System object: phased.ConformalArray
Directivity of conformal array
D = directivity(H,FREQ,ANGLE)
D = directivity(H,FREQ,ANGLE,Name,Value)
D = directivity( computes
the Directivity of a conformal
array of antenna or microphone elements,
frequencies specified by the
FREQ and in angles
of direction specified by the
The integration used when computing array directivity has a minimum sampling grid of 0.1 degrees. If an array pattern has a beamwidth smaller than this, the directivity value will be inaccurate.
H — Conformal array
Conformal array specified as a
phased.ConformalArray System object.
H = phased.ConformalArray;
Specify optional pairs of arguments as
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.
Directivity of Conformal Array
Compute the directivity of a circular array constructed using a conformal array System object™.
Construct a 21-element uniform circular sonar array (UCA) of backbaffled omnidirectional microphones. The array is one meter in diameter. Set the operating frequency to 4 kHz. A typical value for the speed of sound in seawater is 1500.0 m/s.
N = 21; theta = (0:N-1)*360/N-180; Radius = 0.5; myMic = phased.OmnidirectionalMicrophoneElement; myMicFrequencyRange = [0,5000]; myMic.BackBaffled = true; myArray = phased.ConformalArray; myArray.Element = myMic; myArray.ElementPosition = Radius*[zeros(1,N);cosd(theta);sind(theta)]; myArray.ElementNormal = [ones(1,N);zeros(1,N)]; c = 1500.0; fc = 4000;
Steer the array to 30 degrees in azimuth and compute the directivity in the steering direction.
lambda = c/fc; ang = [30;0]; w = steervec(getElementPosition(myArray)/lambda,ang); d = directivity(myArray,fc,ang,... 'PropagationSpeed',c,... 'Weights',w)
d = 15.1633
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
where Urad(θ,φ) is the radiant intensity of a transmitter in the direction (θ,φ) and Ptotal 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.
Grating lobes due to array element spacing greater than ½ wavelength may introduce numerical errors in the computation of array directivity.