HW 7.4,8.1 -- Plane Waves in Lossy Media

Questions of the Day:

• Explain plane wave reflection at normal incidence. 
• How do you calculate the following values for  a plane wave normally incident on a layered material (2-3 layers, or more) using the Smith Chart:
  • Reflection coefficient (anywhere in the model)
  • Transmission coefficient (anywhere in the model)
  • E,H fields (including their magnitudes, polarization, and direction of propagation, be able to write their equations) (anywhere in the model)
  • How do you handle boundaries terminated by perfect conductors?

Remember that the reflection and transmission coefficients here are for VOLTAGE or E field.  To find power reflection and transmission, be sure to square them!

TURN IN   'enough' worked examples to convince me that you are able to do the calculations above.

Wait a minute ! What problems should I do?  How many of them should I do?  Why didn't I just give you an assignment?

Because ...

As Engineers, we constantly (like every day) encounter things we don't know.  Some of these things other people know (such as how to calculate lossy plane waves).  Other things no one else knows either (such as research questions).  We need to be able to figure out WHAT it is we need to know, how to find that information, how to tell when we know it, and how to test ourselves to see if we are right.

So ... let's start here.

WHAT do you need to know?  Well, that is listed above.  But there are some nuances here.  There is no point in doing EVERY possible plane wave example of course, because you will never remember all of them anyway.  So what do you really need to know?  What is every reasonable case you can expect to see, and how do you handle those?  You are told the maximum number of layers will be 3.  As you learn this method, think if things would be different if you had more or fewer layers ...  What are some of the special cases you may need to consider (perfect conductors, for example, or how to convert from E to power)?

HOW can you find this information?  Well, to start, you have a little experience with Smith Charts already, and a bunch of resources there.  So, have those handy and refer back to them as needed.  And you have a little experience with Plane Waves already, have that handy too.  What are you still missing?  How to put them together, how to handle attenuation, and how to handle E (which is a vector) instead of V (which is a scalar), for instance.  And of course there are the lecture notes, the videos, the book, and online resources.  And your friends!  If you are not already studying together, you are missing out... your engineering friends are going to be great resources your entire career.  That is what we mean by 'networking'... keep in touch with everyone who knows stuff you need to know.

How can you tell if you know this material?  Well, to start, you have the old exams.  For a class, that is not a bad way to go.  But what about out in industry?  What will you do then to be sure your answers are right?  Very often we use simulations (or analytical results) to check our measurements or designs.  Do you have simulation software here?  Yes!  Several links provided in the Smith Chart lecture can help you here.  Are there other simulation methods too?  Yes, you can learn about these in future EM courses Links to an external site. including Microwave I, Antennas, Numerical EM, and Advanced EM.

CAREER:

Hey, Dr. Furse, Do I really need to know all this stuff? I'm never going to need this again ...  I'm going to be a VLSI designer, a digital engineer, and I don't care about all of this plane wave stuff anyway! 

Signal Integrity Engineering Links to an external site. (SI) (being sure the signals behave as they should for high speed circuit design) (There are a lot of free tutorials on the site I linked here)

Electromagnetic Compatibility Links to an external site. (EMC) (required testing to be sure your device doesn't interfere with everyone else's devices) (I linked up a job board here to give you an idea what EMC engineers do.)

Both of these career choices evaluate lossy EM fields.  EMC routinely evaluates plane wave exposures.  SI uses more near field evaluation, but often again relies on simple attenuation models such as these seen for plane waves.