beamwidth
Description
beamwidth(
plots the 2-D power pattern (in dB) of the subarray
,freq
)subarray
for all azimuth
angles at a fixed elevation angle of zero degrees. The plot displays the half-power
beamwidth (in degrees) at the frequency specified in freq
(in Hz) and
the angles (in degrees) in azimuth at which the magnitude of the power pattern decreases by
3 dB from the peak of the main beam.
beamwidth(
computes and plots the beamwidth with the specified parameter subarray
,freq
,Name,Value
)Name
set
to the specified Value
. You can specify additional name-value pair
arguments in any order as (Name1,Value1,...,NameN,ValueN
).
Example: beamwidth(subarray,5e8,'Cut','Elevation')
Examples
Plot Beamwidth of Rectangular Lattice Array
Plot the beamwidth of a rectangular lattice array composed of two uniform rectangular arrays. Consider the antenna elements of the array to be cosine antenna elements.
First, construct a phased.CosineAntennaElement
object.
myAnt = phased.CosineAntennaElement
myAnt = phased.CosineAntennaElement with properties: FrequencyRange: [0 1.0000e+20] CosinePower: [1.5000 1.5000]
Next, construct a 5-by-5 uniform rectangular array by creating a phased.URA
object.
myArray = phased.URA([5 5],[0.5 0.5],'Element',myAnt,... 'ElementSpacing',[0.15 0.15])
myArray = phased.URA with properties: Element: [1x1 phased.CosineAntennaElement] Size: [5 5] ElementSpacing: [0.1500 0.1500] Lattice: 'Rectangular' ArrayNormal: 'x' Taper: 1
Use two of these 5-by-5 uniform rectangular arrays to construct a 5-by-10 rectangular lattice. Construct the lattice using the phased.ReplicatedSubarray
object.
myRSA = phased.ReplicatedSubarray('Subarray',myArray,... 'Layout','Rectangular','GridSize',[1 2],... 'GridSpacing','Auto','SubarraySteering','Phase')
myRSA = phased.ReplicatedSubarray with properties: Subarray: [1x1 phased.URA] Layout: 'Rectangular' GridSize: [1 2] GridSpacing: 'Auto' SubarraySteering: 'Phase' PhaseShifterFrequency: 300000000 NumPhaseShifterBits: 0
Now visualize the 10dB beamwidth of the obtained lattice across the azimuth plane (0 degrees elevation). The subarray is phase steered toward 24 degrees azimuth. Assume the operating frequency of the array to be 1 GHz.
stv = phased.SteeringVector('SensorArray',myRSA); beamwidth(myRSA,1e9,'dBDown',10,'SteerAngle',24,'Weights',stv(1e9,24))
ans = 16.4600
Calculate Beamwidth and Angles of Two ULAs
Calculate the 3 dB beamwidth of a 10-element uniform linear array (ULA) composed of two 5-element ULAs across the azimuth plane and at 0 degrees elevation. By default, the antenna elements are isotropic. Assume the operating frequency of the array to be 500MHz.
myArray = phased.ULA('NumElements',5)
myArray = phased.ULA with properties: Element: [1x1 phased.IsotropicAntennaElement] NumElements: 5 ElementSpacing: 0.5000 ArrayAxis: 'y' Taper: 1
myRSA = phased.ReplicatedSubarray('Subarray',myArray,... 'GridSize',[1 2])
myRSA = phased.ReplicatedSubarray with properties: Subarray: [1x1 phased.ULA] Layout: 'Rectangular' GridSize: [1 2] GridSpacing: 'Auto' SubarraySteering: 'None'
[BW,Ang] = beamwidth(myRSA,5e8)
BW = 6.1200
Ang = 1×2
-3.0600 3.0600
Input Arguments
subarray
— Subarray of sensor elements
Phased Array System Toolbox™
System object™
Subarray of sensor elements, specified as one of the following System objects:
freq
— Frequency used to calculate beamwidth
scalar in Hz
Frequency used to calculate the beamwidth, specified as a scalar in Hz.
Example: 5e8
Data Types: double
Name-Value Arguments
Specify optional pairs of arguments as
Name1=Value1,...,NameN=ValueN
, where Name
is
the argument name and Value
is the corresponding value.
Name-value arguments must appear after other arguments, but the order of the
pairs does not matter.
Before R2021a, use commas to separate each name and value, and enclose
Name
in quotes.
Example: beamwidth(subarray,5e8,'Cut','Azimuth','CutAngle',45)
plots
the beamwidth of the subarray that is operating at a frequency of 0.5 GHz, with the slice
direction set to 'Azimuth'
, and the cut angle set to 45
degrees.
Cut
— Slice direction in azimuth-elevation space
'Azimuth'
(default) | 'Elevation'
The slice direction in azimuth-elevation space along which the beamwidth is
computed, specified as the comma-separated pair consisting of
'Cut'
and 'Azimuth'
for the azimuth plane,
and 'Cut'
and 'Elevation'
for the elevation
plane.
CutAngle
— Angle for plane to get required 2-D cut
0
(default) | scalar
Corresponding angle (in degrees) for the plane to get the required 2-D cut,
specified as the comma-separated pair consisting of 'CutAngle'
and a scalar. If 'Cut'
is specified as
'Azimuth'
, then 'CutAngle'
(Elevation)
should lie between [−90, 90] degrees. If 'Cut'
is specified as
'Elevation'
, then 'CutAngle'
(Azimuth)
should lie between [−180, 180] degrees.
Data Types: double
dBDown
— Power value from peak of main lobe
3
(default) | Inf
| positive scalar
Power value (in dB) from the peak of the main lobe, specified as the
comma-separated pair consisting of 'dBDown'
and a positive
scalar. The default value is 3 dB, which translates to half-power beamwidth. To
calculate the first-null beamwidth, specify the 'dBDown'
value as
Inf
.
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
PropagationSpeed
— Propagation speed
3×10^8
m/s (speed of light) (default) | positive scalar
Propagation speed, specified as the comma-separated pair consisting of
'PropagationSpeed'
and a positive scalar (in m/s).
Data Types: double
Weights
— Weights applied to array
length-N column vector
Weights applied to the array of sensor elements, specified as the comma-separated
pair consisting of 'Weights'
and a length-N
column vector, where N is the number of elements in the
array.
Data Types: double
SteerAngle
— Subarray steering angle
[0
; 0
] (default) | scalar | length-2 column vector
Subarray steering angle (in degrees), specified as the comma-separated pair
consisting of 'SteerAngle'
and a scalar or a length-2 column
vector. If the steering angle is a scalar, the value represents the azimuth angle and
the elevation angle is assumed to be 0. If the steering angle is a vector, the angle
is specified in the form of [AzimuthAngle; ElevationAngle].
Dependencies
This parameter is applicable when you set the
SubarraySteering
property of subarray
object
to either 'Phase'
or 'Time'
.
Data Types: double
ElementWeights
— Weights applied to each element in subarray
matrix of all ones (default) | matrix | cell array
Weights applied to each element in the subarray, specified as the comma-separated
pair consisting of 'ElementWeights'
and a matrix or a cell
array.
For a ReplicatedSubarray
object,
ElementWeights
must be a
NSE-by-N matrix, where NSE
is the number of elements in each individual subarray and N is the
number of subarrays. Each column in ElementWeights
specifies the
weights for the elements in the corresponding subarray.
For a PartitionedArray
object, if the individual subarrays have
the same number of elements, ElementWeights
must be an
NSE-by-N matrix, where NSE
is the number of elements in each individual subarray and N is the
number of subarrays.
Each column in the WS
property of the
subarray
object specifies the weights for the elements in the
corresponding subarray. If subarrays in the PartitionedArray
object
have different number of elements, ElementWeights
can be one of
the following:
NSE-by-N matrix –– NSE indicates the number of elements in the largest subarray and N is the number of subarrays.
1-by-N cell array –– N is the number of subarrays and each cell contains a column vector whose length is the same as the number of elements of the corresponding subarray.
If WS
is a matrix, the first K entries in
each column specify the weights for the elements in the corresponding subarray.
K is the number of elements in the corresponding subarray. If
WS
is a cell array, each cell in the array is a column vector
specifying the weights for the elements in the corresponding subarray.
Dependencies
This parameter is applicable when you set the
SubarraySteering
property of subarray
object
to 'Custom'
.
Data Types: double
Output Arguments
bw
— Angular beamwidth
scalar in degrees
Angular beamwidth of the subarray, returned as a scalar in degrees.
Data Types: double
angles
— Angle values of beamwidth
1-by-2 vector in degrees
Angle values of the beamwidth, returned as a 1-by-2 vector. The two elements in the
vector [amin,
amax] define the beamwidth
bw
as
amax−amin.
Version History
Introduced in R2020b
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