4

Data Conversion in Software Defined Radios

Brad Brannon, Chris Cloninger, Dimitrios Efstathiou, Paul Hendriks, Zoran Zvonar

Analog Devices

Data converters are one of the key enabling technologies for the software defined radio (SDR). Regardless of the interpretation of the definitions – software radio, software defined radio, software based radios – the challenge of moving the analog-digital boundary closer to the antenna is the critical step in establishing the foundation for increasing the content and capability of digital signal processing (DSP) in the radio. SDR technologies have provided the incentives for the breakthrough in converter technologies pushing the state-of-the-art [1]. In this chapter we review the foundations and technologies of data conversion from the perspective of their usage in SDRs, exploring capabilities, constraints, and future potential.

4.1 The Importance of Data Converters in Software Defined Radios

The use of converters in SDR depends upon the overall radio architecture. A summary of sampling techniques for the various receiver architectures described in Chapters 2 and 3 is given in Table 4.1.

Table 4.1 Summary of sampling strategies for SDR receivers

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Direct sampling (Nyquist sampling) satisfies the conditions of the sampling theorem for bandlimited analog signals, requiring that the sampling rate is at least two times the highest frequency component ...

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