eee161 applied electromagnetics laboratory...

Dr. Milica Markovic Applied Electromagnetics Laboratory page 1

EEE161 Applied Electromagnetics Laboratory 1

Instructor: Dr. Milica MarkovicOffice: Riverside Hall 3028

Email: [email protected]:http://gaia.ecs.csus.edu/˜milica

1 Learning Objectives

In this lab you will

1. Analyze the effects of coaxial cable to step and sinusoidal voltage at the input and the outputof the cable.

2. Interpret phase and time delay as they relate to voltages and currents on transmission lines.

3. In ADS create a workspace, schematic diagram

4. perform Transient simulation with a coaxial cable

5. Label nodes, then use an equation in data window to display results

6. display simulation data, tune the circuit parameters and save files.

2 Report

Consult with your lab instructor what kind of report they want to see! For example, ina doc file, snip the text of the problem assigned, then just cut and paste in a word file the circuitand the simulation you performed. Explain the steps you are taking, and thoroughly explain eachsimulation results figure. Have you expected these results or not? Do you think the simulation iscorrect? How does the simulation relates to other simulations performed? Submit ONE report pergroup in SacCT.

3 ECS Login

You need to have ECS login and password. This login is different from CSUS login (akaSaclink login) that you use to check your email. If you don’t have the login, go to theRiverside Hall second floor computer lab and request a login from IT. You will not beable to login to ECS computers unless you have ECS login.

California State University Sacramento EEE161 revised: August 28, 2017


4 Coaxial Cables - Background

Coaxial cables are used extensively in electrical engineering. Some examples are: Distribution ofCable TV, Connection between antennas and power amplifiers in base stations for cell phones, someinternet cables are coaxial (what is usually called an Ethernet cable is a twisted-pair cable, not coax).Figure 3 shows an RG-59 coaxial cable.

Figure 1: RG-59 Coaxial Cable. A-Plastic Cover, B-Woven Copper Shield, C-Dielectric Insulator,D-Solid Copper-Clad Steel Wire. https://en.wikipedia.org/wiki/Coaxial cable

Google −→ Search for and download Data Sheet for Pasternack RG-59 coaxial cable. An excerptfrom RG-59 data sheet is shown if Figure 4.

5 Speed of electromagnetic waves

Electromagnetic waves propagate in air (εr = 1) with the speed of light c=3 108ms

. However, indielectrics where εr > 1, the speed is:

v =c√εr

(1)

Which dielectric is used in RG-59? Calculate the speed of waves in RG-59, then compare it withthe data sheet. How is data sheet expressing the speed? Can you explain what is this the percentageof?

Now you know how to calculate the speed of electromagnetic wave. How much time will anelectromagnetic wave need to travel over an 11.5 inch line if the dielectric in the line is PE (Polyethy-lene)? This time is called ”time-delay” τ . Remember that the waves travel with constant speed,Equation 2. If the distance traveled is d, and the speed is v, what it the time τ , Equation 3, thatthe signal needs to travel distance d? Be careful with units. The speed of em waves, c, is given in m

s

and the distance is given in inches. You need to convert units first.


https://en.wikipedia.org/wiki/Coaxial_cable


Figure 2: Excerpt from RG-59 Data Sheet

v =d

t(2)

τ =d

v(3)

Next, we want to know if a sinusoidal signal at frequency f = 0.5GHz is delayed for about thetime τ , what will the phase shift be? The sinusoidal signals are written as v(t) = sinωt. If the signalis delayed for the time τ , then the delayed signal v(t − τ) is given in Equation 4. If we multiplythrough ω with t and τ to get Equation 5

v(t− τ) = sin (ω(t− τ)) (4)

v(t− τ) = sin (ωt− ωτ) (5)

From here, by inspection, we see that the ”phase” is given by Equations 6-7.

θrad = ωτ (6)

θrad = 2πfτ (7)

In degrees, using unit conversion, the phase shift is

θdeg = 360 f t (8)



6 Coaxial Cables - Background

Coaxial cables are used extensively in electrical engineering. Some examples are: Distribution ofCable TV, Connection between antennas and power amplifiers in base stations for cell phones, someinternet cables are coaxial (what is usually called an Ethernet cable is a twisted-pair cable, not coax).Figure 3 shows an RG-59 coaxial cable.

Figure 3: RG-59 Coaxial Cable. A-Plastic Cover, B-Woven Copper Shield, C-Dielectric Insulator,D-Solid Copper-Clad Steel Wire. https://en.wikipedia.org/wiki/Coaxial cable

Google −→ Search for and download Data Sheet for Pasternack RG-59 coaxial cable. An excerptfrom RG-59 data sheet is shown if Figure 4.

7 How to login to Hydra to access ADS

We will use Keysight’s (former Agilent, even former-er HP) ADS. You can simulate circuits usingvarious simulation techniques in ADS: AC simulation, Transient simulation, Small-Signal simulation,Harmonic Balance simulation, Envelope simulation etc. Each of these is targeted to a specific typeof circuit and application. In this class we will first use Transient simulation. This is a simpletime-domain simulation, which means that the circuit is solved by solving differential equations forvoltages, just like what you did in ENGR17. Transient simulation results will display ”transients”as well as ”steady-state” solution for voltages and currents. Transients are voltages and currentsthat occur in the circuit when we turn on the generator, and before they settle to their permanent,steady-state values.

First login to the computer that your lab is held in with ECS login and password.

1. If you are accessing Hydra from computers running Linux (for example from RVR3009), followdirections provided by the instructors.

2. If you are accessing Hydra from computers running Windows, search for ”Remote DesktopConnection”. To Login use


https://en.wikipedia.org/wiki/Coaxial_cable


Figure 4: Excerpt from RG-59 Data Sheet

ECS\USERNAME

and your password.

3. It is very important NOT to close any black windows that will start poping up when you loginto Hydra. If you do close one by accident, just log out, and log back in again.

4. Find ADS on the list of programs. It is usually called ”Advanced Design System (year)”.

5. Open a new workspace, by following step-by-step instructions given in Figure 5.

6. You have to save this new workspace on T: drive. ADS will not allow you to save it to C: drive!If you don’t have the T: drive, check step c) above!

7. Click on the Schematic icon on the top bar of the “Advanced Design System (year) (Main)”window.

8. Do not select any templates, and cancell ”Schemtic Wizard” window

9. The Schematic Window should open.

8 Setup a transient simulation of a coaxial cable with step

voltage in ADS

Sometimes it is not quite clear why do we need to study coaxial cables. After all, in EEE117 lab weuse coaxial cables to connect the generator to the breadboard, but we don’t make any assumptions



(a) Go toStart, AllPrograms,AdvancedDesign System

(b) Close this window (c) This is the main ADS window.

(d) Create new workspace. (e) Name your new workspace as HW1 wrk,then click next, next,...,finish

Figure 5: Create a new workspace.



or considerations about it. This is because the frequency of the signals we’re using in EEE117 isvery low. When the frequency increases, transmission line effects become significant. In this sectionwe’ll start studying how and why transmission lines effects occur in circuits.

We will use ADS to setup the simulation shown in Figure 9(a) on a schematic diagram. Open aschematic diagram in ADS and under TLines ideal, select COAX MDS, and place it on the schemat-ics, as shown in Figure 6(a). Now, using data sheet from Figure 4 enter the correct parameters A,Ri, Ro. For Ro use the outside radius of the coax. Set T=0, Er=2.25 (Coaxial cable’s dielectric isPE - Polyurethane), leave Cond1 and Cond2, Mur, TanD as they are.

As shown in Figure 7, from time-domain sources pull-down menu, select VtStep, and from LumpedElements pull-down menu select a resistor. Set the resistance of the resistor to 75Ω. From Simulation-

Transient pull-down menu select TRANS . To setup the transient simulator, double click on theTransient Simulation on your schematic diagram. Then:

1. Set Start time to 0 ns (it is likely already set to 0ns)

2. Set Stop time to 10 ns

3. Set MaxTimeStep to 0.1 ns (this is the sampling rate - you will learn more about that inEEE180)

4. Click on the Integration tab and set the ”Time step control method” to Fixed. This meansthat the simulator will use only the time step specified.

Now, label the input and output voltage nodes with Vin and Vout by using ”NAME” icon on top

of the schematic diagram window: To simulate the circuit, click on the Simulate pull-down menufrom the top of the schematic diagram, then click on Simulate (or click on the gear icon on top ofthe schematic diagram, or press F7 on the keyboard).

New ”Data Display” window will open. Follow directions as shown in Figure 8 to display inputand output voltage. You should end-up with the Data Display as shown in Figure 9.

Q−→Why is the otput signal delayed for about 1.43 ns? In your answer, use at least the followingvocabulary words: speed of electromagnetic waves, dielectric, dielectric constant, coaxial line length,time delay.

9 Setup a transient simulation of a coaxial cable with sinu-

soidal voltage in ADS

Now, you will repeat the previous simulation with a sinusoidal generator. Save the schematic diagramyou made with a different name. For example, ”sinusoidalsignal”. Then remove the step voltage andfrom the same pallete (time-domain signals) replace it with

V_1 Tone



(a) Placing a model of a coaxial cable in ADS (b) Schematic representation of a coaxialcable model parameters in ADS

(c) Description of coaxial cable model parameters in ADS.

Figure 6: Simulation of coaxial cable in ADS.

. Label the input node with Vin and output node with Vout. Simulate the circuit and display theinput and output voltages as a function of time (this is the default for transient simulation). Observethe time delay, as shown in Figure 11.

Q−→ How does this time delay compare with the step simulation? Explain why is this so.Now, follow instructions on how to add an equation to the ”Data Display” as shown in Figure 12.

Display the rest of the plots as shown in Figure 11. When you are ploting input and output voltage,you have to select ”Add Vs” then select equations, and new variable you just defined. See Figure 12.



(a) Resistor under theLumped-Element pallete.

(b) Time-domain step voltageunder Time-Domain voltages.

(c) Transient simulation under theAimulation-Transient pallete

Figure 7: Location of various circuit elements under Palette.



(a) Click on rectangular plots and place it in Data Window. (b) Select the variable that you want to display,click add.

Figure 8: Presenting simulation results in ADS.



(a) Transient simulation of voltages at the input and outputof a coaxial cable.

(b) Simulation results.

Figure 9: Simulation of coaxial cable in ADS.



Figure 10: Schematic diagram of a setup for transient simulation of a sinusodial signal on a coaxialcable.



(a) Transient simulation of sinusoidal voltages at the input and output of a coaxial cable.

(b) Simulation results.

(c) Simulation results.

Figure 11: Simulation results of the sinusoidal voltages at the input and output of a coaxial cablein ADS from Figure 10.



(a) Select Eqn (b) Type your equation.

(c) Your equation is displayed. (d) Click on rectangular plots in Data Win-dow(not shown above), then select Equationsas shown, and pick gain from the list.

Figure 12: Plotting equations example.


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