bode
Bode plot of frequency response, or magnitude and phase data
Syntax
Description
bode(
creates
a Bode plot of the frequency response of a dynamic
system model sys
)sys
. The plot displays
the magnitude (in dB) and phase (in degrees) of the system response
as a function of frequency. bode
automatically
determines frequencies to plot based on system dynamics.
If sys
is a multi-input, multi-output (MIMO)
model, then bode
produces an array of Bode plots,
each plot showing the frequency response of one I/O pair.
If sys
is a model with complex coefficients, then
in:
Log frequency scale, the plot shows two branches, one for positive frequencies and one for negative frequencies. The plot also shows arrows to indicate the direction of increasing frequency values for each branch. See Bode Plot of Model with Complex Coefficients.
Linear frequency scale, the plot shows a single branch with a symmetric frequency range centered at a frequency value of zero.
bode(sys1,sys2,...,sysN)
plots the frequency
response of multiple dynamic systems on the same plot. All systems
must have the same number of inputs and outputs.
bode(sys1,
specifies a
color, line style, and marker for each system in the plot.LineSpec
1,...,sysN,LineSpecN)
bode(___,
plots
system responses for frequencies specified by w
)w
.
If
w
is a cell array of the form{wmin,wmax}
, thenbode
plots the response at frequencies ranging betweenwmin
andwmax
.If
w
is a vector of frequencies, thenbode
plots the response at each specified frequency. The vectorw
can contain both negative and positive frequencies.
You can use w
with any of the input-argument
combinations in previous syntaxes.
Examples
Input Arguments
Output Arguments
Tips
When you need additional plot customization options, use
bodeplot
(Control System Toolbox) instead.
Algorithms
bode
computes the frequency response as
follows:
Compute the zero-pole-gain (
zpk
(Control System Toolbox)) representation of the dynamic system.Evaluate the gain and phase of the frequency response based on the zero, pole, and gain data for each input/output channel of the system.
For continuous-time systems,
bode
evaluates the frequency response on the imaginary axis s = jω and considers only positive frequencies.For discrete-time systems,
bode
evaluates the frequency response on the unit circle. To facilitate interpretation, the command parameterizes the upper half of the unit circle as:where Ts is the sample time and ωN is the Nyquist frequency. The equivalent continuous-time frequency ω is then used as the x-axis variable. Because is periodic with period 2ωN,
bode
plots the response only up to the Nyquist frequency ωN. Ifsys
is a discrete-time model with unspecified sample time,bode
uses Ts = 1.
Version History
Introduced before R2006a