User`s guide

Chirp
5-65
•Target frequency (Hertz), f
i
(t
g
)
•
Target time (seconds), t
g
The following table summarizes the sweep values at specific times for all
Frequency sweep settings. For information on the formulas used to compute
sweep values at other times, see “Block Computation Methods”.
Block Computation Methods
The Chirp block uses one of two formulas to compute the block output,
depending on the
Frequency Sweep parameter setting. For details, see the
following sections:
•“Equations for Output Computation”
•“Output Computation Method for Linear, Quadratic, and Logarithmic
Frequency Sweeps”
•“Output Computation Method for Swept Cosine Frequency Sweep”
Equations for Output Computation. The following table shows the equations used by
the block to compute the user-specified output frequency sweep, f
i
(t), the block
output, y
chirp
(t), and the actual output frequency sweep, f
i(actual)
(t). The only
time the user-specified sweep is not the actual output sweep is when the
Frequency sweep parameter is set to Swept cosine.
Note The following equations apply only to unidirectional sweeps in which
f
i
(0) < f
i
(t
g
). To derive equations for other cases, you may find it helpful to
Table 5-1: Instantaneous Frequency Sweep Values
Frequency
Sweep
Sweep Value at t = 0 Sweep Value at t = t
g
Time When Sweep Value is Target
Frequency,
f
i
( t
g
)
Linear
f
0
f
i
(t
g
) t
g
Quadratic
f
0
f
i
(t
g
) t
g
Logarithmic
f
0
+ 1 f
i
(t
g
) t
g
Swept cosine
f
0
2f
i
(t
g
)-f
0
t
g
/2