Том 61, № 3 (2016)

A new version of the modified method of discrete sources (MMDSs) is proposed for the solution of the 2D and 3D (vector) problems of diffraction of the point source field by a dielectric body. The case when the source is located at a small distance from a scatterer is considered. The method is tested for the example of the problem of diffraction of a point source field by an infinite dielectric cylinder and a dielectric sphere. It is shown that the discrepancy of the boundary conditions is substantially lower when the suggested variant of the MMDSs is used for various geometries of a scatterer.

The possibility of solution of the problem of wave propagation through an interface of two dissipative media with the help of a trigonometric vector model is shown. Two invariants independent of the dissipation of these media are revealed: (i) the sum of projections of vectors of reflected and transmitted waves onto the polar axis, which is equal to the projection of the vector of the incident wave onto the same axis, and (ii) the sum of projections of vectors of these waves onto the normal to the polar axis, which is equal to zero.

The further development of the concept related to passive direction finders (DFs) equipped with an energy-measurement channel is implemented. The goniometric-energy method of passive detection and ranging, according to which the slant distance to a target can be determined from its emission in the form of a constant-envelope signal, is generated as applied to the given stationary DFs. In the spatial case, the passive location problem is solved using the time-dependent behavior of the generalized radiolocation coefficient. A complex algorithm is constructed with the aim at jointly estimating the given coefficient and the detection range under the condition that rectilinear uniform motion of an emitting target is simulated on the estimation interval. The computational experiment results are presented to confirm the possibility of practical application of the proposed method.

The features of Gaussian pulse reflection from a nonlinear medium with the resonance frequency dependence of permittivity are investigated. The results of numerical analysis of the equations describing the light-field distribution in reflected pulses with s and p polarizations are presented. The influence of the intensity, incidence angle, carrier frequency, and incident-pulse duration on the reflected pulse envelope shape is discussed.

Signal generation in systems with crossed electric and magnetic fields is demonstrated. The generation effect is obtained in an ac magnetic field.

Two approximations of the geometrized theory are constructed, which make it possible to consider nonparaxial plane relativistic beams emitted in the T-mode with an improved description of the nearcathode region with allowance for the third derivatives of the electric field on the emitting surface and the second derivative of its curvature. In the region of influence of the singularity, the cathode shape and the field on the cathode are related to the configuration of the basic current tube and the variation of the potential on it. The results are adapted to the case of a relativistic planar gyrotron.

An approach to the construction of wideband bandpass filters of microstrip and stripline designs, which have an extended stopband and can incorporate lumped capacitors, is proposed. This approach is based on resonators with the enhanced frequency diversity of fundamental and parasitic resonance frequencies and coupling circuits formed according to an assigned rule. The potential of the filters achieved due to the proposed technique is established. In particular, a very wide passband whose ratio of cuttoff frequencies is 5: 1, as well as the stopband greater than an octave at a level of 40 dB, is demostrated to be attainable. When the passband is narrower, the stopband can exceed two octaves. The given approach can be applied to filters operating in a broad frequency range, including to that corresponding to centimeter and meter waves. The experimental data are presented.

The theory making it possible to rather accurately predict a complete set of characteristics (signals, noises, and photoelectric parameters) inherent to all components of the photodiode-based focal plane array (FPA) under design and optimize its parameters has been developed. The theory relies on a new approach to the determination of FPA irradiance, which ensures its calculations at any shape of the diaphragm in the light-insulating shield. Both staring and scanning FPAs, the latter of which operate under the condition of time delay and accumulation, are discussed. The theory has been verified using a 320 × 256 FPA. The calculated dependences of the signals and noises of photoelectric components are compared with the experimental values obtained at different accumulation times and background irradiation temperatures. The theoretical data are revealed to be in complete agreement with the experiment, confirming the model validity. The theory will be undoubtedly useful for designers, manufacturers, and users of FPAs. The model can easily be extended to systems with FPAs.

The results of investigation of profiles formed by ion-beam etching of semiconductor structures through a photolithographic mask are presented. The minimum dimensions of unmasked regions on the surfaces of two studied structures are 2 and 5 μm, respectively. It is demonstrated that the etching rate reduces with reduction in the width of the unmasked gap. The effect of reflection of the ion beam from vertical walls formed during etching may be used for fabrication of submicron separating mesaregions.

The results of measurements of the root-mean-square (rms) surface roughness of CdZnTe substrates by confocal microscopy (CM), atomic force microscopy (AFM), and X-ray reflectometry (XRR) are compared. It is determined that CM yields the highest rms roughness values, AFM assumes an intermediate position, and XRR measurements produce results that are an order of magnitude lower than those obtained with the use of the other two techniques. It is demonstrated that CM rms roughness values depend to a considerable extent on the type of the microscope objective used in experiments. Probable reasons for the discrepancy between the obtained results are discussed.

The temperature dependence of the minority charge carriers diffusion length in the active photosensitive layer of a matrix photodetector based on MCT heteroepitaxial structure grown by molecular beam epitaxy is studied.

A comparative analysis of the correlators of steady-state thermal and photoinduced stochastic fields (SFs) of concentrations and currents of mobile charge carriers in IR photodiodes and homogeneous semiconductors is presented. It is demonstrated that the correlators of thermal and photoinduced SFs of concentrations of mobile charge carriers are determined using conceptually identical expressions for any structure of the p–n junction and arbitrary polarity of applied voltage whereas the correlators of the SFs of photoinduced and dark currents are determined using conceptually identical expressions only for the reverse-biased p–n junction with a relatively wide base.