azel2phithetapat

Convert radiation pattern from azimuth-elevation coordinates to phi-theta coordinates

Syntax

pat_phitheta = azel2phithetapat(pat_azel,az,el)

pat_phitheta = azel2phithetapat(pat_azel,az,el,phi,theta)

pat_phitheta = azel2phithetapat(___,'RotateZ2X',rotpatax)

[pat_phitheta,phi_pat,theta_pat] = azel2phithetapat(___)

Description

pat_phitheta = azel2phithetapat(pat_azel,az,el) converts the antenna radiation pattern, pat_azel, from azimuth and elevation coordinates to the pattern, pat_phitheta, in phi and theta coordinates. az and el are the azimuth and elevation angles at which the pat_azel values are defined. The pat_phitheta matrix covers theta values from 0 to 180 degrees and phi values from 0 to 360 degrees in one degree increments. The function interpolates the pat_azel matrix to estimate the response of the antenna in a given phi-theta direction.

pat_phitheta = azel2phithetapat(pat_azel,az,el,phi,theta) also specifies phi and theta as the grid at which to sample pat_phitheta. To avoid interpolation errors, phi should cover the range [0,180], and theta should cover the range [0,360].

pat_phitheta = azel2phithetapat(___,'RotateZ2X',rotpatax) also specifies rotpatax to indicate the boresight direction of the pattern along the x-axis or the z-axis.

[pat_phitheta,phi_pat,theta_pat] = azel2phithetapat(___) also returns vectors phi_pat and theta_pat containing the phi and theta angles at which pat_phitheta is sampled.

Examples

Convert Radiation Pattern to Phi-Theta

Convert a radiation pattern to φ/θ form, with the φ and θ angles spaced 1 degree apart.

Define the pattern in terms of azimuth and elevation.

az = -180:180;
el = -90:90;
pat_azel = mag2db(repmat(cosd(el)',1,numel(az)));

Convert the pattern to φ/θ space.

pat_phitheta = azel2phithetapat(pat_azel,az,el);

Plot Converted Radiation Pattern

Plot the result of converting a radiation pattern to $$\varphi /\theta$$ space with the $$\varphi$$ and $$\theta$$ angles spaced 1 degree apart.

The radiation pattern is the cosine of the elevation.

az = -180:180;
el = -90:90;
pat_azel = repmat(cosd(el)',1,numel(az));

Convert the pattern to $$\varphi /\theta$$ space. Use the returned $$\varphi$$ and $$\theta$$ angles for plotting.

[pat_phitheta,phi,theta] = azel2phithetapat(pat_azel,az,el);

Plot the result.

H = surf(phi,theta,mag2db(pat_phitheta));
H.LineStyle = 'none';
xlabel('phi (degrees)');
ylabel('theta (degrees)');
zlabel('Pattern');

Convert Radiation Pattern to Alternate Phi-Theta Coordinates

Convert a radiation pattern to the alternate phi-theta coordinates, with the phi and theta angles spaced one degree apart.

Create a simple radiation pattern in terms of azimuth and elevation. Add an offset to the pattern to suppress taking the logarithm of zero in mag2db.

az = -180:180;
el = -90:90;
pat_azel = mag2db(cosd(el).^2'*sind(az).^2 + 1);

imagesc(az,el,pat_azel)
xlabel('Azimuth (deg)')
ylabel('Elevation (deg)')
colorbar

Convert the pattern to phi-theta space.

[pat_phitheta,phi_pat,theta_pat] = azel2phithetapat(pat_azel,az,el,'RotateZ2X',false);
imagesc(phi_pat,theta_pat,pat_phitheta)
xlabel('Phi (deg)')
ylabel('Theta (deg)')
colorbar

Convert Radiation Pattern for Specific Phi/Theta Values

Convert a radiation pattern to $$\varphi /\theta$$ space with $$\varphi$$ and $$\theta$$ angles spaced 5 degrees apart.

The radiation pattern is the cosine of the elevation.

az = -180:180;
el = -90:90;
pat_azel = repmat(cosd(el)',1,numel(az));

Define the set of $$\varphi$$ and $$\theta$$ angles at which to sample the pattern. Then, convert the pattern.

phi = 0:5:360;
theta = 0:5:180;
pat_phitheta = azel2phithetapat(pat_azel,az,el,phi,theta);

Plot the result.

H = surf(phi,theta,mag2db(pat_phitheta));
H.LineStyle = 'none';
xlabel('phi (degrees)');
ylabel('theta (degrees)');
zlabel('Pattern');

Input Arguments

pat_azel — Antenna radiation pattern

real-valued Q-by-P matrix

Antenna radiation pattern as a function of azimuth and elevation, specified as a real-valued Q-by-P matrix. pat_azel contains the magnitude pattern. P is the length of the az vector, and Q is the length of the el vector. Units are in dB.

Data Types: double

az — Azimuth angles

real-valued length-P vector

Azimuth angles at which the pat_azel pattern is sampled, specified as a real-valued length-P vector. Azimuth angles lie between –180 and 180, inclusive. Units are in degrees.

Data Types: double

el — Elevation angles

real-valued length-Q vector

Elevation angles at which the pat_azel pattern is sampled, specified as a real-valued length-Q vector. Azimuth angles lie between –90 and 90, inclusive. Units are in degrees.

Data Types: double

phi — Phi angles

[0:360] (default) | real-valued length-L vector

Phi angles at which the pat_phitheta pattern is sampled, specified as a real-valued length-L vector. Phi angles lie between 0 and 360, inclusive. Units are in degrees.

Data Types: double

theta — Theta angles

[0:180] (default) | real-valued length-M vector

Theta angles at which the pat_phitheta pattern is sampled, specified as a real-valued length-M vector. Theta angles lie between 0 and 180, inclusive. Units are in degrees.

Data Types: double

rotpatax — Pattern boresight direction selector

true (default) | false

Pattern boresight direction selector, specified as true or false.

• If rotpatax is true, the pattern boresight is along the x-axis. In this case, the z-axis of phi-theta space is aligned with the x-axis of azimuth and elevation space. The phi angle is defined from the y-axis to the z-axis and the theta angle is defined from the x-axis toward the yz-plane. (See Phi and Theta Angles).

• If rotpatax is false, the phi angle is defined from the x-axis to the y-axis and the theta angle is defined from the z-axis toward the xy-plane. (See Alternative Definition of Phi and Theta).

Data Types: logical

Output Arguments

pat_phitheta — Antenna radiation pattern in phi-theta coordinates

real-valued M-by-L matrix

Antenna radiation pattern in phi-theta coordinates, returned as a real-valued M-by-L matrix. pat_phitheta represents the magnitude pattern. L is the length of the phi_pat vector, and M is the length of the theta_pat vector. Units are in dB.

phi_pat — Phi angles

real-valued length-L vector

Phi angles at which the pat_phitheta pattern is sampled, returned as a real-valued length L vector. Units are in degrees.

theta_pat — Theta angles

real-valued length-M vector

Theta angles at which the pat_phitheta pattern is sampled, returned as a real-valued length-M vector. Units are in degrees.

More About

Azimuth and Elevation Angles

The azimuth angle of a vector is the angle between the x-axis and the orthogonal projection of the vector onto the xy plane. The angle is positive in going from the x axis toward the y axis. Azimuth angles lie between –180 and 180 degrees. The elevation angle is the angle between the vector and its orthogonal projection onto the xy-plane. The angle is positive when going toward the positive z-axis from the xy plane. By default, the boresight direction of an element or array is aligned with the positive x-axis. The boresight direction is the direction of the main lobe of an element or array.

Note

The elevation angle is sometimes defined in the literature as the angle a vector makes with the positive z-axis. The MATLAB^® and Phased Array System Toolbox™ products do not use this definition.

This figure illustrates the azimuth angle and elevation angle for a vector shown as a green solid line.

Phi and Theta Angles

The phi angle (φ) is the angle from the positive y-axis to the vector’s orthogonal projection onto the yz plane. The angle is positive toward the positive z-axis. The phi angle is between 0 and 360 degrees. The theta angle (θ) is the angle from the x-axis to the vector itself. The angle is positive toward the yz plane. The theta angle is between 0 and 180 degrees.

The figure illustrates phi and theta for a vector that appears as a green solid line.

The coordinate transformations between φ/θ and az/el are described by the following equations

$$\begin{array}{l}\sin el=\sin \varphi \sin \theta \\ \tan az=\cos \varphi \tan \theta \\ \cos \theta =\cos el\cos az\\ \tan \varphi =\tan el/\sin az\end{array}$$

Alternative Definition of Phi and Theta

The phi angle (φ) is the angle from the positive x-axis to the vector’s orthogonal projection onto the xy plane. The angle is positive toward the positive y-axis. The phi angle is between 0 and 360 degrees. The theta angle (θ) is the angle from the z-axis to the vector itself. The angle is positive toward the xy plane. The theta angle is between 0 and 180 degrees.

The figure illustrates φ and θ for a vector that appears as a green solid line.

$$\begin{array}{l}\varphi =az\\ \theta =90-el\\ az=\varphi \\ el=90-\theta \end{array}$$

Extended Capabilities

C/C++ Code Generation

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

Usage notes and limitations:

Does not support variable-size inputs.

Version History

Introduced in R2012a