Software-defined-radio (SDR) technology at one time was automatically associated with the type of secure communications needed by the Armed Forces. But, as with many things based on electronic components, that has changed a great deal in recent years. SDR-based products are now available for amateur-radio operators, as well as for commercial and consumer radio users. In fact, as some of the critical components for SDR systems—such as analog-to-digital converters (ADCs) and digital-to-analog converters (DACs)—have improved in performance and dropped in price, the market for SDR-based products has seemingly expanded to the consumer level. It appears that SDR technology will be embraced by healthy markets in commercial, military, and even industrial areas.


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An ideal SDR configuration can be as simple as an antenna, ADC, DAC, and programmable processor (to control the data converters). The concept of changing the characteristics of a radio through software has actually been around for almost 30 years, with the possibility of using software and hardware together in this way coming from a laboratory at defense contractor E-Systems (now part of Raytheon Co.). With the security inherent in the programmability of these radios, it is easy to see why so many military radio architects would become entranced by the technology, especially with the growing availability of affordable data converters capable of supporting broadband communications.

At the same time, with the modern consumer’s appetite for instant communications and high-data-rate wireless communications, SDR technology represents a viable approach for commercial service providers wanting to field equipment that can adapt to ever-changing wireless standards. Organizations such as the Wireless Innovation Forum (WIF) have registered their support for SDR technology, as well as their desire for this technology to achieve a strong position in both commercial and military communications applications.

One of the more visible users of SDR technology is NASA on the International Space Station. Earlier this year, NASA began using its Space Communications and Navigation (SCaN) test bed for experiments to develop advanced communications, networking, and navigation functions in space. The SCaN test bed uses a new generation of SDR technology that promises to bring new cost savings and efficiency to NASA as it develops high-speed data communications solutions for the future. SDRs for the platform have already been developed under cooperative agreements with NASA by General Dynamics and Harris Corp.

According to International Space Station Program Manager Michael Suffredini, “The space station serves as a dynamic test bed for the technologies needed for future human and robotic exploration. SCaN is an example of the technologies that are being matured in low-Earth orbit and used to increase science return of many different types of spacecraft.” John Rush, Technology and Standards Director for SCaN at NASA Headquarters in Washington, DC, adds: “With the development and deployment of this test bed, NASA has enabled significant future advancements by gaining knowledge and understanding of SDR development.”

The test bed has been applied to learning more about communications in space using S- and Ka-band frequencies. It will also be used for an experiment with NASA’s latest Tracking and Data Relay Satellite (TDRS), to demonstrate a TDRS spacecraft acquiring and successfully auto-tracking a Ka-band user in low-Earth orbit. This test bed is expected to be operational for as long as six years aboard the space station. It is meant to offer experimental opportunities to NASA, industry, academia, and other government agencies. The experiments contribute data to the Space Telecommunications Radio Standard Compliant repository; they enable future hardware platforms to use common, reusable software modules to reduce development time and costs.

SDR Kit Options

To aid SDR developers, a growing number of radio and components suppliers are offering board-level and system-level SDR kits. For example, earlier this year CML Microcircuits unveiled its model DE9941 SDR 1 Demonstration Board, which combines the company’s model CMX998 Cartesian Feedback Loop Transmitter, model CMX994 Direct-Conversion Receiver, and model CMX7164 Multimode Wireless Data Modem integrated circuits (ICs). About the size of a credit card, the SDR board (see "SDR Board Eases Radio System Design") supports a variety of modulation formats, including  quadrature amplitude modulation (QAM), frequency-shift-keying (FSK), and Gaussian minimum-shift-keying (GMSK) modulation. It is usable to about 1 GHz with frequency-synthesized operation and is ideal for product conceptualization and development. The SDR 1 Demonstration Board operates on a single +3.6-VDC, 2-A supply.

More recently, Pentek introduced its model 8266 personal computer (PC) development system. It is preconfigured to speed application development for the Pentek Cobalt® Virtex-6 and Onyx® Virtex-7 FPGA PCI Express software radio and data acquisition input/output (I/O) boards. Each model 8266 is delivered with the selected Pentek hardware configured for either Microsoft Windows or Linux operating system and ReadyFlow® BSP drivers and software examples, fully installed and tested.

The company’s Vice President, Rodger Hosking, explains: “The Model 8266 is offered as a standard pre-integrated platform, saving our customers valuable time and cost in selecting, assembling and configuring components for a high-performance, real-time development system.” He notes that “we resolve the typical hardware, operating system, and software compatibility obstacles inherent in new PC development platforms. All hardware is installed in appropriate slots, fully configured with proper cabling, power and cooling strategies, and optimized BIOS and operating system settings. The customer simply needs to remove the system from the package and start developing. As an added benefit, the tested and proven configuration of the Model 8266 streamlines Pentek customer support.”


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Pentek works closely with a customer to evaluate system requirements and define the SDR development platform best suited for the final application. The Model 8266 includes the company’s drivers and board support libraries, as well as example applications and the firm’s Signal Analyzer—a full-function analysis tool for displaying signals in the time and frequency domains. The Model 8266 SDR platform, which can be configured with 64-b Windows or Linux operating system, is based on an Intel Core i7® processor and high-performance PCIe motherboard. All necessary coaxial and timing cables are installed and tested, providing SMA connectivity for all analog I/O lines.

Texas Instruments also offers an SDR developer’s kit: its TI Small Form Factor (SFF) Software Defined Radio (SDR) Development Platform based on the firm’s data converters and a model TMS320DM6446 digital-signal-processing (DSP) system-on-chip (SoC) device. The kit supports an RF range of 360 to 960 MHz with a 70-MHz intermediate frequency (IF) and selectable channel bandwidths of 5 or 20 MHz. It provides -110 dBm typical receive sensitivity and typical RF gain of 22 dB. It is designed to operate on an IBM-compatible personal computer with Pentium III or better microprocessor running the Windows XP Professional operating system. It supports a variety of software development tools, including Texas Instruments Code Composer Studio™ Integrated Development Environment, the Xilinx ISE Foundation for FPGA development from Xilinx, the Xilinx System Generator for DSP software tools, and MATLAB® and Simulink™ software from The MathWorks.

1. The bladeRF board-level radio enables system designers to add SDR capabilities to their designs. (Photo courtesy of Nuand.)

Nuand offers its bladeRF board-level SDR developers’ platform (Fig. 1) which connects to a computer via USB 3.0 bus and captures a 12-b 40 MHz bandwidth from 300 MHz to 3.8 GHz. Available open-source software drives provide support for GNURadio among other communications standards. The bladeRF board measures 5.0 x 3.5 in. and is capable of 28-MHz full-duplex channels and can operate in a 2 x 2 MIMO configuration.

2. The NI FlexRIO SDR bundle simplifies radio development by including usable software with the programmable radio hardware. (Photo courtesy of National Instruments.)

A number of test-instrument manufacturers also provide SDR developer kits, including National Instruments with its NI FlexRIO SDR bundle (Fig. 2). It includes the firm’s model NI 5791 transceiver, NI FlexRIO field-programmable-gate-array (FPGA) module, and LabVIEW software. The transceiver, which is built into a four-slot PXI Express housing, covers as much as 100-MHz real-time bandwidth from 200 MHz to 4.4 GHz with an 80-dB dynamic range. It employs a standard LabVIEW software design flow already familiar to many engineers to simplify radio development. In terms of SDR software, one of the leaders is Green Hills Software. The firm’s INTEGRITY™ real-time operating system (RTOS) has been widely used on SDR programs, notably on those that depend on the SCA v2.2 interface. It is the first operating system to be certified to the latest IEEE POSIX.1-2003 specification. The RTOS is designed to provide central processing unit (CPU) time, memory, and file system resource guarantees in support of critical radio functions and SDR waveforms. It uses brick-wall partitioning to ensure that applications and waveforms always have the resources needed to run and cannot corrupt other applications or waveforms already running.

Although SDR technology started with military users in mind, it is quickly being adopted for commercial and even amateur-radio applications. Organizations such as the Amateur Radio Relay League and companies such as FlexRadio Systems are enabling amateur-radio operators to apply SDR technology to their pursuits. In fact, the FLEX-6000 series transceivers from FlexRadio Systems are SDR designs that have found favor among amateur radio enthusiasts, especially for use in ham radio festivals. These transceivers offer two independent signal capture units (SCUs) as they are known—enabling the SDRs to perform diversity reception over bands from 0.033 to 77.000MHz and 135 to 165 MHz—bringing amateur-radio operation to a new level of sophistication.