Main Content

beamwidth

Compute and display beamwidth of an array

Description

example

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.

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')

example

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

Examples

collapse all

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: [1x1 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)

ans = 6.9200

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: [1x1 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

collapse all

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

Example: 3e8

Data Types: double

Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside quotes. You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

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: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

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

collapse all

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 amaxamin.

Introduced in R2020b