As processing power and memory become ever cheaper, engineers increasingly solve problems in software and firmware rather than hardware. This trend is nowhere more apparent than in software-defined radio (SDR). Applying digital signal processing techniques to RF input, SDRs deliver performance coupled with an impressive degree of flexibility for applications ranging from military to public safety to commercial uses like RFID.
The exact definition varies depending upon who is doing the defining, but we can loosely characterize an SDR as one in which some or all of the physical-layer components are executed in software. In this roundup, you can review the fundamentals, familiarize yourself with the challenges, understand test, and discover the most recent advances in the field.
Fundamentals of SDR
Before you can think about new developments, you have to have a common set of definitions and operating assumptions. Start out with this three-part tutorial from:
Basics of Software Defined Radio, Part 1: Learn the fundamental definitions, architectures, and the trade-offs involved in dynamic characteristics such as data rate, channel bandwidth, and modulation schemes.
SDR Basics: Receivers: Before you can move into the digital domain, you need an analog front end. Superheterodyne architectures provide a good solution.
SDR Basics Part 3: Transmitters: Tactical military radios need to transmit as well as receive. Here, too, devices leverage either super-heterodyne or direct conversion schemes, depending on the application.
Looking for more background? Review the Software Defined Radio Handbook to learn how SDRs replace conventional analog receivers with digital downconverters and upconverters. Enhance your understanding with a review of board- and system-level implementations, as well as off-the-shelf SDR products for embedded systems.
Making SDR practical
Theory provides an essential foundation, but to go to the next step, you need tips, tools, and examples. Take a look at the design features below to find out more.
Despite the power and popularity of SDR, it still presents challenges to design engineers. Read a rundown on the pros and cons and discover techniques you can use to overcome these problems in Software defined radio: defining the challenges.
SDRs are complex systems that require analysis from the component through system levels in order to achieve the desired performance. Find out about design techniques and some of the development and simulation tools they can simplify your life in Optimize SDR performance.
Want an example of how it's done? Read Hands on RF: Handle multiple waveforms in a software-defined radio platform. Today’s tactical and commercial software-defined radios must have the flexibility and processing power to support a growing number of wideband and broadband waveforms including an extensive library of legacy waveforms. Here, the authors describe how they used the partial reconfiguration and isolation design flow capabilities of the Xilinx Zynq-7000 Extensible Processing Platform (EPP) to support various waveforms, reduce part count from five devices to one, and save power.
Testing is an essential part of engineering. An SDR needs to operate at high data rates over multiple channels. It needs enough bandwidth to conform to multiple standards. When you have a unit capable of running a variety of different tasks, the number of testing scenarios expands significantly. Find out more about the problems and solutions in Understanding SDRs and their RF Test Requirements.
Enhanced ADCs have enabled the development of wideband SDR solutions that offer high-channel-count, high-frequency operation. In these applications, traditional ADC specifications such as the effective number of bits (ENOB) no longer apply, however. Find out why, and the correct criteria to apply in Software Defined Radio: Don’t Talk to Me about ENOBs, Part 1 and Part 2.