2. Introduction to SDR What is SDR? What is SDR? • Software- Defined Radio • Signal manipulation (e.g. modulation, demodulation, filtering) performed in software • A digital signal processor (DSP) replaces analogue hardware of traditional radios ) Technical aspects of SDR
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4. A Typical SDR Block diagram Block diagram of a typical SDR Receiver Transmitter BPF BPF LPF ADC DSP DAC LPF Analogue Front-End Analogue Front-End Technical aspects of SDR
5. A Typical SDR The digital processor The digital processor and its software • Signal processing (modulation, demodulation, etc.) is performed inside the digital processor • Variety of suitable devices: • DPSs • • • • Digital Signal Processor ICs. Highly specialised number-crunchers Low power consumption Excellent SDRs, especially for mobile applications • General-purpose microprocessors • e.g. a personal computer (PC) • Very flexible • Radio functionality can share resources with other applications • Very cost-effective for static installations, e.g. cellphone base stations • FPGAs • Reconfigurable at the digital logic level • Can be used to create custom digital processors for SDR • Extremely high processing speeds possible • Less flexible than DSPs or µ Ps Technical aspects of SDR
6. A Typical SDR Signal theory and DSP software Signal theory and DSP software • Modulation is performed using software techniques such as direct-digital synthesis . • Demodulation is done using software techniques such as digital fi ltering, digital phase-locked loops and coherent demodulation. • One part of SDR software design is concerned with signal processing algorithms • Another part of SDR software design involves architectural considerations: • scheduling • reusability • data flow Technical aspects of SDR
7. A Typical SDR Signal conversion Signal conversion • In any SDR, digital-to-analogue or analogue-to-digital conversion is required at some point • Signal conversion must be higher than twice the highest frequency in the signal [Nyquist’s Theorem] • High-resolution converters only available up to a few hundred MHz sampling rate • Signal quality often deteriorates at high sampling rates • Advantageous to let software work at low IF, and perform signal translation in hardware • SDR’s signal translation hardware: RF front-end Technical aspects of SDR
8. Introduction to SDR The advantages of SDR The advantages of SDR • Highly reconfigurable • Software upgrades of commercial radios • Generic hardware can be used for a variety of applications • Software prototyping faster and cheaper than hardware prototyping • Mathematically sophisticated signal processing techniques can be performed in the “digital domain” (software) • Libraries of software radio components are easily created and shared • Digital manipulation of signals is ideal, unencumbered by the non-linearities that plague hardware Technical aspects of SDR io
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10. Conclusions Conclusions • SDR means: • Reconfigurable radios • More generic hardware • Reduced rate of hardware obsolescence • Lower cost of entry to radio development • Excellent tool for the experimenter • Simple transition between computer simulation and implementation • Becoming increasingly popular in industry • A technology to watch! Software-Defined Radio Technical aspects of SDR
