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Amplifiers

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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Breakthrough Power Amplifier Module for Handset Applications

June 1, 2003
This is the best time to be a consumer of electronic products. Wireless mobile devices, especially cellular handsets, have more features, are smaller and have better battery life than ever before. The cellular handset manufacturing industry is continuously challenged to deliver high performance, cost-effective, small form function products to...
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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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A Cellular Band Power Amplifier/Duplexer Module

April 1, 2003
Wireless communications handsets are increasing in functionality through the addition of features such as GPS, color displays and PDA functions. At the same time the handset is maintaining a roughly constant price and size target. Because of this trend, handset manufacturers are requiring higher levels of integration from component...
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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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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...
April 1, 2003
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...
April 1, 2003
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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Memory Effect Reduction for LDMOS Bias Circuits

Memory effects have taken a very important role in today's design of base station power amplifiers. For example, they are responsible for limiting the cancellation when pre-distortion is applied to a power amplifier system.<sup>1</sup> This study show...
February 1, 2003
Electrical memory effects are defined as changes in amplitude and phase of distortion components caused by modulation frequency. There are several ways of measuring memory effects. One of the most common is to plot the phase and amplitude of the distortion parameters with respect to the tone spacing in...
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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...
February 1, 2003
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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Effects of Grounding and Bias Circuit on the Performance of High Frequency Linear Amplifiers

The design of a high frequency amplifier is normally based on the S-parameters supplied by the manufacturer of the active device. However, in a practical design, these parameters are affected by the DC bias network and the grounding of the active devic...
February 1, 2003
In the design of high frequency power amplifiers, one of the parameters is the stability of the active device. The stability of the active device is determined by the Rollet stability factor K. If K > 1, then the active device is unconditionally stable and the design of the...
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