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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