Page 17 - DSP Integrated Circuits

2 Chapter 1 DSP Integrated Circuits

design, specification, DSP algorithm, system and circuit architecture, logic, and
integrated circuit design. Hence, changes in classical design methodologies and in
the organization of design teams may be necessary. We will therefore discuss the
most common design methodologies used for the design of DSP systems. We will
also present a novel methodology and apply it to some common DSP subsystems.
The problem of designing special-purpose DSP systems is an interesting
research topic, but, more important, it has significant industrial and commercial
relevance. Many DSP systems (for example, mobile phones) are produced in very
large numbers and require high-performance circuits with respect to throughput
and power consumption. Therefore, the design of DSP integrated circuits is a chal-
lenging topic for both system and VLSI designers. DSP integrated circuits are also
of economic importance to the chip manufacturers.

1.2 DIGITAL SIGNAL PROCESSING

Signal processing is fundamental to information processing and includes various
methods for extracting information obtained either from nature itself or from
man-made machines. Generally, the aim of signal processing is to reduce the infor-
mation content in a signal to facilitate a decision about what information the sig-
nal carries. In other instances the aim is to retain the information and to
transform the signal into a form that is more suitable for transmission or storage.
The DSP systems of interest here are the so-called hard real-time systems, where
computations must be completed within a given time limit (the sample period). An
unacceptable error occurs if the time limit is exceeded.
Modern signal processing is mainly concerned with digital techniques, but
also with analog and sampled-data (discrete-time) techniques, which are needed in
the interfaces between digital systems and the outside analog world [9,11]. Sam-
pled-data systems are generally implemented using switched capacitor (SC) [10]
or switched current (SI) circuits. Most A/D and D/A converters are today based on
SC circuit techniques. An important advantage of SC circuits is that they can eas-
ily be integrated with digital CMOS circuits on the same chip. Recently, analog cir-
cuits such as anti-aliasing filters have also become possible to implement on the
same chip. A fully integrated system-on-a-chip is therefore feasible by using a suit-
able combination of circuit techniques. This will affect both performance and cost
of DSP systems.
Generally, complex signal processing systems are synthesized using sub-
systems that perform the basic DSP operations. Typical operations are frequency
selective and adaptive filtering, time-frequency transformation, and sample rate
change. In Chapters 3 and 4, we will review some of the most common signal pro-
cessing functions used in such subsystems. The aim is to provide a background for
three typical DSP subsystems that will be used as case studies throughout the
book.

1.3 STANDARD DIGITAL SIGNAL PROCESSORS

In principle, any DSP algorithm can be implemented by programming a stan-
dard, general-purpose digital signal processor [1]. The design process involves