RF AND IF DIGITIZATION IN RADIO RECEIVERS: THEORY, CONCEPTS,
AND EXAMPLES
Jeffery A. Wepman and J. Randy Hoffman
1
Hardware development of analog-to-digital converters (ADCs) and digital signal
processors, including specialized integrated circuits, has advanced rapidly within
the last few years. These advances have paved the way for development of radio
receivers using digitization at the IF and in some cases at the RF. Applications for
these receivers are expected to increase rapidly in areas such as cellular mobile,
satellite, and personal communications services (PCS) systems. The constraints
placed on these receivers due to hardware limitations of these devices are
investigated in this paper. Some examples of state-of-the-art ADCs, signal
processors, and specialized integrated circuits are listed. Various quantization
techniques, nonlinear compression devices, postdigitization algorithms for
improving dynamic range, sampling downconverters, and specialized integrated
circuits are discussed as they are expected to be useful in the development of
these types of receivers. Several examples of radio receivers employing
digitization at the IF and RF are also presented.
Key words: analog-to-digital converters; automatic gain control devices; digital signal
processors; digitization; logarithmic amplifiers; quantization; radio receivers;
sampling downconverters; signal-to-noise ratio; spurious free dynamic range
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