Software Defined Radio

SDR - A Software-Defined Radio (SDR) system is a radio communication system where components that have typically been implemented in hardware (e.g. mixers, filters, amplifiers, modulators/demodulators, detectors. etc.) are instead implemented using software on a personal computer or other embedded computing devices. While the concept of SDR is not new, the rapidly evolving capabilities of digital electronics are making practical many processes that were once only theoretically possible.

A basic SDR may consist of a computer (PC) 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 done using special-purpose hardware. Such a design produces a radio that can receive and transmit a different form of radio protocol (sometimes referred to as a waveform) just by running different software.




software-defined radio


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DEFINITION - Software-defined radio (SDR), sometimes shortened to software radio (SR), refers to wireless communication in which the transmitter modulation is generated or defined by a computer, and the receiver uses a computer to recover the signal intelligence.? To select the desired modulation type, the proper programs must be run by microcomputers that control the transmitter and receiver.

A typical voice SDR transmitter, such as might be used in mobile two-way radio or cellular telephone communication, consists of the following stages.? Items with asterisks represent computer-controlled circuits whose parameters are determined by the programming (software).

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Microphone
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Audio amplifier
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Analog-to-digital converter (ADC) that converts the voice audio to ASCII data *
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Modulator that impresses the ASCII intelligence onto a radio-frequency (RF) carrier *
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Series of amplifiers that boosts the RF carrier to the power level necessary for transmission
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Transmitting antenna

A typical receiver designed to intercept the above-described voice SDR signal would employ the following stages, essentially reversing the transmitter's action.? Again, items followed by asterisks represent programmable circuits.

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Receiving antenna
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superheterodyne system that boosts incoming RF signal strength and converts it to a constant frequency
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Demodulator that separates the ASCII intelligence from the RF carrier *
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Digital-to-analog converter (DAC) that generates a voice waveform from the ASCII data *
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Audio amplifier
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Speaker, earphone, or headset





BENEFITS

* A family of radio “products” to be implemented using a common platform architecture, allowing new products to be more quickly introduced into the market.
* Software to be reused across radio "products", reducing development costs dramatically.
* Over-the-air or other remote reprogramming, allowing "bug fixes" to occur while a radio is in service, thus reducing the time and costs associated with operation and maintenance.

* Reduce costs in providing end-users with access to ubiquitous wireless communications – enabling them to communicate with whomever they need, whenever they need to and in whatever manner is appropriate.

* New features and capabilities to be added to existing infrastructure without requiring major new capital expenditures, allowing service providers to quasi-future proof their networks.
* The use of a common radio platform for multiple markets, significantly reducing logistical support and operating expenditures.
* Remote software downloads, through which capacity can be increased, capability upgrades can be activated and new revenue generating features can be inserted.



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