Radio Frequency Design Project 3: Agilent ADS and Cadence 6 Software Tutorials, continued

Radio Frequency Design Project 3

Agilent ADS and Cadence 6 Software Tutorials, continued

Overview

Remain in same project groups for the semester.

The objective of this project is to work with s-parameters

NOTE: Use the Project Report Template and keep answers to questions on consecutive sheets of paper with all plots at the end.

IN NO CASE may code or files be exchanged between students, and each student must answer the questions themselves and do their own plots, NO COPYING of any sort! Nevertheless, students are encouraged to collaborate in the lab session.

Only turn in requested plots ( Pxx ) and requested answers to questions ( Qxx ).

Part 1

In this part, the behavior of a transmission line with mismatch on one end is investigated.
Power conservation and issues of "where the power goes" are explored.

Download the following zip-file (you may need to hold down the shift key while you click on the link):
RFcourse2012_proj3_wrk.zip

Move the zip-file into the apps/ads directory, and unzip it

You should find a new directory RFcourse2012_proj3_wrk created in apps/ads

Run ADS

Go down through the directory tree to RFcourse2012_proj3_wrk and double-click it to open the workspace

Then in the workspace, double-click the p3res1 schematic, and the following schematic should appear.

Save a snapshot of the schematic and paste it into your report. ( P1 )

Make sure that your plots, component values, legends, axes, and fonts are legible in your report!

Double-click the "gear" icon (shown below) in the upper right of the window to simulate.

Click the "rectangular plot" icon in the pop-up data plotting tool.

Drop the plotting box in the visible area, and in the pop-up window select data to plot as follows:

Select DataSet -> S(1,1) -> Add -> dB
Select DataSet -> S(2,1) -> Add -> dB
Select DataSet -> S(2,2) -> Add -> dB

Select the plot options as shown below to plot S11, S22, and S21 from -15 to 0 dB in 1 dB steps. (the picture below may show -20 to zero)

Double-click each y-axis label to set the trace options for 2.5 point thick dot, short-dash, and solid traces as shown below. You must do this so that the plots can be read when printed in grayscale on a printer.

Save a snapshot of the s-parameters plot and paste it into your report. You should have a "flat-line" plot of S11, S22, and S21. ( P2 )

Make sure that your plots, legends, axes, and fonts are legible in your report!

Does the Term 1 device act as a 50 ohm source/load for port 1? yes/no ( Q1 )

What is the impedance looking to the right from Term1 (i.e., what is the impedance of R2 in series with R1 in parallel with Term2, as illustrated below)? ( Q2 )

What is the impedance looking to the left from Term2 (i.e., what is the impedance of R1 in parallel with R2 in series with Term1, as illustrated below)? ( Q3 )

Note: the S-parameters are plotted only from the perspective of the TERM devices, so the power transmitted to the right TERM device is only the power delivered to the TERM resistor. (It doesnt "know" anything about what is going on with the other resistor.)

Draw a schematic on a sheet of paper with a 50 ohm 2 volt rms source (2Vrms open circuit) in series with a 60 ohm resistor in series with a load comprised of two 50 ohm resistors in parallel (just as in the circuit p3res1). Questions Q4 - Q7 relate to hand calculations using this hand-drawn schematic.

What is the voltage across the two 50 ohm resistors (R1 and Term2) that are in parallel? ( Q4 )

What is the power in mW (milliwatt) delivered to one of the two parallel resistors.? ( Q5 )

What is the maximum power in mW available available from the source (i.e., draw a new schematic with a single 50 ohm load)? ( Q6 )

How many dB down is the power in Q5 relative to Q6? (10 log10( Q5/Q6 ) ) ( Q7 )

Is your answer to Q7 the same as S21 in plot P1? yes/no ( Q8 )
... i.e., there should be somewhere/something in the experiment that reflects this correspondence?

For Q9 - Q13, assume that the maximum available power from the source is 1 watt:
(The answers to the questions below should agree with the foregoing calculations in Q4-Q8 AND with plot P2 for the above ADS schematic at low frequency, otherwise you have an error somewhere. The answers should scale in proportion to the power sources.) )

What is power in mW delivered to the right-hand TERM2 in the above ADS schematic? (This would correspond to the power delivered to one of the two 50 ohm load resistors in parallel in your hand-drawn schematic.) ( Q9 )

What is the power in mW delivered to the 50 ohm resistor R1 (not TERM2) in the above ADS schematic? (This would correspond to the power delivered to the second one of the two 50 ohm loads in parallel in your hand-drawn schematic.) ( Q10 )

What is the power in mW reflected back to the left TERM1 in the above ADS schematic? (The left hand term would correspond to the 50 ohm internal resistance of the TERM1 source in your hand-drawn schematic.) ( Q11 )

What is the power in mW delivered to the 60 ohm resistor R2 in the above ADS schematic? ( Q12 )

What is total power in mW delivered from the 1 watt source? (The total power delivered to R1, R2, and TERM2 in your hand-drawn schematic.) ( Q13 )

Does the sum of the power delivered to R1, R2, and TERM2 (not TERM1) plus the reflected power equal the maximum available power of 1 Watt? yes/no ( Q14 )

What is the total resistance to ground seen by the Term 1 source (excluding the internal resistance of Term 1), as illustrated below? ( Q15 )

What is the reflection coefficient (gamma) seen by the source (Term 1)? ( Q16 )

What is the VSWR seen by the source (Term 1)? ( Q17 )

What is the total resistance to ground seen by the load (excluding the internal resistance of Term 2)? ( Q18 )

What is the reflection coefficient gamma seen by the load (Term 2)? ( Q19 )

What is the VSWR seen by the load (Term 2)? ( Q20 )

Part 2

In this part, the behavior of a transmission line with mismatch on one end is investigated.
Power conservation and issues of "where the power goes" are explored.

Go down through the directory tree and open the schematic for p2txline1, and double-click the p2txline1 schematic and the following schematic should appear.

Save a snapshot of the schematic and paste it into your report. ( P3 )

Double-click the "gear" icon (shown below) in the upper right of the window to simulate.

Click the "rectangular plot" icon in the pop-up data plotting tool.

Drop the plotting box in the visible area, and in the pop-up window:

Select DataSet -> S(1,1) -> Add -> dB
Select DataSet -> S(2,1) -> Add -> dB

Select the plot options as shown below to plot S11 and S21 from -10 to 0 dB in 1 dB steps. (the picture below may show -20 to zero)

Save a snapshot of the s-parameters plot and paste it into your report. You should have a "flat-line" plot of both S11 and S21. ( P4 )

What is the line impedance? (from formula or linecalc). Hint: check the MSUB item on the schematic for substrate thickness and dielectric constant
( Q21 )

What is the total impedance to the left of the line (i.e., what is the total source impedance seen to the left of the line, the impedance of TERM1 )? ( Q22 )

What is the total impedance to the right of the line (i.e., what is the total load impedance seen to the right of the line, as illustrated below)? ( Q23 )

And so ... you should conclude a mismatch with reflections.

Note that the S-parameters are plotted only from the perspective of the TERM devices, so the power transmitted to the right TERM device is only the power delivered to the TERM resistor. (It doesnt "know" anything about what is going on with the other resistor.)

Draw a schematic on a sheet of paper with a 50 ohm 2 volt rms source (2Vrms open circuit) and a load comprised of two 50 ohm resistors in parallel. At extremely low frequencies, this is a good model of the circuit since the transmission line is electrically short at dc (i.e., much less than a quarter wave). Questions Q24 - Q27 relate to hand calculations using this hand-drawn schematic.

What is the rms voltage across the two 50 ohm resistors that are in parallel? ( Q24 )

What is the power in mW delivered to one of the two parallel resistors.? ( Q25 )

What is the maximum power in mW available available from the source (i.e., replace the two 50 ohm resistors with a single 50 ohm load)? ( Q26 )

How many dB down is the power in Q5 relative to Q6? (10 log10( Q5/Q6 ) ) ( Q27 )

How does your answer to Q7 relate to the plot P4? ( Q28 )
... i.e., is there somewhere/something in the plot that reflects this?

For Q29- Q33, assume that the maximum available power from the source is 1 watt:
(The answers to the questions below should agree with the foregoing calculations in Q4-Q8 AND with plot P1 for the above ADS schematic at low frequency, otherwise you have an error somewhere. The answers should scale in proportion to the power sources.) )

What is power in mW delivered to the right-hand TERM in the above ADS schematic? (This would correspond to the power delivered to one of the two 50 ohm load resistors in parallel in your hand-drawn schematic.) ( Q29 )

What is the power in mW delivered to the 50 ohm resistor (not TERM) in the above ADS schematic? (This would correspond to the power delivered to the second one of the two 50 ohm loads in parallel in your hand-drawn schematic.) ( Q30 )

What is the power in mW reflected back to the left TERM in the above ADS schematic? (The left hand term would correspond to the 50 ohm internal resistance of the source in your hand-drawn schematic.) ( Q31 )

What is power delivered from the 1 watt source? (The total power delivered to both load resistors in your hand-drawn schematic.) ( Q32 )

Does the sum of the power delivered to the 50 ohm resistor (not the TERMS) in the above ADS schematic plus the power delivered to right-hand TERM plus the reflected power equal the maximum available power? ( Q33 )

Click the "Smith plot" icon in the data plotting window, shown below.

Drop the plotting box in the visible area, and in the pop-up window:

Select DataSet -> S(1,1) -> Add
(only plot S11 on the Smith chart)

Click on the plot options, click Coordinate->both, select Grid, and select admittance line type as long dash, and pick a green color. Click OK and the Smith Chart should appear. To figure out which end of the curve is at what frequency, Select Marker->New from the Dataplot menu bar and click on one end of the plotted curve. Then Edit->Undo to delete the marker. (see below for an example of how the Smith chart should look ... depending on the shade of green you choose)

Change the stop frequency of the simulation to 25 MHz, re-simulate the circuit, and Print the Smith chart plot and turn it in. Note: You should have almost a "circle"for the plotted data. ( P5 )

Part 3

In this part, simulations are performed on a simple 2-resistor voltage divider circuit using Cadence software.

From a Linux terminal, Cadence6/Virtuoso should be available in the menu (Mosaic->Engineering->Electrical->Cdence->Cadence6)

From a PC terminal, you must first open a remote Linux session, (Start->AllPrograms->Mosaic->LinuxConnect->ToAnyServer), then proceed as for a Linux terminal

Create a new library "rfProj3" using MenuBar::File::New::Library from the Library Manager menu bar, and use the input parameters as shown below to create a 0.5 micron design

Make sure that you attach the proper tech library (ami 0.6u c5n) as shown below

Note: sometimes the software hides the popup window behind the windows

As shown below, highlight your new library on the left pane of library manager window, and create a new cell named "resDive_cell" using the MenuBar::File::New::CellView from library manager menu bar.

This circuit will be a simple 2-resistor voltage divider

Always name your circuit cells with the suffix "_cell" to indicate they are some smaller subcircuit of a larger circuit

Make sure that the "open with" option is "Schematics XL" (red arrow below)

NOTE: a common bug in Cadence is that the "new file" popup window is hidden behind your other windows

Next, add a pair of 50 ohm resistors from our ami05_c6_customlib library to the schematic using the "create instance" toolbar button at the red arrow below

Make sure you select the ami05_c6_customlib library (blue arrow below)

Make sure you select the R50 device (green arrows below)

You can rearrange locations of things on your schematic by using the "default selection" toolbar item (red arrow below)

Add the pins pin_in, pin_out, and pin_gnd using the "create pin" toolbar buton at the red arrow below

Make sure all pins are inputOutput as shown below (green arrows)

Wire the circuit using the wiring toolbar item shown at the blue arrow below, and the final circuit should appear as follows

Check and save your schematic using the "check and save" toolbar item at the yellow arrow above.

If any errors are found, a popup should appear.

Print the schematic of your "resDiv_cell" as above and turn it in. ( P6 )

Select one of your resistors, and type "q" on your keyboard, and you should see the object properties popup as below, where you can inspect/edit properties of a device

Next, create a symbol for your circuit using MenuBar::Create::Cellview::FromCellview as illustrated below

In the popup shown below, make sure the toviewname is symbol, fromviewname is schematic, and the type is schematicSymbol

In the pop-up, set the pin locations as follows (red arrows below)

The symbol should be created as shown below (green arrow below)

Check and save the symbol (red arrow above)

Close all of your schematic and symbol windows

Ceate a new schematic, as before.

Name this schematic "resDiv_cell_sparam"

Note: always name testbenches with a prefix the same as the name of the cell being tested and with a suffix indicating the test being done

This new circuit/cell will be the testbench (containing the external test circuits) for doing s-parameter testing of the "resDiv_cell" cell. Create the new testbench using the MenuBar::File::New::CellView from library manager menu bar, as shown below.

Make sure that the "open with" option is "Schematics XL"

Next, add an instance of our new "resDiv_cell" from our rfProj3 library to the schematic by using the "create instance" toolbar button at the red arrow below

Make sure you select the rfProj3 library (blue arrow below)

Make sure you select the resDiv_cell device (green arrows below)

You should see your symbol appear in the schematic as shown above, after you click in the schematic

(Sometimes if your cell has a odd center defined, the symbol may be placed off-screen out of sight)

Next, add an instance of a ground symbol to your schematic by using the create-instance toolbar button again The ground comes from the analogLib sources/global library, as shown below

Next, add an instance of a "psin" port to your schematic using the create-instance toolbar button again.

The psin port comes from the analogLib sources/ports library, as shown below

Wire the schematic as shown above.

Check and save your schematic using the "check and save" toolbar button at the yellow arrow above.

If any errors are found, a pop-up should appear.

Save the schematic of your cell as above and turn it in. ( P7 )

Finally, create the simulation setup

Run ADE-XL from the MenuBar::Launch::ADEXL command in the schematic editor of the new testbench as shown below

Make sure to use the "create new view" option on the popup (blue arrow below)

The ADE-XL window should then appear as shown below

Click on the schematic tab (blue arrow above)

The testbed schematic should become visible as below

Then select MenuBar::ADEXL::Create::Test, as below:

The Test Edior window should appear (red arrow below), along with the testbench being chosen:

Choose the cell of your testbench (blue arrow above), as in the popup above, and click OK

The ADE-XL test editor should appear, as shown at the red arrow above, behind the popup.

Note for future reference: If we used a variable in our testbench, we would next need to run MenuBar::Variables::CopyFromCellView to load them into the window, and enter values for them in the window. We do not have to do that here, since we have no variables defined in our testbench schematic.

Click on the MenuBar::Analysis::Choose (purple arrow below)

Set up the s-parameter analysis as follows:

Click the "sp" button for s-parameter analysis (red arrow below)

Then, click the select button (blue arrow below) to enable you to select your two "psin" sources from the schematic

After selecting, you should see ports "/PORT0 /PORT1" (green arrow below).

Note for future reference: if this was a transient analysis instead of s-parameters, you would select the output ports using the MenuBar::Ouptputs::ToBePlotted::SelectOnSchematic

Note: a bit of an oddity is that when plotting s-parameers S11 is for /PORT0 and S22 is for /PORT1

Finally, set your sweep from 0.01 GHz to 0.1 GHZ (yellow arrow below)

After clicking OK, the test editor should appear as below

Note that your new "sp" analysis should now appear in the analyses pane

Return to your ADE-XL window, and in the left pane, expand the "Tests" item to verify that the "sp" s-parameter analysis is present (blue arrows below)

Then, click the green "run simulation" toolbar button (red arrow below)

If the simulation runs properly, you should see "finished" in the lower left corner area (green arrow below)

Return to the ADE-XL tab as below (blue arrow below)

Then, click the ResultsBrowser button (red arrow below) to see the plotting window for s-parameters.

The Visualization and Analysis XL tool should appear as below

Select the "dB20" processing (red arrow below)

Select the "sp-sp" data (red arrow below)

Select S11 and S21 (green arrows below)

Right click over S11 and select the "Plot Signal" option (yellow arrow below)

When the plot appears, the background will be black. Right-click to set a white background as below.

Right-click the traces to set the colors different as above, and with S11 as a solid line "thick," and S21 as a dashed line "thick."

You should see the S-parameters plotted as above.

Save the plot of your s-parameters similar to above and turn it in. ( P8 )

Hint: it is easy to check if your answers are correct by using ADS to run the same simulation.

Change the "Default" near the red arrow above to "impedance" as shown below (blue arrow below)

As before, right-click S11 (red arrow below) and choose the "new window" plot option in the popup menu

Right-click::View::FitSmith in the Smith chart plotting area to fit it as below

Save the plot of your Smith chart as above and turn it in. ( P9 )

Finally, make sure to save all of your test settings from within ADE-XL.

Use MenuBar::Session::SaveState from within TestEditor as shown below

Make sure to save the state in the CellView (red arrow below)

Note: If you closed Test Editor and the window is not open, you can reopen it by right-clicking the test item under "Tests" in "Data view" pane on the left side of the ADEXL window

Note: from within ADEXL there is a second type of saving an overall ADEXL state from the ADEXL MenuBar as MenuBar::File::SaveSetupState It does not appear that this second type of saved state saves the test setup of the test editor pane

You should be able to see your saved test state from within Library Manager as follows, with the saved test setup "spectre_state1" at the red arrow below

Save the image of your Library Manager showing your saved test setup as above and turn it in. ( P10 )

We will talk more about the Smith chart next time

In the IEEE Microwave Symposium Jul 1991 paper "Recollections on microwave theory ," N. Marcuvitz describes in 1941 at MIT how they used their hands or cheeks to determine if microwave energy was coming down a waveguide. This was before high frequency detectors were widely available. (Note that cellphones were in wide use 50 years later!) For even greater sensitivity than the cheek, what part of their face did they use to sense microwaves? ( Q34 )

In what year was the patent issued for the silicon catwhisker crystal detector device (equivalent to silicon diode) to Greenleaf Whittier Pickard (US Patent 836,531)? ( Q35 )

Report
NOTE: Use the Project Report Template and keep answers to questions on consecutive sheets of paper with all plots at the end.

Do not add extraneous pages or put explanations on separate pages unless specifically directed to do so. The instructor will not read extraneous pages!

Only turn in requested plots ( Pxx ) and requested answers to questions ( Qxx ). All plots must be labeled P1, P2, etc. and all questions must be numbered Q1, Q2, etc. YOU MUST ADD CAPTIONS AND FIGURE NUMBERS TO ALL FIGURES!!

Copyright © 2010-2012 T. Weldon
Cadence, Spectre and Virtuoso are registered trademarks of Cadence Design Systems, Inc., 2655 Seely Avenue, San Jose, CA 95134. Agilent and ADS are registered trademarks of Agilent Technologies, Inc.