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Design Project #1: Matching Transformers
In this project you will design and test three matching networks:
a) A Quarter-wave transformer b) A 4-section Binomial transformer c) A 4-section Chebychev transformer
P ROJECT S COPE
In this design, we will attempt to match a real load of RL = 120 Ω to a
transmission line with a 50 Ω characteristic impedance at a frequency of
4.0 GHz.
The bandwidth of the 4-section transformers is defined by Γm = 0.2.
Assume TEM wave propagation in the transmission lines, and the
transmission line dielectric constant is ε r = 16.0.
PROJECT TASKS
1) Design each of the three matching networks, determining both the characteristic impedance and physical length (in cm) of each section.
2) Use the design equations in your notes/book to determine the expected bandwidth for each design.
3) Implement each design on ADS software. Analyze the circuit by
evaluating Γ in (^ ω) from 0 to 8 GHz. Display the results as (make sure
you use enough frequency points—at least 100— in the analysis!):
a) a Smith Chart plot of Γ in (^ ω). Note this is a parametric plot of reflection coefficient Γin as a function of frequency —not as a
function position (i.e., not Γ ( z)!).
b) a Cartesian plot of Γ in( ω) versus frequency (i.e., linear scale).
c) a Cartesian plot of 10 log 10 Γ in(^ ω)^2 versus frequency (i.e., dB
scale). Make sure that you use a log scale that makes sense (e.g., 50 dB from top to bottom).
Q1: Do the plots indicate that your designs are correct? Explain why you think so. Give specific numerical examples.
Q2: Observe the parametric plot Γ in(^ ω) on the Smith Chart. Use the
adjustable markers to determine at what frequencies the curve is far from the center of the chart, and at what frequencies the curve is near the center. Explain why this result makes sense.
Q3: Likewise determine the frequencies at which the parametric Smith Chart plot of Γ in(^ ω) is precisely at the center of the chart (i.e., the
curve intersects the center point). Explain why this result makes sense. Locate these same frequencies on the Cartesian plots. What are the
values of Γ in(^ ω) and 10 log 10 Γin( ω) 2 at these frequencies? Explain why
this result makes sense.
4) Use the adjustable markers on the plots to determine the bandwidth of each design.
Q4: You will find that the bandwidths of your design will not be exactly the bandwidths predicted by the design equations. Explain why that is. Hint: It is not because “ADS has errors”!
them, etc. I assume you know the material that has been presented in class. What I don’t know is if you can take that material and: 1) design a matching network that works and; 2) explain the behavior of that design when analyzed on ADS.
3. Thus, I am looking for quality over quantity. I do not want this to be a massive report requiring tons of writing. Make the points that you want to make in a clear and complete manner, and then stop writing! However, do not confuse the word “ why ” with the word “what ”. I have frequently asked you to explain why an observation is true, or why something happened, or why an observation makes sense. Students often instead just tell me what is observed, or what happened when something was changed—do not do this!
For example:
Me: Explain why water appears on the outside of a cold glass on a humid day.
Bad student response: “Because the outside of the glass slowly becomes wet”.
4. You must describe the synthesis process you used to design the matching networks. I require that your computations be presented in your report. I must be able to see where the error was made if your results or design are erroneous. I want to see all the general equations used, and then the values used for the variables in the equations, and then the numeric results of the equation.
You may put detailed computations in one or more organized appendices. These appendices can be handwritten. However, do not destroy the flow or organization of your report by providing fundamental information in the appendix only. In other words, I do not want to have to search through the appendix to find fundamental design parameters (e.g., the
characteristic impedances, bandwidth, etc.)—the appendix is for computation details.
5. Moreover, the report should flow from one section to another as one continuous document. Often I receive a set of independent pieces, stacked together and called a report—do not do this! To this end, figures, tables, and appendices should be labeled, number, and titled and referred to in the report. For example, “Figure 2 provides the parametric plot of Γ in (^ ω) for…”, or “The details of the computation can
be found on page 3 of Appendix 2”.
Likewise, the titles of each figure must be descriptive.
A descriptive title : Parametric plot of Γ (^) in(^ ω) for Binomial transformer
design and resistive load.
A non-descriptive title: Plot of Γ in(^ ω)
GRADING AND E VALUATION
1. Each student team (2 people max.) must work alone on this project— the design and analysis must represent each team’s effort and knowledge only. Working with other teams will be considered academic misconduct and all students involved will receive a zero grade. You are forbidden from viewing the report of other project teams— past or present. 2. However, you may ask your colleagues about how to operate or in any way use ADS. 3. Likewise, you may confer with fellow students about any general questions about the theory of wideband, multi-section matching networks. However, these questions must be general!
EECS 723 Project #1 Evaluation
Authors: ______________________________________
1. Report organization clarity and professionalism – Was the report well written and organized? Was it easy to understand and follow? Did the authors appear to take the assignment seriously and work hard to produce a professional product? Did the report include all the required elements? 2. Design effectiveness – Is the design effective and accurate? Does it appear to be designed by a knowledgeable microwave engineer? Does it meet the technical specifications of the project? 3. Design synthesis – Does the report describe well the synthesis of the design? Are the design equations and calculations clearly, completely, and unambiguously stated? 4. Design analysis – Is the analysis of the design and its observed behavior complete and unambiguous? Is the analysis correct? Were all questions satisfactorily answered? Did the author’s appear to know why their observations and measurements were correct? Did the authors show sufficient insight in the analysis?
Comments:
ADS INFORMATION
1. You will find on the website an ADS Overview (Parts 1 and 2). It will give you a quick tutorial on the general operation of the software. Further assistance can be found in the help file of ADS. Of particular interest is the “Quick Tour”, which can be found by selecting Help -> Topics and Index. 2. There are several types of analyses that can be performed by ADS. The overview provides examples for “DC” and “Transient” analyses. However, this project will require only the S-Parameter analysis (i.e., Simulations_S-Param). 3. The only circuit elements you will need for this project are:
a) Port Termination (Term) - This device is an element of the Simulations_S-Param category. This device is used to define the ports of a multi-port network for S-parameter analysis. Its design parameter is the port impedance (i.e.,Z 0 ). For this project, we will need only one of these devices, connected to the input of the matching network. As such, the simulation will determine onlyS 11 (port 1 being the input to the matching network). Note that this
means that S 11 = Γin if the port impedance is Z 0 = 50 Ω.
b) Ideal Transmission Line (TLIN) – This device is simply a length of ideal transmission line. Its design parameters are characteristic impedance and electrical length (at a specific design frequency). This device is an element of theTLines-Ideal category.
Note that this schematic contains all of the required devices except the inductor. You will obviously need to add several more sections of transmission line for your designs. You can simply modify this design, or start from scratch with a new design file.
6. The display file contains formatted Cartesian and Smith Chart plots:
m1f req=6.73GHz dB(S(1,1))=-20.
m1f req=6.73GHz dB(S(1,1))=-20.
-50 2 4 6 8 10 12 14 16 18
0
10
f requency (GHz)
|Gamma|^
(dB) m
Title goes here
m2f req=1.441E10Hz S(1,1)=0.129 / 49.736impedance = Z0 * (1.16 + j0.23)
m2f req=1.441E10Hz S(1,1)=0.129 / 49.736impedance = Z0 * (1.16 + j0.23)
freq (2.000GHz to 18.00GHz)
S(1,1)
m
Title goes here
Again, you should save the display file to your own disk space, using a name of your choosing. You may (in fact are encouraged) to modify or add to the display formats in any way. These two files are provided as an aid to you; you may ignore them completely if you wish.
Note that the markers can be moved in ADS by “clicking and dragging” them to a new point on the graph. Likewise, double-clicking on the plots launches a window that allows you to format the graphs in any way you see fit.
Finally, use a vertical log scale that makes sense. Typically, 40 to 60 dB of vertical scale is all that is required (i.e., do not give me a 200 dB log scale!).
7. Note that you can copy all graphics from ADS by selecting the graphics and typing “Ctrl-C”, and then pasting into a MS document.
