RESP = step(H,FREQ,ANG) returns
the array elements' responses RESP at
operating frequencies specified in FREQ and directions
specified in ANG.

Note:
The object performs an initialization the first time the step method
is executed. This initialization locks nontunable
properties and input specifications, such as dimensions, complexity,
and data type of the input data. If you change a nontunable property
or an input specification, the System object™ issues an error.
To change nontunable properties or inputs, you must first call the release method
to unlock the object.

Input Arguments

H

Array object.

FREQ

Operating frequencies of array in hertz. FREQ
is a row vector of length L. Typical values are within the range specified
by a property of H.Element. That property is named FrequencyRange or FrequencyVector,
depending on the type of element in the array. The element has zero
response at frequencies outside that range.

ANG

Directions in degrees. ANG can be either
a 2-by-M matrix or a row vector of length M.

If ANG is a 2-by-M matrix, each column
of the matrix specifies the direction in the form [azimuth; elevation].
The azimuth angle must be between –180 and 180 degrees, inclusive.
The elevation angle must be between –90 and 90 degrees, inclusive.

If ANG is a row vector of length M, each
element specifies a direction's azimuth angle. In this case,
the corresponding elevation angle is assumed to be 0.

Output Arguments

RESP

Voltage responses of the phased array. The output depends on
whether the array supports polarization or not.

If the array is not capable of supporting polarization,
the voltage response, RESP, has the dimensions N-by-M-by-L. N is
the number of elements in the array. The dimension M is
the number of angles specified in ANG. L is
the number of frequencies specified in FREQ.
For any element, the columns of RESP contain
the responses of the array elements for the corresponding direction
specified in ANG. Each of the L pages
of RESP contains the responses of the array elements
for the corresponding frequency specified in FREQ.

If the array is capable of supporting polarization,
the voltage response, RESP, is a MATLAB struct containing
two fields, RESP.H and RESP.V.
The field, RESP.H, represents the array's
horizontal polarization response, while RESP.V represents
the array's vertical polarization response. Each field has
the dimensions N-by-M-by-L. N is
the number of elements in the array, and M is the
number of angles specified in ANG. L is
the number of frequencies specified in FREQ.
Each column of RESP contains the responses of
the array elements for the corresponding direction specified in ANG.
Each of the L pages of RESP contains
the responses of the array elements for the corresponding frequency
specified in FREQ.

Create a 4-element ULA and find the response
of each element at the boresight. Plot the array response at 1 GHz
for azimuth angles between –180 and 180 degrees.

ha = phased.ULA('NumElements',4);
fc = 1e9;
ang = [0;0];
resp = step(ha,fc,ang);
c = physconst('LightSpeed');
plotResponse(ha,fc,c)