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.

Software-Defined Radio for Reconfigurable Communications

During the last decade, programmable digital radio systems have been replacing fixed analog radio systems as programmable hardware components have become more capable, inexpensive and available, and wireless communications applications have demanded reusable, reconfigurable and flexible radios.

• Traditional digital radio systems used application-specific integrated circuits (ASICs) and digital signal processors (DSPs).

• An SDR system implements many internal (baseband) operations with software or firmware.

• As hardware components evolve, future SDR systems may also allow programmable radio frequency (RF) bands within the RF section.

• SDR technologies allow fewer devices to support communications requirements, reducing size, weight and power.

• SwRI has developed SDR platforms, waveforms, transceivers, and SDR satellite communication terminals.

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.

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

• Specialty antennas, including smart antennas

SDR Architecture Research

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

• SDR architectures

• Implementation of SDR 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

	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.

Digital Predistortion

Internal research conducted at SwRI has produced 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 model-based design tools that describe:

• Communications requirements

• Processing requirements

• Available hardware

• Relevant properties of the alternative software architectures

The design space was 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

• Hardware components

  • Number

  • Type

• Channel parameters

  • Modulation scheme

  • Channel data rate

• Costs

  • Size

  • Weight

  • Power

  • Engineering costs

  • Purchase costs

• Transceiver capabilities

• In-flight reconfigurability

• Reprogrammability

This tool allowed the design space to be both quickly searched and incrementally refined in regions of higher payoff.

	Tapered-Aperture Small Helix (TASH) Antenna, a type of specialty antenna

Specialty Antennas, Including 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 antennas

• Electrically small antennas

• Low-observable antennas

• Phased array radar systems

• Antennas with 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 our software-defined radio capabilities, or how you can contract with SwRI, please contact Jeremy Price at jprice@swri.org or (210) 522-6292.  We can offer you the best approach for solving your SDR problem.

softwareradio.swri.org