getting started with ads

7/30/2019 Getting Started With ADS

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ADS Startup Tutorial v2 Page 1 of 17

South Dakota School of Mines & Technology 2/4/04

GETTING STARTED WITH ADS

Advanced Design System (ADS) from Agilent Technologies is an extremely powerful designtool for many aspects of electrical and computer engineering including Microwave, RF and

digital systems engineering. It also contains a complete simulation package for electrical

circuits including DC, steady-state (AC), and transient (time-varying) analysis. Morepowerful than PSPICE, ADS can analyze extremely complicated circuits seen in EE 322

Electronics IIand EE 481Microwave Engineering. ADS can also display DC values directlyon the schematic just like PSPICE.

A quick tutorial containing a DC analysis/simulation and a Transient analysis/simulation ispresented in this manual. For a more complete description, please visit the ADS help files at

C:\ads2003a\doc\manuals.htm or http://eesof.viewmark.com/docs/.

1. Beginning a Project

Figure 1 below shows the first screen you will see when you run ADS. You need to start a

New Project before you do anything else. ClickFile New Project and enter the name of the

folder where you would like your project stored. ClickOK and you will be presented with

the Schematic Layout Interface shown in Fig. 2.

Figure 1: ADS Startup Screen

2. Placing Parts

Begin by laying out your circuit. The interface here is very similar to SPICE. You can eitherplace generic parts (resistors, capacitors, inductors, etc.) or choose a specific component part

number (2N2222A transistor, 1N4148 diode, etc.).


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To insert a generic component into the schematic, locate the drop-down menu in the upper

left-hand corner of the screen. From this menu, select a Category (Lumped, Sources,

Simulation). All components (i.e. parts) available in this category will appear on the left-hand panel (Fig. 2). Resistors, Capacitors, and Inductors can be found under the Lumped

Components Category. When you are done placing a certain component, hit the Esc key. To

rotate a component, first select it with the mouse, and then press Ctrl + R.

To select a specific part, clickInsert Component Component Library. , which will

bring up the screen found in Fig. 3.

Figure 2: Placing Components in the Schematic Layout Interface

To place this specific component, select the library in the left hand pane and the component in

the right hand pane, or clickTools Find and type the component number. Next, clickEdit

Copy Library/Component. Once you close the window, the component will be availablefor use.

Categories

Components

Ground

Symbol

Wire Symbol


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Figure 3: Using the Component Library

When placing sources, use the Source Category that corresponds to the type of analysis youare interested in. For example, for transient analysis use a time domain source.

The symbol for ground can be found at the top of the ADS window in the lower toolbar, justto the right of the drop-down component lists. Wires are drawn by clicking Insert Wireor

by clicking the Wire symbol (Fig. 3) in the lower toolbar.

Now you are ready to specify your component parameters. ADS defaults to listing their

parameters right on the schematic, so they can be changed there or you can double click onthe part and change them as you would in SPICE.

Two examples of circuit simulation and analysis are shown below. The first circuit

demonstration is a simple DC voltage divider (Fig. 4). The later demonstration is a transient

analysis of a common-emitter amplifier (Fig. 11).

Wire Symbol


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Figure 4: Voltage Divider Circuit

3. DC Analysis/Simulation

Setup

Figure 4 shows the proper layout of the circuit we will be simulating. Construct the circuit in

ADS if you wish to follow along.

Before you can simulate your circuit, you will need to add a Simulation Component to your

design as shown in Fig. 5. This is one of the biggest differences from other simulation

packages such as PSPICE.

ClickSimulation DC in the drop-down category box and add the DC component.


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Figure 5: Adding Simulation Components

If you wish to view the DC values directly on the schematic, skip the next step and go directly

to the subsection titled Simulation.

The last step required before simulating is to label any nodes or wires so you can view the dc

voltage values at these locations after simulations. To label the nodes or wires, click the red

Name button located in the lower toolbar next to the wire symbol. This will bring up thewindow shown in Fig. 6. You can type in the name you want (Output, Input, Vo, etc.) and

then click the wire or the node of interest. When you are finished naming the nodes, press the

Esc key.

Figure 6: Naming Nodes

Simulation

Component

Simulation

Category

Name Button

Simulate Button


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SimulationNow you are ready to simulate. To begin a simulation, press the Simulate button next to the

red Name button, or clickSimulate Simulate in the menu.

Once the numerical computations are completed, the screen shown in Fig. 7 will appear.

Figure 7: Simulation Output Screen

If you wish to create a table please continue, otherwise skip to the subsection titled Displaying

DC Values on Schematic.

To create a plot, click the button in the left-hand pane corresponding to the type of plot youwould like (in this case the fifth type of plot, which is a table).

Plot Type


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Figure 8: Plot Properties

The properties window shown in Fig. 8 will appear (to bring the properties window up again,just double click on the plot). The first tab (Plot Type) lets you select the type of plot and

which variables you would like to plot. The nodes and wires you labeled in the circuit should

be shown in the list. To plot the voltages at the labeled points, just select them in the left-hand list and click>>Add>> to transfer them over to the right-hand list.

You may enter more complicated expressions for the traces (e.g., one quantity divided by

another) by clicking the Advanced button and editing the trace expression (an example of

this is shown later in Fig. 22). Insert mathematical operators (/, *, +, _, etc.) as you normallywould.

When you have selected your traces, clickOK and the list shown in Fig. 9 will appear.


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Figure 9: Initial Plot

The list shown in Fig. 9 gives the DC values of the current and voltage calculated from the

simple DC circuit we have constructed. Any number of values can be displayed in this list.

Displaying DC Values Directly on the Schematic

To display DC values directly on the schematic (Fig. 10), select Simulate Annotate DC

Solution from the drop-down menu after the simulation is complete. Voltages are displayed

next to their corresponding nodes while currents are displayed near the tick marks on the

components. ADS always assumes that the current is directed into the element at the node

designated by the tick mark. If you suspect your current is negative of what it should be,rotate the component 180 degrees (Ctrl + R) so the tick mark is on the positive side of the

element.

Occasionally, the reported current and voltage values may appear on top of each other. If this

occurs, try moving the wire and then selecting Simulate Clear DC Annotation to removethe values and selecting Simulate Annotate DC Solution to display the values once again.


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Figure 10: Displaying DC Values directly on Schematic

The following section describes how to work with Transient Analysis/Simulation. The

same basic steps should be taken to set up your schematic. Transient Analysis incorporates

added features (compared to DC Analysis) and allows you to use some of the more advancedcapabilities of ADS.

Tick Mark on component

DC Values


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Figure 11: Completed Schematic

3. Transient Analysis/Simulation

Figure 11 shows the proper layout of the circuit we will be analyzing. Before you can

simulate your circuit, you will need to add a Simulation Component to your design.

ClickSimulation Transient in the drop-down category box and add the Trans component

as shown in Fig. 12.

Figure 12: Adding Simulation Components

Simulation Category

Simulation

Component


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As with the components, you can change the simulation settings right on the schematic or by

double clicking on the Simulation Component, which will bring up the window shown below

in Fig. 13.

Figure 13: Setting up Simulation Components

Set appropriate start and stop times as well as a step size. Make sure your step size is small

enough to give adequate points for a smooth graph.

The last step required before simulating is to label any nodes or wires of interest so that youcan graph these voltages later. To label the nodes or wires, click the red Name button locatedin the lower toolbar next to the wire symbol. This will bring up the window shown in Fig. 14.

You can type in the name you want (Output, Input, Vo, etc.) and then click on the wire or the

node of interest. When you are finished naming the nodes, press the Esc key.


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Figure 14: Naming Nodes

Now you are ready to simulate. To begin a simulation, press the Simulate button next to the

red Name button, or clickSimulate Simulate in the menu.

Once the numerical computations have completed, the screen shown in Fig. 15 will appear.

Figure 15: Simulation Output Screen

Rectangular Plot

Name

Simulate


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To create a plot, either click the button in the left hand pane corresponding to the type of plot

you would like (the top one is Rectangular, the third is Smith Chart, etc.) or click Insert Plot.

The properties window shown in Fig. 16 will appear. To bring up the properties window

again, just double click on the plot. The first tab (Plot Type) lets you select the type of plotand the variables you would like to plot. The nodes and wires you labeled in the circuit

should be shown in the list. To plot voltages at the labeled points, just select them in the left-

hand list and click>>Add>> to transfer them over to the right-hand list.

Figure 16: Plot Properties

You may enter more complicated expressions for the traces (e.g., one quantity divided by

another) by clicking the Advanced button and editing the trace expression (an example ofthis is shown later in Fig. 22). Insert mathematical operators (/,*,+,_,etc.) as you normally

would.

When you have finished selecting your traces, clickOK and the plot shown in Fig. 17 will

appear.

Note: If your plot looks more jagged or otherwise differently than you expected, you may want

to try reducing your time step size on the simulation component and re-simulating.


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Figure 17: Initial Plot

If you wish to make adjustments to the graph, you can do so by double clicking on the graph

to bring up the properties window and selecting the second tab (Properties). Here, among

other tasks, you can title and label the graph. The Properties Tab can be seen below in Fig.18.

Figure 18: Properties Tab


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You can also adjust the axis scale. To do so, click on the axis you would like to change in the

left hand pane. Unclick theAuto Scale check box and put in the new axis limits. When you

are done making changes, clickOK and the graph will be updated to reflect the new limits.

Once your plot is constructed, you can measure specific values anywhere on the plot using

markers. To add a marker, clickMarker Newand then click the trace you would like

to place the marker on. Your window should now look similar to Fig. 19. You can then dragthe marker, or use the arrow keys, to move the marker to the location on the plot where you

wish to measure a specific value.

Figure 19: Using Markers

5. Frequency Domain Simulation and Impedance Calculations

In order to simulate a circuit in the frequency domain, you must select the correct simulationcomponent.

ClickSimulation AC in the drop down category box and add the AC component as shown

in Fig. 20.

Then simulate as you normally would.


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Simulation Category

Figure 20: AC Simulation Component

To compute impedance, the I_Probe component (Fig. 21) must be added.

ClickProbe Components in the drop down category box and add the I_Probe component.

You will also need to label the wire.

I_Probe Category

Figure 21: Impedance Component

Create a Rectangular Plot. ClickAdvanced and enter your expression for impedance (V/I)(Fig. 22).


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Type Expression

Advanced

Figure 22: Simulation Expression

After the expression has been entered, add a new marker as shown in Fig. 19. Place the

marker on the trace at the frequency that you wish to find the impedance of your circuit.

Right-click on the marker box and choose Item Options. Finally, change the complex formatafter clicking the tab Readout to real and imaginary as shown in Fig. 23.

Right Click-Item Options Real and Imaginary

Figure 23: Plot of Impedance

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