Types of DSPs
Digital Signal Processor
A Digital Signal Processor is a special-purpose CPU
(Central Processing Unit) that provides ultra-fast instruction sequences,
such as shift and add, and multiply and add, which are commonly used
in math-intensive signal processing applications.
DSPs are not the same as typical microprocessors
though. Microprocessors are typically general purpose devices that run
large blocks of software. They are not often called upon for real-time
computation and they work at a slower pace, choosing a course of action,
then waiting to finish the present job before responding to the next
user command. A DSP, on the other hand, is often used as a type of embedded
controller or processor that is built into another piece of equipment
and is dedicated to a single group of tasks. In this environment, the
DSP assists the general purpose host microprocessor.
Digital Signal Processing
Digital Signal Processing is a technique that converts
signals from real world sources (usually in analog form) into digital
data that can then be analyzed. Analysis is performed in digital form
because once a signal has been reduced to numbers, its components can
be isolated, analyzed and rearranged more easily than in analog form.
Eventually, when the DSP has finished its work,
the digital data can be turned back into an analog signal, with improved
quality. For example, a DSP can filter noise from a signal, remove interference,
amplify frequencies and suppress others, encrypt information, or analyze
a complex wave form into its spectral components.
This process must be handled in real-time - which
is often very quickly. For instance, stereo equipment handles sound
signals of up to 20 kilohertz (20,000 cycles per second), requiring
a DSP to perform hundreds of millions of operations per second.
Because different applications have varying ranges
of frequencies, different DSPs are required. DSPs are classified by
their dynamic range, the spread of numbers that must be processed in
the course of an application. This number is a function of the processor's
data width (the number of bits it manipulates) and the type of arithmetic
it performs (fixed or floating point). For example, a 32-bit processor
has a wider dynamic range than a 24-bit processor, which has a wider
range than 16-bit processor. Floating-point chips have wider ranges
than fixed-point devices.
Each type of processor is suited for a particular
range of applications. Sixteen-bit fixed-point DSPs are used for voice-grade
systems such as phones, since they work with a relatively narrow range
of sound frequencies. Hi-fidelity stereo sound has a wider range, calling
for a 16-bit ADC (Analog/Digital Converter), and a 24-bit fixed point
DSP. Image processing, 3-D graphics and scientific simulations have
a much wider dynamic range and require a 32-bit floating-point processor.
DSP chips are used in sound cards, fax machines,
modems, cellular phones, high-capacity hard disks and digital TVs. According
to Texas Instruments, DSPs are used as the engine in 70% of the world's
digital cellular phones, and with the increase in wireless applications,
this number will only increase.Digital signal processing is used in many
fields including biomedicine, sonar, radar, seismology, speech and music
processing, imaging and communications.
According to Forward Concepts, the market for
DSP chips is growing at twice the rate of the semiconductor industry as
a whole. They predict that over the next few years the digital signal
processing business will increase by 33% annually, leading to an overall
market of $11 billion in 1999. About $4.5 billion of this will be for
general purpose DSPs.
Additional sources of information*
Signal Processing - Intro to DSP
is.com - digital signal processing
Digital Signal Processing Page
Companies providing DSPs
*The WAVE Report is not responsible for content on additional sites