Hardware Reference
In-Depth Information
subjected to variations in temperature, pressure, and humidity. In either case,
the multiple windowing capability allows the user to form a complete picture
of the performance of a system without recourse to a number of discrete graphs
and displays.
DADiSP supports a number of advanced mathematical functions including
trigonometric and logarithmic functions. These can be applied to any valid
signal, scalar, or signal-scalar expression. When applied to a signal, they are
applied successively to each point of the signal and the resulting signal is dis-
played in the current window. When applied to scalars (integers, real numbers, or
complex numbers) the resulting value is displayed at the bottom of the screen.
The calculus functions are provided for determining derivative and integral
functions. Since the signals are discrete, DADiSP provides a means of per-
forming left derivative and right derivative calculations. Four of these functions
(
DERIV
,
LDERIV
,
RDERIV
, and
INTEG
) take one signal as an argument and return
a new one.
AREA
takes two additional arguments, the starting and ending points
within a signal.
Note also that
AREA
returns a scalar whereas the other four calculus
functions return signals. The algorithm for calculating the integral is a mod-
ification of Simpson's Rule and is more accurate than a simple trapezoidal
approximation.
DADiSP's statistical functions provide information about a signal (or two
signals in the case of
LINREG2
).
MEAN
and
STDEV
return appropriate values
which can be nested in more complicated expressions.
STATS
does not return
a signal but displays both the mean and standard deviation at the bottom of the
screen.
LINREG
and
LLNREG2
display the regression coefficients and then create
a new signal (i.e. the line generated by the linear regression) which is useful for
over-plotting.
AMPDIST
generates a new signal which constitutes a bar graph
distribution for a signal. The function accepts a real-number argument which
is the incremental value (
DELTA X
).
DADiSP contains facilities for frequency domain analysis. Fourier analysis
is provided with both the Discrete Transform and the much faster Fast Fourier
Transform (FFT).
PARTSUM
creates a new signal which is equivalent to the par-
tial sums of two input signals whilst
SUMS
adds any number of signals together.
MOVAVG
provides a smoothing function while
AVG
takes the point-by-point
average of a group of signals.
A powerful range of signal editing functions are also provided.
EXTRACT
cre-
ates a new signal by extracting part of an existing signal while
REVERSE
simply
changes the polarity of a given signal and
CONCAT
concatenates any number of
signals. Signal generating functions are preceded by the letter
G
. An endless
variety of waveforms can be synthesized through combination of functions (e.g.
GSINH
will generate the waveform of a hyperbolic arcsine function).
A simple example of using DADiSP is shown in Figure 10.17. The six
windows (W1 to W6) are populated with data using the following Worksheet
entries:
W1: gsin(128, 1/128, 1)
W2: gsin(128, 1/128, 3) /3
W3: gsin(128, 1/128, 5) /5
W4: gsin(128, 1/128, 7) /7
W5: W1+W2+W3+W4
W6: spectrum(W5);sticks
