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Exact mathematic models were developed for traveling wave antennas with a constant slot width based on the dyadic Green function, taking into account both the main and cross-polarization components of the field in the far radiation zone. The possibility of using these models as basic models for studying the electrodynamic properties of traveling wave antennas with a different slot configuration (linearly, exponentially tapering, etc.) is justified. The influence of the geometric parameters of the investigated traveling wave antennas on their characteristics was studied by means of using the established mathematic models. It has been found that in the electrodynamic E plane, with an increase of the length and width of the slot, the main beam of the radiation pattern narrows, which leads to an increase the directed properties of the antennas. In the electrodynamic Hplane, the width of the main beam of radiation pattern decreases only as the length of the slot of traveling wave antennas increases and does not depend on its width in practice. It was shown that the established theory results of the study are well consistent with the results of experiments, which also revealed the limitations of the applicability of the developed models. Analysis of traveling wave antennas characteristics was carried out at central frequency of 10 GHz in the frequency range of 8-12 GHz.

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Background. Symmetric slot lines on a perfectly reflecting half-plane are good mathematical models for slot antennas on an ideal plane of finite dimensions, which in practice have a high gain and operate over a wide frequency band. These antennas are used in ultra-fast information processing systems based on microwave and optical volume integrated circuits. Aim. The work presents a solution to the problem of radiation of a perfectly reflecting half-plane, which was excited by a symmetric slot line with a different law of slot expansion. Methods. The problem was solved by the Fourier variable separation method, by which the Green tensor function was obtained, which connects the two components of the antenna radiation field with the excitation field in the gap. Results. It is shown that in the far zone, the radiation field of an ideally reflecting half-plane has two components: the main and crosspolarization. The Green tensor function has a complex form and consists of two terms. The analysis of the Green tensor function shows the participation of each term in the formation of a field in the far zone, demonstrates the mechanism of radiation and leads to known special cases for slot radiators. Conclusion. The validity of the presented mathematical model is confirmed by experimental research.

A sensor for precise measurements of low flow rates of specialized liquids, including medical liquids, is developed. Through the use of the sensor, it is possible to automate the process of precision dosing of liquids in real time. Keywords: flow sensor, contactless method, drip chamber of infusion system, translucent element.Special attention is now being paid to the problem of increasing the efficiency and precision of measurements of the rate of flow of liquids [1][2][3]. Precision in the measurement of low flow rates of liquids is of great importance in the chemical and biochemical branches of industry and in medicine, for example, for measurements of the rates of flow of solutions of medicines in infusion systems, liquid chemical substances, including catalysts and titers when dosing medicinal compounds, solutions, etc. [4].Existing methods of measurements and devices for implementing these methods [3, 5-7] suffer from a number of drawbacks, for example, large overall dimensions of the devices and the complexity of their construction, low precision of measurements of low flow rates of liquid, and low sensitivity. In addition, with the use of the contact method of measurement, which is employed in practically all devices, a sensor cannot be employed in corrosive and toxic media. These drawbacks reduce the precision with which low liquid flow rates are measured and limit the range of application of the sensors.A measurement instrument by means of which high precision may be achieved and, at the same time, an output signal from the sensing element transformed for subsequent processing, analysis, and generation of control actions is needed for automatic control of the rate of flow.A sensor [8] of low liquid flow rates ( Fig. 1) has been developed to realize precise measurements of low flow rates of specialized liquids. The sensor consists of a case 3 with opaque covers 1, 14 within which mounting screws 2, 13, lens mounts 4, 12, and plates with slit-like horizontal slots 5, 11 are installed. A transparent element 8 is situated in an opening 22 perpendicular to the axis of the case 3. A source of radiation (laser light-emitting diode) 20 with leads 21 is placed in mounting screw 2 while a photodetector (optoelectronic transistor or photodiode) 16 with leads 15 is placed in mounting screw 4. A scattering lens 19 designed in the form of a glass cylinder is mounted in lens mount 4 and a collecting lens 17 in lens mount 12. The translucent element 8 is supplied with an inlet 9 and outlet 18 for liquid and a drop former 10. The two lens 17 and 19 and the two plates with slit-like horizontal slots 5 and 11 form an optical system 6 that transforms the light flux from the radiation source 20 and creates a measurement plane 7 within the transparent element 8.The diameter of the transparent element 8 must be at least three times the diameter of a drop of the liquid being measured and must be greater than the length of the slots in plates 5 and 11. The length of the slot in plate 11 is slightly greater