how to learn low level RF design

I'm excited!! Thanks for all the hints and tips folks! I am sure there are many people like me who want to learn this and now all these guidelines will be immortalized.

Im getting that Experimental methods in RF design book for sure,and I will look at the other ones too. I found a library with it and I will try to get the others too. Hope they dont mind if I keep it all for a while :)

Here's my understanding of it, I think, more or less possibly... wrote this a little while ago, here's the quote:

Wideband stuff is pretty easy: resistors are, for the most part, well behaved, and with resistance squashing the more unpleasant reactances in the circuit, you're free to push the boundaries. In wideband circuits, that means reducing those resistances until the reactances just start to bite back, then tweaking the circuit (or layout, or...) until the waveform simply looks good.

But in RF, you're intentionally tempting those parasitics with juicy LCs, lumped constants that you so wish to be ideal. And they can be pretty nice, with high Qs for high selectivity. But without that resistance, parasitics like lead inductance are free to party. You can try building an amplifier for one frequency, but if it works better as an oscillator at any other frequency, its amplification is pretty well doomed.

So I think it's exactly the fault of putting in a tuned circuit (most likely the capacitor in particular) which creates all those horrible VHF-UHF+ oscillations that so often spoil RF work. I think it's valuable to have experience in wideband as well as tuned circuits, especially where stability and power converge. When you're building a wideband amp, it has to carry a lot of current, because it's class A and it's fast. RF power outputs carry a lot of current because they're outputs, and they're fast because that's the point, but what's more, they're fast well above and below the one frequency you need them, so they are both similar to, easier than and harder than a wideband circuit!

Now, I haven't had much experience with tuned amplifiers, but I think I've gotten enough of a feel for these things that this might actually be right.

But I still say RF is black magic. ;-)

Tim

Additionally,

figure out what each of the following components does by going to websites of manufacturers of these components and reading their application notes on them:

Isolator/circulator , PIN diode, Coupler, 3dB hybrid coupler, Power splitter, PIN diode/ PIN diode switch, Mixer (read all app notes you can find on mixers), "off the shelf" filter (Read how to spec them and tradeoffs , and figure out different types of filters), SAW device, Voltage Controlled Oscillator, varactor diode. PI/T attenuators. [ ok, just thought of simple path: just go to "minicircuits" web site and read every ap note they have and look at all their components and figure out what they do]

Also, spend a lot of time thinking about sine waves and cosine waves. Phase shifts, multiplication of sines/cosines. Figure out what happens when you add two same exactly same frequency sigs together (Hint you get same freq, with a phase shift and amplitude adjustment). Spend time understanding concept of group delay and phase shift.

I'd suggest perusing microwaves101.com as well for a lot of those items... despite the name of the web site, a lot of the information is targeted towards VHF and UHF designs as well. A few of the guys hanging out in the forums there are Real, Live, Microwave Engineers, and their williness to answer lesser-experienced people's questions is invaluable.

"[ ok, just thought of simple path: just go to "minicircuits" web site and read every ap note they have and look at all their components and figure out what they do]"

Good idea. MiniCircuits actually has surprisingly few app notes given how many parts they have, and the bulk of them seem to have been written a couple decades ago, but the technology is still largely the same and the quality is good.

---Joel

o.

He could be Prezident.

by r.meck and g.white:

The library is good, but if you find it valuable enough to keep around,

Google: "experimental methods in rf design"

There are many places you can buy it to keep in your library. Your own library is a good thing too.

I probably shouldn't mention this since you have lots of good book references already, but for RF, one book I have is a near-miss great introduction. The book is "High Frequency Circuit Design" by James Hardy

I say near miss because it covers a lot of ground and prsents the subjects in a very clear way -- all good so far -- but the book badly needed a better editor.

Been a while since I looked at the problems, but I think I remember examples where the math didn't quite work, a schematic or diagram that wasn't quite right, stuff that made you scratch your head until you figured out the book was just a little bit wrong.

So I only mention this book because 90+% of it was very good, but the mistakes made it frustrating, especially if you were just learning. I just did a google to see if there was a newer version that might be better, but no. Seems just the one flawed version.

I still go to it for generally good straightforward coverage of many RF topics, but I now hold a grain of scepticism if something doesn't seem quite right and double check with other sources.

Another good way is to get your Amateur Extra license. Get the study guides from the ARRL, they actually present the theory as opposed to drilling you on the question pool.

to

IF amps.

you

for me.

That is a little bit different viewpoint.

It is not that anything you contributed is actually incorrect. But do you have to be nasty about it?

Arrogant overeducated nutter. "Clap, Clap, Clap, back in the box"

This freaky love of GPS derived references astounds me. There is NO technical justification for it. MARKETING.

But I still say RF is black magic. ;-)

Tim

It's the biasing of JFETs that appears to be a dark art to me. Can get them to do most of what I want, but not that last little bit... And can't seem to find any info on this subject other than "It's best to use something like Electronics Workbench."

Dave

Nah. After one or two decades things become quite normal :-)

They aren't much different than tubes, except that the bias voltages are almost an order of magnitude lower and production spread in the pinch-off region is very high. Easily +/-50%. On the bonus side they are more than two orders of magnitude cheaper than tubes were. And you don't get zinged so often.

What's wrong with Merrill I. Skolnik's 'Radar Handbook'?

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I would not know. But the target audience, the style and intended result are different.