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Subsystems and Systems

A Cost-effective Solution for Frequency Conversion of BTS Transmitters

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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A Dynamic Approach to Synthesizer Design

New developments in direct digital synthesis-based synthesizer technology
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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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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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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