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Subsystems and Systems

Application of GTEM Cells to Wireless Communication Transceiver Designs

The GTEM cell has been widely accepted as a sufficient tool in electromagnetic compatibility for both radiated susceptibility tests and radiated emission tests. In this article, the relationships among basic quantities such as input power, electric fie...
September 1, 2003
The gigahertz transverse electromagnetic mode (GTEM) cell was first proposed in 1987 1 and subsequently patented in 1989 by D. Konigstein and D. Hansen 2 as a high frequency variant of the transverse electromagnetic mode (TEM) cell, which is also known as the Crawford cell. 3 The GTEM cell...
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A Cost-effective Solution for Frequency Conversion of BTS Transmitters

August 1, 2003
As the wireless industry moves to implementation of 3G standards, wireless service providers are looking for ways to make the transition with the most rapid time-to-market and minimized design cost of new equipment. The TXC Series transmitting converters are designed for this environment, and allow base transceiver station (BTS)...
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Active CATV Splitters with High Isolation and Linearity

August 1, 2003
Splitting an RF input signal within a VCR or television was never much of a design challenge for manufacturers when the signal was analog. That changed dramatically, however, when CATV systems made the transition from analog to digital to provide addressability, video on demand, Internet access and other services....
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Defense Priority Ratings: Know the Rules

June 1, 2003
From the time a Department of Defense (DoD) program lands on the classified "secret" document known as the Master Urgency List (MUL), most orders placed to complete that program will have a priority rating. Most contractors and subcontractors who deal with these orders must therefore have a working understanding...
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A Dynamic Approach to Synthesizer Design

New developments in direct digital synthesis-based synthesizer technology
May 1, 2003
Broadband synthesizers based on direct digital synthesis (DDS) technology have traditionally led the industry in frequency agility and switching performance, but have also led in high NRE and recurring costs. These high costs stem from the custom nature of DDS-based synthesizers and have resulted in digital synthesizers being primarily...
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A GSM Standard Band Selective Repeater

May 1, 2003
In recent years, GSM systems have been deployed using many base transceiver stations (BTS). However, in some areas, such as basements of buildings, tunnels and valleys, there may be no signal, and in some regions fading may occur. These problems can be solved cheaply by implementing repeaters. Figure 1...
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An Aircraft Single-antenna FM Radio Altimeter

Advantages of a frequency modulated single-antenna radio altimeter, including lower cost and weight, improved accuracy and higher altitude range
May 1, 2003
As is well known, there are two general types of altimeter systems - a pulse radar altimeter and a frequency modulated, continuous wave (FM-CW) radio altimeter. Aircraft radio altimeters typically operate at altitudes from 0 to 8000 feet utilizing separate antennas for transmit and receive. Such radio altimeters have...
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Design and Operation of Automatic Gain Control Loops for Receivers in Modern Communications Systems

This article is intended to provide insight into the effective operation of variable gain amplifiers (VGA) in automatic gain control (AGC) applications.
May 1, 2003
This article is intended to provide insight into the effective operation of variable gain amplifiers (VGA) in automatic gain control (AGC) applications. Figure 1 is a general block diagram for an AGC loop. The input signal passes through the VGA to produce the output level to be stabilized. The...
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New Types of Millimeter-wave Noise Sources

April 1, 2003
Used for remote sensing in various applications and environments, microwave and millimeter-wave radiometers (RM) require frequent calibration. Microwave radiometers measure noise temperature using a suitable antenna which is designed to match a scene of interest, as shown in Figure 1 . In a technical sense, if the antenna's main...
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An Adaptive Feedforward Amplifier for WCDMA Base Stations Using Imperfect Signal Cancellation

This article describes a new adaptive feedforward amplifier for a WCDMA system using an imperfect signal cancellation. Due to the complicated signal statistics, the distortion generated by the error amplifier is significantly reduced by an imperfect si...
April 1, 2003
As wireless systems evolve from second- to third- or fourth-generation, the linearity, efficiency and bandwidth requirements for power amplifiers become more stringent. Many techniques, including feedforward, envelope feedback and manifold types of predistorters, have been employed to effectively satisfy these performance requirements and to reduce the production costs for...
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