patternAzimuth

System object: phased.IsotropicHydrophone
Namespace: phased

Plot isotropic hydrophone directivity and response patterns versus azimuth

Syntax

patternAzimuth(hydrophone,FREQ)
patternAzimuth(hydrophone,FREQ,EL)
patternAzimuth(hydrophone,FREQ,EL,Name=Value)
PAT = patternAzimuth(___)


Description

patternAzimuth(hydrophone,FREQ) plots the 2-D element directivity pattern versus azimuth (in dBi) for the element hydrophone at zero degrees elevation angle. The argument FREQ specifies the operating frequency.

patternAzimuth(hydrophone,FREQ,EL), in addition, plots the 2-D element directivity pattern versus azimuth (in dBi) at the elevation angle specified by EL. When EL is a vector, multiple overlaid plots are created.

patternAzimuth(hydrophone,FREQ,EL,Name=Value) plots the element pattern with additional options specified by one or more Name=Value pair arguments.

PAT = patternAzimuth(___) returns the element pattern. PAT is a matrix whose entries represent the pattern at corresponding sampling points specified by the "Azimuth" parameter and the EL input argument.

Input Arguments

hydrophone — Isotropic hydrophone

phased.IsotropicHydrophone System object™

Isotropic hydrophone, specified as a phased.IsotropicHydrophone System object.

Example: phased.IsotropicHydrophone

FREQ — Frequency for computing directivity and pattern

positive scalar

Frequency for computing directivity and pattern, specified as a positive scalar. Frequency units are in hertz.

• For an antenna or microphone element, 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 directivity is returned as –Inf. Most elements use the FrequencyRange property except for phased.CustomAntennaElement and phased.CustomMicrophoneElement, which use the FrequencyVector property.

• For an array of elements, FREQ must lie within the frequency range of the elements that make up the array. Otherwise, the array produces no response and the directivity is returned as –Inf.

Example: 1e8

Data Types: double

EL — Elevation angles

1-by-N real-valued row vector

Elevation angles for computing sensor or array directivities and patterns, specified as a 1-by-N real-valued row vector. The quantity N is the number of requested elevation directions. Angle units are in degrees. The elevation angle must lie between –90° and 90°.

The elevation angle is the angle between the direction vector and the xy plane. When measured toward the z-axis, this angle is positive.

Example: [0,10,20]

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.

Type — Displayed pattern type

"directivity" (default) | "efield" | "power" | "powerdb"

Displayed pattern type, specified as the equal-sign-separated pair consisting of Type and one of

• "directivity" — directivity pattern measured in dBi.

• "efield" — field pattern of the sensor or array. For acoustic sensors, the displayed pattern is for the scalar sound field.

• "power" — power pattern of the sensor or array defined as the square of the field pattern.

• "powerdb" — power pattern converted to dB.

Example: "powerdb"

Data Types: char

Azimuth — Azimuth angles

[-180:180] (default) | 1-by-P real-valued row vector

Azimuth angles, specified as the equal sign separated pair consisting of "Azimuth" and a 1-by-P real-valued row vector. Azimuth angles define where the array pattern is calculated.

Example: Azimuth=[-90:2:90]

Data Types: double

Output Arguments

PAT — Element directivity or pattern

P-by-N real-valued matrix

Element directivity or pattern, returned as an P-by-N real-valued matrix. The dimension P is the number of azimuth values determined by the 'Azimuth' name-value pair argument. The dimension N is the number of elevation angles, as determined by the EL input argument.

Examples

Azimuth Pattern of Isotropic Hydrophone

Examine the azimuth pattern of an isotropic hydrophone at 30° elevation. The frequency range is between 1 kHz and 10 kHz. Specify the voltage sensitivity as a vector.

First, set up the hydrophone parameters.

fc = 3e3;
hydrophone = phased.IsotropicHydrophone(FrequencyRange=[1,10]*1e3, ...
    VoltageSensitivity=[-100,-90,-100]);
patternAzimuth(hydrophone,fc,30)

Plot a smaller range of azimuth angles using the Azimuth parameter.

patternAzimuth(hydrophone,fc,30,Azimuth=[-20:20])

More About

Directivity

Directivity describes the directionality of the radiation pattern of a sensor element or array of sensor elements.

Higher directivity is desired when you want to transmit more radiation in a specific direction. Directivity is the ratio of the transmitted radiant intensity in a specified direction to the radiant intensity transmitted by an isotropic radiator with the same total transmitted power

$$D=4\pi \frac{U_{\text{rad}}\left(\theta ,\phi \right)}{P_{\text{total}}}$$

where U_rad(θ,φ) is the radiant intensity of a transmitter in the direction (θ,φ) and P_total is the total power transmitted by an isotropic radiator. For a receiving element or array, directivity measures the sensitivity toward radiation arriving from a specific direction. The principle of reciprocity shows that the directivity of an element or array used for reception equals the directivity of the same element or array used for transmission. When converted to decibels, the directivity is denoted as dBi. For information on directivity, read the notes on Element Directivity and Array Directivity.

Version History

Introduced in R2017a