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	Software-defined radio demo system. UHF radio using OSSIE SCA (Open Source SCA Implementation::Embedded)

A software-defined radio (SDR) uses software to modulate and demodulate digitized radio signals. An SDR performs signal processing using software algorithms, producing a radio that receives and transmits signals in a software-controllable fashion. Engineers at Southwest Research Institute (SwRI) have conducted research and development projects on many different aspects of SDR. Research is being conducted in:

• Architecture research

• Digital predistortion

• Model-based design tools

• Smart antennas

Architecture Research

The Communications Engineering and Embedded Systems Department at SwRI has conducted research in:

• SDR architectures

• Implementation of architectures on general-purpose processors and other flexible hardware components

• Adaptation of architectures for specialty applications, such as:

  • Quick-boot SCA (software component architecture), used for military SDRs

  • New military radios, required to be JTRS- (Joint Tactical Radio System) compliant SDRs

Digital Predistortion

	Four-channel WCDMA signal at 2.14 GHz with and without digital predistortion. The WCDMA signal is wideband code division multiple access, one of the 3G standards.

Internal research conducted at SwRI has resulted in a set of algorithms for digital predistortion including:

• Nonlinear compensation

• Memory effects compensation

• Linear compensation

• Crest-factor reduction

Commercial funding has also been awarded to develop proof-of-concept subsystems for digital predistortion in 3G (3rd generation) cellular systems.

Model-Based Design Tools

SwRI engineers have developed model-based design tools for SDR and other radio systems. In a project completed for a major aerospace company, SwRI developed a set of models that describe:

• Communications requirements

• Processing requirements

• Available hardware

• Relevant properties of the alternative software architectures

The design space is then analyzed using objective cost and capability metrics. The tool developed for this project used the models to examine the impact of design choices, such as software architecture, middleware, number and type of hardware components, and channel parameters (modulation scheme, channel data rate), on costs (size, weight, power, engineering costs, purchase costs) and transceiver capabilities (in-flight reconfigurability and reprogrammability). This tool allows the design space to be both quickly searched and incrementally refined in regions of higher payoff.

	Tapered-Aperture Small Helix (TASH) Antenna

Smart Antennas

SwRI engineers have extensive experience in developing specialty antennas and are now conducting research in smart antennas. Areas of study in specialty antenna research include:

• Broadband

• Electrically small

• Low-observable

• Phased array radar systems

• Other special attributes

Smart antenna systems can adaptively point the main antenna beam in the direction of a desirable transceiver and point one or more antenna nulls towards interfering signals. Alternatively, smart antennas can be made to resonate at different frequencies, depending upon the need to emulate different radios or use a different part of the spectrum with fewer interferers.

For more information about software-defined radio capabilities at SwRI or how you can contract with SwRI, please contact Mike Pilcher at mpilcher@swri.org or (210) 522-2083. We can offer you the best approach for solving your SDR problem.
 

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Southwest Research Institute® (SwRI®), headquartered in San Antonio, Texas, is a multidisciplinary, independent, nonprofit, applied engineering and physical sciences research and development organization with 11 technical divisions.

August 18, 2008