Antenna system for monitoring radiofrequency spectrum

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Article

Antenna system for monitoring radiofrequency spectrum

Rahimov B.N., Doctor of science, Tashkent University of information technologies, Head of department of Teleradiobroadcasting systems.

Xotamov A., Assistant of Tashkent University of Information Technologies, Samarkand branch

Gubenko V.A., PhD in technics, Tashkent University of information technologies

Berdiyev A.A., Assistant of Tashkent University of Information Technologies

Summary

The article describes the developed antenna system for use in the measuring equipment intended for monitoring radio frequency air.

The article describes the developed antenna system for use in measuring equipment. It is intended for monitoring radio frequency air. A technical description of the antenna system is given. The results of measurements and their comparison with the results obtained with the help of standard antennas included in the measuring equipment are presented. This system increases the speed of the antenna complex monitoring radio twice.

Key words: Radiomonitoring, measuring antenna, log-periodic antenna, horn antenna, selsyn-sensor.

Аннотация

В статье приводится описание разработанной антенной системы для использования в составе измерительного оборудования. Оно предназначено для мониторинга радиочастотного эфира. Дается техническое описание антенной системы. Приводятся результаты измерений и их сравнение с результатами, полученными с помощью штатных антенн, входящих в состав измерительного оборудования. Данная система антенного комплекса увеличивает скорость радио мониторинга в два раза.

Ключевые слова: Радиомониторинг, измерительная антенна, логопериодическая антенна, рупорная антенна, сельсин-датчик.

Introduction

measuring equipment antenna system

Currently, the active use of the electromagnetic resource associated with the development of systems and means of radio communication and radio engineering, as well as various electronic and electromechanical systems, leads to a significant appearance of an additional electromagnetic background, which complicates so uneasy state of interference situation and aggravation of problems of electromagnetic compatibility.

Particularly complex electromagnetic situation develops in large cities, where the main sources of electromagnetic fields of the radio frequency range are television and radio transmitting centers, mobile communication base stations and a huge variety of other systems and devices emitting electromagnetic fields.

For optimal allocation of radio frequency resources and avoidance of collisions in the joint operation of radio and electronic devices, it is necessary to constantly monitor the radio ether, effectively detecting interference problems of a local and general nature. From this point of view, it is necessary to use high-precision measuring equipment, which allows to solve the above-mentioned problem.

One of the main elements of such measuring equipment is the antenna. To a large extent, the antenna determines the accuracy of the measurements and, accordingly, the reliability of their results.

There is a wide variety of measuring antennas included in the measurement systems used for monitoring radio ether. However, until now solutions are being sought for the creation of a universal antenna, which makes it possible to carry out measurements in a very wide frequency band with minimal errors. One possible solution to such a problem may be the creation of an antenna system consisting of several antennas operating in certain frequency ranges, but together overlapping the entire investigated radio-ether range.

This article proposes and considers an antenna system, which can be used as part of measuring equipment for monitoring radio air.

Main part

The main task of radio monitoring is to study the radio ether in the frequency band in which all major radio systems and devices operate.

Under the research, we mean the effective emitter location of various radio sources, the measurement of their electromagnetic field levels and the analysis of the congestion of the radio-frequency spectrum.

Antenna, being the first and most important element of measuring equipment, should have the following technical characteristics:

a wide band of operating frequencies;

high stability of ratio amplification;

high stability of the shape of the radiation pattern in the main planes in the entire band of operating frequencies;

convenient exploitation and unification of the structure;

The measuring equipment includes:

wide-range non-directional antennas of various applications;

sets of antenna systems for automatic direction finding in traffic, on parking lots and for stationary posts;

sets of antenna modules with directional properties for manual direction finders for open and covert use.

As seen, most often in the measurement equipment uses sets of antennas, each of which has its own range and directional properties.

When monitoring the radio frequency spectrum of a particular band, it is necessary to use an antenna with a corresponding band of operating frequencies. Therefore it is necessary to use either universal broadband antenna or change the antenna when switching from one range to another.

We developed an antenna system designed for operation as part of measuring equipment for monitoring radio air. The system consists of two antennas: log-periodic, operating in the frequency band 80 ... 1000 MHz, and a horn antenna operating in the 1 ... 12 GHz band.

The log-periodic antenna consists of twenty-one elements, with a design period of т = 0.84 and the angle a = 450. The length of the collective antenna line is 1.57 meters. The length of the longest vibrator (one side) is 0.83 meters, the shortest - 0.4 meters.

Fig. 1 - General scheme of the antenna system

The conducted antenna studies showed that its amplification factor in the operating band is practically unchanged and is 12 dB, and the protective action factor is 18 dB.

As the second antenna, the measuring horn antenna P6-23A is used, which has the following technical characteristics:

frequency range - 1 ... 12 GHz;

Effective area:

at a frequency of up to 6 GHz - 150 sm2;

at a frequency above 6 GHz - 130 sm2;

HF path - 50 Ohm;

Error of effective area - 20%;

SWR - 1.5;

antenna input (cross section AA) - coaxial;

Input resistance - 50 Ohm;

level:

side lobes - not more than 10 dB;

transverse polarization - not more than 20 dB.

Figure 1 shows a generalized scheme of the antenna system. Both antennas are fixed on a common traverse, which, in turn, is fixed to a vertical mast. In the system, it is possible to change the direction of monitoring in the meridian (horizontal) plane, and also to change the polarization of the antennas.

The horizontal spacing between the antennas is 1.5 meters, which allows to solve the problem of mutual influence of the antennas on each other.

Figure 2 shows the complete block diagram of the system, which consists of the developed antenna system, the switching system, the stationary radio monitoring system Rohde & Schwarz UMS100, with the possibility of connecting the portable receiver Rohde & Schwarz PR100, the antenna control unit, and the computer terminal.

Fig. 2 - Structure diagram of the antenna system

Let us consider the design features of the developed antenna system.

In the system, it is possible to change the polarization of both antennas by means of an electric motor that can be controlled remotely by giving commands through a computer terminal. For each antenna its own polarization or the same polarization for both antennas can be set.

The mast on which the antennas are installed changes its position with the help of a second engine, which can also be controlled remotely by giving commands through the same computer terminal. Thus, it is possible to control the monitoring direction operatively, in real time, by changing the viewing angle of the antenna system to the point of arrival of the investigated signal from zero to three hundred and sixty degrees.

In the rotary system, a Selsyn-sensor-receiver is used, which synchronously, with an accuracy of 0.1 degrees, sets the angle of rotation of the antennas specified by the operator on the computer terminal.

The appearance of the antenna system is shown in Fig.3

Fig. 3 - Appearance of the developed antenna system

With the help of the developed antenna system, measurements of the electric field strength were made, which was created by various sources of radio emission in different regions of the Samarkand region of the Republic of Uzbekistan. Table 1 shows the results of measurements obtained with the developed antenna system and standard antennas included in the measuring equipment of Rohde & Schwarz UMS100.

Table 1 - Results of measurements of electric field strength

Analysis of the measurement results shows that the difference between the results obtained with the developed antenna system and the standard antennas is from 5 dBpV / m to 26 dBpV / m.

For example:

at the frequency of 465.850 MHz, the difference is 5 dBpV / m,

at the frequency of 100.5 MHz, the difference is 7 dBpV / m,

at the frequency of 872.500 MHz, the difference is 14.4 dBpV / m,

at the frequency of 2117.5 MHz, the difference is 16 dBpV / m,

at the frequency of 2670 MHz, the difference is 13.2 dBpV / m,

at the frequency of 1877.4 MHz the difference is 26 dBpV / m.

In this way, it can be stated that the developed antenna system gives more accurate results than with the use of standard antennas, which are part of the measuring equipment.

In addition, due to the possibility of remote control (in manual or automatic modes) by the antenna system, the measurement process gets much simpler, which is very important for the difficult field conditions of hot regions of the Republic of Uzbekistan.

Conclusion

In this article, a description has been given of the developed electronic-mechanical antenna system, which can be used as part of modern measurement equipment for radio monitoring.

The advantage of the design is that it greatly simplifies the measurement work, since during the measurement it is often necessary to change the height of the suspension of the measuring antennas, their orientation in the horizontal plane and polarization.

The use of selsyn transmitter and motors together with the computer control system allows to increase the accuracy of measurements and to reduce the physical load on the operators conducting the measurements. This is especially important for long-term studies in complex field conditions at high or low ambient temperatures and other climatic influences on the mobile radio monitoring terminal.

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