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ISSUE DATE: JUNE 2005 | |
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June 2005 - In This Issue [Cover Story] Software Shaves Spurs In Frequency Planning Frequency planning is a critical first step in the design of a radio communications system. Several frequency schemes are usually considered to ensure system reliability as well as compatibility with existing systems and compliance with applicable regulations. External performance is typically controlled by a regulatory agency, such as the Federal Communications Commission (FCC) or European Telecommunications Standards Institute (ETSI), and the designer must comply with requirements before... — Rulon VanDyke [News] Technology Fills Homeland-Security Gaps Shortly after September 11, 2001, the Department of Homeland Security (DHS) was taxed with protecting the United States from any terrorist threat. Due to the immensity of this task, it is no surprise that the DHS has had to withstand some controversy and criticism. Just recently, for example, a New York Times article reported that problems could easily arise from the department's means of securing ports ("Loopholes Seen in U.S. Efforts to Secure Ports," May 25, 2005). Ports have often... — Nancy Friedrich [Design Features] Design Improves 4.3-GHz Radio Altimeter Accuracy Short-range radio altimeters are important safety and navigational tools in small aircraft. Usually designed as short-range frequency-modulated (FM) radars in the 4.2-to-4.4-GHz band,1 their main applications are for instrument-based approaches and landings for larger commercial aircraft, although they are also suitable for smaller aircraft and even unmanned air vehicles (UAVs). The accuracy and resolution of aviation altimeters is usually limited to a few feet due to the limited... — Matjaz Vidmar [Design Features] Reducing ADC Quantization Noise Analog-to-digital converters (ADCs) provide the vital transformation of analog signals into digital code in many systems. They perform amplitude quantization of an analog input signal into binary output words of finite length, normally in the range of 6 to 18 b, an inherently nonlinear process. This nonlinearity manifests itself as wideband noise in the ADC's binary output, called quantization noise, limiting an ADC's dynamic range. This article describes the two most popular methods... — Richard Lyons , et al. [Design Features] Slot Boosts Bandwidth Of WLAN Patch Antenna Wireless local-area networks (WLANs) at 5 GHz offer the impressive data rates (54 Mb/s) that have helped them grow in popularity. The broad bandwidth of these systems—from 5.15 to 5.85 GHz—also poses a challenge for RF circuit and antenna designers. Fortunately, it is possible to cover the full 5-GHz band using a compact patch antenna. Traditionally, patch antennas are limited in bandwidth, typically less than 5 percent. But numerous approaches have been developed to... — Louis Fan Fei [Design Features] Efficiently Design And Model MMICs With Passive Elements Monolithic microwave integrated circuits (MMICs) are often thought of as active devices, since they rely strongly on the capabilities of small-gate transistors and diodes. But passive elements are also an important part of these circuits, and computer simulations too often are limited in accuracy of their passive-component models, especially for arbitrarily shaped components for which no analytical models exist. In such cases, electromagnetic (EM) simulators commonly are used. What follows... — Keefe Bohannan [Product Technology] Cables Connect Test Gear To 18 GHz Test cables must deliver high performance levels even when withstanding such daily abuses as being stretched, tugged, and sometimes used as handles for measurement equipment. Such cables can be expensive for lengths of just a few feet. However, when measurement integrity and the accuracy of test results depend on the cable, no price is too high. Still, for engineers who want the high performance without the high price tag, there are the new CBL-Series flexible coaxial test cables from... — Jack Browne [Product Technology] Scope And Probe Capture 40 Gsamples Testing modern high-speed data formats such as Fibre Channel, serial ATA, and PCI-Express poses a challenge for even the best instruments. With rise times exceeding 50 ps on pulse edges, these data formats are now reaching transmission speeds of 4.0 to 8.5 Gb/s. Transients and signal harmonics only add to the testing difficulty. Fortunately, the Infiniuum 80000 series of real-time oscilloscopes from Agilent Technologies (Palo Alto, CA) provides bandwidths of 8, 10, 12, or 13 GHz—with a... — Nancy Friedrich [Editorial] Broadband Access Poses Problems Broadband communications implies the bandwidth that makes service providers salivate. This is not simply broadband runs of optical cables or line-of-sight microwave links. This is broadband access, that elusive "last mile" to the home, with visions of truly fast high-speed Internet access, video on demand, crystal-clear voice and video two-way communications, and just about anything that service providers want to cram into that pipeline to your home. The only problem, and... — Jack Browne |
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