Using Software Defined Radio for Faster Speeds and Increased Bandwidth
Software Defined Radio (SDR) is a construct for performing radio functions by means of software on a computer or embedded system. SDR isn’t a new concept, and many of the techniques are well established. However, there have been challenges when it comes to the practicalities of the more demanding SDR applications driven largely by ADC/DAC limitations trade-offs. With ever-faster ADC and DACs at better resolution, many of these compromises are being overcome – or at least be limited to higher parts of the frequency spectrum where the fast, high-resolution digitizers with current generation wideband front end cannot reach.
Wideband is an important element for SDR to avoid limiting it to single-frequency ranges and to be able to deal with several channels (or channel) at once. This is especially true for Cognitive radio. A cognitive radio introduces intelligence, allowing it to adapt as needed and even learn when appropriate. Having wideband performance is needed to allow room to dynamically manage the spectrum and radio parameters. SDRs offer many elegant advantages, outlined below, but true wideband spectral coverage at good resolution requires current and emerging technology.
Fortunately, high-end SDR is becoming a more accessible solution without needing to resort to scanning tuners or stacked digitizers with fixed parallel tuners. Today’s ADCs are able to fully digitize parts of the multi-GHz including L-band and some S-band frequencies at native 12-bit resolution, and into X-band at 8-bit resolution. At these speeds and resolutions, tuner-less radios are becoming a more practical solution.
Built on generic building blocks, the philosophy behind SDR is that common hardware, typically a computer can change the overall radio function by making changes to the software. An ideal SDR would be able to digitize the frequency spectrum of interest directly from an antenna, present the data to a DSP processor, and output to an application – and also the reverse for a transmitter.
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- Demanding SDR applications
- Analog receiver architecture
- Sub-sampling options
- The future of SDR