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German Battlefield Electronics Link Communications, Sensors

March 1999
By Robert K. Ackerman
E-mail About the Author

Digitized signals allow versatile tactical radio units, networked radar systems and wireless command posts.

New very high frequency radios are sharing the airwaves with sensor systems in battlefield networking. Both communications and radar units have become portable enough that they now are mobile nodes in an interlocking information web.

Increased digitization is allowing command networks to move information about a theater of operations like a traffic policeman controls vehicle flow through a busy circle. The same technology is enabling planners to simulate radio networks to improve deployment efficiency and to reduce interference and electronic countermeasure vulnerability.

Many of these elements are emerging from SEL Defense Systems, Pforzheim, Germany. The company is upgrading its long-standing radio systems while adding new digital units designed to interoperate on the digitized battlefield.

A series of very high frequency (VHF) radios is geared toward future battlefield communication needs. The SEM 173/183/193 family covers the range from lightweight manpack to high-power relay/dual station. These radios operate from 30 megahertz to 108 megahertz, and their 3,120 available channels can be doubled by dividing the 25-kilohertz channel spacing in half.

The basic SEM 173 is a manpack version that weighs only 5.2 kilograms (11.4 pounds). A smart handset provides operator control, and the radio has a detachable front panel with integrated speaker and microphone. Three modes offer fixed frequency, automatic channel selection and frequency hopping operation. The system is designed to accommodate options such as advanced mobile subscriber access, selective calling and packet radio.

For electronic counter-countermeasures, the radio features integrated encryption and message modification as well as postponed transmission. For frequency hopping, the unit employs multidimensional hopping to overcome anticipated fast frequency hopping countermeasures.

To enable high-volume data exchange, the radio system uses forward error correction with a data rate of up to 9.6 kilobits per second. Synchronous and asynchronous data equipment, such as weapon and reconnaissance systems, personal computers and printers, can be connected via standard V.24 and RS 232-C interfaces.

All these features are inherent in higher-level configurations. A vehicular adapter converts the basic unit into a SEM 183 vehicle station. This gives it extended range along with increased mobility. Adding a power amplifier to the 183 transforms it into the SEM 193. This unit offers a range of more than 30 kilometers (19 miles). A 183 can be teamed with a 193 for a vehicle-mounted relay/dual station. The ultimate configuration is the vehicle-mounted high-power SEM 193/193 relay/dual station.

Two other tactical radios evolved from the company’s basic tactical radio system, the SEM 70/80/90. The new units, the SEM 91 and SEM 93, are differentiated by their platforms—helicopter and vehicle, respectively. The commonality of these two radios provides direct links between army aircraft and ground vehicles. Their frequencies range from 30 megahertz to 79.975 megahertz, with 2,000 channels spaced 25 kilohertz apart.

Both units feature forward error correction for a data rate of up to 9.6 kilobits per second. They differ from the earlier 70/80/90 series in their advanced digital signal processing, encryption and electronic counter-countermeasures, and radio frequency front ends.

As with the SEM 173 family, the SEM 91 and 93 offer operational modes of fixed frequency, automatic channel selection and frequency hopping. Fixed frequency operations feature analog voice along a common international standard; and digital voice, both clear and encrypted, that is fully operational with the U.S. single-channel ground and airborne radio system and radios with North Atlantic Treaty Organization cryptography gear. A clear voice override automatically recognizes a clear or encrypted call.

The automatic channel selection mode provides clear digital voice and data. The electronic counter-countermeasures hopping mode offers encrypted digital voice and data. Digital voice and data in an automatic channel selection can be expanded by encryption and an antispoofing capability. The system offers a direct switchover between this electronic counter-countermeasures automatic channel selection and its hopping mode equivalent. Both units offer automatic over-the-air distribution of operation variables, including cryptography.

Both units can function as relays in all radio operation modes. The vehicle-mounted SEM 93 offers 0.4, 4 and 40 watts of output power. The helicopter-borne SEM 91 is fixed at 10 watts. In unencrypted voice transmission, the units interoperate with VHF radios in accordance with STANAG 4204. Encrypted voice transmission is compatible with VHF radios that have cryptography units operating with the same logic.

Setting up an area radio system under adverse conditions comes under the domain of the KESS deployment planning and simulation tool. This software system allows users to configure a theater radio system taking into account enemy electronic countermeasures, terrain conditions, electromagnetic interference, bandwidth use and station selection.

A key KESS element is its capability to generate propagation models in two or three dimensions. This evolved from German government studies on the effects of diffraction, dispersion and reflection. Describing wave propagation three-dimensionally provides a more accurate depiction of radio performance, according to company officials. The system can simulate the multiple-path propagation of radio waves at the physical level.

The system’s propagation models cover frequencies ranging from 20 megahertz to 20 gigahertz. They can be expanded into the extremely high frequency range under certain circumstances. Field measurements cover the 20-megahertz to 1-gigahertz range with a total connectivity length of about 1,400 kilometers (875 miles), depending on terrain and actual frequency ranges.

An operator can obtain quantifiable analysis for transmission quality, radio engineering accessibility, band utilization and interference minimization. The three-dimensional propagation model can help determine full area coverage calculations for local receive power; spatial expansion; forecasting and simulation of field strength differences among transmitting stations; optimum transmitting frequencies in local and distant geographical areas; and the ideal number of transmitter locations.

Users employ a modular software system. The interface resides at the top layer, where an operator can select functions and define the scope, and application-specific modules handle the tasks that emerge with radio engineering problems. Other algorithms address terrain profile calculation and Fresnel ellipse determination. This can take place for directional radio planning or for area-covering radio field calculations in area network planning.

An object-oriented database covers a host of variable data such as system, elevation, vegetation, construction and radio station equipment. It also includes map material and an antenna library. All the system’s software layers communicate through standardized interfaces.

Perimeter surveillance is the specialty of a small portable radar system that can be mounted on a tripod or installed in vehicles. The BOR-A 550 can detect a range of mobile objects on the ground or at sea as far as 40 kilometers (25 miles) away.

The unit employs digital swept frequency modulation technology and a semiconductor transmitter. The day/night all-weather system can perform 360-degree monitoring or can monitor within user-defined sectors. An operator can program alarm zones for an acoustic alarm.

Users can control the radar unit with a personal computer. Its controls employ self-explanatory menus from the Microsoft Windows operating system. A classification algorithm allows the unit to automatically classify targets within types, including convoys, tanks, vehicles, ships, boats and humans. According to SEL officials, its moving target indicator capability is combined with new signal processing to allow the system to detect rubber boats in heavy seas.

The BOR-A 550 is designed to supplement the RATAC-S artillery fire direction radar. It can be set up as a remote detection station connected by integrated services digital network (ISDN) or radio to an overall surveillance network. A user can control it from 300 meters away with connecting cable or several kilometers distant using wireless links. Several of the units can be networked with other radars in a single command and control system for multilayer surveillance, or a series of networked BOR-A 550 units can be controlled by a single unit.

In addition to battlefield applications, the radar is suited for coastline surveillance and border control against drug smugglers, weapons traffickers, terrorists and illegal immigrants, according to company officials. Other applications include sensitive area and object protection. Its three modules permit rapid deployment.

Controlling all these systems on the battlefield is the mission of the firm’s CPnet broadband integrated command post communication network. This system is being implemented in the German army as BIGSTAF, for Breitbandige Integriete Gefechtsstandfernmeldnetz, or broadband integrated command post communications network.

The network system consists of two major subsystems. A fiber optic subsystem includes a network access unit, an internetworking unit and a network control unit. A millimeter-wave radio subsystem features a radio control unit, a 60-gigahertz radio frequency unit and a 51-gigahertz radio frequency unit. Either or both of these system components can build up a CPnet. Wireless connectivity among the network access units allows users to tie into the network simply by hooking into nearby access units.

The fiber optic network serves as the basis for a conventional CPnet. It is a bus system using local area network standard IEEE 802.3 Ethernet and EURO COM. Modular gateways offering different trunk interfaces allow connection to wide area networks.

The 60-gigahertz radio network allows local area connectivity without fiber or interception. An attenuation spike at this frequency limits detection and interference to less than 500 meters. Each radio can serve as a repeater station, which establishes redundant communication paths. The 51-gigahertz radio network is geared toward subcommand posts serving large command posts at echelons above division. The system’s radio network can be set up and operated without any frequency or radio network planning.

According to company officials, CPnet can be set up or taken down in less than 15 minutes. Its network architecture, which comprises several self-sustained network access units, is modular and distributed. This provides it with a self-healing capability when a communication link is lost or the network topology is modified.