Radio beam and combined systems
The American company Southwest Microwave produces a wireless radio beam system M.I.L. PAC 316, which is a development of the well-known system M.I.L. PAC 310B.
The two-position microwave sensor M.I.L. PAC 316 (Fig. 9) consists of a transmitter and receiver on three-support stands, two autonomous battery power supplies, a radio transmitter of alarm signals and a set of cables.
The length of the sensor's sensitive zone is up to 244 m, the angle of radiation divergence is 3.5° horizontally and vertically, which ensures a zone width of no more than 7 m at maximum range. 6-channel radiation modulation prevents crosstalk in multi-zone security systems.
The M.I.L. PAC 316 microwave sensor operates at a frequency of 24.162 GHz (K-band).
The current consumption of the receiver and transmitter is 58 mA and 130 mA, respectively (at a voltage of 12 V) and ensures continuous operation of the kit for 135 hours from four batteries with a capacity of 5 A h. The radio transmitter of alarm signals is located next to the microwave receiver unit.
The total weight of the kit is 119 kg; the operating temperature range is from -40° to +66° C.
The M.I.L. PAC 385 wireless system from Southwest Microwave is a single-position microwave sensor that combines a microwave transmitter and receiver in one housing.
The design of the transmitter-receiver is similar to the units of the M.I.L. PAC 316 system.
The length of the sensor's sensitive zone is up to 122 m; the system has a zone length limitation function (from 30 to 122 m) and a function for suppressing interference from nearby objects.
The system operates in the K-band with a peak radiation power of 32 mW.
The sensor weighing 21 kg is powered by a 12 V battery, consuming a current of no more than 220 mA.
The system is equipped with a 16-channel modulation system.
The system, upgraded in 2007, differs in its design in that the control elements are not located under the protective cap of the microwave module, but are located on the rear panel of the module.
The wireless mobile microwave barrier from the Italian company CIAS is built on the basis of the well-known two-position sensors of the ERMO 482x PRO series, which use a pattern recognition system based on the principles of «fuzzy logic».
The MMD System (Fig. 11) includes a microwave transmitter and receiver on three-support stands, batteries, an alarm transmitter, and a multi-channel radio receiver. The length of the system's sensitive zone is up to 200 m.
The autonomous power supply is sufficient for 20 days of continuous equipment operation.
Rigid transport boxes are used to transport the system modules.
The American company Perimeter Products, Inc. produces microwave sensors used for quickly deployable field security systems.
Various modifications of the TMPS-21000 series devices are used here as single-position or dual-position sensors.
All sensors are made in standardized housings (Fig. 12) and are powered by built-in batteries that operate without recharging for approximately 30 hours.
Alarm signals are transmitted to the guard post via a radio line.
Two-position sensors of the TMPS-21100 type are used to organize linear boundaries around temporary vehicle parking areas.
The length of one security zone of such a sensor is up to 150 m; the sensors have an adjustable detection zone width and a range-cut-off mode to eliminate the influence of objects located outside the security zone.
The single-position sensor of the TMPS-21200 type, which is a radar sensor, is placed in the center of the protected area, for example, on the upper plane of the protected aircraft or car. The sensor antenna forms a sensitive area in the form of a cylinder with a radius of up to 48 m.
The operating frequency of the sensor is from 5.725 to 5.850 GHz; the range of detected object speeds is from 0.025 to 31 m/sec.
In the TMPS-21300 version, the single-position sensor has a hemispherical sensitivity diagram and is designed to protect the territory of objects from air intrusions.
The radius of the sensitive hemisphere is adjustable from 22 to 78 m.
The sensor generates an alarm signal according to a specified algorithm, reacting only to entry into the protected area, only to exit from it, or to both actions of the intruder.
The range of recorded object speeds is from 0.44 to 26.7 m/sec (from 1.6 to 96 km/h).
Wireless perimeter sensors sometimes use two or more physical principles. In particular, such combined sensors are produced by the English company Arkonia.
The Hornet wireless security kit consists of a passive IR sensor of the ARK9130 series and a single-position microwave sensor — a radar sensor (Fig. 13).
The passive IR sensor is mounted on the radar body and is used to turn on the microwave sensor if a moving object enters the field of view of the thermal sensor.
Alarm signals are transmitted to the control post using a built-in radio transmitter.
The alarm signal also contains the results of processing the sensor signals (“person”, “car”, “movement from right to left”, etc.).
The Hornet kit is powered by built-in lithium-ion batteries or external accumulators.
The radars operate in the J-band (10–20 GHz), the radar output power is 8 mW.
The alarm signal transmitter power is 1–3 W.
Built-in battery voltage – 12 V; standby current – 0.7 mA, active current – 500 mA.
System operating temperature range – from -40°C to +58°C.
Arkonia also produces wireless security kits that structurally combine ARK9130 series passive IR sensors with video cameras.
This kit, equipped with an autonomous power supply and a radio channel for transmitting video signals, can effectively solve the problems of protecting individual sections of the perimeter.
This wireless system, called Spectre, is shown in Fig. 14. An IR sensor with a range of 40 m is mounted on the body of the video camera.
When the IR sensor is triggered, the video camera is activated and «still frames» in the form of JPEG files along with identification marks are transmitted via a GSM or GPRS channel to the desired e-mail address.
The color video camera and IR sensor are powered by a built-in lithium-ion battery, which is enough to transmit 1000 still images without recharging.
Radio wave systems
Several years ago, the Canadian company Senstar-Stellar developed its wireless radio wave system Repels.
The sensitive elements of the system are two parallel cables (receiving and transmitting), which are attached to the support posts (Fig. 15). The upper cable is located at a height of 1.5 m above the ground, the lower one – at a height of 0.1 m.
The sensitive zone is about 2 m wide and 2 m high. The maximum length of one zone is 100 m.
When rolled up, the cables are wound onto a reel built into the body of the electronic unit. When installing, there is no need to cut the cables or mount connectors on them, so one person can deploy such a system in 30 minutes.
The developers note that the system is insensitive to small animals, tree foliage and atmospheric interference.
The system is powered by LR20 alkaline batteries; one set of batteries is enough for 1 month of continuous operation.
The system is supplied with a ground installation kit (posts, tension cords, hammer) or a solid base installation kit (anchor supports with fasteners, posts, tension cords).
During transportation, the system is packed in two covers; the dimensions of the folded system components are 173 x 25 x 25 cm (posts and fasteners) and 41 x 43 x 18 cm (electronic unit).
The total weight of the system with a ground installation kit is 20 kg.
The American company DeTekion produces portable radio wave systems of the Wave-Guard series with sensitive elements in the form of two «radiating» coaxial cables (Fig. 16), which are laid on the ground along the boundaries of the protected object.
The system operates on 16 discrete frequencies in the range of 66–88 MHz. The PSP–100-V complex provides protection for two zones 50 m long, the four-zone PSP–200-V complex is designed for perimeters 200 m long (Fig. 17).
The two-zone or four-zone processor and power supplies are housed in a special case equipped with connectors for quick connection of sensitive cables. The same case contains a radio transmitter of alarm signals with a telescopic antenna. The batteries provide the kit with 48 hours of operation; a separately supplied solar battery can be used to recharge the batteries.
Geoquip (UK) is releasing a rapidly deployable version of its RAFID radio wave system. The new RAFID-RDS system is designed to protect temporary facilities and is used primarily for military purposes.
The sensor cables, which act as transmitting and receiving antennas, are laid directly on the ground.
The electronic units of the system are equipped with special connectors and can be supplemented with radio channel equipment for transmitting alarm signals.
Systems with seismic sensors.
It should be noted that perimeter security technologies are also widely used to protect other long-distance objects – trunk cables, pipelines, etc.
Israeli company Magal launches PipeGuard system, designed to protect underground oil pipelines.
The system is a set of autonomous sensor units mounted above the protected pipeline, at a depth of 50–80 cm below the ground surface.
Each sensor unit contains 4 geophone seismic sensors, the signals of which are processed by a local analyzer.
The alarm signal transceiver and power batteries are located in the same housing with the analyzer. The photo (Fig. 18) shows the components of the system's sensor module — geophone sensors, an electronic unit, a transceiver antenna and an autotest device.
The PipeGuard system geophone sensors are located along a line perpendicular to the pipeline axis.
The applied method of processing signals from individual geophones made it possible to provide a sensitivity diagram of the sensor module in the form of two narrow petals oriented along the pipeline line.
The length of the sensor's sensitive zone is 150 m in both directions.
This allows sensor units to be located at distances of about 300 m from each other.
Alarm signals from a separate sensor module are transmitted to two adjacent modules, and they, in turn, sequentially transmit them further, to the nearest regional monitoring and control station, which are located at distances of up to 20 km from each other.
The PipeGuard system is designed to detect only those seismic signals that occur when attempts are made to penetrate an underground pipeline — opening the ground with a shovel, hoe, drilling rig, etc.
The system does not react to «non-alarming» factors, such as the movement of people, transport, precipitation. The analyzer «learns» to recognize real signals directly at the installation site and allows not only to classify the type of intrusion, but also to determine the probability of the registered signals matching the typical images stored in the database of each sensor module.
The autotest device is a generator of pulsed acoustic signals that are recorded by geophones located nearby.
Autotesting allows not only to check the functionality of the sensor module, but also to measure the propagation speed of seismic signals, which depends on the soil parameters at the moment (density, temperature, humidity, etc.).
The results of autotesting are taken into account by the analyzer when processing signals and provide not only recognition and classification of signals, but also the ability to determine the angular coordinate of the intrusion point.
The sensor module is powered by special high-capacity lithium batteries.
The battery life depends on the intensity of the specific module; the expected battery discharge time is at least one year.
Conclusion
It is obvious that all wireless perimeter security systems have common specific features that distinguish them from stationary security systems.
It seems impossible to single out any one system that could be considered the best and most universal.
A common feature of most of the described systems is low power consumption, allowing the use of autonomous power sources for a long time.
Almost all wireless systems use radio frequency channels to transmit alarm signals to the guard post.
Wireless perimeter security systems often have requirements for the concealment of the installation of sensors and other components.
At the same time, it is very important that a quickly deployable autonomous system is easy to install and configure in the field and does not require highly qualified personnel for maintenance.
The systems described above meet the listed requirements to a greater or lesser extent.
It is obvious that when choosing a wireless security system, many factors must be taken into account — terrain, facility configuration, surrounding natural conditions, industrial interference, etc.
This requires serious training of designers and system integrators, who must be well versed in the variety of modern security technologies.
Wireless systems for perimeter protection are actively developed and manufactured by Russian companies.
However, the limited volume of this publication does not allow us to describe modern domestic equipment of this class. We hope that a separate article can be devoted to this.