About Passive Circuit DesignGuide

The Passive Circuit DesignGuide documentation provides an introduction to the Passive Circuit DesignGuide. The complexity of the Advanced Design System (ADS) is made easily accessible through the automated capability. A first-time or casual ADS user can begin using the capability of ADS quickly, while experienced ADS users can perform tasks faster than ever before. The Step-by-Step Example describes how a microstrip line and a coupled-line filter can be designed and verified, and a layout generated, in a few minutes.

The Passive Circuit DesignGuide provides SmartComponents and automated-assistants for the design and simulation. All SmartComponents can be modified. You simply select a SmartComponent and, with little effort, redesign or verify their performance. The Using SmartComponents section answers many common questions relating to DesignGuide use and the SmartComponent Reference describes each SmartComponent in detail. The section Using Automated Assistants introduces Automated Assistants.

Step-by-Step Example

The step-by-step example takes you through the design, analysis and sensitivity simulation of a microstrip line and a coupled-line filter. After completing this example, you should have a basic understanding of the Utility and be ready to begin using the tool. Follow these steps to begin:

• Setting Up the Design Environment

• Designing and Analyzing a Network
  

  Note You should already be familiar with the basic features of Advanced Design System. For help with ADS basic features, refer to the Schematic Capture and Layout documentation.

Setting Up the Design Environment

Before you can use the Passive Circuit DesignGuide, you must set up the design environment by using these steps:

• Setting DesignGuide Preferences

• Opening a Project,

• Opening a Schematic Window,

• Opening the Passive Circuit DesignGuide,

• Displaying the SmartComponent Palette.
  

  Note Before beginning, you must have installed the DesignGuide with appropriate licensing codewords.

Setting DesignGuide Preferences

All DesignGuides can be accessed through either cascading menus or dialog boxes. You can configure your preferred method in the ADS Main window or from the Schematic window.
To configure access through menus or dialog boxes:

1. From the Main or Schematic window, choose DesignGuide > Preferences .
2. In the DesignGuide Menu Style group box, choose either Use a selection dialog box or Use cascade menus .
   
3. Close and restart the program for your preference changes to take effect.
   

   Note On PC systems, Windows resource issues might limit the use of cascading menus. When multiple windows are open, your system could become destabilized. Therefore, the dialog box menu style might be best for these situations.

   The ADS Main window DesignGuide menu contains these choices:
   DesignGuide Developer Studio > Start DesignGuide Studio is only available on this menu if you have installed the DesignGuide Developer Studio to open the initial Developer Studio dialog box.

DesignGuide Developer Studio > Developer Studio Documentation is only available on this menu if you have installed the DesignGuide Developer Studio to open the DesignGuide Developer Studio documentation.

Note Another way to access the DesignGuide Developer Studio documentation is by selecting Help > Topics and Index > DesignGuides > DesignGuide Developer Studio from any ADS program window.

Add DesignGuide opens a directory browser in which you can add a DesignGuide to your installation. This is primarily intended for use with DesignGuides that are custom-built through the Developer Studio.

List/Remove DesignGuide opens a list of your installed DesignGuides. Select any that you would like to uninstall and choose the Remove button.

Preferences opens a dialog box that enables you to:

• Disable the DesignGuide menu commands (all except Preferences) in the Main window by unchecking this box. In the Schematic and Layout windows, the complete DesignGuide menu and all of its commands are removed if this box is unchecked.
• Select your preferred interface method, either cascading menus or dialog boxes.

Opening a Project

The ADS design environment is set up within a project.
To create a new project:

1. From the ADS Main window, choose File > New Project or click Create a New Project on the toolbar.
   
2. In the dialog, define the location of the project and assign a project name.

Opening a Schematic Window

A new schematic design is needed to contain the lowpass component for this example.
To open a Schematic window:

1. From the ADS Main window, choose Window > New Schematic or click New Schematic Window on the toolbar. A new Schematic window appears.
   

   Note Depending on how your ADS preferences are set, a Schematic window can appear automatically when you create or open a project.

2. In the Schematic window, choose File > New Design to create a design named Example .

Opening the Passive Circuit DesignGuide

The Passive Circuit DesignGuide is accessed from the DesignGuide menu in the Schematic window.
To open the Passive Circuit DesignGuide:

1. In the Schematic window, choose DesignGuide > Passive Circuit > Microstrip Control Window . The Control window opens.

Using the Control Window

All Utility features are available from the Control window. The Control window houses menus, a toolbar, and SmartComponent manipulation controls. The menus and toolbar buttons perform the basic functions of design, delete, and display the SmartComponent palette. Full features are available from each of the tab pages on the window. The window can be placed anywhere on the screen. Explore each tab page by clicking on the tab at the top of each page. Explore the window menus as well to familiarize yourself with the basic Utility capabilities.

The pull down lists at the top of the control window are designed to help you navigate multiple schematic windows and SmartComponents. You can use the Current Schematic drop-down list box to select any of the currently opened schematic windows. This field is updated any time the Passive Circuit Control Window is selected from the Tools menu. From the SmartComponent drop-down list box, you can select any of the SmartComponents on the currently selected schematic window.

To close the Control window:

• Select File > Exit DesignGuide from the Control window menubar. (You can also close the window by clicking the x at the top of the window.)

Continue the step-by-step example by Designing and Analyzing a Network.

Designing and Analyzing a Network

In this step-by-step example, you design a microstrip line, and complete the design, analysis, and optimization of a branch-line coupler. A microstrip line can be designed easily given a substrate definition, its characteristic impedance, and length. Using the Utility follows a normal design flow procedure:

• Select components needed for your design from the component palettes Displaying the SmartComponent Palette and place the component in your design Placing Components in the Design.

• Provide specifications (Changing Component Parameters).

• Design and analyze the component Designing the SmartComponent and Optimizing the Branch-Line Coupler.
  

  Note Before starting this section of the step-by-step example, confirm your setup (Setting Up the Design Environment).

Displaying the SmartComponent Palette

The DesignGuide contains six SmartComponent palettes that provide quick and easy access to the SmartComponents. The six available component palettes are:

• All contains all of the SmartComponents.
• Lines contains the simple line element SmartComponents.
• RLC contains the distributed resistor, inductor, and capacitor SmartComponents.
• Couplers contains the coupler and power divider SmartComponents.
• Filters contains the distributed filter SmartComponents.
• Match contains the distributed and lumped matching SmartComponents.
  A blue accent in the upper-left corner of a palette button indicates the component is a SmartComponent.

You can display the SmartComponent palettes in one of these ways:

• By clicking Component Palette on the Control window toolbar
• By choosing View > Component Palette from the Control window menu
• By selecting the palette from the Component Palette drop-down list box in the Schematic window toolbar (directly above the palette).

Placing Components in the Design

To place a component in the design:

1. Display the Passive Circuit - Lines palette.
2. Click MSUB on the component palette to select the component.
   
3. Click within the schematic window to place the component.
   • You can change the orientation of the SmartComponent before placement by selecting from the Insert > Component > Component Orientation commands or by selecting Rotate by -90 repeatedly from the schematic toolbar.
   • The place component mode remains active until you choose End Command from the schematic toolbar.
     

     Note When a SmartComponent is placed initially, a temporary component is used to place and specify the parameters for the SmartComponent. This component does not contain a subnetwork design. After the DesignGuide has been used to design the SmartComponent, the temporary component is replaced with a permanent component. The SmartComponent is renamed to DA_ComponentName_DesignName and an autogenerated design is placed inside the SmartComponent's subnetwork design file. Subsequently, if the SmartComponent parameters are edited, the DesignGuide must be used again to update the subnetwork design file.

Changing Component Parameters

To edit the component parameters:

1. In the Schematic window, double-click the MSUB component to open the component parameter dialog.
2. Change the substrate thickness (H) to 20 mil and the dielectric constant (Er) to 5 .

   Note See Placing and Editing SmartComponents for details on changing parameters in the design window or component dialog box.

To place the SmartComponent in the design:

1. Click MLine on the component palette to select the component.
   
2. Click within the schematic window to place the component.

To edit the component parameters:

1. In the Schematic window, double-click the MLine component to open the component parameter dialog.
2. Change the center frequency (F) to 5 GHz , the characteristic impedance (Zo) to 75 Ohm , and the electrical length (Lelec) to 0.25 wavelengths .

Designing the SmartComponent

You can design and analyze the SmartComponent from the Control Window.
To start the simulation:

1. On the Design Assistant tab, select DA_MLine1 from the SmartComponent drop down.
2. Click Design to start a simulation and generate the design for the SmartComponent.

Examining the SmartComponent Design

You can look at the details of the autogenerated design inside the SmartComponent's subnetwork.
To examine the component's subnetwork:

1. Select the component DA_MLine1 .
2. Click Push Into Hierarchy on the schematic toolbar.
3. After examining the design, click Pop Out on the schematic toolbar to close the view.
   

Deleting the SmartComponent

• To delete the DA_MLine1 SmartComponent, choose Tools > Delete SmartComponent from the Control window. Do not delete the MSUB component .

  Note The Delete button on the Control window is different from the Delete button on the ADS schematic window toolbar.

Designing and Analyzing a Branch-Line Coupler

A branch-line coupler can be designed as easily as a microstrip line.
To design and analyze a branch-line coupler:

1. In the Passive Circuit - Couplers palette, select BLCplr and place the component in the Schematic window.
2. Click the BLCoupler component and change the center frequency (F) to 5 GHz .
3. Choose the BLCoupler component in the SmartComponent drop-down list box on the Control Window and then click the Design Assistant tab.
4. Click Design to generate the design for the SmartComponent.
5. Click the Simulation Assistant tab on the Control Window and enter 1 GHz start frequency, 10 GHz stop, 20 MHz step (accept default display specifications).
6. Click Simulate to analyze the SmartComponent. The analysis results are shown here.
   
7. Close the Display window by choosing File > Close Window from the menu.

Optimizing the Branch-Line Coupler

The branch-line coupler as designed in the preceding section has a center frequency of 5.5 GHz, which is different from the desired 5 GHz. The difference is due to limitations of the synthesis method used to generate the design. However, the Optimization Assistant can be used to optimize the design so that the center frequency is as specified.

To optimize the design:

1. Click the Optimization Assistant tab on the Control Window and click Optimize to optimize the SmartComponent.
2. Click the Simulation Assistant tab on the Control Window.
3. Deselect the Automatically display results check box.
4. Click Simulate to re-analyze the branch-line coupler.

Displaying Branch-Line Coupler Analysis Results

If a SmartComponent has been analyzed with the Simulation Assistant, the analysis results can be displayed using the Display Assistant. The results from the branch-line coupler designed and analyzed above can be displayed quickly by following these simple steps.

To display results:

1. Click the Display Assistant tab on the Control Window and click the Display button to display the existing simulation results.
   
2. Choose File > Close Window from the menu to close the Display window.
   This completes the step-by-step example.