phased.IsotropicAntennaElement

Isotropic antenna element

Description

The phased.IsotropicAntennaElement object creates an antenna element with an isotropic response pattern. The object models an antenna element whose response is unity in all directions. An isotropic antenna does not support polarization.

To compute the response of the antenna element for specified directions:

1. Create the phased.IsotropicAntennaElement object and set its properties.

2. Call the object with arguments, as if it were a function.

To learn more about how System objects work, see What Are System Objects?.

Creation

Syntax

antenna = phased.IsotropicAntennaElement

antenna = phased.IsotropicAntennaElement(Name,Value)

Description

antenna = phased.IsotropicAntennaElement creates an isotropic antenna System object™, antenna, with default property values.

antenna = phased.IsotropicAntennaElement(Name,Value) creates an isotropic antenna object, antenna, with each specified property Name set to the specified Value. You can specify additional name-value pair arguments in any order as (Name1,Value1,...,NameN,ValueN).

Properties

Unless otherwise indicated, properties are nontunable, which means you cannot change their values after calling the object. Objects lock when you call them, and the release function unlocks them.

If a property is tunable, you can change its value at any time.

For more information on changing property values, see System Design in MATLAB Using System Objects.

FrequencyRange — Operating frequency range

[0 1e20] (default) | nonnegative, real-valued, 1-by-2 row vector

Operating frequency range of the antenna, specified as a nonnegative, real-valued, 1-by-2 row vector in the form [LowerBound HigherBound]. The antenna element has no response outside the specified frequency range. Units are in Hz.

Data Types: double

BackBaffled — Backbaffle antenna element

false (default) | true

Backbaffle the antenna element, specified as false or true. Set this property to true to baffle the response on the backside of the antenna element. In this case, the antenna response to all azimuth angles beyond ±90° from broadside (0° azimuth and 0°elevation) is zero. When the value of this property is false, the back of the antenna element is not baffled.

Data Types: logical

Usage

Syntax

RESP = antenna(FREQ,ANG)

Description

RESP = antenna(FREQ,ANG) returns the antenna voltage response RESP at operating frequencies specified in FREQ and in directions specified in ANG.

Input Arguments

FREQ — Operating frequency of antenna element

nonnegative scalar | nonnegative, real-valued, 1-by-L row vector

Operating frequency of antenna element, specified as a nonnegative scalar or nonnegative, real-valued, 1-by-L row vector. Frequency units are in Hz.

FREQ must lie within the range of values specified by the FrequencyRange or the FrequencyVector property of the element. Otherwise, the element produces no response and the response is returned as –Inf. Most elements objects use the FrequencyRange property except for phased.CustomAntennaElement, which uses the FrequencyVector property.

Example: [1e8 2e6]

Data Types: double

ANG — Azimuth and elevation angles of response directions

real-valued, 1-by-M row vector | real-valued, 2-by-M matrix

Azimuth and elevation angles of response directions, specified as a real-valued, 1-by-M row vector or a real-valued, 2-by-M matrix, where M is the number of angular directions. Angle units are in degrees. The azimuth angle must lie in the range –180° to 180°, inclusive. The elevation angle must lie in the range –90° to 90°, inclusive.

• If ANG is a 1-by-M vector, each element specifies the azimuth angle of the direction. In this case, the corresponding elevation angle is assumed to be zero.

• If ANG is a 2-by-M matrix, each column of the matrix specifies the direction in the form [azimuth; elevation].

The azimuth angle is the angle between the x-axis and the projection of the direction vector onto the xy plane. This angle is positive when measured from the x-axis toward the y-axis. The elevation angle is the angle between the direction vector and xy-plane. This angle is positive when measured towards the z-axis. See the definition of Azimuth and Elevation Angles.

Example: [110 125; 15 10]

Data Types: double

Output Arguments

RESP — Voltage response of antenna

complex-valued M-by-L matrix

Voltage response of antenna element, returned as a complex-valued M-by-L matrix. In this matrix, M represents the number of angles specified in ANG and L represents the number of frequencies specified in FREQ.

Data Types: double

Object Functions

To use an object function, specify the System object as the first input argument. For example, to release system resources of a System object named obj, use this syntax:

release(obj)

Specific to Antenna and Transducer Element System Objects

beamwidth	Compute and display beamwidth of sensor element pattern
directivity	Directivity of antenna or transducer element
isPolarizationCapable	Antenna element polarization capability
pattern	Plot antenna or transducer element directivity and patterns
patternAzimuth	Plot antenna or transducer element directivity and pattern versus azimuth
patternElevation	Plot antenna or transducer element directivity and pattern versus elevation

Common to All System Objects

step	Run System object algorithm
release	Release resources and allow changes to System object property values and input characteristics
reset	Reset internal states of System object

Examples

Plot Isotropic Antenna Element Response

Create an isotropic antenna operating over a frequency range from 800 MHz to 1.2 GHz. The operating frequency is 1 GHz. Find the response of the antenna at boresight. Then, plot the polar-pattern elevation response of the antenna.

antenna = phased.IsotropicAntennaElement( ...
    'FrequencyRange',[800e6 1.2e9]);
fc = 1e9;

Obtain the response at boresight.

resp = antenna(fc,[0;0])

resp = 1

Plot the response pattern.

pattern(antenna,fc,0,[-90:90],'CoordinateSystem','polar', ...
    'Type','powerdb','Normalize',true)

Isotropic Antenna Does Not Support Polarization

Create an isotropic antenna element using the phased.IsotropicAntennaElement System object™ and show that it does not support polarization.

antenna = phased.IsotropicAntennaElement('FrequencyRange',[1.0,10]*1e9);
isPolarizationCapable(antenna)

ans = logical
   0

The returned value 0 shows that the antenna element does not support polarization.

Directivity of Isotropic Antenna Element

Compute the directivity of an isotropic antenna element in different directions.

Create an isotropic antenna element system object.

antenna = phased.IsotropicAntennaElement();

First, specify that the directions of interest all at an elevation angle of zero degrees. The seven azimuth angles are centered around boresight (zero degrees azimuth and zero degrees elevation). Set the frequency to 1 GHz.

ang = [-30,-20,-10,0,10,20,30; 0,0,0,0,0,0,0];
freq = 1e9;

Compute the directivity along the constant elevation cut.

d = directivity(antenna,freq,ang)

d = 7×1

     0
     0
     0
     0
     0
     0
     0

Next, specify that the directions of interest all at an azimuth angle of zero degrees. All elevation angles are centered around boresight. The five elevation angles range from $-20$ to $+20$ degrees, inclusive. Set the frequency to 1 GHz.

ang = [0,0,0,0,0; -20,-10,0,10,20];
freq = 1e9;

Compute the directivity along the constant azimuth cut.

d = directivity(antenna,freq,ang)

d = 5×1

     0
     0
     0
     0
     0

For an isotropic antenna, the directivity is independent of direction.

Plot Pattern and Directivity of Isotropic Antenna

Create an isotropic antenna element. Then, plot the antenna power pattern and directivity.

First, create the antenna.

antenna = phased.IsotropicAntennaElement;

Draw an azimuth cut of the power pattern at 0 degrees elevation. Assume the operating frequency is 1 GHz.

fc = 1e9;
pattern(antenna,fc,[-180:180],0,...
    'Type','power',...
    'CoordinateSystem','rectangular')

Draw the same azimuth cut of the antenna directivity.

pattern(antenna,fc,[-180:180],0,...
    'Type','directivity',...
    'CoordinateSystem','rectangular')

Elevation-Cut of Isotropic Antenna Pattern

Construct an isotropic antenna operating in the frequency range from 800 MHz to 1.2 GHz. Compute the response at boresight at 1 GHz. Display the power pattern of the antenna at 1 GHz.

antenna = phased.IsotropicAntennaElement(...
    'FrequencyRange',[800e6 1.2e9]);
fc = 1e9;
resp = antenna(fc,[0;0])

resp = 1

Plot the elevation power pattern of the antenna in polar coordinates.

pattern(antenna,fc,0,[-90:90],'Type','powerdb','CoordinateSystem','polar')

3-D Isotropic Antenna Pattern

Construct an isotropic antenna operating over a frequency range from 800 MHz to 1.2 GHz. Then, plot the 3-D antenna field pattern.

Construct an isotropic antenna element.

antenna = phased.IsotropicAntennaElement(...
    'FrequencyRange',[800e6 1.2e9]);

Plot the 3-D magnitude pattern of the antenna at 1 GHz from $-30$ to $30$ degrees in both azimuth and elevation in 0.1 degree increments.

fc = 1e9;
pattern(antenna,fc,[-30:0.1:30],[-30:0.1:30],...
    'Type','efield',...
    'CoordinateSystem','polar')

Directivity Pattern of Isotropic Antenna Element for Span of Azimuth Angles

Plot an azimuth cut of the directivity of an isotropic antenna element at 0 degrees elevation for all azimuth angles and at 30 degrees elevation for a small span of azimuth angles. Assume the operating frequency is 500 MHz.

Create the antenna element.

fc = 500e6;
antenna = phased.IsotropicAntennaElement('FrequencyRange',[100,900]*1e6);

Plot the pattern for all azimuth angles at 0 degrees elevation.

patternAzimuth(antenna,fc,0)

Plot the pattern for a reduced span of azimuth angles using the Azimuth parameter.

patternAzimuth(antenna,fc,30,'Azimuth',[-20:20])

Directivity Pattern of Isotropic Antenna Element for Span of Elevation Angles

Plot an elevation cut of directivity of an isotropic antenna element at 45 degrees azimuth for all elevation angles and at 45 degrees for a span of elevation angles. Assume the operating frequency is 500 MHz.

Create the antenna element.

fc = 500e6;
antenna = phased.IsotropicAntennaElement('FrequencyRange',[100,900]*1e6);

Plot the directivity for all elevation angles.

patternElevation(antenna,fc,45)

Plot the directivity for a span of elevation angles using the Elevation parameter.

patternElevation(antenna,fc,45,'Elevation',[-20:20])

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• pattern, patternAzimuth, and patternElevation object functions are not supported.

• See System Objects in MATLAB Code Generation (MATLAB Coder).