Software Defined Radio (SDR) is a collection of hardware and software technologies that enable reconfigurable system architectures for wireless communications. SDR provides an efficient and comparatively inexpensive solution to the problem of building multi-mode, multi-band, multi-functional communications devices that can be enhanced using software upgrades. As such, SDR can really be considered an enabling technology that is applicable across a wide range of areas within the wireless industry.

SDR enabled communications devices can be dynamically programmed in software to reconfigure the characteristics of equipment. In other words, the same piece of "hardware" can be modified to perform different functions at different times. This allows the manufacturer to concentrate development efforts on a common hardware platform.

Joe Mitola is quoted as saying, "A software radio is a radio whose channel modulation waveforms are defined in software. That is, waveforms are generated as sampled digital signals, converted from digital to analog via a wide band DAC and then possibly up converted from IF to RF. The receiver, similarly, employs a wide band Analog to Digital Converter (ADC) that captures all of the channels of the software radio node. The receiver then extracts, down converts and demodulates the channel waveform using software on a general purpose processor."

Just getting started with SDR and want to learn more about the concept? Just click on Answer.com.

The SDR-1000™ from FlexRadio Systems was the very first complete Software Defined Radio (SDR) transceiver interface to a Personal Computer for amateur radio use. It provided everything needed to convert a PC into a high performance, 11KHz-65MHz general coverage receiver with 160M-6M (2M optional) Amateur Radio band transmit capability. The SDR-1000 is described in detail in a four part article series in QEX Magazine.

The SDR-1000™ incorporated a novel Quadrature Sampling Detector to provide high dynamic range with minimal components. An Analog Devices AD9854 quadrature DDS and 200MHz 1ps jitter clock oscillator provides continuous coverage with very low phase noise.

What started out as an experimenters kit was wildly received by the ham radio community and evolved into a full featured transceiver. The introduction of FlexRadio PowerSDR™ replaced the original VisualBasic SDR software and in a short time contained all of the feature functionality one would expect with a all-band, all mode amateur radio transceiver.

The FLEX-5000 represents the next evolutionary advancement in software defined radio hardware. The FLEX-5000 Family, which consist of the FLEX-5000A™ and the FLEX-5000C™ are three ultra-high performance transceivers that were built completely from the ground up, taking the best design features of the SDR-1000 and adding some of the most innovative ideas that allow all aspects of the hardware to be software controlled. The FLEX-5000 Family uses the highest performance wide-band ADC and DACs available, which is where the incredible dynamic range performance comes from. No longer are consumer sounds cards needed for this function. Also, radio control and I/Q audio transfer from the radio hardware to the computer is now accomplished over a single FireWire connection. BITE better known as Built In Test Equipment, is included in all FLEX-5000 transceivers.  This give the FLEX-5000 to ability to be self calibrated without having to have any external test equipment such as signal generators because they are built right in.