Boris Afanasievich Belyaev

A Halbach magnetic system has been developed that generates a uniform field in the plane of thin magnetic films (TMFs) produced using magnetron sputtering technology. The magnetic field of the system is approximately 60 times stronger than the gradient field of the magnetron over an area of 60 × 48 mm². This significantly reduces the nonuniformity of the TMF magnetic characteristic distribution over the sample area. The system is constructed using four magnetic bars, each composed of eight cobalt–samarium magnets measuring 10 × 10 × 10 mm. The reduction in nonuniformity of the magnetic characteristic distribution over the TMF area has been confirmed by measurements using a scanning ferromagnetic resonance spectrometer on 12 samples, each ~55 nm thick, obtained by simultaneous sputtering a Ni₈₀Fe₂₀ target onto 12 × 12 × 0.5 mm quartz glass substrates.

The characteristics of a planar optical resonator made of quartz glass surrounded by silver mirrors have been studied when their thickness was varied. The frequency responses of band-pass filters on planar structures obtained by vacuum deposition on quartz glass (SiO₂) substrates of three quartz layers, which are half-wavelength resonators separated from each other, from the substrate, and from the free space by four layers of silver (Ag), were measured. The thicknesses of the Ag and SiO₂ layers were determined on the basis of the specified filter passband parameters by synthesizing one-dimensional models using electrodynamic analysis. The experimental frequency dependencies of the real and imaginary parts of the complex permittivity of silver have been considered. The measured frequency responses of the manufactured prototypes of red, green, and violet filters are in good agreement with the characteristics obtained during synthesis. Systematic studies of filters with a central passband frequency of 300 THz (wavelength of 1 µm) and a relative bandwidth of 2‒20%, containing from 3 to 6 resonators, have been carried out. The high performance of the developed filters demonstrates their potential for their use in optical devices.

The coupling coefficients of disk-shaped dielectric resonators interacting through a two-conductors stripline resonator placed in the rectangular diaphragm of a metallic case have been studied. It has been found that the capacitive interaction of the resonators changes to inductive when the eigenfrequency of the stripline resonator is lower than those of dielectric resonators. This feature makes it possible to design small-size multicavity bandpass filters with additional capacitive and inductive couplings, which are expected to offer a high selectivity and a small spread of the group delay time in the passband. Using the electrodynamic analysis of a 3D model, a small-size 12th-order filter with center frequency f₀ = 3.925 GHz of the 45-MHz-wide passband has been synthesized. The width of the passband was measured at a level of 1 dB from the minimal loss level. In the designed filter, a two-conductors stripline resonator is used to provide differing-in-sign additional couplings between disk-shaped resonators and couple feed lines at the input and output. This improves the filter manufacturability and raises the mechanical strength of the device. The characteristics of the filter confirm that the proposed design is promising for creating small-size frequency-selective devices for space communication.

A channel bandpass filter of the satellite communication multiplexer has been developed around a design consisting of 12 coaxial resonators. To cut the group delay time and considerably improve the selectivity of the device, two additional inductive and two additional capacitive couplings between nonadjacent resonators have been applied. This makes it possible to provide two zero poles near the right and left edges of the passband. To reduce the spread of the passband’s transmission factor, a special method was applied that allows one to somewhat decrease reflection losses near the edges of the bandpass of the filter. This, in combination with the electrodynamic analysis of a 3D model developed for the given design, makes it possible to synthesize a small-size filter with the center frequency of the bandpass f₀ = 4 GHz and its width Δf = 45 MHz measured at a level of 0.8 dB from minimal losses. The measured characteristics of the filter prototype are in good agreement with calculation data.

The parameters of a resonator consisting of two dielectric plates with gratings of strip conductors between the layers in the form of squares, and on the outer surfaces in the form of square meshes having the same subwavelength period, have been determined. The quality (Q) factor of the resonator, which has been measured at the normal wave incidence, is determined by the ratio of the widths of the internal and external conductors. Using electrodynamic analysis of a 3D resonator model, the propagation of plane linearly polarized electromagnetic waves when their angle of incidence φ deviates from the normal to the plane of the layered structure has been studied. It is found that for the parallel polarization of the wave, the Q factor of the observed half-wave resonance with increasing φ first drops to a minimum when approaching the Brewster angle, and then increases as φ → 90°. In the case of the perpendicular polarization of the wave, the Q factor of the half-wave resonance gradually increases with increasing φ, approaching the maximum value at φ → 90°.

An inspection probe is the key component of a scanning ferromagnetic resonance spectrometer, which is used to measure spectra of electromagnetic radiation absorption in local areas of thin magnetic films. The degree of locality is determined by the area of the measuring aperture in a probe (0.1–2.2 mm²). The spectrometer sensitivity has been significantly increased by miniaturizing the oscillating circuit with a high intrinsic quality factor of the autodyne oscillator and by replacing the round measuring aperture of the probe head with a square one. The square shape of the measuring aperture increases the homogeneity of the high-frequency magnetic field distribution in it. A set of replaceable probes with a required pitch has been designed to cover the frequency range of 0.1–4.0 GHz. The signal-to-noise ratio of a probe with an aperture area 1.0 mm², measured on a permalloy film with a thickness of 2 nm is 8 dB or more. It is shown that the effective saturation magnetization monotonically reaches the saturation M_S = 843 G with frequency rise and abnormally increases by a factor of ~1.6, to M_S = 1359 G at low frequencies. The applicability of the developed probes to study the nature of formation and the peculiarities of the magnetic-inhomogeneity distribution over a sample area is demonstrated by using 25-nm-thick permalloy films (dimensions, 10 × 10 mm²) deposited in a dc magnetic field on monocrystalline langasite substrates.

Frequency-selective devices with ultra-high frequencies bandpass filters, in particular, are among the most important elements of tropospheric and space communication systems and special radio equipment. The characteristics of all the studied microwave devices were obtained by numerical electrodynamic analysis of their 3D models. While modeling, substrates with the same permittivity ε = 9,8, thickness h = 1 mm were used to compare the obtained data objectively. The first construction consists of three electromagnetically coupled pin microstrip quarter-wave resonators. The considered ultra-wideband filter is configured in such a way that the maximum level of power reflection in its passband does not exceed 14 dB, while its order N equals 9. The device has relatively high frequency-selective properties, however, the asymmetric shape of its frequency response is an obvious disadvantage. To eliminate the above-mentioned drawback of the filter, it is necessary to organize the inductive and capacitive coupling between its multimode resonators so that they relatively compensate each other at certain frequencies. The second construction meets these requirements: its external resonators, as well as those in the first device, are quarter-wave three-mode, and the internal resonator is half-wave two-mode. Such an ultra-wideband filter has a high steepness of both slopes of the frequency response, due not only to the eighth order, but also to the attenuation poles located on both sides of the passband. At the same time, compared to the filter implemented only based on three-mode resonators, it is also 16% smaller. With a considerable increase in the number of two-mode and three-mode hairpin resonators used in the designs of microstrip filters, the number of possible combinations of these resonators grows significantly. At the same time, the frequency-selective properties of such devices can differ. The third construction includes a pair of external three-mode resonators and a pair of internal two-mode resonators, so the increase in the number of filter sections in this case is due to the increase in the number of two-mode half-wave resonators in the design. At the same time, such an ultra-wideband filter of the tenth order also has high frequency-selective properties, but its significant improvement, in comparison with the selective properties of the second filter, is not observed. The fourth construction is implemented with a central two-mode resonator, on both sides of which there is a pair of three-mode resonators, so the increase in the number of sections to five in this case is due to the increase in the number of three-mode resonators. Such an ultra-wideband filter of the fourteenth order stands out from all the devices considered above by its higher frequency-selective properties. So, it is worth noting the greater steepness of the low-frequency slope of its passband, as well as the shape of its frequency response, which is quite close to symmetrical. Therefore, microstrip filters based on hairpin resonators were investigated. The developed devices have not only extended passbands, but also high frequency-selective properties. At the same time, the results of the research revealed that the designs of filters with a central two-mode resonator with three-mode ones on both sides of which, single or paired, are distinguished by frequency response shape close to symmetrical, due to the presence of attenuation poles on it.

Из пермаллоевых (Fe20 Ni80 ) пленок толщиной 50, 100 и 200 нм, полученных магнетронным напылением на подложки из кварцевого стекла, методом лазерной литографии изготавливались полоски длиной 20 мм и шириной от 0.1 до 2 мм. В первой серии образцов одноосная магнитная анизотропия, наведенная присутствием во время напыления постоянного магнитного поля в плоскости пленок, ориентирована вдоль длинных осей полосок, а во второй серии ортогонально им. Анизотропные свойства образцов определялись из угловых зависимостей полей ферромагнитного резонанса, измеряемых на сканирующем спектрометре. Обнаружено, что в первой серии образцов с уменьшением ширины полосок анизотропия монотонно увеличивается в несколько раз, почти не изменяя своего направления. У образцов второй серии она сначала уменьшается почти до нуля при определенной ширине полоски, а затем быстро растет, одновременно поворачиваясь на ∼ 90◦. Феноменологический расчет одноосной анизотропии однородно намагниченных пленочных полосок хорошо согласуется с экспериментом.

Designs of optical bandpass filters have been developed on planar structures, which were obtained by vacuum deposition onto quartz glass (SiO2) substrates of three layers also of quartz, which are half-wavelength resonators separated from each other, from free space, and from the substrate by four layers of silver (Ag). The thicknesses of the Ag and SiO2 layers were determined based on the given parameters of the filter passband by parametric synthesis of one-dimensional models using electrodynamic analysis. In this case, experimental frequency dependences of the real and imaginary parts of the permittivity of silver were used. The measured frequency responses of the manufactured prototypes of red, green and purple filters are in good agreement with the responses obtained during synthesis.

Using electrodynamic analysis of the 3D model of a plane-parallel ideal dielectric plate, the propagation of plane linearly polarized electromagnetic waves is investigated in the case when their angle of incidence φ deviates from the normal to the plane of the plate. It is found that in the case of parallel polarization, when the electric field vector lies in the plane of incidence and magnetic field vector is parallel to the plane of plate, the Q factor of the observed half-wave resonance first decreases to its minimal value with increasing φ as the Brewster angle is approached, and then increases, tending to infinity as φ → 90°. In the case of perpendicular polarization, when the magnetic field vector lies in the plane of incidence and the electric field vector is parallel to the plane of the plate, the Q factor of the half-wave resonance gradually increases with increasing φ, also tending to infinity as φ → 90°. However, the dependences of the observed monotonic increase in the resonance frequencies with the angle of incidence are identical for both polarizations. The results of experiment with a plane-parallel plate made of ultrahigh molecular weight polyethylene with a dielectric constant of 2.5, which has been performed using broadband horn antennas, are in good agreement with the results of the electrodynamic calculation based on the 3D model.