卷 62, 编号 5 (2017)

In this review, we consider elements with a fractal impedance (henceforward, fractal elements, FEs). Advantages and drawbacks of various engineering and technological implementations of FEs are estimated. It is shown that promising FEs appropriate for production and solution of a wide range of scientific and engineering problems are structures on the basis of resistance-capacitance distributed parameter components (RC-DPCs) with the R–C–NR layer structure. It is established that RC-DPC FEs make it possible to implement fractal impedances with complex fractional-power frequency dependence. Examples of physical implementation of RC-DPC FEs are presented.

An antenna in form of a dense multifilar helix of thin metal ribbons on a spherical surface with lower order transverse-electric and transverse-magnetic modes is considered. Averaged boundary conditions taking into account the capacitances between the edges of ribbons are formulated. Formulas for calculating the angle of inclination of ribbons and the required inter-edge capacitance from a given resonance frequency and approximate ellipticity coefficient are obtained. The inclination of the axes of the polarization ellipse and an improved ellipticity coefficient are determined. The fractional bandwidth of the antenna is expressed via the improved limits of the fractional bandwidth of linearly polarized antennas. The limits of the fractional bandwidth of circularly polarized antennas are found. It is established that the maximum fractional bandwidth is reached if the ellipticity coefficient is slightly different from unity.

A strip array with a period small with respect to the wavelength is considered. The far field of this array is described by the nonlocal equivalent boundary conditions. It is shown with the help of the active power theorem that a near field transferring the active power along metal strips exists in the strip. The relationships connecting the far field on the strip surface with the active power of the near field are derived. It is demonstrated with the help of the Lorentz lemma that the near field has a nonzero quadratic shape and the relationships connecting it with the far field are obtained. A method of determination of the far field components on the array surface that are normal to the array plane is proposed. This method allows one to take into account the finite values of the quadratic forms.

A method for calculating the input impedance of a loop antenna (LA) located on a dielectric cylinder is developed. The integral equation (IE) for the unknown function of the current density distribution on the LA surface is obtained. A numerical method for the IE solution is described. An approximate formula for calculation of the LA input impedance is proposed. Plots of the input impedance on the LA length are given.

The universal interrelation between the maximum radar range and detection quality indices, namely, correct detection and false alarm probabilities, is found in an explicit form for different laws describing the distribution of the fluctuations of the effective target’s reflecting surface. The literature sources known to the authors even have no formulation of the given problem.

Technology of high-speed digitization of subnanosecond radio pulses, which is constructed via counting frame sampling, is discussed. The basis of the circuit architecture of the frame sampler involving the high-speed logic built around hyperfine complementary metal‒oxide‒semiconductor structures, as well as the basis of the array of picosecond delay lines, is formulated. It is demonstrated that the strobe-frame-sampling technology excludes high-frequency clocking and, consequently, minimizes the circuit power consumption and ensures picosecond time resolution of a recovered signal, corresponding to a sampling rate of up to 100 G sample/s implemented in practice. The software model of the frame sampler making it possible to investigate and parametrically synthesize the circuit topology of high-speed digital devices is developed in the Simulink environment.

A complete hydrodynamic pattern of a 3D relativistic electron beam in a nonuniform external magnetic field near the start surface of an arbitrary shape in the case of emission in the T-mode is constructed.

Problems of the synthesis of ultrawideband fixed phase shifters with a new structure of the electric circuit of the phase-shifting channel formed by means of connection of two identical elements consisting of weakly coupled stepped transmission lines with stubs have been solved. The advantage of the proposed structure over the available structures is shown.