ISSUE DATE: MARCH 2005  OPTIONS
Communications Technology

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March 2005 - In This Issue

[Cover Story]
Broadband Amps Boost Linear Power To 26.5 GHz
Microwave amplifiers were once designed in the bands favored by communications or military systems integrators, such as 2 to 4 GHz and 2 to 8 GHz. The influence of wireless applications changed those bands of interest to more narrowband coverage, such as the 800-to-900-MHz area of cellular systems, the 1800-to-2100-MHz range of Personal Communications Systems (PCS), and the 2.4- or 5-GHz bands of wireless local-area networks (WLANs). However, an increasing number of military and...  — Jack Browne

[News]
Frequency Synthesizers Generate Clean Signals
Frequency synthesizers account for many of the RF and microwave signals in communications, radar, and test systems. Synthesizers come in many forms and performance levels, from tiny phase-locked-loop (PLL) integrated circuits (ICs) to rack-mountable subsystems and precision test instruments with programmable control. What follows is a brief sampling of synthesizer suppliers and their latest products. Instrument-grade frequency synthesizers offer some of the highest performance...  — Jack Browne

[Design Features]
Tackling SE Testing On Microwave Cables
Shielding effectiveness (SE) is a key parameter when considering microwave coaxial cable assemblies and connectors for applications with strict electromagnetic-compatibility (EMC) requirements. Measuring the shielding or screening (as the IEC prefers1) effectiveness of microwave coaxial cables is not trivial, however, and requires a full understanding of the terminology and techniques practiced essentially by a distinct subset of the microwave industry concerned with EMC....  — Rudy Fuks

[Design Features]
Method Validates SAR Measurement Systems
Safety standards for setting acceptable levels of nonionizing radiation have been established for operating frequencies to 3 GHz.1-3 While such standards cover a wide range of wireless devices, a growing number of consumer wireless devices operate in the range from 5 to 6 GHz, even in the absence of international testing standards. The key metric for assessing wireless devices used in proximity to the body is the specific absorption rate (SAR), which can be expressed in units of...  — Dr. Mike I. Manning , et al.

[Design Features]
Analyzing 4:1 TLTs For Optical Receivers
Transmission-line transformers (TLTs) provide broadband impedance transformation in a wide variety of RF circuits. When using TLTs, analysis of the frequency response is an important consideration.1,2 Such analyses usually assume that the load and source are impedance matched through the transformer, although this is not always the case. At times, matching between the primary and secondary impedances of a TLT is either impractical or undesirable. An example of this is...  — Hughes De Saint Salvy , et al.

[Product Technology]
Clock-Recovery Module Sets Low-Jitter Standards
Jitter is one of the limiting factors in modern high-speed data-communications systems. Measuring jitter requires a reference source with almost ideal stability in order to detect the phase variations in the system or component under test. For that purpose, the model 83496A multirate optical/electrical clock recovery module has been developed for the model 86100C Infiniium digital communications analyzer (DCA-J) from Agilent Technologies (Palo Alto, CA). The module, which empowers the...  — Jack Browne

[Editorial]
Changes Affecting Communications
Advances in technology are changing the way that most folks communicate. Electronic communications can be traced back to Samuel Morse, his famous code, and the telegraph, with many changes to that basic technology in the years that followed. Ironically, Morse was not an engineer or scientist but a professional artist. An overheard shipboard conversation on electromagnets during his travels led to a vision and the invention of the telegraph. Morse's first transmission, from the...  — Jack Browne