Winter 2025 Course Journal: EECS 330¶
Course Title: Intro to Antennas
Motivation¶
I'm a ham radio operator… but at what cost? Truth be told I didn't have a lot of fun on my Baofeng UV-5R. The passion wears off. The exams are not challenging, just tedious, with a focus on the "what" rather than the "why". Therefore, I enrolled in this course to find out.
Before the midterm¶
Despite being an intro to antennas, antennas didn't show up until halfway in. The first half was about plane waves, such as propagation in lossless/lossy media and normal/oblique reflection/transmission.
Honestly it's kind of boring.
Labs¶
There are two types of labs: actual equipment and computer simulation (using Ansys HFSS). The actual ones are as fun as are tedious. HFSS, on the other hand, is just tedious.
Once we had to roll a aluminum ball off a slope and measure its speed with a Doppler radar. It was ridiculous. I had expected that, since we were to make a calibration curve relating frequency shift to speed, the speed of the ball would be precisely controlled. Nope. It was a wooden slope with an arbitrary angle, with markings every 2 cm drawn with a pencil. The ball was released from the slope by hand. I would trust the Doppler radar more than my hands thank you very much.
On the next actual lab, we had fancy equipment like an RF signal generator, an amplifier, and a power detector, each of which somehow requires a different DC voltage. The power detector outputs a voltage, which we could read from a multimeter. The voltage was fluctuating all the time; just pick a random sample. The only way to relate voltage to power is readinfg off a curve on a datasheet by eye; cope. Worse, the power is in dBm and we need to convert that to mW.
The HFSS labs are just following instructions to make 3D models to simulate antennas. Here's the radiation pattern of a dipole:
Midterm¶
It's closed-book, with one cheatsheet allowed. Despite my efforts to fit everything on it, there were some niche terms on the exam such as the loss tangent. But other than that, things are manageable if you just substituted for variables in the formula.
After the midterm¶
We finally move on to actual antennas. The most basic one is the Hertzian dipole: an extremely short dipole antenna, short enough to assume constant current on its length. With integration, we can derive characteristics of every other dipole antenna, such as radiation pattern, directivity, radiation resistance, and efficiency. Basically the takeaway is, if you vary the length, you get wildly different antennas.
We then discussed antenna arrays, which is just putting a bunch of antennas in a pattern (we only covered linear) and controlling them as a group. Each can carry a different amplitude and phase. By adjusting the phase difference, we can steer the beam to focus energy to different directions, which is neat when you have a stationary antenna and moving target.
This is the end of math that involves complex numbers, and the beginning of math that involves ridiculously small numbers. We got the Friis formula, which tells you how much energy you can hope to receive given transmitting power, gains of both antennas, distance between them, and wavelength.
Then we get an abstraction of aperture antennas like horn antennas and reflector dishes, in a handwavy way. Then radar, which is like, middle school math, just multiplication and division.
We spent like a week on waveguides, but did not get into details, nor were they on the final. We did get to see a couple millimeter-wave waveguides Prof. Mortazawi brought in, and they're pretty damn precise. It blew my mind that, the way you couple a waveguide to a coax cable is just a stub of wire that is precisely lambda over two or four (I forgot), and that'll shoot out (or absorb) the E field.
Furcon banter¶
[9:00 on the Monday after MCFC, attendance: 2]
Prof (to me): Why are you wearing a mask? Are you sick?
Me: No I went somewhere crowded over the weekend.
Prof: Where?
Me: Convention.
Prof: What kind?
Me: Furry convention.
Prof: What?
Me: Furry convention.
Prof: You have to speak louder, I can't hear you.
Me: It's, like. A convention for art and stuff.
Prof: Oh, like an art fair?
Me: Like an art fair.
Prof (gestures at almost empty classroom): Well if you're wearing a mask I'm gonna take mine off.
Final¶
We were allowed three cheatsheets, and the exam was more or less a plug-and-chug experience. There's really not much to say about it except that I was dealing with some crazy small numbers (10 to the power of -108 — it turns out if you enter "1E-108" in a TI-36 it throws a syntax error because the E key only works with powers within ±99)
End of course¶
It's a typical course with Young-and-Freedman vibes. We're just following a textbook, applying formulas, doing labs. It taught me enough to know what to expect from an antenna, their electrical parameters, and the context in which they matter.
The course coincided with me advancing into ham radio, and getting trained to operate W8UM's rig. The course was one of the motivations. However, it is becoming evident that RF will not be the major part of my career. With that in mind, I'm quite happy with the depth EECS 330 went.