Although an antennas role is often underestimated, this component is critical to the performance of both fixed and mobile wireless devices.
The cellular market and other wireless technologies owe their success to the constant engineering of software, materials, components, and more. One of the most important components in any wireless product is of course the antenna, as it both sends and receives the radio waves that make wireless communication possible. To make sure that this vital component can meet the needs of current and future wireless communications, a host of antenna manufacturers continue to devote themselves to the ongoing development of cutting-edge antennas.
In the infrastructure arena, for example, TenXc Wireless, Inc. (Ottawa, Canada) released the Wideband Bi-Sector Array for Advanced Wireless Services (AWSs) and Universal Mobile Telecommunications System (UMTS) 2100 licensed operators (Fig. 1). By improving spectral capacity, this array will enable operators to deliver current and future multimedia services. The Wideband Bi-Sector Array operates across the full 1710-to-2170-MHz band. Its compact radome design combines the equivalent of two broadband sector antennas in one single 16-in. (40-cm)-wide package. The Bi-Sector Array's asymmetric patterns and single dual-sector panel vow to deliver maximum-capacity performance gains in higher-order sectorization site applications. At the same time, those features simplify implementation and reduce site-antenna count.
The array's "drop and insert" RF design maps to standard 65-deg. sector coverage. It therefore enables hot-spot deployment in existing networks without re-engineering surrounding sites. By increasing spectrum efficiency, the Bi-Sector Array products promise to provide up to double the service capacity using existing site infrastructure. The Wideband Bi-Sector Array can be deployed in existing Personal Communications Service (PCS) 1900-MHz and Digital Cellular System (DCS) 1800-MHz network sites. They also will ease third-generation (3G) network technology deployment.
In urban areas, cellular-network performance is often at the mercy of site negotiations for network rollout and renewal. To smooth this negotiation process, the Optimizer Rooftop antennas from Radio Frequency Systems (Meriden, CT) minimize visual impact without sacrificing performance. The Optimizer Rooftop is an all-in-one solution comprising a star-configuration base, mast, tri-sector antenna cluster, and RF cabling (Fig. 2). Its mast is a slim-line, 3-in.diameter structure that tilts into place. It supports both the tri-sector antenna cluster and optional RF conditional module. The low-profile antenna cluster houses three RFS Optimizer sector antennas. Each ones provides a full ±20deg. of azimuth adjustment.
Three Optimizer Rooftop models are available: two fixed-height models (10 and 13 feet high, respectively) and a variable height/telescopic version (13 to 18 feet). It comes with a choice of nine different RFS Optimizer antennas that encompass the suite's broadband, side-by-side, triple-band, and dual-band antennas. These antennas span frequency bands from 900 through 2200 MHz. Additional options include fully integrated tower-mounted-amplifier (TMA) modules and antenna tilt control units (ACUs). The Optimizer Rooftop typically exerts a rooftop pressure of just 31 lbs./square ft. It retains stability in winds of up to 155 mph. The model features provisions for add-ons like microwave-antenna, remote-radio-head, and a growing suite of WiMAX-ready antenna solutions.
Although cellular-site antennas continue to provide core network support, indoor antennas are increasingly being utilized to fill the coverage gaps in cellular and other wireless networks. The SENCITY indoor Distributed Antenna Systems (DASs) from Huber+Suhner, Inc. (Essex, VT), for example, suit various purposes while providing a high level of efficiency. For its part, the SENCITY Optima broadband, omni-directional antenna supports all major communication systems, such as AMPS, CDMA, GSM, WiFi, and WiMAX. Thanks to its elongated connector, this antenna can be fixed on ceilings with a thickness of up to 30 mm. The SENCITY Optima family currently comprises two antenna series. The SWA 0764/360/6/30/V covers the frequency range of 0.69 to 6.40 GHz while the SWA 1864/360/6/30/V covers 1.71 to 6.40 GHz. The impedance for both series is 50 Ω. The voltage standing-wave ratio (VSWR) is less than 2.0:1. The Optima antennas provide gain up to 8.5 dBi, linear vertical polarization, and 3-dB horizontal beamwidth of 360 deg. They handle maximum power of 10 W at +25°C.
The V5808, which targets 5.8-GHz point-to-multipoint local-area networks, can be deployed indoors or outdoors. Astron Wireless Technologies, Inc. (Sterling, VA) recently debuted this 5.8-GHz, 8-dB omni-directional antenna. By leveraging microstrip collinear patch-array technology, the V5808 achieves gain stability across the frequency band. In addition, it provides a clean radiation pattern. The V5808 is built using an ABS plastic, UV-stabilized radome.
As they evolve in existing markets, new antennas also must be spawned to satisfy emerging technologies. Antenna designers are finding themselves increasingly focused on making products for radio-frequency identification (RFID), Bluetooth, wireless local-area networks (WLANs), Ultra Wideband (UWB), and WiMAX. In the WiMAX arena, for example, PCTEL, Inc. (Chicago, IL) recently introduced the first in its line of MAXRAD high-gain sector panel antennas. This antenna covers the 2.5-to-2.7GHz frequency band. It is available in a 65-deg. bandwidth. To deliver RF coverage as the industry transitions from fixed to mobile WiMAX, the antenna offers optimized radiation patterns. It provides 18 dBi of gain in a 48-in.-tall radome structure.
All of the antennas in this family feature integrated Variable Electrical Tilt (iVET) for WiMAX base stations. To enable rapid and cost-effective network optimization, iVET vows to remove or eliminate the site access logistics that are required for antenna changes or adjustments. The iVET functionality is completely enclosed in the antenna radome structure with no added external components. Using a distribution-network and phase-shifter design, the MAXRAD WiMAX antenna provides matched down-tilt on both polarizations as well as calibration accuracy.
Global Positioning System (GPS) applications also are driving antenna development. GPS is being implemented in a growing number of cellular phones, automobiles, and more. Taoglas (Wexford, Ireland) just launched a range of miniature antenna systems for the telematics market. These systems incorporate the 13-mm2 AP12-A antenna, which boasts 26 dB gain. This antenna is only 0.5 mm in height.
The AP12-A ceramic patch antenna was developed with Cirocomm with a two-stage, 25-dB low-noise amplifier (LNA). It is available in plug-and-play format for on-board integration with GPS receiver modules via IPEX's coaxial cable and connector. The AP12-A offers power consumption of 13 mA typical at 3 V. It delivers low noise of less than 1.9 dB. The company also announced the PA22—a surface-mount, tri-band GSM ceramic antenna that is designed for automated SMT processes.
Integration seems to be a growing trend in GPS antennas. In February, Antenova Ltd. (Cambridge, UK) announced a single-package solution that unites RF with a passive antenna. The GPS RADIONOVA RF antenna module integrates a receiver integrated circuit (IC) with the company's single-ended, internally balanced antenna in a 7 X 34.5 X 4-mm package. It has a low-profile connector for vertical mounting. With the balanced-antenna technology, GPS RF antenna modules can operate independent of component placement and groundplane size. The module's frequency is 1575 MHz. The RF system noise figure is 2.3 dB. The antenna module features a single-feed, balanced 50-W connection. For efficient operation, it requires a printed-circuit board with a groundplane as small as 20 X 40 mm.
Although many wireless new-product designs still set their sights on the cellular industry, other wireless standards— such as WiMAX—have garnered their share of the market. And that share seems to be steadily increasing. With the continual emergence of new standards and technologies, antenna manufacturers will not be able to let up on their current product-development pace. In fact, they will probably find themselves increasingly designing antennas that simultaneously serve cellular and WiMAX networks, GPS, and more.