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Subsystems and Systems

A GSM Standard Band Selective Repeater

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
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.
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

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...
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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Design of a Predistorter Controlling Individual Orders of Intermodulation Using a New Harmonic Generator

A new type of predistortion linearizer is presented which uses individual orders of intermodulation to linearize a power amplifier. This new predistortion linearizer has two harmonic generators, each consisting of four diodes biased independently. Sinc...
In multi-carrier power amplifiers, a feedforward technique is generally adopted due to its extremely linear and broadband characteristics. 1 However, the feedforward technique requires large circuits and is expensive because of its complexity. It uses two cancellation paths, and delay lines are inserted in each path to adjust the...
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A Novel Adaptive Feedforward Amplifier Using an Analog Controller

A novel adaptive design for a feedforward amplifier linearizer with an analog controller is proposed in this article. Compared with previous adaptive linearizing methods, this new design does not require any pilot signal or intentional signal distortio...
For the third-generation (3G) mobile radio standards, a very high linearity transmitter that can support high crest factor signals is necessary. High linearity and high efficiency are critical issues in amplifier design. In fact, as the power amplifier operates close to the saturation region where both high efficiency and...
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Quick Mating N Connectors for RF Applications

In today's competitive environment designers and engineers are looking for any features that can give them the edge. When it comes to RF connectors, areas where that advantage can be gained are in the speed of installation, flexibility of connection and efficient utilization of space. The QuickLock family of...
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Precision Test Cable Assemblies to 40 GHz

The Accu-Test™ products are a family of precision cable assemblies that are designed for use in the DC to 40 GHz frequency range, intended to facilitate accurate measurements and exhibit low loss characteristics at a competitive price for precision test and measurement applications. The family is currently comprised of...
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A Method to Predict the Level of Intermodulation Products in Broadband Power Amplifiers

This article derives a formula to mathematically predict the level of intermodulation products generated in a broadband, multi-carrier power amplifier. The prediction method uses the level of a harmonic as a reference from which to extrapolate the leve...
Multiple RF exciters feeding a broadband power amplifier and a broadband antenna system has become an increasingly popular form of system architecture throughout the frequency spectrum. This architecture, shown in Figure 1 , has several desirable features, the most popular of which is the reduced real estate requirement. Modern...
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