Download this article in .PDF format
This file type includes high resolution graphics and schematics when applicable.

In today’s rapidly evolving and dynamic wireless world, hardware that can adapt to a myriad of different environments is becoming more critical. From tactical communications to the common smartphone, highly configurable hardware can remove the design/development and end-user costs associated with having to upgrade system hardware for a simple feature change. Instead, a software upgrade can be instantly transmitted through the existing wireless infrastructure as soon as an upgrade becomes available.

By developing their own software, users also can implement a host of desired features without significant knowledge of the underlying hardware. Such scenarios—which would have been a dream only a few years ago—are now very much a reality, thanks to software-defined radios (SDRs) and Universal Software Radio Peripherals (USRPs; Fig. 1).

To create a layer of digital abstraction, SDRs leverage the power of modern general-purpose processors (GPPs) and clever reprogrammable-logic systems, such as field-programmable gate arrays (FPGAs). De-embedding the hardware from the digital plane eliminates the need to physically adjust RF/microwave components to enable behavioral feature changes, such as implementing the latest LTE standards. When an SDR operates as a USRP with virtual hardware instrumentation, it can extract and analyze information within complex RF signals.

Modern SDRs

Highly accurate analog-to-digital converters (ADCs), which are placed on either generic or application-specific peripherals, map RF signals that are moved to a lower frequency. The ADCs can digitize those signals using downconversion. These signals are then converted into digital recreations of the waveforms. Processing is done using digital-signal-processing (DSP) techniques that are often implemented with the DSP cores of aFPGA.

Clearly, such flexible radio architectures could enable the same hardware to be used to implement a wide range of telecommunications applications. This task could be done on the fly, without the designer needing significant RF/microwave knowledge, and potentially using community-generated code. As a result, this approach easily translates into dramatically lower development and upgrade costs.

Tactical radio systems

Beyond telecommunications, SDR features also offer a host of advantages. Among other benefits, for example, tactical radios could adjust their communication algorithms based upon field conditions. Test and measurement instruments can receive cost-effective, software-licensed upgrades, which allows them to advance with the latest techniques. For their part, consumer products gain the ability to adapt to various wireless network situations for an optimum user experience. The applications that can benefit from SDR approaches are essentially infinite, given the ability to more easily generate the software backbone.

James Kimery, director of marketing for National Instruments, states, “Today, what’s driving a lot of momentum with SDR technology is that the software elements are available. Software is more plentiful and there is a community where code is shared, which helps with rapid adoption.” Yet the hardware to implement advanced SDR technology is still relatively expensive for certain applications. As a result, SDRs are more often used in applications in which the cost of the initial unit is offset by inexpensive upgradability and versatility. A few examples include tactical/public-safety radios, cellular base stations, test and measurement testbeds for interference/network mimicry, and rapid prototyping.

Tactical SDRs

As the range of SDR applications is vast, so is the rest of the SDR landscape—especially considering form factors, capabilities, software tools, and companies offering SDR solutions. Companies like Rohde & Schwarz offer highly rugged and flexible SDRs for mission-critical systems (Figs. 2 and 3). For low-cost rapid-prototyping structures, firms like Analog Devices and Peregrine make whole RF-transceiver systems-on-a-chip (SoCs) that lend themselves to SDR implementation.

Download this article in .PDF format
This file type includes high resolution graphics and schematics when applicable.