New in the class of radio wave two-position detectors.

New in the class of radio wave two-position detectors.

New in the class of radio wave two-position detectors

Despite their great popularity and prevalence, more and more questions arise regarding their selection and conditions of use. The large range of manufactured detectors and their insufficiently clear classification constantly “confuse” consumers, as evidenced by the ever-increasing number of errors, which are not cheap. Re-installation of sections and “attachment” of incorrectly installed equipment lead to an increase in material and labor costs for installers. Our task is to try to bring order to the classification and determine the place of each detector in the perimeter security system. This task is not very simple and is beyond the scope of this publication, but we will try to “shed light” on this problem.

Soviet roots. In Russia, everything started with government agencies — the military-industrial complex and non-departmental security, there simply could not be other options by definition of the USSR. Detectors, mainly millimeter range («Pion» and others), protected only objects of state importance. The design was based on devices on parabolic antennas, powerful diode (avalanche-flight and «Gann») generators and detectors, analog methods and «hard» logic. The main frequencies used were in the range from 9 to 36 GHz. Detectors had a fairly narrow detection zone, and the radiation power in the pulse reached several watts, there was some danger to health and long-term presence of people near the transmitting units, at best, was limited by operating instructions.
In addition, the detectors were designed in such a way that the polarization vectors of their plane-polarized antennas were parallel or perpendicular to the surfaces of the earth, barriers, etc.

At present, much has changed dramatically; transistor microwave generators and amplifiers have appeared, and, in connection with the introduction of microprocessors, signal processing has been improved. High generator power is no longer required, and advances in filtering and signal isolation have made it possible to reduce radiation to the level of «natural» background.

All these achievements are reflected in the two-position radio wave detectors produced by the Scientific and Production Center «Omega-microdesign» «Prizma-1» (2005), «Prizma-2» (2010) and «Prizma-3» (2011).

The two-position radio wave detectors include transmitting and receiving antennas emitting microwave energy. A volumetric electromagnetic field (sensitive zone) in the form of an ellipsoid of rotation is formed between the antennas.

One of the undeniable advantages of detectors of this type is their resistance to precipitation, temperature fluctuations and almost all types of interference.

The adjustment of the «Prizma» detectors is carried out in two stages: 1) adjustment, 2) threshold adjustment. Using the indicator readings and information from the reference table in the «Installation and Operation Manual», the maximum amplitude of the received signal and the response thresholds are set. The applied synchronization methods make scanning of working radio pulses practically impossible, which eliminates the possibility of blocking the detection properties of the detector and, as a consequence, unauthorized violations of the boundary.

Reliable metal housings, the absence of thermoplastic materials in the design and protection of connecting cables ensure the stability and reliability of the design when operating in any climatic conditions.

Prizma-1 Series

  Purpose
Monitoring of open, straight perimeter sections, from 3 to 500 m long, without foreign objects in the sensitive area.

Application
They are used in open areas, the detection zone width can reach 6 meters (in the middle of a 500 meter section). They are used when it is necessary to create a fairly wide, truly volumetric detection zone, almost completely overlapping the width of the exclusion zone of an open boundary or gates, hangars, etc.

Advantage
The ability to detect intruders approaching the axis of the detection zone and overcoming the protected boundary by almost any method, even crawling.

However, despite their advantages, these detectors have a rather serious drawback. As a result of adding up the «direct» and reflected from foreign objects waves, linearly polarized in one plane, the total signal is weakened or strengthened depending on the phase ratio of the added waves on the receiving antenna of the detector. The influence of surfaces and individual objects located in the detection zone due to interference leads to «unpleasant» consequences, false alarms, and sometimes even to complete loss of functionality. So it is necessary to ensure that the barrier or the expected snow cover are at a sufficient distance from the axis of the detection zone.

Therefore, the use of radio wave detectors until 2007 was mainly limited to «open» areas with a sufficient exclusion zone, without foreign objects, poles, trees, etc.

New detection method. In 2007, a new detection method was patented (Patent of the Russian Federation No. 2348980), which, when applied to radio wave detectors, made it possible to eliminate the noted drawback, and «introduced» new properties into the detectors.

The essence of the invention is to form a plane-polarized electromagnetic field with a polarization vector formed at an angle of 45 degrees relative to adjacent surfaces (ground, fence, high snow cover, etc.). Signals reflected by adjacent surfaces reach the receiving antenna at an angle of 90 degrees relative to its polarization vector and are practically «invisible». The main requirement was the absence of foreign objects only in the «line of sight» zone, called the main detection zone. This invention marked the beginning of the production of absolutely new radio wave detectors of the «Prizma-2» and «Prizma-3» series, which have no analogues in the world.

Prizma-2 Series 

Purpose
Monitoring of straight sections of the perimeter, from 1 to 500 meters long, in the presence of foreign objects (poles, tree trunks, building walls, fences, etc.) in the detection zone.

Application
To protect the metal fence of the lattice (mesh) type and to form a detection zone directly on the fence. The detection zone is adjacent to the fence from the inside (as if “sticking” to it) and practically does not go outside, beyond the territory of the facility.
In conditions of dense urban development with restrictions on the width of the exclusion zones, but without losing control over the upper and lower parts of the detection zone.

Advantages
1.  Possibility of installing detector units directly on the surface of the fence, walls of buildings.
2.  Possibility of installation in areas of intensive traffic along the protected line.
3.  Possibility of transverse overlap of the detection zone with a lattice (mesh) fence without deteriorating the performance of the detector.
4. Reduced probability of false alarms by eliminating the influence of reflected signals when forming a sensitive zone.
5. Possibility of installation along the ground surface with a high level of snow cover, directly reaching the detector units, without fear of false alarms or loss of product functionality.
6. Possibility of adjusting the transverse dimensions of the detection zone (from wide to narrow) by changing the threshold values.
7. Possibility of blocking the canvas of fences, walls of buildings and structures. The width of the main zone is equal to the size of the antenna block (about 30 cm) throughout the entire protected area. The width of the additional zone can be adjusted by sensitivity settings and reach 4 meters over a section of 500 meters.

Based on the above-mentioned patent, production of 24-Gigahertz detectors «Prizma-3» with an ultra-narrow detection zone has begun. However, it is necessary to take into account that excessive narrowing of the detection zone leads to simultaneous loss of control over the upper and lower parts of the site. Which allows the intruder to cross the border «unnoticed» under the detection zone or above it.

Prizma 3 Series
Purpose
Control of straight perimeter sections, from 3 to 200 meters long with a detection zone, in cross-section equal to the aperture (size) of the blocks.

Application
When it is necessary to create an ultra-narrow detection zone, in places with a limited width and height exclusion zone, to protect the top of the fence, window openings, roofs of buildings and structures. It is used as an alternative to optical and infrared detectors, allows you to exclude the triggering factor for small animals and birds.

Advantages
1. Ultra-narrow detection zone.
2. Possibility of covering areas above water surfaces, entrances to water areas, docks. Monitoring of ships at berths and docks.

It follows from the above that radio wave detectors of the «Prizma-2» and «Prizma-3» series, manufactured using the new method, regardless of the operating frequency and other «typical» characteristics, have distinctive properties, practically not competing with «Prizma-1» detectors on open borders.
In order to avoid «confusion» in the class of radio wave detectors and lead to a correct understanding of the place of each type in the security system, it is necessary to divide it into at least two subclasses.
At this stage, it is possible to at least note the main properties of the detectors in the name:
1) «interference-dependent» — with a polarization vector parallel or perpendicular to the surfaces, for open areas;
2) «interference-independent» — with a tilted polarization vector, for any areas.
Of course, the proposed names reflect the physical properties very superficially, but they can help designers and installers in the correct selection of detectors.

Publications on the topic of classification will be continued in both printed and electronic publications, information on the «Prism» detectors can be obtained on the websites of the Scientific and Production Center «Omega-microdesign»: tso-perimetr.ru .

_________________________________________________________________________
Deputy Director for Research of the Scientific and Production Center «Omega-microdesign» Andrianov E.Yu.
Lieutenant of the internal service,
engineer of the TSO, AiEP department, FBU MCIO FSIN of Russia Girich V.S.
Head of the Marketing and Advertising Department of the Scientific and Production Center «Omega-microdesign» Garkin O.I.