An Omni-directional Antenna for Industrial and Transportation Applications
Wireless communications has revolutionized the way our society functions. It is a key element of modern life and its reach is extending far and wide, with new applications constantly coming to the fore. To address the increasing demand to connect the various types of devices and networks, HUBER+SUHNER has developed the new SENCITY(r) SWA-0825/360/5/30/DFRX30 antenna, which is a rugged omni-directional multiband antenna for GSM 900, GSM 1800, GSM 1900, UMTS, 2.4 GHz band and GPS/Galileo, aimed specifically at industrial and transportation applications.
The need for and proliferation of antennas in the transportation and industrial sectors is increasing rapidly. For instance, a modern car is equipped with numerous antennas for different tasks: mobile communication, GPS navigation, Bluetooth connection between the mobile phone to the radio, the car key, etc. Also, more and more antennas are being used in industrial applications such as industrial automation, sensor data transfer, heavy vehicles like mine trucks, fork lifts, wind turbines, trains and ships.
In car applications the focus is primarily on short-range communication and the need for antennas to be as small and as cheap as possible, whereas in the industrial sector the need is for high reliability, protection against vandalism, high electrical performance (gain, VSWR) and the need to resist the impact of vibration, water, salt, dust and chemicals.
Antennas are used for mobile communication, WiFi, ZigBee/Bluetooth, WiMAX or RFID applications. There is a large variety of existing products that focus on the car industry and these products have been used in the industrial environment as well. However, there are often issues with both electrical performance and mechanical stability.
The SENCITY® SWA-0825/360/5/30/DFRX30 antenna addresses these issues. It measures 145 by 100 by 40 mm and can operate in a temperature range of -40° to +85°C. In multiband its frequency ranges are 870 to 960 MHz, 1710 to 2170 MHz and 2400 to 2500 MHz. Impedance is 50 Ω and VSWR is 1.7. Polarization is linear, vertical and the maximum power is 100 W (CW) at 50°C.
In GPS/Galileo the frequency range is 1575.42 MHz ± 1.023 MHz, impedance is 50 Ω and VSWR is 1.6. The operating voltage is 3.0 to 5.0 VDC feed at the center conductor of the GPS antenna. Polarization is RHCP, gain LNA is 27 dB and the noise figure is 1 dB.
The antenna is 2002/95/EC (RoHS) compliant and also meets: IP68 (when correctly installed) EN50155, high current protection according to DB specifications (protection against short circuit of 40 kA) and electromagnetic compatibility (EN50121-3-2) standards.
These standards are particularly significant for industrial and transportation applications. It is important to put them into context for antennas operating outdoors and in harsh environments. A high level of salt in the air can cause corrosion of the product. It may be subject to shock and vibration and needs to be resistant to water and dust ingression, all of which are covered by EN 50155.
Figure 1 Water testing of SENCITY antenna.
Most products meet an IP65 or even IP66 level, but vehicles are often hosed down with a high-pressure cleaning device. This is the case when cleaning the roofs of trains. Thus, the higher IP rating of the SENCITY SWA-0825/360/5/30/DFRX30 antenna is significant. Figure 1 shows an antenna being water tested.
The antenna is also protected against high voltage impacts. This could be a lightning strike or, for trains, contact with the catenary line that can carries up to 28 kV. In fact, for the roof-top application of antennas on trains there has to be protection in case of a contact with the catenary line (UIC Code 533). If the catenary line breaks, it could damage the radome of the antenna and detach the metallic radiator and the high voltage could create a fire inside the vehicle.
Figure 2 Effect of galvanic corrosion.
Another serious consideration when designing the new antenna was galvanic corrosion, which often reduces the lifetime of an installed product in an outdoor environment. Figure 2 shows the effect of galvanic corrosion. Choosing the right material mix helps to reduce the corrosion effect. Thus, the SENCITY SWA-0825/360/5/30/DFRX30 antenna has been developed following the MIL-F-14072A (EL) standard with regards to surface combinations.
Other design considerations were fire and rain (and hail). With regards to the antenna's behavior in a fire, the design goal was to limit any toxic materials and to reduce the flammability of the product (NF F101-16, DIN 5510 or BS 6853). Also, trains running at up to 400 km/h or antennas on industrial vehicles will not stop running in bad weather, so the SENCITY antenna has passed tests against hail and rain.
Cables, connectors, filters and the radio unit also have to meet strict requirements. As a specialist for connector solutions, HUBER+SUHNER provides a particular solution for the contact between connector and radiator. It avoids completely the soldering process to guarantee optimal breakout.
Figure 3 The selection of the cable assembly for the antenna is critical.
The selection of the cable assembly (shown in Figure 3) is also significant. Usually, the cable will be selected by the parameters related to loss and bending radius. Additionally, in the industrial and transportation environment, the shock and vibration requirements need to be considered. H+S offers EN 50155 railway approved diplexer products to split mobile applications from WiFi or WiMAX frequencies. Also, the integrated GPS antenna is protected by the mechanical design of the broadband radiator antenna.
Antennas in industrial and transportation applications are special products that have to meet tough requirements and the electrical performance and mechanical performance can be more important than price. For the SENCITY SWA-0825/360/5/30/DFRX30 antenna the design goal is to ensure high reliability and to cope with different installation scenarios. The product has been designed to withstand vandalism, corrosion, UV radiation, temperature drops, vibration, hail impact, rain, snow and cleaning over a long period without maintenance.
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