[[Image:Back_icon.png|30px]] '''[[EM.Cube#EM.Picasso_Documentation | Back to EM.Picasso Tutorial Gateway]]'''
[[Image:Download2x.png|30px]] '''[http://www.emagtech.com/downloads/ProjectRepo/EMPicasso_Lesson5.zip Download projects related to this tutorial lesson]'''
==Getting Started==
| Rectangle Strip
| PEC_1
| len × widlen
| (0, 0, 1.524mm)
| (0°, 0°, 0°)
Run a quick single-frequency PMOM analysis of your periodic patch array. At the end of the simulation, the port characteristics are reported as:
S11: 0.113472 103832 -0.516921j623762j
S11(dB): -53.527129980919
Z11: 3425.179527 169482 -4952.083836j320437j
Y11: 0.009554 007467 +0.013720j015521j
Visualize the current distribution and 3D radiation pattern of your antenna. Note that the computed radiation pattern is the product of a 4×4 array factor and the radiation pattern of the periodic patch unit cell. A high directivity value of D<sub>0</sub> = 53.02 04 (or 17.24dB25dB) is predicted.
<table>
==Steering the Beam of the Periodic Patch Array==
[[EM.Picasso]] allows you to steer or scan the beam of a periodic antenna array in any Theta and Phi direction. In [[EM.Picasso]], you can do this with periodic strip and probe gap sources through their property dialog. Open the property dialog of the probe source "PS_1". At the bottom of this dialog, click the button labeled {{key|Periodic Scan Angles...}}. In the scan angles Periodic Scan Angles dialog, you can enter values for "Scan Theta(deg)" and "Scan Phi(deg)" in degrees. Their default values are zero. This means that by default there is no phase progression among the elements of the infinite periodic array.
In order to steer the beam of an antenna array to the spherical angles (θ, φ), a two-dimensional phase progression among the array elements is required along the X and Y directions given by the following equations:
<math>\Psi_y = - \pi \sin\theta sin\phi</math>
In order to steer the array beam to θ = φ = +45°, you need phase progressions equal to Ψ<sub>x</sub> = Ψ<sub>y</sub> = -90° that is equal phase progression along both X and Y directions. Enter a value of 45 degrees for both Scan "Theta (deg)" and Scan "Phi (deg) in the scan angles Periodic Scan Angles dialog and return to the probe source dialog.
<table>
Run a PMOM analysis of your periodic array with steered beam. At the end of the simulation, the port characteristics are reported as:
S11: 0.149246 080215 -0.600599j702658j
S11(dB): -43.168086008887
Z11: 2818.446489 654343 -5552.380161j447612j
Y11: 0.007339 006020 +0.014287j016925j
Now visualize the 3D radiation pattern of the array with the steered beam.
| 1
|-
| feed_Xfeed_x
| feed_ratio*len
| 15
| 0.5*lambda0_unit
| 95
|}
Next, define two new variables called "feed_y" and "wid" according to the table below.
{| class="wikitable"
|-
! scope="col"| Variable Name
! scope="col"| Definition
|-
| feed_y
| -3.6
|-
| wid
| 51
|}
</table>
The patch array you just created is a finite-sized rectangular grid configuration of the probe-fed patch antenna you analyzed earlier. The wizard automatically generates an array object called "Patch_array" out of a key element, which is a single probe-fed patch antenna in this case. The initial key object is called the "primitive" and becomes part of the newly created array object. You can change the array properties including its number of elements and element spacings along the three principal directions. You can also access the properties of the primitive and modify them as well. Once you change the primitive, all the other elements of the array object are automatically updated accordingly. Note that the inter-element spacing in both X and Y directions has been set equal to a variable called "spacing", defined to have a value of half the free-space wavelength. Press "Edit Primitive" button and open the "Rectangular Strip Properties" dialog of the patch_array object and "Feed_array" and make the changes shown in the figures below:
<table>
</td>
</tr>
</table>
Make the changes for "Feed_array" shown in the figure below:
<table>
<tr>
<td>
</table>
Sometimes it is preferred to plot the radiation patterns on a dB scale. To do so, double-click on the legend to open up the Output Plot Settings dialog. You can also open this dialog from the contextual menu of the total 3D radiation pattern item in the navigation tree. In the '''Scale''' section of the dialog, select the "dB" radio button. The directivity is now displayed on the dB scale: D0 = 17.23dB24dB.
<table>
<tr>
<td>
[[Image:Tempo_L4_Fig7A_newPicasso_L5_dBunit.png|thumb|left|600px|The output plot settings dialog.]]
</td>
</tr>
</table>
Next, visualize the 3D radiation pattern of the array. The directivity of the 4 × 4 patch array has now reduced to D0 = 3233.4163, but the side lobe have completely disappeared as you would expect from the antenna array theory.
<table>
== Steering the Beam of the Finite-Sized Patch Array ==
Just as you can steer the beam of an infinite periodic array, you can also steer the beam of a finite-sized antenna array. This can be done from the source array dialog. Open the property dialog of the source array "PS_1" and click the button labeled {{key|Array Weights...}}. Change the '''Weight Distribution''' back to the '''Uniform''' type. At the bottom of this dialog, you will see zero default values for the "Phase Progression" along the X, Y and Z directions. In the case of beam steering, your planar array's elements must have a nonzero phase progression along the X and Y directions. Earlier you found that to steer the beam of the array to θ = φ = 45°, you need equal phase progressions of -90° along both X and Y directions. Enter a value of -90 in the respective boxes of the source array dialog.
<table>
</table>
Run a new PMOM analysis of your array with a binomial uniform amplitude distribution and phase progressions of -90°. Note that the mesh of the structure does not change due to the changes in the source definition. The linear system still has the same size N = 7,552. However, you will notice that the steered beam case would take 749 BiCG iterations and much longer time to converge. Visualize the current distribution and 3D radiation pattern of the array.
<table>