AN3559| Application Note
Maxim/Dallas > App Notes > A/D and D/A CONVERSION/SAMPLING CIRCUITS BASESTATIONS / WIRELESS INFRASTRUCTURE HIGH-SPEED SIGNAL PROCESSING WIRELESS, RF, AND CABLE Keywords: high performance, RF, modulator, heterodyne, transmitter, multi-carrier, direct conversion, IF, CDMA2000, WCDMA, OFDM, OIP2, OIP3, noise floor, LO, ACLR, UMTS, Tx, digital-to-analog converter, DAC, interpolation filter, cascade, reject mixer
Jun 01, 2005
APPLICATION NOTE 3559
High-Performance RF Modulator Enables Multi-Carrier Communications Transmitters
Cellular transmitters rely on high-performance RF modulators to maintain linearity and dynamic range. With the growth of multi-carrier transmitters, RF modulators must maintain a low noise floor while delivering good highlevel performance, usually determined by second- and third-order intercept points. The following article discusses these requirements and explains how the MAX2022 meets the requirements for a typical four-carrier WCDMA transmitter architecture.
Overview
Today nearly all cellular base stations employ super heterodyne architectures to transmit/receive RF signals. These architectures require two or more up/down conversion stages, intermediate filtering, and analog signal processing. Figure 1 shows a typical dual-conversion, cellular-base-station transmit block diagram. Many of these transmitters were implemented as single-carrier systems. Multi-carrier transmitters replicate single-carrier transmitters multiple times, thus introducing substantially more system hardware. To reduce transmitter cost, many system designers are turning to multi-carrier transmitters and direct-conversion RF architectures.
Figure 1. Typical super heterodyne transmit architecture.
The Challenges of a Multi-Carrier Architecture
Multi-carrier architectures reduce the number of transmit channels. Direct-conversion architectures reduce the number of components in each channel by converting RF signals directly up from baseband. Both architectures require components with wider dynamic range and higher linearity to meet overall system requirements. Figure 2 shows a typical block diagram of a direct-conversion transmitter architecture. Note the significant reduction in stages in this direct-conversion architecture. Multiple mixers, amplifiers, IF and RF filters are all replaced by a single integrated solution.
AN3559 Application Note maxim Download PDF
Add this permalink to your bookmarks for future download of AN3559 ApplicationNote
Permalink: http://application.emcelettronica.com/maxim/AN3559
