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AGILENT TECHNOLOGIES INDIA PVT LTD

Antenna Design Workshop

using Agilent EEsof Tools

(ADS & EMPro) Comprehensive Hands On Workshop

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Workshop Agenda:

Session 1: Design and Simulation of Patch Antenna

Lab1: Patch Antenna Design

Lab2: Patch Antenna with Finite Ground

Session 2: Patch Antenna Optimization

Session 3: Patch Antenna with Coax Feed

Lab1: Using Momentum for Coax fed patch antenna

Lab2: Using FEM simulator for Coax fed patch antenna

Session 4: Patch Antenna Array Design

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Session 1: Design and Simulation of Patch Antenna

Theory:

A microstrip antenna in its simplest configuration consists of a radiating patch on one side of a dielectric

substrate, which has a ground plane on the other side. The patch conductors usually made of copper or

gold can be virtually assumed to be of any shape. However, conventional shapes are normally used to

simplify analysis and performance prediction. The radiating elements and the feed lines are usually

photo etched on the dielectric substrate. The basic configuration of a microstrip patch antenna is shown

in figure1

Fig. 1 Basic configuration of Microstrip Antenna

The radiating patch may be square, rectangular, circular elliptical or any other configuration. Square,

rectangular and circular shapes are the most common because of ease of analysis and fabrication. Some

of the advantages of the microstrip antennas compared to conventional microwave antennas are

Low weight, low volume

Low fabrication cost,

Easy mass production,

Linear and circular polarization are possible with simple feed,

Easily integrated with MIC,

Feed lines and matching networks can be fabricated simultaneously with

antenna structures

Patch antennas find various applications stating from military to commercial, because of their ease of

design and fabrication. Patch arrays are extensively used in phased array radar applications and in

applications requiring high directivity and narrow beamwidth.

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Lab1: Design of a Patch Antenna at 2.4 GHz

Step1: Calculating Patch Antenna Dimensions

1. Select an appropriate substrate of thickness (h) and dielectric constant (r) for the design of the patch antenna. In present case, we shall use following Dielectric for design:

a. Height: 1.6 mm

b. Metal Thickness: 1.4 mil (1 oz. Copper i.e. 35um)

c. Er: 4.6

d. TanD: 0.001

e. Conductivity: 5.8E7 S/m

2. Calculate the physical parameters of the patch antenna as shown in the geometry in Figure 2

using the given formula.

Fig. 2 Geometry of the Square Patch Antenna

The width and length of the radiating surface is given by,

r

cW=L=(2f )

= 29.2mm

where,

velocity of light c = 3 X 108

m/s

Frequency, f = 2.4 GHz

Relative Permittivity r = 4.6

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The depth of the feed line in to the patch is given by,

H=0.822*L/2 = 12 mm

The other dimensions are,

Y= W/5 = 5.8 mm

X = Z = 2W/5 = 11.7 mm

Step2: Creating Patch Antenna Geometry:

1. Create a new workspace, name it as Lab5_PatchAntenna_wrk

2. Open the new layout cell and name it as Lab1_Patch

3. Use Insert ->Polygon and use Select Insert -> Coordinate Entry and enter following coordinates

one by one and keep on clicking Apply at each coordinate entry:

(0, 0)

(0, 29.2)

(29.2, 29.2)

(29.2, 0)

(17.5, 0)

(17.5, 12)

(16.1, 12)

(16.1, -10)

(13.1, -10)

(13.1, 12)

(11.7, 12)

(11.7, 0)

(0, 0)

Click OK and press Space Bar to end the polygon drawing command.

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Step3: Antenna Simulation

1. Connect a pin at the feed point of the antenna as shown below

2. Go to the EM setup window and click on Substrate and click on New to accept the 25 mil

Alumina template. Define the substrate as below, modify the default substrate height, Er, TanD

and conductor height and define it as Copper (select it from Add from Database list). Changing

name of the dielectric is optional as it has no bearing on the simulation. Click on cond and

change it Intrude Into Substrate and enter the height as 35 micron.

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3. Set the Simulation Frequency range as 2.1GHz 2.7GHz (adaptive sweep) and Add a new Single

Point of 2.4GHz as shown below

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4. Click on Simulate and observe the simulation results in data display

Step4: Antenna Radiation Pattern

1. For Far-Field Antenna Pattern, go to EM->Post Processing->Far Field and select the desired

frequency (e.g. 2.4 GHz) and click on Compute.

2. Far field computation will be done and results will be displayed in the post processing window

as shown below. We can use Window->Tile and then go to Plot Properties (from the bottom

tabs) and then select Far Field->Antenna Parameters to see all the required data.

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3. Goto Far Field Cut tab and select the Phi and click on Display Cut in data display button

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4. Once done, we will be able to see far field cut in the ADS data display as shown below

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Lab2: Patch Antenna with Finite Ground

1. From Lab1_Patch layout, click on File->Save As and provide the new name as

Lab2_Patch_FiniteGnd. Select Save the entire cell option so that we also save the EMsetup

done for earlier design.

2. In the new layout design click on Substrate Editor to open the infinite ground plane substrate

which was used in earlier lab.

3. Select File->Save As and provide name as substrate1_finitegnd

4. Left click on the Bottom cover of the substrate and select Strip Plane so that we can map a

conductor layer here for finite ground modeling.

5. Once done, we shall see an Air dielectric layer added at the bottom of FR4 dielectric and with a

STRIP plane active at the junction of bottom side of FR4 and AIR dielectric. Right click on this

junction and select Map Conductor Layer as shown below.

6. By default cond2 layer will be mapped as per the default layer numbers provided in layer

technology file of ADS.

7. Click on cond2 and define following:

a. Conductor = Copper

b. Operation = SHEET

c. Thickness = 35 micron

8. Click on Save and exit the substrate editor dialog

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9. In the layout window, change the entry layer to cond2 as shown below

10. Select Rectangle drawing icon and click on Insert->Coordinate Entry and do following:

a. Enter first coordinate as (-15,-10) click Apply

b. Enter second coordinate as (44.2, 44.2) and click OK to see following layout with finite

ground pattern

c. Click on Pin icon and place a Pin very close to P1 pin which is already there on cond

layer for Antenna feed

d. Complete Layout will look similar to one shown below

11. Go to Click on EMsetup and go to Substrate icon and select substrate1_finitegnd from the drop

down list.

12. Click on Ports option and you will notice 2 ports, right click on P2 and select Delete so that it

appears under Unconnected Layout Pins

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13. Drag and drop P2 from here to the GND terminal for P1 so that Port setup appears as below:

14. Click on Simulate icon to start simulation and observe the data display to observe the shift in

Antenna S11 response.

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Session 2: Patch Antenna Optimization

1. Open Lab1_PatchAntenna and click on File->SaveAs, provide new name as

Lab3_PatchOptimizaton_Layout

2. Select EM->Component->Parameters and enter variable as width, set nominal value = 29.2 mm

which is our initially calculated value for width of Patch Antenna, enter Perturbed Value = 34.2

mm (this is the dimension which we shall use when we created perturbed design to assign width

variable to our Patch geometry)

3. Click Add and a new pop-up window will appear asking us to perturb the design with this new

perturbed value of width. Enter deltaX = -2.5 mm, deltaY=0 (as we dont want any change in Y-

direction) and select left corners of patch antenna geometry (Hint: From outside patch antenna

geometry, left click on mouse and drag a rectangle till left 2 corners are covered and release the

mouse left button, this action shall select the left 2 corners)

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4. Click Apply button and you will notice that left edge gets shifted by -2.5mm. Now enter

deltaX=2.5mm, deltaY=0 and select right side corners and click Apply button and you should

notice that right side edge moves by 2.5mm and if we measure the width of Patch Antenna it

should be 34.2 mm with +/- 2.5mm perturbation on either side so during optimization when

width is changed patch antennas width will change equally on left and right hand side.

5. Click OK and dismiss the perturbation dialog and you shall notice that a parameter width is

added to the parameter list and original layout is visible

6. Enter a new variable, length and set Nominal Value =29.2 mm (as per our initial calculations)

and set Perturbed Value as 34.2mm. Click on Add button.

7. In the pop up window enter deltaX=0, deltaY=5mm as we will apply entire perturbation on +Y

axis so that the inset feed length on the lower Y side to remain unchanged. Select top 2 corners

of the patch geometry as shown in next snapshot

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8. Click Apply and you will notice that the upper edge moves up by 5mm. Click OK and notice that

another variable length is added to the parameter list window

9. Now, we shall apply perturbation on inset feed length..enter new parameter name as

inset_length, set Nominal value as 12 mm (as per our earlier calculations) and Perturbed Value

as 13 mm and click Add

10. Select 4 corner points of the inset by dragging a rectangle from outside patch geometry as

shown in next snapshot

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11. Click Apply to see that inset length increases by 1 mm. Click OK and dismiss the perturbation

dialog.

12. Enter a new parameter name as inset_width and set Nominal value = 1.4 mm (as per our earlier

calculations) and Perturbed value as 2.4 mm and click Add

13. Enter deltaX=1 mm, deltaY=0 and select 2 right side corner of the edge as shown below and click

Apply and notice that this edge will move by 1 mm on the right hand side

14. Enter deltaX= -1 mm, deltaY=0 and select left side corner points as shown below and click Apply

to see left side edge moves left by 1mm

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15. Click OK to see all the required optimization parameters getting added to the parameter list as

shown below

16. Click OK to dismiss the parameter dialog box and save the layout design.

17. Open the substrate and make the cond as SHEET conductor to save some of the optimization

time in the lab. In normal cases it is recommended to leave it as THICK CONDUCTOR.

18. Just for the sake of this training exercise, we shall optimize the Patch Antenna to operate at 5

GHz. In a normal case it is never recommended to use EM optimization blindly as it could be a

time consuming process. For optimum EM optimization it is recommended to have results

which are close to what we want and final level optimization can be perform by EM simulator.

19. Go to EMsetup and in the Frequency Plan, enter the frequency sweep from 4.9 GHz 5.1 GHz

and modify the single frequency point = 5GHz as shown below

20. Go to Model/Symbol option in EMsetup window and select Options Create EM Model when

Simulation is launched and Create Symbol when simulation is launched

21. Click Simulate to perform Momentum simulation and observe the data display when simulation

is finished as shown in next snapshot.

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22. This S11 plot clearly indicates that current Antenna is not matched at 5 GHz at all and this is

what we are going to optimize by changing the layout parameters so that we can observe good

return loss at 5 GHz. Close the layout and other windows which may be open currently.

23. From the Main ADS window, open a new Schematic cell and name it as

Lab3_PatchAntenna_Optimization

24. Keep Main ADS window and this new schematic window side by side and drag and drop

Lab3_PatchOptimization_Layout from the Main ADS window to this schematic window to place

the layout as an component in schematic to optimize the patch antenna design as shown below.

Notice the parameters on this Patch Antenna layout component which are same as what we

defined earlier in the layout.

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25. This Patch Antenna component now is a parametric EM component whereby we can

optimize/modify the associated parameters which as width, length etc to optimize the Patch

Antenna for specific frequency. Please note that substrate over which this antenna is designed

remains the same as in original design.

26. Before we run optimization, it is always good to run a nominal S-Parameter simulation on this

EM component to ensure that it is representing the same data which was obtained with EM

simulation earlier (this is not mandatory but good practice to ensure that data integrity is

maintained). Insert the S-Parameter controller and Termination component and connect to

Patch Antenna element as shown below. Set up Start = 4.9 GHz, Stop = 5.1 GHz and Step = 10

MHz in the S-Parameter controller and perform simulation and notice that the results are the

same as obtained in earlier EM simulation.

27. From Opt/Stat/DOE library palette, insert a Goal and Optimization controller as shown below

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28. Double click on Goal and set its parameter as shown below

29. Double click on Optimization controller, set Optimizer Type as Random and Number of

Iterations = 50

30. Select Simulation->Simulation Variables setup and go to Optimization tab and select all the

patch antenna parameters to be optimizable and change the Min as shown below.

31. Click on Optimization icon to start the optimization process and following window will

show progress during optimization

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32. Optimization was stopped in between and schematic was updated with following component

values and results.

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Session 3: Patch Antenna with Coax Feed

Objective: Patch Antenna is often fed using a Coaxial cable/connector. This lab demonstrates 2 ways of

performing this simulation using ADS.

Lab1: Using Momentum simulator for Coax fed Patch Antenna

1. Create a new workspace with units as mm. Create a new layout cell with name Patch_Coax1

2. In the layout window, draw following:

Patch Surface:

a. Use cond drawing layer and click on Rectangle icon.

b. Select Insert->Coordinate Entry and enter coordinate as (0,0) and click Apply

c. Enter other coordinate as (65,40) and click OK

Lower Feed Point:

a. Change the entry layer to cond2 and click on Rectangle icon.

b. Select Insert->Coordinate Entry and enter coordinate as (4.4,4.4) and click Apply

c. Enter other coordinate as (18.8,20.4) and click OK.

Coax Center Feed:

a. Change Entry Layer as pcvia1 and click on Circle icon

b. Select Insert->Coordinate Entry and enter coordinate as (13.3,12.4) and click Apply

c. Enter other coordinate as (12.32,12.4) and click OK. This shall make a circle representing

center conductor of coax feed at center point of (13.3, 12.4) with a radius of 0.98mm

Ground Clearance:

a. Change Entry Layer to hole and click on Circle icon

b. Select Insert->Coordinate Entry and enter coordinate as (13.3, 12.4) and click Apply (this is

the same center point as for center conductor feed)

c. Enter other coordinate as (9.8,12.4) and click OK. This shall create a circular clearance at

center of (13.3,12.4) with the radius of 3.5mm to avoid shorting of center feed with ground

plane)

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3. Click on Substrate icon and define a new substrate to look as provided snapshot:

Set the properties of Sub1 and Sub2 as below:

Height = 5 mm

Er =2.2

TanD = 0.005

Substrate Setup:

a. cond is STRIP layer where we have drawn patch antenna

b. hole layer junction is mapped as SLOT (click on junction and change the Interface as SLOT layer.

Anything on SLOT will be used as a ground reference for patch antenna and it is always used or

drawn in inverted logic i.e. means we need to draw shape in layout wherever you dont want

metal to be present (this is by default definition in ADS). SLOT mode helps in reducing simulation

time and memory requirements and is very useful for larger problems.

c. cond2 layer is a STRIP layer where we have drawn bottom feed layer for our antenna.

d. pcvia1 is the center feed mapped as VIA from cond to cond2 layer.

e. cond and cond2 layers are of 35 micron with Copper conductivity

Save the substrate and exit the substrate editor dialog.

Place a Pin on cond2 layer so that it can provide the required excitation/termination for our Momentum

simulation.

Completed layout will appear as shown below (in case below, layers have been changed to Outline

mode for more clarity.

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Click on EMsetup icon to open the EM setup window and click on 3D EM Preview to see isometric view

of our Patch Antenna design (we have turned off visibility of top and bottom Air layers for better

viewing purpose, note that hole layer was mapped as SLOT hence it provides inverted view of what we

have drawn in layout):

Setup Frequency sweep from 2GHz 3GHz and click on Simulate icon to see S11 plot as below

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Lab2: Using FEM simulator for coax fed Patch Antenna

FEM simulator in ADS provides additional capability of modeling more realistic coax feed by including

center pin, dielectric filling, outer metal shell etc. This lab shall provide a typical way on how it can be

done easily in ADS and then simulation can be performed using FEM simulator integrated within ADS.

Open a new Layout cell with Name Patch_CoaxFeed_FEM

Step1: Coax Modeling

1. Select entry layer to bond and select rectangle icon

2. Select Insert->Coordinate Entry, enter first coordinate as (0,0) and click Apply

3. Enter second coordinate Entry as (1.6,1.6) and click OK. Press Esc key to end the command

4. Change entry layer as cond2 and select circle icon

5. Select Insert->Coordinate Entry, enter first coordinate as (0.8, 0.8) and click Apply

6. Enter second coordinate as (0.1,0.8) and click OK. Press Esc key to end the command.

7. Change the entry layer as diel and select circle icon



10. Change the entry layer as pcvia1 and select circle icon



13. Change the entry layer to cond and select circle icon



16. Change the entry layer to hole and select Circle icon



19. Select the circle drawn on pcvia1 layer and go to Edit->Advanced Copy/Paste->Copy to Layer

and select layer as bond. This action will create a face on bond layer where we attached the

mail signal port later.

Boolean Operations:

In order to create the coax feed, we need to perform Boolean operation so that we can create

proper assembly good assembly of components. Select Edit->Boolean Logical

1. First, lets create the Coax metal face, setup Boolean operation as shown below, make sure All

Shapes is selected and Delete Original is selected under bond layer and bond layer is selected

after = sign so that resulting figure will appear on bond layer. Click Apply.

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2. Now let us create the gap for center pin (which is pcvia1 layer) through the diel layer, set up

Boolean operation as shown below. Make sure Delete original is selected for diel layer and diel

layer appears after = sign so that resulting figure appears in diel layer.

3. Now let us create the metal covering for our dielectric filling. Setup Boolean operation as shown

below. Make sure delete original is selected for hole layer and hole layer appears after = sign

(remember we made hole diameter little bigger than diel via and after this operation it will

appear as thin ring representing metal coating on our dielectric filling. This will overlap with

bond layer and provide short connection to our ground plane at the back of patch antenna

dielectric.

Patch Antenna:

1. Change Entry layer to cond and select Rectangle drawing icon.

2. Select Insert->Coordinate Entry, enter first coordinate as (-6.7, -1.2) and click Apply

3. Enter second coordinate as (8.3,8.03) and click OK. Press Esc to end the command.

4. These actions will make a Patch Antenna with dimensions of 15x9.25mm and the feed point at

X=7.5 and Y=2 from lower left corner of Patch Antenna.

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Substrate Definition:

Click on Substrate Editor icon on layout window and select File->New and provide new substrate name

as Coax_Patch_FEM. Accept the 25mil Alumina substrate template.

Modify the 25mil Alumina template as shown below.

Select Technology->Material Definition and add two dielectric materials as shown below:

Modify following in the substrate:

1. Select diel VIA in substrate window and assign FPE material to it from the list on right hand

side of the window

2. Select Substrate below cond layers and define the material as RO4350 and define thickness as

0.762mm

3. Modify bottom two substrates to be AIR material with 2mm thickness. While the overall length

of Coax feed is 4mm but it is always advisable to avoid very thick substrate when VIA is passing

through it hence in our case this is split into two sections of 2mm each.

4. Select cond layer and assign thickness as 35um

5. Select bond layer and assign thickness as 35um

6. Make sure cond2 layer interface/junction to SLOT. This layer shall act as infinite conductivity

ground plane.

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Notes:

1. FPE: This material will be used for diel VIA layer

2. RO4350 is our actual dielectric on which our Patch Antenna is placed.

3. Thickness of cond and bond layer to be defined as 35um (1oz. conductor thickness)

4. All metals are kept as Perfect Conductors in this example (users can add Copper in Conductor

material list and assign the same to metal layers wherever applicable.

FEM Simulation of Coax Fed Patch:

1. Place 2 ports on bond layer, 1 at the center of the Circular pad (Pin1) and another (Pin2) at the

rectangular pad as shown below (all other layers were made hidden for clarity purposes)

2. Click on EMsetup icon on layout windows EM simulation toolbar

3. Select Substrate option and select correct substrate from the drop down box for our FEM

simulation.

4. Go to Ports, define the Ports as P1 +ve and P2 as ve as shown below (use the same method as

described under Finite ground section):

5. Define the Frequency Plan and setup frequency sweep from 8 GHz 12 GHz with 50 points

(max.)

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6. Select the Output plan and make sure, that Save fields for: All generated frequencies is selected.

This will enable us to plot Far Field Pattern at all simulated frequencies.

7. Go to Options->Solver and change the Matrix solve method to Direct (Direct solver consumes

more memory but it is faster than Iterative method, selection can be made as per RAM available

in the PC. For this case it would take @700MB of RAM so we can use Direct solver)

8. Go to 3D viewer icon to see 3D view of our geometry as shown below (note that few layers have

been switched off for better 3D view)

9. Click on Simulate icon to start FEM simulation. Once finished data display as shown below would

be available:

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10. Click on Far field plot icon, From Solution setup tab select 10 GHz and observe the far-field plot

as shown below

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Session 4: Patch Array Antenna Design

Objective: Create and simulate a Patch Array Antenna at 2.4 GHz

1. Create the Patch Antenna geometry as per calculations done in 1st

lab (or copy/paste)

2. Place Patch Antenna feed point at (0,0) coordinate to make job easier for creation of our patch

array.

3. Place a Pin for simulation at the center of feed line. This step will ensure that all copied

instances will also have simulation pins else we will need to keep it manually.

4. Copy/Paste antenna element using Insert->Coordinate Entry and enter coordinates as (50,0),

(100,0) and (150,0). Click Apply between every coordinate entry

5. Press Esc button to cancel the command. Select this entire row and then select Insert-

>Coordinate Entry and enter coordinates as (0,-50), (0,-100), (0,-150)

For Patch Array design, separation between elements are usually kept as 0.7*lamda 0.8*lamda. In our

case 50mm is 0.75*lamda at 2.4 GHz on 1.6mm FR4 substrate.

6. Once done geometry will look as below:

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7. Define substrate same as done in 1st

lab.

8. Setup simulation from 2.3GHz 2.5 GHz and click on Simulate

9. Once done, simulation results as shown below will be available:

10. Insert a new rectangular plot and plot S from the list of available measurement and it will plot

complete S-matrix allowing designers to see Cross Coupling etc as may be required.

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11. Click on the Far Field icon and select 2.4 GHz frequency to compute far field pattern of the

Antenna Array as shown below:

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