I have an electrical engineering qualification and new to microwave engineering, but really never did much RF or microwave when studying.

I want to build a very basic and simple waveguide microwave system say using WR 340 waveguide to produce a plasma. I am fully aware of the dangers of microwaves.

My ultimate aim is a very rough first attempt without a circulator and isolator but hoping to generate a plasma.

Can this be done without gear like meters for power measurement and use of HFSS etc? It doesn't have to perfect...just a basic long rectangle box waveguide with a rectangle WR 340 cross section waveguide.

Where do I start? I'm very committed to do this.


1 Answer 1


Well, you say you're aware of the dangers of microwave, and yet you want to build this without any meters: don't.

Generating plasma sounds like you want that waveguide to transport significant power. With significant power comes the fact that even minor leaks become dangerous, and that every reflection within the assembly towards the source potentially damages your source and causes further harm.

Whereas for lower-power systems I'd say "a basic waveguide really only is a rectangular pipe of calculated dimensions made from a good conductor", I'll point out here that for higher powers, you really want good interconnections at each end of that pipe.

Sadly, high precision and things choke flanges are exactly what makes waveguides a bit more expensive than regular plumbing.

For the general design of a waveguide: The math works out pretty nicely, so what you calculate in dimensions using basic RF hand-analysis based on the modes you want to allow does fit the dimensions of real-world wave guides, so you'll probably actually get away without simulation software, if, and only if, you're not planning to do anything fancy (bends, polarization modifiers, impedance matchers…).

Where do I start? I'm very committed to do this.

Pozar: Microwave Engineering. Buy it, read it.

It's not my favourite book (not even on the topic), but it is the standard book and will probably make you able to read more specialized literature later on easily.

Yes, commitment starts with practicing using Maxwell's Equations until you hate them.

  • \$\begingroup\$ Thanks for the info, the microwave source is about 250W. I'll take your warnings on board. All I want to do is something that on the surface ( from a beginners point of view ) is make a simple box of the right dimensions to set up what I think would be a standing wave in the right spot in the waveguide to generate a pasma. Its the tuning knowledge that seems to escape me - I guess I was after some initial "rules of thumb" tuning principles to try and scope out a basic framework of understanding , then zero in on the maths ( which I will do ). \$\endgroup\$
    – user196795
    Aug 25, 2018 at 10:18
  • \$\begingroup\$ in microwave engineering things tend to work the other way around: you start by learning the math, understand them, and then throw in the black magic voodoo experience wisdom to make things work better. The dimensions of your resonator are pure math, however, and you'll be able to calculate them 1/3 through the book I've mentioned. \$\endgroup\$ Aug 25, 2018 at 10:32

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