Download EECS 420 – Electromagnetics II Lab

EECS 420 – Electromagnetics II Lab
Lab 3b – Time Domain Reflectometry using ADS
Part 1: Introduction to ADS
The installed version of Advanced Design System (ADS) runs on Windows only and is
installed on the Windows boxes located in Commons as well as on the Dunwoodie
Laboratory.
Create a directory named ADS in your account (H: Drive)
Open ADS by running the following menu command: Start->Programs->Advanced
Design System 2003C->Advanced Design System (this runs the following
command: C:\ADS2003C\bin\ads.exe). The main ADS window is shown in Figure 1
below.
1.
2. Figure 1: Main ADS Window
The “startup directory” is c:\users\default\. Create a new project by choosing File->New
Project. Either type in the path yourself as shown below or use the browse feature to
find the ADS directory you created on your user account. Name the new project
“design1” as shown in Figure 2 below. Click “OK” when you are done.
3.
4. Figure 2: New project dialogue box
When you create a new project, the schematic window will automatically open. Close all
secondary windows by choosing File->Close All. When a new project is created, a
directory named “design1_prj” is created with several configuration files and subdirectories. In general, you should modify files within this directory through ADS
only. These directories should be showing in your display as shown in Figure 3
below. Browse through the subdirectories and turn on/off the View->Show All Files
preference. Your schematics will be stored in the networks subdirectory.
5.
6. Figure 3: Main ADS window with design1_prj opened
To create a new design/schematic within your project, press File->New Design. Name
your new design DC_Simulation as shown in Figure 4 below. Make sure all of the
other settings are the same as those in the figure. Schematics show the electrical
connections, but they don’t show the physical dimensions. Layouts show the physical
and electrical connections. When you actually fabricate your design, you must create
a layout from your schematic. Click “OK” when you are done.
7.
8. Figure 4: New design dialogue box
When you click “OK”, the schematic window in Figure 5 below should open. Note the
title bar that tells us that we are editing a schematic called “DC_Simulation”. You
can save the schematic by pressing Ctrl-S or File->Save Design. The box circled in
red (broken line) allows us to choose appropriate component tool bar (library).
Currently the “Lumped Components” library is selected and you should see a vertical
toolbar with various lumped components to choose from. Place a resistor on your
schematic by clicking on the resistor icon (w/o a box around it). When you move the
cursor over the drawing part of the schematic window, the ghost of the resistor will be
shown. Place the part on your schematic with a left mouse click. Note that you are in
“place component” mode and you can place as many resistors as you need. Right
now, just place two resistors. Get out of “place component” mode by pressing the
“Esc” key or by right clicking the mouse and choosing End Command.
9.
10. Figure 5: Schematic window with the “DC_Simulation” schematic opened
Note that if you know the part name (R for resistor), you can type it in directly in the
dialogue box circled in blue (solid line). Place the following components for your
simulation:
Syntax of the following list is “Library: Part Type (part name)”
a. Need two “Lumped-Components: Resistor (R)” – should have already placed
these in the previous step.
b. Need one “Sources-Freq Domain: DC voltage source (V_DC)”
c. To place a ground, click on this icon:
Figure 6 below shows the completed circuit.
11.
12. Figure 6: Completed circuit for DC simulation
Once the components are placed, arrange the components as shown in figure 6 and
then connect the components with wires as shown by pressing Ctrl-W or Insert>Wire. Note that each resistor that you place shows its part name (R), instance name
(R1 or R2), and its nominal value (50 Ohm). Similarly, the DC voltage source shows
its part name (V_DC), instance name (SRC1), and its nominal value (1.0 V).
Save your design by pressing Ctrl-S or File->Save Design.
Now that we have created the circuit, we are ready to simulate. For this circuit we will be
doing a DC simulation. Choose the “Simulation-DC” library. Place a DC simulation
controller on your schematic by clicking on this icon
and
then clicking in
your schematic window. When we run the simulate command, all the simulation
controllers will run.
simulation.
In this case we only have one simulation controller: DC
Before we simulate, run simulation setup by choosing Simulate-
>Simulation Setup. The dialogue box in Figure 7 below should appear. Set the
settings as shown. Make sure the “Open Data Display when simulation completes”
checkbox is disabled. We will be displaying our DC simulation results directly on the
schematic rather than in a separate “Data Display” window. Press the “Apply” button
to save the settings and then the “Cancel” button to close the dialogue box.
13.
14. Figure 7: Simulation setup
Run the simulation by pressing F7 or choosing Simulate->Simulate. A simulation
window should pop up and the following information should appear in the text box
along with some other messages:
----------------------------------------------------------Simulation finished: dataset `DC_Simulation' written in:
`H:\class\420\ADS\design1_prj\data'.
----------------------------------------------------------Resource usage:
Total stopwatch time: 1.07 seconds.
If an error occurs, double-check your schematic and each of the steps above.
Print the DC simulation results on the schematic by choosing Simulate->Annotate DC
Solution. Your schematic should look like Figure 8 below.
15.
16. Figure 8: DC simulation results
Edit the component parameters for R1 (your R1 resistor may be named differently than
the one in Figure 8, therefore, to clarify, the R1 resistor is the resistor directly
following the positive terminal of the DC voltage supply). You can do this in four
different ways:
a. Double click on the R1 resistor.
b. Right click on the R1 resistor and choose “Edit Component Parameters”
c. Select the R1 resistor and choose Edit->Component->Edit Component
Parameters.
d. Left clicking on the component parameters on the display and changing them
directly.
The first three methods will open the parameter as shown in Figure 9. Change the
instance name to R_Generator.
17.
18. Figure 9: Component parameter box for R1
Change the instance name of the other resistor to R_Load and the nominal value to
R  2 kOhm :
19.
20. Figure 10: Component parameters for R2
Simulate the design (press F7) and place the DC results on the schematic window (choose
Simulate->Annotate DC Solution).
Delete the load by selecting it and pressing “Delete”.
Choose the “Lumped-
Components” library and put a capacitor (part name = C) where the load was.
Simulate the circuit and observe the current through and voltage across the
capacitor. Repeat this for an inductor (part name = L) as well. Note: To rotate a
part ninety degrees select the part and press Ctrl-R.
YOU DON’T HAVE TO INCLUDE UP TO THIS POINT IN YOUR REPORT.
Part 2: Time Domain Reflectometry
1. If you have closed ADS, re-open ADS by running the following menu command:
Start->Programs->Advanced Design System 2003C->Advanced Design System.
Then open your project by clicking on
.
Close all windows by choosing File->Close All. Then open a new design by choosing
File->New Design. Set the settings as you did in part 1, only name the design
TDR_Simulation. Choose “OK” when you are done.
Figure 111: New design for TDR Simulation
Add the following components to your design as shown in Figure 112 below. Set the
components parameters as shown in figure 12.
a. “Lumped-Components: Capacitor (C)” (rotate component with Ctrl-r)
b. “Lumped-Components: Resistor (R)”
c. “Source-Time Domain: Voltage Step (VtStep)”
d. “TLines-Ideal: Ideal Transmission Line (TLIN)”
e. “Simulation-Transient: Transient simulation controller (Tran)”
f. Ground from tool bar.
This setup is similar to what we did in Lab 3a. The voltage source is a unit step
function which turns on at time = 0 [ns] and rises to 1 [V] instantly. This voltage
propagates down the transmission line TLIN, but is split in half because of the
voltage division that occurs between generator resistance RG and the characteristic
impedance Z of the transmission line. The initial voltage wave is shorted through the
capacitor and so the reflected wave completely cancels the forward wave. Then as
the capacitor becomes an open circuit the reflected wave transitions from -0.5 [V] to
0.5 [V]. We will look at the voltages at the output of the generator and across the
load. Label these nodes as shown in the figure 12. To label a node, click on
.
This opens the dialogue box shown in Figure 113 below. Type in the label VG and
click on the wire between R1 and TL1. Type in the label VC and click on the wire
between TL1 and C1. To remove a node label, you can erase the node name in the
dialogue box and then click on the wire or select the wire and choose Edit>Wire/Pin Label->Remove Wire/Pin Label.
Figure 112: TDR simulation
Figure 113:Adding node names
Setup your simulation by choosing Simulate->Setup Simulation. Set the settings as
shown in Figure 114 below. Click on “Apply” to save the settings and then “Cancel”
to close the dialogue box.
Figure 114: Simulation setup for TDR simulation
Now simulate your design by typing F7 or choosing Simulate->Simulate. Wait until the
data display window opens as shown in Figure 115 below. The data that is generated
from a simulation set is called a data set. The viewer that we use for a dataset is
called the data display. We can control where the data is stored and we can control
which data display is connected to the schematic. Both the data set and the data
display can be saved in separate files. In the data display window, the data display
name shows up in the title bar.
Figure 115: Data display window for TDR simulation
Add a rectangular plot by clicking on
. Place the rectangular plot on your data
display as you would a component. When you do this, a plot traces and attributes
window will open. Select VC and click on “>>Add>>”. Then select VG and click on
“>>Add>>”. We have added two traces: VC versus time and VG versus time. When
a transient simulation is done, the assumed x-axis is time. If we want to explicitly set
the x and y axes we would choose “>>Add Vs…>>”. Your plot attributes window
should look like Figure 116 below. Click “OK”.
Figure 116: Plots traces and attributes window
You should see the graph in figure 17 if your schematic and simulation are setup
correctly. If it doesn’t, double check that each of the steps above.
Figure 117: Transient voltages plot
Repeat this simulation for the two series and the two parallel loads from Lab 3a. Use
the same component values as in Lab 3a. Copy the figures for these four loads and
include them in your report. Give a brief (no equations) description of why the
graphs look the way they do – focus on initial and steady states and remember that
the voltages displayed in figure 17 are total voltages, not just reflected voltages.