## Project 2

S-parameters

### Overview

Work in assigned project groups.

The objective of this project is to simulate and measure 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.

### Part 1: Measurements

• We will measure s-parameters of a 6-foot length of 50-ohm transmission line terminated by a 25 ohm load
• The 25 ohm load will be comprised of the 50-ohms port 2 of the instrument in parallel with a 50-ohm termination through a BNC-tee connector
• Set up the S-parameter measurement as illustrated below, with a BNC tee and 50-ohm term at port 2 to create the 25 ohm load
• Have the instructor adjust the display to the following format:

Figure 001
• Check that the start/stop are 1 MHz and 50 MHz (bottom left above), and that the two Smith charts are S11 and S22 (blue arrows above)
• Adjust marker1 to 1 MHz, and adjust marker2 to where the plot crosses the Smith chart on the right (as shown in the simulation below).
• See the arrows in the previous photograph for the location of the marker controls.
• Save a cellphone picture (for this instrument a USB port is not available) of the network analyzer display as above (but with markers correctly positioned) and paste it into your report.    SEE BELOW FOR THE REPORT TEMPLATE
• What are the two un-normalized impedances (assume closest pure resistance) at the two markers, and what is the transformer ratio (ratio of the 2 resistances)?
• Compute reflection coefficient Gamma, and return loss seen from port1 at 1MHz (assume the transmission line is a wire).
• From the upper right plot of S11 in dB, what is the measured S11 in dB at 1 MHz?
• Why do you "see a circle" on the Smith chart of S11, but not on the Smith Chart of S22?

### Part 2: Simulation

• S-parameter simulations
• Download the 7zap archive as follows:
• Download the 7zap archive RFcourse2015_proj2_wrk.7zap to your  ads directory
• Use MenuBar::File::Unarchive to extract the project into your ADS directory as follows

• You should find a new directory RFcourse2015_proj2_wrk created in apps/ads
• Run ADS and open the new RFcourse2015_proj2_wrk workbook by double-clicking it
• We will be making S-parameter measurements that correspond to a situation similar to our project 2 simulation.
• Open the p2sparamLine schematic in the workbook by clicking that schematic design file.

• Run the simulation, and you should S-parameters and Smith chart somewhat different from that illustrated below:

• Right-click and select "copy cell" to make a copy of this design
• Edit the new copy so that it reflects the scenario in the lab.
• Change the transmission line to a TLIN component as shown above, but with 50 ohms impedance and with E=90 at whatever frequency in MHz best corresponds to your lab measurements, set source Term1 to 50 ohms, and load Term2 to 50 ohms, and add a 50-ohm resistor in parallel to term2 to ground.  Change the S-parameter sweep to go from 1 to 50 MHz in 1 MHz steps.  Adjust to an appropriate-length the TLIND line such that it reflects your measurements using the the approximately 6-foot long line in the lab (if you want to estimate it before going into the lab, assume a velocity of 0.7 c, and length of 6 feet).
• Save a snapshot of your new schematic and paste it into your report.
• Run the simulation, and plot the Smith chart (somewhat different from that illustrated below):
• Set two markers as above (one at 1 MHz and the other at where it crosses the axis on the right side
• What are the two un-normalized impedances  (assume closest pure resistance) at the markers, and what is the transformer ratio (ratio of the 2 impedances)?
Save your schematics and plots before exiting ADS

### Report Data

• ============================    WARNING !!    ====================================
• **** WARNING **** YOU MUST USE THE PROJECT REPORT TEMPLATE Below:
• See the Project Report Template at bottom of this page
• A well-written report/paper is EXPECTED
• STRONGLY RECOMMEND that you read IEEE authorship series: How to Write for Technical Periodicals & Conferences
• Clearly describe everything, including:
• variables in block diagrams
• variables in formulas
• units of variables kHz, pF, nH, m, s,
• all traces on plots
• all curves on plots
• all results in any tables
• Minimum required data content for your report and demos
• Required theory/formulas numbered as below:
• (1) Reflection coefficient formula at port 1 at 1 MHz for 50-ohm source, 50-ohm line, and 25 ohm load
• (2) S11 formula at 1 MHz for 50-ohm source, 50-ohm line, and 25 ohm load
• (3) Theoretical S21 at 1 MHz for 50-ohm source, 50-ohm line, and 25 ohm load. Hint: you must compute the power delivered to term2 delivered from the source.
• Required figures:
• Any illegible plots receive zero credit (must be able to read all numbers, axes, labels, curves, grids, titles, legends)
• All plots must of professional quality as in IEEE papers
1.  LEGIBLE ADS schematic of the system, with appropriate caption.
2.  LEGIBLE smith-chart plot of simulated S11
3. LEGIBLE dB plot of simulated S21 and S11 on a dB scale from 0 to -10 dB
4.  LEGIBLE cellphone picture of measured s-parameters like Figure 001 of this webpage
• Required tabular data content:
1. Table of s-parameters at 1 MHz (assume approximately dc) with 3 columns: parameter, theoretical value, simulated value
• Row 1: theoretical and simulated S11
• Row 2: theoretical and simulated S21
• Row 3: theoretical and simulated S12
• Row 4: theoretical and simulated S22
• See report template below

NOTE ReportTemplate: Use the Project Report Template

YOU MUST ADD CAPTIONS AND FIGURE NUMBERS TO ALL FIGURES!!

Copyright © 2010-2018 T. Weldon

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