4 - Digital signal processing

Abstract

This chapter discusses digital signal processing (DSP). DSP is an image of complex mathematical formula requiring banks of computers to perform even trivial tasks such as filtering out high-frequency signals from low-frequency ones. Digital processing does not suffer from component aging, drift, or any adjustments that can plague an analogue design. They have high noise immunity and power supply rejection and because of the embedded processor, they can easily provide self-test features. The ability to modify the coefficients dynamically and, therefore, the filter characteristics, allows complex filters and other functions to be implemented easily. The processing power needed to complete the multiply-accumulate processing of the data does pose some interesting processing requirements. The chapter highlights one major criterion that a DSP processor must fulfill. It explains that to maintain the periodic sampling necessary to stop distortion and maintain the algorithm's integrity, the processing must be completed within a finite number of instructions. This immediately raises the question of how to handle interrupts, program loops, etc. Most of the processor enhancements are centered around this issue. DSP can be performed by ordinary microprocessors although their more general-purpose nature often limits performance and the frequency response. A good example of a DSP function is the finite impulse response (FIR) filter.