The intention of this article is to provide a tool for the design of a predistorter, a component intended to correct unwanted nonlinear effects in power amplifiers. In order to come up with a design, a concept of predistortion is discussed. The conclus...
October 1, 2003
This article continues the trend of previous publications, 1,2 to simplify the prediction of RF performance of systems designed for wireless digital communications. The first shows the correlation between sidelobes and intermodulation (IM) products. Sidelobes are the result of the spectrum re-growth when a digitally modulated signal is applied...Read More
September 1, 2003
A versatile new three-stage buffer amplifier has been introduced that is ideal for use as a receiver front end low noise amplifier, but, as a result of its dual bias configurations, it can also be used as a driver amplifier or LO buffer with good linearity and higher gain....Read More
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....Read More
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...Read More
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...Read More
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...Read More
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...Read More
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...Read More
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...Read More
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...Read More