Journal of Communications Technology and Electronics

We present a miniature two-port resonator with an Ω-shaped coplanar coil designed to excite optically detected magnetic resonance at 2.87 GHz in a diamond sample hosting nitrogen-vacancy (NV-centers). The resonator architecture was chosen because its fabrication does not require patterning planar structures on the diamond. The dimensions were calculated, and electromagnetic simulations using the finite-element method were performed to obtain the S-parameters both without and with the diamond included. After fabrication, the S-parameters were measured with a vector network analyzer. For the resonator with the diamond mounted on it, at 2.87 GHz we obtained a minimum reflection coefficient |S₁₁| ≈ −24.85 dB, a loaded quality factor Q_H ≈ 44.2, and a −3 dB bandwidth of about 66 MHz.

A waveguide structure is presented for the RF front end of a sideband-separating heterodyne receiver operating in the 0.8–1 mm band, based on two single-ended superconductor–insulator–superconductor (SIS) mixers. The microwave properties of the following elements are investigated: a 90° quadrature hybrid, a directional coupler, a T-junction power divider, and a transition section; their amplitude and phase frequency responses are calculated. For the 90° hybrid, the amplitude imbalance does not exceed 1.5 dB, the phase imbalance including reflections stays within 2°, and both return loss and isolation are better than –25 dB. In addition, a full waveguide assembly was simulated with the SIS-mixer reflections taken into account. The resulting sideband rejection of the entire waveguide structure, including mixer reflections, is no worse than 20 dB across the band.

The possibility of increasing the sensitivity of the marine electrode sensor several times when receiving long-term narrow-band low-frequency radio signals is shown due to compensation for the noise component caused by pulsations in the speed of movement of the liquid relative to the sensor electrodes.

The interaction of the resonant modes in the exchange-coupled two-layer canted antiferromagnet/ferromagnet heterostructure has been theoretically investigated. Expressions describing the dependence of the resonant frequencies of magnetization oscillations on the external magnetic field have been obtained by the method of Hamiltonian formalism. The effect of the coupling strength between the ferro- and antiferromagnetic layers on the width of the anti-crossing gap between the resonant mode of ferromagnet and the soft mode of antiferromagnet and on the magnitude of the external magnetic field at which hybridization is observed has been investigated. It is shown that increase in the antiferromagnet/ferromagnet exchange coupling constant leads to increase in the width of the anti-crossing gap and the magnitude of the external magnetic field at which hybridization is observed.

A scalable method for the synthesis of zinc ferrites Zn_xFe_3–xO₄ (with a doping degree of x = 0; 0.125; 0.25; 0.5; 1) by controlled oxidation of an iron and zinc mixture during mechanochemical synthesis is proposed. Comprehensive studies of the processes occurring during mechanochemical synthesis were carried out using X-ray diffraction analysis, Mössbauer spectroscopy and measurement of magnetic properties. It was shown that zinc ions in the synthesized ferrites occupy both tetrahedral and octahedral positions, which leads to a decrease in the saturation magnetization to 44 Am²/kg with an increase in the doping degree to x = 1. An increase in the doping degree leads to a monotonic decrease in the coercivity to 40.3 Oe, which can be used to obtain materials with desired properties.

This work presents a comprehensive study of the correlation between the structural/ferroelectric properties of Hf_0.5Zr_0.5O₂ (HZO) thin films – the functional layers for ferroelectric non-volatile memory – and their thickness in the 5–10 nm range. X-ray diffraction analysis revealed the predominant presence of the polar orthorhombic Pca _{2 1} phase in all samples. The highest content of (002)-oriented domains, corresponding to the vertical orientation of the polar axis, was found in the 8 nm thick films. Electrical measurements demonstrated an inverse relationship between film thickness and the breakdown field, which varied from 6.5 MV/cm (5 nm) to 4.5 MV/cm (10 nm). A pronounced improvement in switching endurance was observed with decreasing thickness: films of 5–6 nm maintained stable ferroelectric characteristics up to 10⁹–10¹⁰ switching cycles at an electric field of 3.0 MV/cm. Analysis of the I–V characteristic dynamics during wake-up with bipolar pulses showed that the parameter stabilization process is accompanied by a merging of the switching current peaks and an increase in the remanent polarization up to 30 μC/cm². It was established that degradation in thin films begins significantly later (after >10⁶ cycles) than in thick ones (10⁴–10⁵ cycles). This is presumably associated with the inhibitory effect of the amorphous phase on the kinetics of diffusion and drift of charged defects. The obtained results are valuable for the development of reliable ferroelectric memory devices, demonstrating an optimal combination of high remanent polarization and cycling stability in ultra-thin HZO films.

The excitation of pseudowedge waves in piezoelectric wedges using interdigital transducers on their surface has been investigated. The frequency dependence of propagating waves in a wedge made of lithium niobate on the orientation of the crystal under various boundary conditions has been calculated. This allowed for an evaluation of the effect of wedge face metallization on the propagation characteristics of both wedge and surface acoustic waves within it. Two-dimensional and three-dimensional finite element models were developed to study the conditions for the existence of leaky wedge waves and the possibility of their excitation. The ranges of crystal orientations where pseudowedge waves are observed were determined. Two widely used cuts of lithium niobate were considered: Z-cut and Y-cut. The effect of non-reciprocal wave propagation in lithium niobate was demonstrated for two adjacent rectangular wedges with faces formed by equivalent crystallographic planes.

This paper presents a reader transceiver for UHF digital tagging and identification systems, designed for fabrication using 180 nm domestic CMOS technology. The architecture of the transceiver and it main IP-blocks are considered. The results of parameter calculations obtained from CAD simulations are presented. The possibility of using the transceiver in ISO 18000-6 standard systems has been confirmed.