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Industry News

A Small 4 GHz Antenna Suitable for Military Applications

August 13, 2005
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With the increasing volume of data that government authorities and the military have to handle, it is becoming more and more important to have high speed connection for short as well as long haul ranges. Combined with the fact that in many countries the 4 GHz frequency band is reserved for government authorities and military institutions, it is understandable that RFS has developed a small antenna to fill the gap in its product portfolio for the short haul range – the 2 ft. diameter, SB2-44AN CompactLine antenna, which is the first available in the range below 6 GHz.

The antenna’s development took into consideration that wireless radio links are very efficient because they are more flexible to install and require less attention than fixed wired connections. In general, their availability is also greater, which is very important for applications such as fire departments and police stations. As for military applications, it is important for an antenna to be lightweight, rugged and resistant to mechanical loading, as well as being easy to install, especially if it is used for mobile operations.

Main Features

The technical features of this ultra high performance antenna are broad: the low band gain is approximately 25.6 dBi, the mid-band gain, 26.6 dBi and the high band gain, 27.6 dBi. The azimuth fine adjustment and the polarization adjustment are each of the order of ±5°, while the elevation adjustment is approximately ±15°. The mounting pipe diameter ranges from a minimum of 51 mm to a maximum of 114 mm. Also, the survival wind speed averages 250 kph (156 mph) and the operational wind speed 230 kph (143 mph).

To make the antenna as adaptable as possible, it is offered with two different interfaces. The SB2-44AN has a female N-connector to connect a coaxial foam cable, which, due to its flexibility, is the preferred solution for military mobile operations. For fixed point-to-point applications, with longer cable runs between active equipment and antenna, an elliptical waveguide is preferred because of the lower attenuation in comparison to a coaxial cable. Therefore, the SB2-44AD antenna has an integrated waveguide flange IEC 154 PDR-48 and is the perfect solution in combination with the company’s Flexwell waveguide.

Properties

What are the main practical advantages of this new antenna? First, the use of the Cassegrain principle for the feed system minimizes the deviation caused by the metallic waveguide in the radiation area. The antenna is shielded to achieve high side lobe suppression and is covered by a rigid plastic radome, which protects the antenna feeder from external influences. The use of a special aluminum alloy and stainless steel hardware for all the mounting parts also makes the antenna resistant to corrosion. In addition, the weight and size reductions are significant (see Figure 1) as the load on the tower is decreased, resulting in less, and thus lower cost, steelwork. Freight costs are reduced as well.

Fig. 1 The SB2-44AN antenna's compact dimensions.

Aesthetics

Color is not something that would immediately come to mind when considering antennas, but RFS receives requests for advice about refinishing weathered antenna radomes or changing the radome color for aesthetic or non-aesthetic reasons such as camouflage. Any paint selection should be compatible with the radome materials and not interfere with the antenna’s electrical performance. However, there are two primary considerations regarding the choice of paint. The first one is adhesion, since a variety of radome materials are used in the antenna construction and consequently the surface texture will vary (some paints having the best durability may be dangerous to work with and require an EPA-qualified application facility). Preparation is important and all surface contamination must be removed. The second one is the choice of pigment. RF transparency is crucial, so conductive coloring materials such as carbonblack, lead and metallic powders cannot be used. Lighter colors are preferred where practical, to reduce internal temperature extremes which could occur on hot, sunny days. Whatever its color, the SB2-44AN has a low visual impact and simplifies getting authorization for its installation, which can be an important consideration.

Conclusion

To meet the demand for short haul connections and for fixed point-to-point applications, the CompactLine SB2-44AN is the ideal solution because of its small size and lightweight, combined with excellent electrical performance and low visual impact. It operates at frequencies in the 4 GHz frequency band, which, in many countries, is reserved for government authorities and military institutions. This antenna also offers a compact form factor and unrivalled side lobe suppression – a vital attribute in today’s military networks.

Radio Frequency Systems,
Hannover, Germany,
+49 (0) 511 676 2731,
www.rfsworld.com.

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