Software- defined radio - Wikipedia. Software- defined radio (SDR) is a radiocommunication system where components that have been traditionally implemented in hardware (e. While the concept of SDR is not new, the rapidly evolving capabilities of digital electronics render practical many processes which used to be only theoretically possible. Overview[edit]A basic SDR system may consist of a personal computer equipped with a sound card, or other analog- to- digital converter, preceded by some form of RF front end. Significant amounts of signal processing are handed over to the general- purpose processor, rather than being done in special- purpose hardware (electronic circuits). Licensed Amateur Radio operator in 1996 as IW5EDI, active member of ARI Firenze and ARRL; Class 1970, married with two childrens, love experimenting and antenna home. WiNRADiO Communications - Pioneering Software Defined Radio - Manufacturers of SDR Systems for Professional Radio Surveillance and Amateur Applications. Is HAM Radio a dead hobby? By Gerald From Penang Malaysia. Such a design produces a radio which can receive and transmit widely different radio protocols (sometimes referred to as waveforms) based solely on the software used. Software radios have significant utility for the military and cell phone services, both of which must serve a wide variety of changing radio protocols in real time. In the long term, software- defined radios are expected by proponents like the SDRForum (now The Wireless Innovation Forum) to become the dominant technology in radio communications. SDRs, along with software defined antennas are the enablers of the cognitive radio. A software- defined radio can be flexible enough to avoid the "limited spectrum" assumptions of designers of previous kinds of radios, in one or more ways including: [2]Spread spectrum and ultrawideband techniques allow several transmitters to transmit in the same place on the same frequency with very little interference, typically combined with one or more error detection and correction techniques to fix all the errors caused by that interference. Software defined antennas adaptively "lock onto" a directional signal, so that receivers can better reject interference from other directions, allowing it to detect fainter transmissions. Cognitive radio techniques: each radio measures the spectrum in use and communicates that information to other cooperating radios, so that transmitters can avoid mutual interference by selecting unused frequencies. Alternatively, each radio connects to a geolocation database to obtain information about the spectrum occupancy in its location and, flexibly, adjusts its operating frequency and/or transmit power not to cause interference to other wireless services. Dynamic transmitter power adjustment, based on information communicated from the receivers, lowering transmit power to the minimum necessary, reducing the near- far problem and reducing interference to others, and extending battery life in portable equipment. Wireless mesh network where every added radio increases total capacity and reduces the power required at any one node.[3] Each node only transmits loudly enough for the message to hop to the nearest node in that direction, reducing near- far problem and reducing interference to others. Operating principles[edit]. Software defined radio concept. Ideal concept[edit]The ideal receiver scheme would be to attach an analog- to- digital converter to an antenna. A digital signal processor would read the converter, and then its software would transform the stream of data from the converter to any other form the application requires. An ideal transmitter would be similar. A digital signal processor would generate a stream of numbers. These would be sent to a digital- to- analog converter connected to a radio antenna. The ideal scheme is not completely realizable due to the actual limits of the technology. The main problem in both directions is the difficulty of conversion between the digital and the analog domains at a high enough rate and a high enough accuracy at the same time, and without relying upon physical processes like interference and electromagnetic resonance for assistance. Receiver architecture[edit]Most receivers use a variable- frequency oscillator, mixer, and filter to tune the desired signal to a common intermediate frequency or baseband, where it is then sampled by the analog- to- digital converter. However, in some applications it is not necessary to tune the signal to an intermediate frequency and the radio frequency signal is directly sampled by the analog- to- digital converter (after amplification). Real analog- to- digital converters lack the dynamic range to pick up sub- microvolt, nanowatt- power radio signals. Therefore, a low- noise amplifier must precede the conversion step and this device introduces its own problems. For example, if spurious signals are present (which is typical), these compete with the desired signals within the amplifier's dynamic range. They may introduce distortion in the desired signals, or may block them completely. The standard solution is to put band- pass filters between the antenna and the amplifier, but these reduce the radio's flexibility. Ham radio kits pack a lot of value. This page explains how much and why. Real software radios often have two or three analog channel filters with different bandwidths that are switched in and out. History[edit]The term "digital receiver" was coined in 1. United States Department of Defense laboratory. A laboratory called the Gold Room at TRW in California created a software baseband analysis tool called Midas, which had its operation defined in software. The term "software radio" was coined in 1. ![]() Garland, Texas Division of E- Systems Inc. Raytheon) to refer to a digital baseband receiver and published in their E- Team company newsletter. A 'Software Radio Proof- of- Concept' laboratory was developed there that popularized Software Radio within various government agencies. This 1. 98. 4 Software Radio was a digital baseband receiver that provided programmable interference cancellation and demodulation for broadband signals, typically with thousands of adaptive filter taps, using multiple array processors accessing shared memory.[4]In 1. Joe Mitola independently reinvented the term software radio for a plan to build a GSM base station that would combine Ferdensi's digital receiver with E- Systems Melpar's digitally controlled communications jammers for a true software- based transceiver. E- Systems Melpar sold the software radio idea to the US Air Force. Melpar built a prototype commanders' tactical terminal in 1. Texas Instruments TMS3. C3. 0 processors and Harris digital receiver chip sets with digitally synthesized transmission. That prototype didn't last long because when E- Systems ECI Division manufactured the first limited production units, they decided to "throw out those useless C3. RF filtering on transmit and receive, reverting to a digital baseband radio instead of the SPEAKeasy like IF ADC/DACs of Mitola's prototype. The Air Force would not let Mitola publish the technical details of that prototype, nor would they let Diane Wasserman publish related software life cycle lessons learned because they regarded it as a "USAF competitive advantage." So instead, with USAF permission, in 1. Mitola described the architecture principles without implementation details in a paper, "Software Radio: Survey, Critical Analysis and Future Directions" which became the first IEEE publication to employ the term in 1. When Mitola presented the paper at the conference, Bob Prill of GEC Marconi began his presentation following Mitola with "Joe is absolutely right about the theory of a software radio and we are building one." Prill gave a GEC Marconi paper on PAVE PILLAR, a SPEAKeasy precursor. SPEAKeasy, the military software radio was formulated by Wayne Bonser, then of Rome Air Development Center (RADC), now Rome Labs; by Alan Margulies of MITRE Rome, NY; and then Lt Beth Kaspar, the original DARPA SPEAKeasy project manager and by others at Rome including Don Upmal. Although Mitola's IEEE publications resulted in the largest global footprint for software radio, Mitola privately credits that Do. D lab of the 1. 97. Carl, Dave, and John with inventing the digital receiver technology on which he based software radio once it was possible to transmit via software. A few months after the National Telesystems Conference 1. E- Systems corporate program review, a vice- president of E- Systems Garland Division objected to Melpar's (Mitola's) use of the term "software radio" without credit to Garland. Alan Jackson, Melpar VP of marketing at that time asked the Garland VP if their laboratory or devices included transmitters. The Garland VP said "No, of course not — ours is a software radio receiver".
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