Microwave Engineering Europe - November 2008 - (Page 13) COVER FEATURE: BASE STATION TESTING 13 Figure 2: The Agilent Technologies FieldFox Handheld RF Analyzer addresses the needs of Wireless Service Providers for an integrated solution for the installation and maintenance wireless networks. Dealing with this mounting list of potential problems, and the lack of skilled RF field engineers and technicians requires an integrated test solution that minimizes the number of separate test instruments required in the field and that is able to quickly, accurately and easily conduct a number of key measurements. The Agilent Technologies FieldFox Handheld RF Analyzer (Figure 2) has been developed to address this need for an integrated solution for installation and maintenance wireless networks. Cable and antenna testing Cable testing is required to detect the imperfections or disturbances that cause reflection of incident energy throughout the cable length. The detection also has to include Distance to Fault (DTF) measurements to allow the more accurate identification of the position of the fault. Disturbances within a cable length can take the form of a small dent or a change in the diameter of the cable. Periodic effects on the cable can often be caused during the manufacturing process, for example by a drive wheel with a rough spot on a bearing. Cables may also contain one or more discrete faults, for example, due to a bent or damaged cable, contaminated dielectric, a poor cut or a bad connector. Whatever the cause of the fault or imperfection the mismatch that results will cause reflections to occur. The reflections from the individual imperfections sum up to the point that they can be measured as Cable Loss or Return Loss. With periodic faults the energy reflected can appear in the loss measurement as a reflection spike at a frequency corresponding to the spacing of the imperfections. The spacing between the periodic imperfections is one half of the wavelength of the reflection spike. Cable testing techniques included loss measurements (Return Loss, Insertion Loss) and transmission measurements (e.g. VSWR). Return loss measurements are expressed in dB with 0 db being recorded when measuring an open or short circuit and typically 40 to 60 dB being displayed when measuring a load condition. With transmission tests the transmitted and reflected signal combine to create a standing wave. The voltages of the peaks and troughs of the standing wave are measured and expressed in terms of the Voltage Standing Wave Ratio (VSWR). With no reflections, i.e. a perfect transmission system, the VSWR is unity. With higher reflections the VSWR will increase to the point where the reflections become unacceptable. The Agilent FieldFox RF Analyzer includes comprehensive cable testing capabilities. The instrument can be used to test antennas, cables, filters, and amplifiers for the purpose of making return loss, VSWR, insertion loss/transmission, one-port cable loss and DTF measurements. Both return loss and DTF measurements can be made at the same time which helps correlate overall system degradation with specific faults in the cable and antenna system. A key feature of FieldFox is QuickCal, a built-in calibration system, which allows the user to calibrate the cable/antenna tester without having to carry a calibration kit into the field. This simplifies cable and antenna test, ensures accuracy and repeatability at the point of measurement and improves productivity. QuickCal also corrects drift error caused by temperature changes during instrument operation. FieldFox is also calibration-ready at the cable and antenna test port immediately following power up. RF measurements To identify the causes of potential RF problems within a cell site requires an arsenal of RF test instruments. By integrating all of the key RF test tools into one device the Agilent FieldFox RFAnalyzer provides an integrated toolkit for the RF field engineer. Spectrum analyser FieldFox features an optional built-in spectrum analyzer that covers frequency ranges from 100 kHz to 6 GHz. A fast spectrum scan detects interference and RF burst capture to measure intermittent signals. It displays four traces at the same time and allows the user to choose different detector modes. Power meter with USB power sensor FieldFox can connect with the Agilent U2000 Series USB power sensor to make RF/ microwave power measurements up to 24 GHz. It provides true-average power measurements with high dynamic range from -60 dBm to +20 dBm (sensor dependent). The sensor has an internal zeroing function, with no external calibration needed. Network analyser FieldFox has an optional network analyzer mode that provides standard vector network analyzer measurements such as S11 magnitude and phase, S21 magnitude, and a Smith chart display. FieldFox’s sweep speed reduces time-toproblem resolution with test times over 50 percent faster. This enables RF engineers to tackle increasingly complex wireless networks in less time, radically improving productivity. Fast fault location is further enabled by its 1001-point resolution and excellent dynamic range. Conclusion Testing a cell site’s antennas, cables, filters, amplifiers, and troubleshooting interference is critical to ensuring good QoS in a network. Although traditional handheld I&M test solutions can address this task, they fail to offer the speed, productivity and flexibility required to meet the needs of today’s RF field engineers and technicians. The FieldFox RF analyzer, with its high level of integration, calibration-ready measurements and fast test times not only provides the measurement functionality today’s Wireless Service Provider’s demand, but offers a dramatic productivity improvement as well. For the Wireless Service Provider the result is the ability to more effectively deploy and maintain today’s complex wireless networks in less time. About the author Giovanni D’Amore joined Agilent Technologies (Hewlett-Packard) in 1999, as an application Engineer providing technical support for RF and microwave instruments including Network and Spectrum Analyzers. Since 2005, he has been part of Agilent’s European marketing organization with responsibility for parametric test instrumentation and, since 2007, the development of the company’s network analyzer business in the EMEA region. Giovanni holds a master degree in Electronic Engineering with specialization in Microwave and Telecommunications from Palermo University (Italy). Further information can be found at www.agilent.com/find/fieldfox. Microwave Engineering ● November 2008 ● www.mwee.com http://www.agilent.com/find/fieldfox http://www.mwee.com
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