITH PHASED ARRAYS

Computer modelling of the acoustic characteristics of signals of direct normal probe with phased array (PFR) in the cast iron with flake and globular graphite was performed. As a result the form of acoustic pulses of a longitudinal wave, depending on the passed by wave distance and the values of attenuation coefficient for different models of cast iron was calculated. The main modeled characteristics of the probe include the directivity characteristic and the change in the amplitude of the signal along the acoustic axis. It is shown that the difference in the PFR directivity characteristics for cast iron with flake graphite of different models and steel is due to two factors – significantly lower longitudinal wave velocities in cast iron compared to steel and a decrease in its operating frequency due to attenuation. In this case, for cast iron with globular graphite, a small change in the width of the diagrams is due only to the lower speed of longitudinal waves in cast iron compared to steel. For cast iron with flake graphite model 3, the phenomenon of nonlinear attenuation due to a decrease in the frequency of the maximum of the signal spectrum during the propagation of a longitudinal wave in cast iron with a corresponding decrease in the frequency – dependent attenuation coefficient is established. Evaluation of the nonlinearity of attenuation for cast iron with globular graphite showed that it is very small. The influence of calculation of initial signal delays on the velocity of longitudinal waves in steel on the directivity characteristics in cast iron, decreasing with increasing focus distance, is established. It is shown that for cast iron with flake graphite there are cases when the direction of transmitting of PFR in cast iron is practically absent.

INVESTIGATION OF THE EFFECT OF ATTENUATION OF ELASTIC LONGITUDINAL WAVES IN CAST IRON WITH FLAKE GRAPHITE ON THE CHARACTERISTICS OF SIGNALS DURING ULTRASONIC TESTING

The model of estimation of damping coefficient of elastic longitudinal waves in cast iron with flake graphite due to their Rayleigh and phase scattering on graphite inclusions, considering the deviation of the modulus of bulk elasticity of the phases of cast iron (metal base and graphite) from the mean value, is developed according to the theory of Mason. At the same time, the characteristics of cast iron used for calculations include the value of the longitudinal wave velocity, the mass content of graphite inclusions and their average size. In the process of studying the effect of attenuation of elastic longitudinal waves in cast iron with flake graphite on the characteristics of signals with narrow, medium width and wide spectra, a difference in the nature of the spectra changes due to frequency-dependent attenuation depending on the nominal pulse frequencies, cast iron models and the distance traveled by the ultrasonic wave is established. It is shown that the shorter the pulse, the greater the shift of the spectrum maximum in the frequency range less than the nominal. The effect of attenuation of longitudinal waves in cast iron with flake graphite on the impulse directivity characteristic of the round piezoplate depending on the cast iron model and pulse spatial length is established. The expansion of pulse directivity characteristics with increasing of the distance traveled by the wave in cast iron is shown, the greater the wider the pulse spectrum.

The Research of the Characteristics of the Ocean Ambient Noise Under Varying Environment

The parabolic equation approximation method is applied to build the model of the vertical spatial correlation and vertical directivity characteristics of ocean ambient noise under varying environment. The random noise sources which have the same intensity are represented by uncorrelated monopoles distributed uniformly over an infinite plane located a certain depth below the sea surface. The spatial properties of noise field are analyzed under the varying ocean environments which are the slope, seamount and varying sound speed profiles. According to the results of simulation, the varying environment changes the propagating paths of noise, so the spatial properties (correlation and directionality) of the noise field change. When the remote noise intensity increases, the noise intensity in low grazing angle and the vertical correlations of nose field become stronger. At last, the experiment’s results support the results of simulation.