Changes

<table><tr><td>[[Image:Picasso_L5_FigTable.png|thumb|left|600px|The variables dialog showing the modified and newly added variables.]]</td></tr></table> At this point, you have a PEC group called PEC_1 and a PEC Via group called "PECVIA_1 " in the navigation tree with the following geometric objects, open the property dialog of the patch object "ANCHOR" and via object "Probe_feed" and make the changes shown in the figures below:

! scope="row"| Prove_feedProbe_feed

You are going to keep the probe source "PS_1" and the current distribution observable "CD_1" the wizard create for you without any changes. Next, open the property dialog of the far-field observable "FF_1" to change some of tge radiaiotn the radiation pattern parameters. Set the '''Angle Increment''' to 1&deg; for both Theta and Phi angles. In the '''Array Factor''' section of the dialog, define a 4&times;4 array with equal X and Y spacing of 95mm as shown in the figure below. Note that default values of the array spacing along the X and Y directions have automatically been set by [[EM.Picasso]] to the periods along those directions.

S11: 0.364201 +103832 -0.382380j623762j

S11(dB): -53.546187980919

Z11: 6525.504298 +69169482 -52.466166j320437j

Y11: 0.007185 -007467 +0.007620j015521j

Visualize the current distribution and 3D radiation pattern of your antenna. Note that the computed radiation pattern is the product of a 4&times;4 array factor and the radiation pattern of the periodic patch unit cell. A high directivity value of D₀ = 5253.86 04 (or 17.23dB25dB) is predicted.

[[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 array beam to &theta; = &phi; = +45&deg;, you need phase progressions equal to &Psi;_x = &Psi;_y = -90&deg; 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.

S11: 0.381509 +080215 -0.402186j702658j

S11(dB): -53.124336008887

Z11: 6318.633841 +73654343 -52.892618j447612j

Y11: 0.006692 -006020 +0.007770j016925j

To build a finite-sized patch array, use the '''Probe-Fed Patch Array Wizard''' [[Image:ProbeFedPatchArrayWizardIcon.png]] to create a default 2 &times; 2 patch array first.

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.

Generate and view the mesh of the patch array and make sure it is consistent. Checkmark the "Simplify Mesh of Small Vias" checkbox.

[[Image:Tempo_L4_Fig7A_newPicasso_L5_dBunit.png|thumb|left|600px|The output plot settings dialog.]]

In the previous part of this lesson, we assumed the all the 16 patch elements were excited using identical probe sources. In other words, the amplitudes and phases of all the 16 lumped sources were assumed to be equal, hence, a uniform weight distribution. [[EM.Picasso]] allows you to define different weights for individual elements of a source array. Open the property dialog of the probe source "PS_1 " and click the button labeled {{key|Array Weights...}}. In the array weight dialog, the Distribution drop-down list gives a number of options: Uniform, Binomial, Chebyshev and Custom. Uniform distribution is the default option as you used in the previous part of this tutorial lesson. Now select "Binomial" for a radiation pattern with minimal side lobes. Close the array weights dialog and then close the lumped source dialog to return to the project workspace. <table><tr><td>[[Image:Picasso_L5_Fig13Bweight.png|thumb|left|480px|The Weight Distribution button in the property dialog of the probe source.]]</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 = 33.1663, but the side lobe have completely disappeared as you would expect from the antenna array theory.

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 &theta; = &phi; = 45&deg;, you need equal phase progressions of -90&deg; along both X and Y directions. Enter a value of -90 in the respective boxes of the source array dialog.

Run a new PMOM analysis of your array with a binomial uniform amplitude distribution and phase progressions of -90&deg;. 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.

[[Image:Top_icon.png|30px]] '''[[#What_You_Will_Learn | Back to the Top of the Page]]''' [[Image:Back_icon.png|40px30px]] '''[[EM.Cube#EM.Picasso_Tutorial_Lessons Picasso_Documentation | Back to EM.Picasso Tutorial Gateway]]'''