beamwidth

Beamwidth of NR rectangular panel array

Since R2023b

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.

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.

Examples

Plot Beamwidth of Sonar Array

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)

ans = 
6.9200

Calculate Beamwidth and Angles of Uniform Linear Array (ULA)

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

array — Array of sensor elements

Phased Array System Toolbox™ System object™

Array of sensor elements, specified as a phased.NRRectangularPanelArray System object.

freq — Frequency used to calculate beamwidth

scalar in Hz

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

Example: 3e8

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(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.

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 equal-sign-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 equal-sign-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) | 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 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

ElementWeights — Subarray element weights

ones() (default) | NSE-by-N matrix | cell array

Weights applied to each subarray element, specified as a NSE-by-N matrix or a cell array. When a matrix, 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.

Dependencies

To enable this parameter, set the SubarraySteering property of the array to "Custom".

Data Types: double | cell
Complex Number Support: Yes

Output Arguments

bw — Angular beamwidth

scalar in degrees

Angular beamwidth of the array of sensor elements, 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 [a_min, a_max] define the beamwidth bw as a_max−a_min.

Version History

Introduced in R2023b