Vol 63, No 3 (2018)

The excitation of the electromagnetic field in the chain of spherical metal nanoparticles by an arbitrary finite source is considered with the account of interactions of all nanoparticles. The contributions of plasmons and waves having the nonexponential spatial field dependence are distinguished. The dispersion of plasmon solutions is determined. The solution of the problem of summation of the diverging sum appearing when the local field is calculated is demonstrated.

The modern educational and scientific publications devoted to describing the principles of operation of radio-navigation systems are analyzed. As a result, contradictions in the used paradigm have been revealed. The new paradigm based on the definition of the timescale concept and eliminating the ascertained contradictions is introduced.

The sliding signal processing method interpreted as the range observation technique for syntheticaperture radar systems is discussed. The given method enables us to shift the observed ranges, thereby eliminating the maximum range restriction inherent to the standard de-ramping processing method. The operational capability of the method is demonstrated using radar images obtained from the single received implementation but exhibiting different detection ranges. It is revealed that the method under consideration is efficient upon reduction of nonlinear distortions caused by the nonideal operation of a voltage-controlled oscillator.

Heterodyne mixing with frequency modulation is employed for detection of torsional resonances of whiskers in rhombic TaS₃ (typical quasi-1D conductor) with charge-density wave (CDW). The dependences of both torque and the feedback signal of torsion on the internal properties of CDW are distinctive features of the proposed method. Sample placement in the vicinity of the electrode that serves as gate is unnecessary. Electromechanical and elastic properties of the CDW systems can be studied with the aid of the proposed method, at least, in the megahertz frequency range.

The possibility of expanding the dynamic range of microwave receivers used in passive radar due to circuit specificities of the input linear circuits is considered. Engineering calculations and graphic dependences of the dynamic range as well as an example of constructive implementation and the results of measuring the main parameters are presented. The conclusion is made on the feasibility and expediency of using in microwave receivers with an extended dynamic range of input linear circuits with disableable amplification stages.

A new type of the electron emission induced by a pulsed electric field with a strength of about 105 V/cm applied to the cathode made of graphene-like structures has been found. Pulsed currents of up to several hundred amperes have been obtained in a range of 1–5 ns. It has been found that the length of the current pulse depends on the strength of the electric field and decreases with an increase in this strength at a constant length of the electric field pulse; the electron emission time as well as the maximum emission current are determined by the value of the bound charge in the region of the cathode surface; and the process relaxation time after extraction of the emission current exceeds 300 ns.

The concept of an ideal quantum wire as a one-dimensional heterostructure whose spectrum contains exactly one bound level of the transverse dimension-quantized motion is introduced. The admissible range of the radii of such a wire is calculated. It is shown that only the quantization of longitudinal levels of motion makes it possible to calculate the energy released (absorbed) upon the fusion of two wires of the same material. In the traditional approach of a continuous longitudinal spectrum, this effect cannot be determined in principle. The influence of a longitudinal magnetic field on the spectrum of ideal wires is considered. It is established that a quantizing magnetic field destroys the unique level with negative energy (relative to the bottom of the continuous spectrum of the environment) but creates a family of positive bound Landau levels. In this case, the density of states in the wire is completely determined by the magnetic field, which makes it possible to control its spectrum and conductivity.

It has been proved that electromagnetic coupling coefficients K of resonators in stripline filters with homogeneous dielectric depend only on geometric parameters of the filter designs and are independent of relative permittivity ε_r (if the dielectric is two-layer, coefficients K depend only on geometric parameters of the filter designs and ratio ε_r2/ε_r1). It has been shown that the revealed earlier influence of permittivity ε_r and the operating frequency on K is only a consequence of the influence of the length of stripline resonators on K: the lesser is the length, the larger is coefficient K. It has been found that these propositions enable consideration of frequency characteristics of the same design of the bandpass filter in different frequency bands by changing εr and performing slight changes in outermost resonators. The results of computer simulation of the transfer of frequency characteristics of a stripline bandpass filter from 3 GHz to 6 and 12 GHz with retaining the fractional bandwidth and selectivity are presented.

A principle of modal filtering and an asymmetric modal filter with broad-side coupling are presented. Prototypes with different parameters are developed and fabricated. Experimental measurements and computer simulation are performed for the time response to a pulse with a duration of about 1 ns. It is shown that the simulated results are in agreement with the experimental data. Attenuation of the input pulse by a factor of 5 is demonstrated for the modal filter with optimal parameters for a 50-Ω circuit.

The influence of indirect transitions of Г-L and Г-Х types in the Brillouin zone on optical and electrophysical characteristics of heteroepitaxial layers of А₃В₅ compounds is estimated by the example of ternary (InGaAs) and quaternary (InGaAsP) compounds. It has been found that consideration of indirect transitions lowers the refractive index of semiconductor compounds by up to 15% in a narrow wavelength range of 0.4—0.6 μm.

The long-term stability of a 640x512 InSb focal plane array (FPA) with a pitch of 15 μm combined with a Stirling cooler and an interface block has been investigated.The dependences of the FPA correctability index on the operation time after a two-point correction of the irregularity have been obtained. The FPAs with two different circuits of the readout LSI cells that differ in the integration capacitance and transmission coefficients are considered. It has been found that, for the InSb FPA, the long-term stability is as high as several hours, which ensures continuous operation of the array in thermal imaging systems without additional calibrations.

The results of the development of a thermal imaging device based on the FEM10M photodetector produced by the Orion Research and Production Association are presented. As a result of the implementation of measures for improvement of the TPK-Z thermal imaging camera so as to comply with a domestic photodetector, the TPK-ZR thermal imaging device based on a domestic multirow array was developed, tuned, and tested. The minimum allowed temperature difference (MATD) and noise equivalent temperature difference (NETD) characteristics of the device are at least as good as the corresponding characteristics of a thermal imager using a foreign photodetector. The complex of image processing algorithms used in the TPK-ZR device makes it possible to obtain thermal images whose quality is not worse then the quality of the images obtained with the TPK-Z device. Further development of the obtained result can be implementation of a series of measures aimed at achieving full automation of calibration processes in the thermal imager.

The characteristics of focal plane arrays (FPAs) based on (quantum-well infrared photodetector) QWIP structures with 384 × 288 elements spaced at the intervals 25 μm are investigated. The difference in spectral and current–voltage characteristics is established for epitaxial QWIP wafers. The output signal is found to vary over the area of photosensitive elements with gradients in different directions. The photoelectric FPA parameters depend strongly on the temperature of the cooled assembly and the bias at the photosensitive element. The noise-equivalent temperature difference is 30 mK at the frame rate 120 Hz and the cooled assembly temperature 65 K.

Methods for calculation and control of impurity difference dose Q_а during the planar procedure of fabrication of avalanche photodiodes (APDs) based on heteroepitaxial InGaAs/InP structures are presented. The developed methods for the difference dose control in avalanche InGaAs/InP structures have been used at various stages of APD fabrication. It has been demonstrated that a tighter impurity dose control from the manufacturer of epitaxial structures, coordination of dose measurement procedures, and correction of diffusion processes for specific impurity doses are needed.