Microstrip patch antennas' two primary limitations are narrow bandwidth and harmonic interference, restricting their application for 2.4 GHz systems. Standard microstrip patch antennas typically only provide a fractional bandwidth between 2 % and 5 %. Because of the higher-order harmonic emissions from microstrip patch antennas, other wireless services may also experience interference from these devices. The proposed design, a pentagon-shaped patch antenna, handles both limitations through geometric innovation rather than complex multi-layer construction. When the base of pentagonal patch is positioned opposite the feed location, surface currents are distributed more uniformly than conventional rectangular geometries, thereby creating a broader resonant response. Strategic ground plane defects produce transmission nulls at harmonic frequencies and introduce additional resonances within the operating band. The introduction of a partial ground plane modifies the conventional cavity-backed radiation mechanism, resulting in monopole-like behavior that contributes to the observed wide impedance bandwidth. ANSYS HFSS 13 electromagnetic simulation verifies that the design provides a 1.85 GHz operational bandwidth between 1.32 GHz and 3.17 GHz, i. e. 82.22 % fractional bandwidth. The integrated defected ground structure forms wide 4.0 GHz to 12.0 GHz stop band. This modification disturbs ground plane current, which results in effective suppression of higher-order harmonics. The aforementioned combination, which is made on an inexpensive single-layer substrate, provides an ideal solution for spectrally pure, wideband wireless systems by doing away with the need for external decoupling components.

Ensuring stabilization of imaging equipment onboard unmanned aerial vehicles is a critical factor for the quality of aerial photography and spectrometric measurements, while objective comparative assessment of the effectiveness of various damping suspensions under real flight conditions remains a methodologically challenging task. Аim of this work was an experimental evaluation of the damping suspensions for UAV payloads effectiveness using integrated analysis of IMU data and computer vision. Studies were carried out on a system based on the Matrice 300 RTK unmanned aerial vehicle and a Raspberry Pi data logger. Damping suspensions operating in compression and tension were compared with rigid mounting. Methods used for video stream analysis to determine the amplitude-frequency characteristics of the imaging system orientation angles were described. Data processing methods from the inertial measurement unit to obtain information on the dynamics of orientation angles are indicated. A method for integrated processing of camera and IMU data is disclosed, which allows combining the low-frequency accuracy of optical flow with the broad bandwidth of inertial sensor measurements. The effectiveness of different types of damping suspensions was investigated at drone flight speeds from 1 to 7 m/s. It was found that the best performance was exhibited by a suspension with silicone dampers operating in compression, which reduced the energy of vibration processes by up to 77 % in the range from 0 to 85 Hz.

Multi-satellite orbital constellations enable transition from single, expensive spacecraft to unified platforms whose aggregate characteristics: global coverage, high reliability and resolution, ability to execute targeted tasks in parallel, flexibility, and scalability – significantly exceed capabilities of a single satellite. However lack of solutions for testing controlled deployment technologies for multi-spacecraft systems necessitates creation of an experimental framework with a step-by-step transition from ground tests to atmospheric and full-fledged orbital missions. This paper presents an architecture and experimental flight models of picosatellite-class spacecraft equipped with a deployment system designed to establish a short-duration probe constellation within the atmospheric flight environment. The developed platforms serve as a testbed for atmospheric experiments, with a primary focus on the validation of technologies for orbital formation flying missions. A launch adapter is implemented as a modular deployer unit featuring a hybrid springmotor separation mechanism capable of releasing two picosatellites in sequence. A portable ground receiving station with support for LoRa and FSK modulation schemes has been developed as part of the system. The paper provides a detailed description of the structural design solutions and fundamental circuit engineering approaches, and presents results of flight testing that demonstrate the applicability of the developed complex to atmospheric monitoring tasks and orbital mission design.

Airborne and spaceborne video-spectral imaging is a key tool for remote sensing of the Earth's surface and atmosphere; however, its accuracy critically depends on rigorous pre-flight calibration and verification of the instrumentation. The aim of this work is to develop and demonstrate a laboratory simulator capable of reproducing reference spectral scenes for the calibration and methodological validation of video-spectral remote sensing systems. The paper presents a laboratory simulator of airborne video spectral measurements of the Earth’s surface and atmosphere «Spectrosynthesizer» intended for testing and calibration of remote sensing instruments. The setup includes a spectral radiance forming subsystem based on an integrating (photometric) sphere with controllable LED and halogen sources, an image forming subsystem with movable test targets, and a registration subsystem. It is shown that the simulator can reproduce a given reference scene radiance spectrum specified either from radiative transfer calculations using the libRadTran model or from spectral library data, while the brightness non uniformity over the exit pupil and the temporal stability of the source meet the requirements for ground calibration of video spectral instruments. Using the BEKAS instrument as an example, the possibility of selecting operating modes under laboratory conditions and subsequently transferring these settings to real flight experiments is demonstrated, which confirms the potential of the proposed simulator for pre flight adjustment and methodological verification of video spectral Earth remote sensing systems.

Engaging the tapping mode in atomic force microscopy does not guarantee intermittent-contact interaction; depending on the parameters combination, the probe–sample system may instead exhibit non-contact (attractive) or mixed behavior. The mixed mode is undesirable due to scanning instability, known as bi-stability of probe oscillations. Aim of this work was to identify influence of probe (spring constant and quality factor), sample (the Young modulus, the Hamaker constant), and scanning (oscillation amplitude of the piezoelectric generator) parameters on the implementation of the bistable interaction mode, as well as to find conditions for achieving stable semi-contact interaction between the tip and sample. Еquation of probe tip oscillations was solved taking into account elastic-adhesive contact of the tip and the sample according to the Johnson–Kendall–Roberts model. Dependencies of the dynamic interaction characteristics of the probe and sample on the distance between them were obtained. These dependencies were analyzed to determine if there was switching between repulsive and attractive interaction modes. Results clearly demonstrated which of the dynamic interaction modes was realized with a particular combination of parameters. Conclusions are applicable in practice to choose probes. The following regularities were obtained. The elastic (actually semi-contact, tapping) interaction mode is realized with an increase in the amplitude of piezoelectric generator oscillations, higher values of the spring constant and quality factor of the probe, the Young modulus of the sample material and/or at lower values of the Hamaker constant of the sample. Higher values of the Hamaker constant and/or lower values of other parameters lead to a mixed interaction regime. Having even higher Hamaker constant and further reduction in other parameters, the adhesion mode (non-contact atomic force microscopy) can be realized.

Traditional destructive methods for evaluating the mechanical properties of materials require the preparation of test specimens, which precludes their application for assessing finished products. Thus, the development of non-destructive testing that provide reliable evaluation of a wide range of properties is a relevant task. Aim of this work was to present the functional capabilities and confirm the effectiveness of the developed UIM-1 measuring system for comprehensive study of mechanical properties of materials using the instrumented indentation method. Method is based on the continuous recording of the "contact force – penetration depth" diagram. The system is equipped with an actuator providing a load of up to 2000 N, a strain gauge force sensor (error ≤ ±1 %), and a photoelectric displacement sensor (resolution 0.1 μm). The implemented measurement procedures comply with ISO 14577-1, STB 2495-2017, GOST 22761-77 and GOST 22762-77. Analysis of the indentation diagram allows determining Brinell and Rockwell hardness without optical measurement of the imprint, elastic modulus (70–200 GPa), ultimate tensile strength (380– 1700 MPa), creep, relaxation, plasticity and anisotropy coefficient. The UIM-1 system is a versatile nondestructive testing tool that provides a set of interrelated mechanical characteristics of materials within a single test.

Polyolefins are widespreadly used in strategically important industries due to their high thermal, sound and vibration insulation properties. During the process of application these materials are subjected to various mechanical influences leading to their deformation and changes in properties. Aim of the work was to study the elastic properties of closed-cell polyolefin foam sheets with different foaming multiplicities under static tension using the acoustic shadow amplitude method. The paper presents a method for experimental studies of an acoustic wave transmission coefficient a static tensile load, based on the use of an amplitude shadow method. During the method implementation amplitude of the acoustic wave passed through the polyolefin foam sheet and the value of the static tensile stress are simultaneously recorded. Studies of the acoustic wave transmission coefficient were carried out on sheets of closed-cell polyolefin foam of the ISOLON 500 brand with different foaming multiplicity and thickness. It was shown that two regions are observed during the stretching of sheets of polyolefin foam: 1) the region of elasticity, in which changes both in the relative elongation of the sample and in the transmission coefficient of the acoustic wave occur linearly, and 2) the region of fluidity, in which a nonlinear dependence is observed. Results obtained were used to determine the destructive tensile stress, the modulus of elasticity, and the structurally sensitive parameter of acoustic strain measurement, the coefficient of elastic-acoustic coupling in transmission, while a significant dependence was observed on the direction of application of the tensile load (along and across the sheet). To confirm these areas of deformation of styrofoam sheets, the recoverability of samples under loads of 30 % and 70 % of the destructive tensile stress was studied. The obtained results confirmed that at 30 % of the ultimate tensile stress, the elastic region is observed, at 70 % of the ultimate tensile stress – the yield region; the results also enabled estimation of the specimens’ elastic properties recovery degree after removal of the tensile load.

Measuring the intermode dispersion in short sections (from units to tens meters in length) of multimode optical fibers is often an actual task. Мethods used based on Mach–Zehnder interferometers have typical disadvantages inherent for interferometric measurement methods. Рurpose of the paper was to develop and experimentally implement a recirculation method for determining the intermode dispersion in short sections of multimode optical fibers and to estimate the measurement error. The recirculation method for measuring the intermode dispersion of multimode optical fibers has been studied. This method consists of measuring the difference in recirculation frequencies, which are formed by the "fast" modes propagating along the optical axis of the fiber and the "slowest" ones propagating at the maximum angle to the axis. An experimental stand of an optoelectronic recirculation system has been developed, providing circulation of a single optical pulse with periodic restoration in amplitude, shape and duration. Dependences of the relative longterm instability of the recirculation frequency with a change in the value of the constant component of the pump current of a semiconductor injection laser and the comparator response threshold have been obtained. It was found that the recirculation frequency stabilizes no earlier than 20 min after the start of recirculation under the experimental conditions, while the maximum value of the relative long-term instability was achieved no more than 3.5·10–6 at a length of multimode optical fibers as 50 m. The analysis took into account change in the response delay of the avalanche photodiode associated with the increase in the avalanche multiplication coefficient. Efficiency of the proposed method in determining the intermode dispersion of short sections of multimode optical fibers was shown; for the test gradient fiber Corning Inficor 600 50/125, the error was 7 %. Using the obtained data and solving the inverse problem of restoring the refractive index profile, it was found that for this type of multimode optical fibers, the refractive index profile parameter was equal to α = 1.96.

Nowadays use of freeform surfaces in optical systems for various purposes – from mobile displays to space optics – becomes increasingly popular. This design solution makes it possible to create a system with a minimum number of components, low weight, and high image quality. However, as the surfaces become more complex, problems arise with their control. Aim of the study was to develop an algorithm for inspecting such surfaces using a coordinate measuring machine and to formulate technical requirements for the measurement process. An analysis of the advantages of freeform optical surfaces is presented. It is noted that due to lack of symmetry and variable profile height, classical measurement methods are not applicable for such parts. The inspection algorithm using a coordinate measuring machine involves two main approaches: high-performance "fast scanning" to assess overall deviations from the nominal value, and more accurate but time-consuming sectional scanning which allows obtaining detailed quantitative data on the surface profile. The paper is mainly focused to the measurement algorithm and process requirements: preliminary temperature adaptation of equipment, mandatory calibration of probes using a ceramic reference ball, and software-controlled limitation of tool movements to protect polished surfaces. The proposed algorithm, based on the use of CAD-models, makes it possible to achieve the required accuracy of monitoring complex surfaces on standard shop‑floor equipment, despite significant time costs compared to aspherical surfaces’ measuring.