GETTING STARTED WITH ADS

Transcription

1 ADS Startup Tutorial v2 Page 1 of 17 GETTING STARTED WITH ADS Advanced Design System (ADS) from Agilent Technologies is an extremely powerful design tool 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. More powerful than PSPICE, ADS can analyze extremely complicated circuits seen in EE 322 Electronics II and EE 481 Microwave Engineering. ADS can also display DC values directly on the schematic just like PSPICE. A quick tutorial containing a DC analysis/simulation and a Transient analysis/simulation is presented in this manual. For a more complete description, please visit the ADS help files at C:\ads2003a\doc\manuals.htm or 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. Click File New Project and enter the name of the folder where you would like your project stored. Click OK and you will be presented with the Schematic Layout Interface shown in Fig Placing Parts Figure 1: ADS Startup Screen Begin by laying out your circuit. The interface here is very similar to SPICE. You can either place generic parts (resistors, capacitors, inductors, etc.) or choose a specific component part number (2N2222A transistor, 1N4148 diode, etc.).

2 ADS Startup Tutorial v2 Page 2 of 17 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 lefthand 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, click Insert Component Component Library., which will bring up the screen found in Fig. 3. Wire Symbol Categories Ground Symbol Components 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 click Tools Find and type the component number. Next, click Edit Copy Library/Component. Once you close the window, the component will be available for use.

3 ADS Startup Tutorial v2 Page 3 of 17 Wire Symbol Figure 3: Using the Component Library When placing sources, use the Source Category that corresponds to the type of analysis you are 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, just to the right of the drop-down component lists. Wires are drawn by clicking Insert Wire or 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 on the 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).

4 ADS Startup Tutorial v2 Page 4 of DC Analysis/Simulation Figure 4: Voltage Divider Circuit 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. Click Simulation DC in the drop-down category box and add the DC component.

5 ADS Startup Tutorial v2 Page 5 of 17 Simulation Category Simulation Component 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 the window 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. Simulate Button Name Button Figure 6: Naming Nodes

6 ADS Startup Tutorial v2 Page 6 of 17 Simulation Now you are ready to simulate. To begin a simulation, press the Simulate button next to the red Name button, or click Simulate Simulate in the menu. Once the numerical computations are completed, the screen shown in Fig. 7 will appear. Plot Type 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 you would like (in this case the fifth type of plot, which is a table).

7 ADS Startup Tutorial v2 Page 7 of 17 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 lefthand 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 normally would. When you have selected your traces, click OK and the list shown in Fig. 9 will appear.

8 ADS Startup Tutorial v2 Page 8 of 17 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 remove the values and selecting Simulate Annotate DC Solution to display the values once again.

9 ADS Startup Tutorial v2 Page 9 of 17 Tick Mark on component DC Values 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 advanced capabilities of ADS.

10 ADS Startup Tutorial v2 Page 10 of Transient Analysis/Simulation Figure 11: Completed Schematic 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. Click Simulation Transient in the drop-down category box and add the Trans component as shown in Fig. 12. Simulation Category Simulation Component Figure 12: Adding Simulation Components

11 ADS Startup Tutorial v2 Page 11 of 17 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 you can graph these voltages later. 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 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.

12 ADS Startup Tutorial v2 Page 12 of 17 Simulate Name 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 click Simulate Simulate in the menu. Once the numerical computations have completed, the screen shown in Fig. 15 will appear. Rectangular Plot Figure 15: Simulation Output Screen

13 ADS Startup Tutorial v2 Page 13 of 17 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 plot and 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 lefthand 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 of this is shown later in Fig. 22). Insert mathematical operators (/,*,+,_,etc.) as you normally would. When you have finished selecting your traces, click OK 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.

14 ADS Startup Tutorial v2 Page 14 of 17 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

15 ADS Startup Tutorial v2 Page 15 of 17 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 the Auto Scale check box and put in the new axis limits. When you are done making changes, click OK 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, click Marker New and then click the trace you would like to place the marker on. Your window should now look similar to Fig. 19. You can then drag the 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 simulation component. Click Simulation AC in the drop down category box and add the AC component as shown in Fig. 20. Then simulate as you normally would.

16 ADS Startup Tutorial v2 Page 16 of 17 Simulation Category Figure 20: AC Simulation Component To compute impedance, the I_Probe component (Fig. 21) must be added. Click Probe 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. Click Advanced and enter your expression for impedance (V/I) (Fig. 22).

17 ADS Startup Tutorial v2 Page 17 of 17 Advanced Type Expression 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 format after 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