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indicator of the quality of the final installation,” Wunder says. “It’s a given that site crews the world over will often spend a great deal of time—and perhaps even re-connectorize or re-run a cable—to ensure the line’s return loss is acceptable.” compared with conventional 1-5/8-inch foam-dielectric coaxial feeder,” he says. “That’s twice the throughput benefit achieved by ensuring your return loss is up from 18 to 23 dB—simply by electing to use Premium Attenuation!” He points out that the difference between The attenuation ‘attributes’ of rigid a poor return loss of 18 dB, and the far more acceptable figure of 23 dB, equates to smooth-wall feeder cable are, according to Wunder, another area that is widely 10 FEEDER SYSTEMS Wunder explains, “a resistive element and dielectric attenuation element.” The resistive element is proportional to the square root of the frequency, while the dielectric element rises in direct proportion with frequency. Rigid smooth-wall cables, Wunder points out, are specifically designed for use at cable television (CATV) frequencies (typically 50 to 550 MHz), rather than the higher frequencies of mobile wireless networks (see Figure 3). “The attenuation figures of smooth-wall cable versus corrugated cable are relatively close at lower frequencies, as the dielectric attenuation is insignificant under these conditions,” he says. “But as the frequency increases—especially at 1800 MHz, 1900 MHz and beyond— the poorer quality of dielectric typically found in commercial smooth-wall coaxial cables causes a rapid increase in attenuation.” This, along with the enormous bending torques required to work with rigid of its conventional predecessor, to ensure the easiest transition for site crews from ‘standard’ to ‘premium’. An important practicality issue is that of connectorization, and backward compatibility of connector stocks. “From a purchasing department’s perspective, the whole issue of connector backward compatibility isn’t a concern—their simplistic argument is that ‘I buy the matching connectors with the cable’,” says Wunder. But this, he says, is only part of the story. “The site reality is that connectors can get misplaced, or are often required on existing sites to re-connectorize existing feeder runs. This is why RFS tailored the dimensions of CELLFLEX ‘A’ Premium Attenuation to ensure backward compatibility with the existing RFS RAPID FIT connector series. There’s no point running a system that requires three or four different connector series, plus re-training and re-tooling, just The path to premium—a carrier’s view For Australian integrated communications group, Optus, electing to use a premium attenuation transmission line solution was largely driven by the needs of its emerging 3G UMTS mobile network. A spokesperson for Optus cited the obvious increase in operating frequency from its demand within any W-CDMA cell means that feeder chain losses can potentially have a significant impact on the available power per service, plus network capacity and coverage. “Low-loss feeder assists in improving the radio path and achieving the data rates existing 2G 900-MHz network to the new demanded by customers,” said the UMTS 2100 MHz as one—but by no means the only—reason for the move to a low-loss feeder solution. Equally significant drivers are the issues of RF power sharing among users and network optimization. “With CDMA-based technology, the RF power is a shared resource among users, as opposed to 2G/GSM services, where all the power is available to one user for an instant spokesperson. “This, in turn, allows cells to be spaced further apart, [which] reduces the required cell density, thus saving capex as well as reducing the opex associated with maintaining these sites.” On the subject of selecting an appropriate low-loss transmission solution, the clear message is to ensure that the transition from the legacy cabling system to the new in time,” the Optus spokesperson said. technology is as uncomplicated and User services in a 3G network can also vary, from voice (which has low RF resource demand), through to high-speed packetswitched data services which demand greater amounts of RF power. This straightforward as possible. “It is critical that the processes do not change,” the spokesperson emphasized. “This is with regards to transmission line handling, storage and installation practices.” potentially wide range of RF power 11 an actual transmission improvement of around 0.05 dB. This stands in stark contrast with what can be achieved by electing to use CELLFLEX ‘A’ Premium Attenuation. “A 40-meter run of 1-5/8-inch CELLFLEX ‘A’ Premium Attenuation operating at 1800 MHz will actually provide a transmission improvement of around 0.1 dB, when misunderstood. Common around the world in its native application as a means of routing cable television signals, the rigid smooth-wall cable is often thought to be ‘low attenuation’. The reality can be explained by the electro-physics of foam-dielectric coaxial cable. “The attenuation of any foam-dielectric coaxial cable is made up of two elements,” smooth-wall cable, makes it particularly impractical for applications outside of trench-based CATV use. Gauvin notes that the poor attenuation performance of smooth-wall coaxial cable at higher frequencies is set to become more problematic in 2006, when the US spectrum regulator, the Federal Communications Commission (FCC), auctions significant portions of 2.1-GHz spectrum for emerging 3G applications. “This represents a 10 percent increase in frequency from regular PCS,” says Gauvin, “so the issue of attenuation will become all the more important.” Practical deciders— smooth transitions But it is the practical issues of site handling, mechanical strength and reliability that are determining which way carriers ultimately elect to go in today’s low-loss feeder stakes. In essence, the premium attenuation cable needs to provide the same look, feel and handling to move from a conventional to a premium attenuation cable—it’s simply not site-practical.” Crush resistance and the general issue of ease of site handling is also one of the most significant deciders in selecting a low-loss transmission line. “When we developed CELLFLEX ‘A’ Premium Attenuation we set out to avoid the installation shortfalls that we’ve seen in other brands, as these issues impact dramatically on the total ‘buy and install’ cost,” Gauvin explains. “We’ve made no compromise at all on the crush strength of our Premium Attenuation CELLFLEX, because retention of crush strength and reliability is an essential on any site. At the end of the day, there’s simply no cost saving to be had—attenuation or otherwise—when a cable fails mechanically and has to be replaced!” CELLFLEX ‘A’ Premium Attenuation series—at a glance When: The complete range of CELLFLEX ‘A’ Premium Attenuation transmission line was launched in mid-2005 Where: Both feeder cables and associated connectors are now available globally. Cable size range: 7/8, 1-1/4 and 1-5/8-inch cable diameters. The 1-1/4-inch variant is also available in ‘ultra-flexible’ (UCF) format. Return loss (VSWR): The CELLFLEX ‘A’ series RAPID FIT connector pair offers reduced return loss across the range—up to 6-dB improvement at 2.2 GHz. Intermodulation (IM) performance: The CELLFLEX ‘A’ Premium Attenuation series cable and connector pair exhibits consistently low and stable IM levels. Attenuation: CELLFLEX ‘A’ Premium Attenuation series boasts a dramatic improvement in attenuation performance—typically between five and eight percent when compared with conventional foam-dielectric coaxial cable. Connector size range: To match all CELLFLEX ‘A’ series sizes, in both type N and 7-16 DIN interface. Jacket options: UV-resistant polyethylene (J) or flame and fire retardant jackets (JFN).
RFS in China, for China As anticipation builds for the eruption of third-generation wireless communications into China, RFS intensifies its local activities with the establishment of RF conditioning and base station antenna design and manufacturing facilities in Shanghai. Over the past decade, China has become a growing hub for mobile activity. Every month the country adds five million mobile subscribers, which represents a significant portion of the larger Asia Pacific region’s wireless market. In response to this growth, Radio Frequency Systems has expanded its Chinese engineering and production capabilities to cater specifically to the local market. The Chinese mobile communications market has been the largest in the world since 2001. A late-comer to wireless technology, China now has more wireless subscribers than fixed. According to Patrick Nobileau, RFS Vice President Base Station Antenna Systems, the Asian mobile market is at a very exciting stage just now. “China is at a juncture where it is building new networks when the rest of the developed world is evolving existing networks,” said Nobileau. “The country is just ‘waiting for 3G’, and the rest of the region is watching.” Now providing local design and manufacture of base station antennas and RF conditioning products, RFS is helping China achieve its network deployment and optimization goals: to increase coverage and capacity, improve QoS, and minimize total lifecycle costs. “The new facilities bring us geographically closer to the international and Chinese base station OEMs,” says Carol Ye, Area Product Manager RF Conditioning. “That means we can respond faster, and more easily, to the requirements of the world’s most dynamic mobile market.” Chinese methods RFS’s newest RF conditioning facility is based in China’s commercial capital, Shanghai, and comprises a manufacturing area of 1800 square meters (19,300 square feet), plus a research and development laboratory covering 300 square meters (3,200 square feet). The facility has been operating since 2002, and since the beginning of 2005 has included an R&D team. The R&D capability was established to meet the product development needs for WIRELESS COMMUNICATIONS The RF conditioning division of RFS China has been providing 12 specific technologies for wireless carriers in China, Taiwan, 13 Vietnam, Indonesia, Pakistan and India. The RFS base station antenna design and manufacturing facility in Shanghai currently produces 60,000 antennas annually. both OEMs and operators in Asia Pacific region. “Doing business in China is very different to what RFS is accustomed to in Europe orthe US,” says Ye. According to Ye, the Chinese corporate culture approaches product development through a more iterative process than those used in other parts of the world. “In the Western world, customers are used to coming to RFS with specific needs that are [usually, but not always] defined through preliminary technical discussions, and then RFS aims to satisfy those,” she says. “This generally begins with a set of specifications set out by RFS and the customer; is followed up by mutual discussions on concepts; and culminates in an RFS prototype—usually within six weeks.” In China, on the other hand, the supplier is expected to be involved a lot earlier in the development process. “Customers come to us with loose conceptual specifications and then discussions begin on what is actually required. Sometimes three or four prototypes are developed before the actual specifications are cemented, so the technical relationship is of a different nature. Importantly, all this must still be completed within a limited number of weeks,” says Ye. Having a local engineering team that is sensitive to regional issues, and can turn designs around quickly, allows RFS to meet these stringent deadlines. Most recently, the RF conditioning division of RFS China has been providing specific technologies such as second and third-generation (2G/3G) diplexers, co-location protection filters and 3G tower-mount amplifiers for wireless carriers in China, Japan, Taiwan, Vietnam, Indonesia, Pakistan and India. Other interesting research and development projects focused on transceiver front-end products—RF modules integrated within the base station—for major Chinese OEMs. “As we develop these products for the Asian market our design engineers ensure continuity by thoroughly documenting all solutions,” says Ye. “This builds strong foundations for future product development where situations might share similar characteristics.” Building a base The same philosophy has been extended to the RFS base station antenna design and manufacturing facility in Shanghai, which currently produces 60,000 antennas annually. Operational since October 2004, this center has the capacity to produce all cellular antenna models from the RFS highperformance Optimizer family. “What’s most in demand in China is the RFS Optimizer cross-polarized variable electrical tilt directional panel antenna,” says Nobileau. “The broadband functionality of these antennas is highly sought-after by wireless carriers and OEMs in this region.” Because of the rapid network growth across the continent, Chinese carriers are increasingly confronted with the cellular challenges faced by network operators globally: a need for high side-lobe suppression, superior gain performance and reduced cell-to-cell interference. At the same time, there is a need to reduce tower and tower occupancy costs, to minimize both roll-out capex and network opex. “Carriers are opting for the dual polarized antennas with variable tilt rather than vertically polarized panel arrays. This is because you need fewer antennas, and can therefore reduce the overall cost of tower structures,” says Nobileau. “It also offers a reduced visual impact, which is particularly important in these areas where base stations are being installed at such a rapid pace.” According to Nobileau, these sorts of matters are easy to resolve when production and design are on location. “We can tailor the product, and the production, to the immediate needs of the market,” he says. “We’re focusing on what the customer actually needs in China—3G and beyond.”
Page 1 and 2: RADIO FREQUENCY SYSTEMS The Radio F
Page 3 and 4: RFS analyzing broadcast RF remotely
Page 5: Get a grip—coaxial transmission l
Page 9 and 10: Ukraine’s Kievo- Pecherskaya Lavr

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