Article
Modeling 3G/WCDMA/HSDPA Handset Transmit System
May 23, 2007
By Chris W. Liu, RF Micro Devices, Inc.
Wideband Code Division Multiple Access (WCDMA) has been chosen as one of the standards for the third generation (3G) cellular systems that are being deployed in various parts of the world. System performances have been well defined in 3GPP standards. However, these system specifications need to be translated down to circuit block level for designers to execute circuit implementation. To optimize the overall system performance, system modeling is the essential tool to allocate system budgets with accurate analysis, and therefore, minimize design iterations and reduce the time to market.
Model of Transmit System
Figure 1 shows the proposed system model of a linear direct conversion transmit system (DCT) for the WCDMA system. This model consists of a number of subsystems or circuit blocks: Digital Signal Generator, Digital to Analog Converters (DAC) and Reconstruction Filters, Modulator, Preamplifier and Power Amplifier, as well as RF Front-end components.
The role of the signal generator is to receive data symbols from the baseband processor, and then create ideal WCDMA digital I/Q signals. The digital I/Q signals are then converted to analog format by the DAC and reconstruction filter. The analog I/Q signals are then fed into a modulator, where the complex WCDMA signal is upconverted and modulated on a RF carrier. The RF signal is amplified by the power amplifier, and then delivered to the antenna through the front-end components such as the duplexer, isolator, coupler, as well as RF switches, etc.
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•Technical Article: Modeling 3G/WCDMA/HSDPA Handset Transmit System
As originally seen in Microwave Product Digest, February 2007.
