beamwidth

Compute and display beamwidth of an array

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Syntax

beamwidth(array,freq)
beamwidth(array,freq,Name,Value)
[bw,angles] = beamwidth(___)

Description

beamwidth(array,freq) plots the 2-D power pattern (in dB) of the array 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.

example

beamwidth(array,freq,Name,Value) plots the beamwidth with the specified parameter Name set to the specified Value. You can specify additional name-value pair arguments in any order as (Name1,Value1,...,NameN,ValueN).

Example: beamwidth(array,3e8,'Cut','Elevation')

[bw,angles] = beamwidth(___) returns the angular beamwidth bw (in degrees). The function also returns the corresponding angle values (in degrees) that mark the beamwidth.

example

Examples

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Open Live Script

Plot the beamwidth of a sonar array operating at a frequency of 2 kHz when the propagation speed of sound in water is 1500 m/s.

The sonar array consists of a 20-element uniform linear array (ULA). Consider the element of the ULA to be a backbaffled phased.IsotropicProjector with a VoltageResponse of 100 Volts and with a FrequencyRange from 10 Hz to 300 kHz. Create a phased.ULA object to model the uniform linear array.

 projector = phased.IsotropicProjector(BackBaffled=true,...
        VoltageResponse=100,FrequencyRange=[10 300000])
projector = 
  phased.IsotropicProjector with properties:

    VoltageResponse: 100
     FrequencyRange: [10 300000]
        BackBaffled: true


myArray = phased.ULA(Element=projector,NumElements=20,...
    ElementSpacing=1500/200e3/2)
myArray = 
  phased.ULA with properties:

           Element: [1×1 phased.IsotropicProjector]
       NumElements: 20
    ElementSpacing: 0.0037
         ArrayAxis: 'y'
             Taper: 1

Using the beamwidth function, calculate and plot the 6 dB beamwidth of the sonar array.

beamwidth(myArray,200e3,dBDown=6,PropagationSpeed=1500)

Figure contains an axes object. The hidden axes object contains 4 objects of type patch, line, text. This object represents 200 kHz .

ans = 
6.9200
Open Live Script

Calculate the half-power beamwidth and angles of a 20-element uniform linear array (ULA) of cosine antenna elements.

Create a phased.CosineAntennaElement object with the 'CosinePower' exponents set to 1.5.

myAnt = phased.CosineAntennaElement
myAnt = 
  phased.CosineAntennaElement with properties:

    FrequencyRange: [0 1.0000e+20]
       CosinePower: [1.5000 1.5000]

Create a phased.ULA object to model a 20-element ULA of cosine antenna elements. These elements are spaced at 0.5 meters on the azimuth plane.

array = phased.ULA(Element=myAnt,NumElements=20)
array = 
  phased.ULA with properties:

           Element: [1×1 phased.CosineAntennaElement]
       NumElements: 20
    ElementSpacing: 0.5000
         ArrayAxis: 'y'
             Taper: 1

Compute the beamwidth and angles of the array when it is operating at 3e8 Hz. Specify the beamwidth to be computed along the elevation plane.

[BW,Ang] = beamwidth(array,3e8,Cut="Elevation")
BW = 
74.8200

Ang = 1×2

  -37.4100   37.4100

Input Arguments

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Frequency used to calculate the beamwidth, specified as a scalar in Hz.

Example: 3e8

Data Types: double

Name-Value Arguments

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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(array,3e8,'Cut','Azimuth','CutAngle',45) plots the beamwidth of the array that is operating at a frequency of 0.3 GHz, with the slice direction set to 'Azimuth', and the cut angle set to 45 degrees.

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.

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

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 first-null beamwidth, specify the 'dBDown' value as Inf.

Data Types: double

Propagation speed, specified as the comma-separated pair consisting of 'PropagationSpeed' and a positive scalar (in m/s).

Data Types: double

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

Output Arguments

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Angular beamwidth of the array of sensor elements, returned as a scalar in degrees.

Data Types: double

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

See Also

Objects