This example shows how to create a MIMO frequency-response model
Frequency response data for a MIMO system includes a vector of complex response data for each of the input/output (I/O) pair of the system. Thus, if you measure the frequency response of each I/O pair of your system at a set of test frequencies, you can use the data to create a frequency response model:
Load frequency response data in
load AnalyzerDataMIMO H11 H12 H21 H22 freq
This command loads the data into the MATLAB® workspace as five column vectors
freq. The vector
freq contains 100
test frequencies. The other four vectors contain the corresponding
complex-valued frequency response of each I/O pair of a two-input, two-output
To inspect these variables, enter:
whos H11 H12 H21 H22 freq
Organize the data into a three-dimensional array.
Hresp = zeros(2,2,length(freq)); Hresp(1,1,:) = H11; Hresp(1,2,:) = H12; Hresp(2,1,:) = H21; Hresp(2,2,:) = H22;
The dimensions of
Hresp are the number of
outputs, number of inputs, and the number of frequencies for which
there is response data.
Hresp(i,j,:) contains the
frequency response from input
j to output
Create a frequency-response model.
H = frd(Hresp,freq);
H is an
frd model object, which is a data
container for representing frequency response data.
You can use
frd models with many frequency-domain analysis commands. For
example, visualize the response of this two-input, two-output system using
By default, the
frd command assumes that
the frequencies are in radians/second. To specify different frequency
units, use the
frd model object. For example:
H = frd(Hresp,freq,'TimeUnit','min','FrequencyUnit','rad/TimeUnit')
sets the frequency units to in radians/minute.