COMPARISON OF THE PARAMETERS OF SIGNALS WITH EXTERNAL ILLUMINATION FOR SUPERVISION OF THE AREA FOR THE PROTECTION OF IMPORTANT STATE OBJECTS

In modern conditions, it becomes necessary to create security systems, surveillance systems, anti-terrorist systems that carry out covert detection and surveillance of small-sized ground objects, including biological ones. Traditionally used single-position radars are ineffective in conditions of a large number of reflections that interfere with and low speed of movement of detected objects (people). The use of several such radars is impractical due to their rather high complexity and cost. In addition, it is impossible to ensure the secrecy of such systems. The construction of radar surveillance systems in the form of semi-active bistatic, including educational, radar systems is promising for the described conditions. One of the important issues in the construction of semi-active bistatic systems is the substantiation of the parameters of external illumination signals and the assessment of the attainable characteristics of such systems when using them. The analysis and definition of the requirements for the characteristics of the illumination signals is carried out. In addition, consider the features of using signals from modern emitting systems in semi-active radars. The basic parameters of the signals are given – the bandwidth, the pulse duration (spectrum width), the power at the transmitter output, the frequency range in which the system operates. The advantages and disadvantages of semi-active radar stations (SA RS), which use such signals, are described. Variants of semi-active bistatic systems with external illumination are determined. The widespread use of modern digital language and telecommunication systems provides the SA RS with effective illumination signals with good correlation properties, which makes it possible to obtain the necessary technical characteristics in a variety of application condition

Study of the secondary characteristics of the bistatic scattering of a combined object in a covert radar surveillance system

The emergence of new means of attack, reconnaissance and methods of sabotage imposes special requirements on the technical means of protecting important state facilities (ISF). Modern trends in the construction of ISF physical protection systems are the integration of engineering barriers, perimeter signaling and detection tools. Detection tools should provide covert receipt of information about the approach of the intruder in "distant" intrigues. To do this, it is possible to use technical means built on the principle of semi-active bistatic radar with an external illumination source. However, in order to identify intruders in the ISF protection zone, it is necessary to have a priori information about the radar visibility of the combined location objects. The combined object is typically a complex object having both metallic and dielectric elements. To this end, a technique has been developed for estimating the radar cross-section (RCS) of combined objects in the field of external illumination. The electromagnetic field (EMF) scattered by a combined object in the meter and decimeter wavelength ranges is calculated as a coherent sum of fields, taking into account their phase, scattered by its metal and dielectric elements. This made it possible to take into account the electromagnetic interaction of the elements of the combined object. The method of integral equations (IE) was used to find the current density and magnetic field strength. The scatter diagrams of the person-intruder, the person-intruder in personal armor protection (PAP) under different conditions of irradiation and reception and illumination frequencies are obtained and analyzed. This made it possible to evaluate the effect of metallic elements on the scatter diagram of the combined object. The obtained a priori information is of significant practical importance at the stage of optimizing signal processing algorithms and designing new means of covert detectio

Effect of Spin Injection from Colossal Magnetoresistance Material into superconducting Thin Film of YBa2Cu3O7-

By specific design of the sample, in which SrTiO3 substrate is fully covered by a thin film of the colossal magnetoresistive material La0.67Ca0.33MnO3 (LCMO) and the latter is partially covered by high-temperature superconductor YBa2Cu3O7- (YBCO), and by using multiple current and voltage contacts, direct evidence of spin injection from LCMO to YBCO is obtained. It is found that spin-polarized electrons injected from LCMO strongly influence not only superconducting, but also normal state of YBCO. The effect of deposition conditions of LCMO and YBCO and the quality of the interface on the spin injection efficiency is clarified. A surprising peak in the temperature dependence of resistance seen on ex-situ sample is explained as combination of two effects: strong influence of spinpolarized electrons on superconductor just below its critical temperature and the interface-controlled shift of Curie temperature of LCMO to low temperatures. Considering expected use of LCMO and YBCO in composite quantum computation circuits, a possibility of their combination with another advanced quantum material, graphene, is explored

Effect of colossal magnetoresistance material La0.67Ca0.33MnO3 on superconducting properties of YBa2Cu3O7-δ thin films

By specific design of the sample, in which SrTiO3 substrate is fully covered by a thin layer of the colossal magnetoresistive material La0.67Ca0.33MnO3 (LCMO) and the latter is partially covered by high-temperature superconductor YBa2Cu3O7-δ (YBCO), and by using multiple current and voltage contacts, direct evidence of the strong effect of LCMO on YBCO is obtained. It is found that LCMO strongly influences not only superconducting, but also normal state of YBCO, and it is argued that this is a consequence of the spin injection from the former to the latter. The effect of the deposition conditions and crystal orientation of YBCO layer on this effect is clarified. A surprising peak in the temperature dependence of resistance seen in ex-situ ab-plane oriented sample is explained as a combination of two effects: influence of spin-polarized electrons on superconductor below its critical temperature and the interface-controlled shift of Curie temperature of LCMO to low temperatures. Considering expected use of LCMO and YBCO in composite quantum computation circuits, their combination with another advanced quantum material, graphene, is explored

Comparison of the Parameters of Signals with External Illumination for Supervision of the Area for the Protection of Important State Objects

In modern conditions, it becomes necessary to create security systems, surveillance systems, anti-terrorist systems that carry out covert detection and surveillance of small-sized ground objects, including biological ones. Traditionally used single-position radars are ineffective in conditions of a large number of reflections that interfere with and low speed of movement of detected objects (people). The use of several such radars is impractical due to their rather high complexity and cost. In addition, it is impossible to ensure the secrecy of such systems. The construction of radar surveillance systems in the form of semi-active bistatic, including educational, radar systems is promising for the described conditions. One of the important issues in the construction of semi-active bistatic systems is the substantiation of the parameters of external illumination signals and the assessment of the attainable characteristics of such systems when using them. The analysis and definition of the requirements for the characteristics of the illumination signals is carried out. In addition, consider the features of using signals from modern emitting systems in semi-active radars. The basic parameters of the signals are given – the bandwidth, the pulse duration (spectrum width), the power at the transmitter output, the frequency range in which the system operates. The advantages and disadvantages of semi-active radar stations (SA RS), which use such signals, are described. Variants of semi-active bistatic systems with external illumination are determined. The widespread use of modern digital language and telecommunication systems provides the SA RS with effective illumination signals with good correlation properties, which makes it possible to obtain the necessary technical characteristics in a variety of application condition

Flexible Magnetoreceptors: Flexible Magnetoreceptor with Tunable Intrinsic Logic for On-Skin Touchless Human-Machine Interfaces (Adv. Funct. Mater. 25/2021)

In article number 2101089, Gaspare Varvaro, Denys Makarov, and co-workers present skin-compliant touchless interactive devices based on spin-valves with out-of-plane sensitivity to magnetic fields and with tunable logic characteristics. This technology will pave the way towards magnetoreceptive human-machine interfaces or virtual- and augmented reality applications, which are intuitive to use, energy efficient, and insensitive to external magnetic disturbances

Three-dimensional magnetic nanotextures with high-order vorticity in soft magnetic wireframes

Additive nanotechnology enable curvilinear and three-dimensional (3D) magnetic architectures with tunable topology and functionalities surpassing their planar counterparts. Here, we experimentally reveal that 3D soft magnetic wireframe structures resemble compact manifolds and accommodate magnetic textures of high order vorticity determined by the Euler characteristic, χ. We demonstrate that self-standing magnetic tetrapods (homeomorphic to a sphere; χ = + 2) support six surface topological solitons, namely four vortices and two antivortices, with a total vorticity of + 2 equal to its Euler characteristic. Alternatively, wireframe structures with one loop (homeomorphic to a torus; χ = 0) possess equal number of vortices and antivortices, which is relevant for spin-wave splitters and 3D magnonics. Subsequent introduction of n holes into the wireframe geometry (homeomorphic to an n-torus; χ < 0) enables the accommodation of a virtually unlimited number of antivortices, which suggests their usefulness for non-conventional (e.g., reservoir) computation. Furthermore, complex stray-field topologies around these objects are of interest for superconducting electronics, particle trapping and biomedical applications