Need a good reference on designing crystal filters

Does anyone know of a good tutorial or reference book that deals with the theory and design of crystal filters? Earlier, somone recommended the ARRL handbook (which I have ordered). Does anyone know of a another good resource (especially one online)?

btw... I'm trying to design (and understand) a very narraw bandpass filter (fc = 60khz for WWVB).

Thanks Stephen

Reply to
Stephen
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Stephen,

Wes Hayward's RF circuit design book is good, although he uses a table-based approach so if you're looking for the derivation of the necessary coupling coefficients you'll have to consult his references. (Even when I was in school, we were made to derive the '1Hz prototype filter' component values in exactly ONE homework problem out of the dozens of filters we did as homework. It's kinda tedious...and the homework problem was something simple like a Butterworth filter as well. For elliptical filters, it's quite involved to obtain the prototype values.) Anyway, though, a good point about Wes's book in that he explains the physical meanings of the coupling coefficient, which is useful in that a large number of books on filter design assume you're going to be using LC-LC-LC... sections rather than the LC-C-LC-... sections that are so much more attractive for Xtal filter

Experimental Methods in RF Design (written by Wes Hayward, Bob Larkin and Rick Campbell) has a fair amount of info as well. In many ways it's more advanced that Wes's own book, and refers to that book as a reference. In either case, be sure to check out Wes's web site

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because it has errata and additional information.

This is a good general purpose link for filter design:

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. If you're looking for a program to do the design for you, the AADE Filter Designer listed is good, and while the link says it's $25, these days it's actually free (Neil Heckt, Mr. AADE, has a note about how he was making orders of magnitude more income from his hardware products than from his software, so he decided to just make the software free).

Cool, I'd love to see the results!

---Joel Kolstad

Reply to
Joel Kolstad

with

recommended

Try:

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I use it and like the presentation.

Or try others on Amazon. There are about 100 plus listed.

Reply to
Clarence_A

recommended

"Handbook of Filter Synthesis" Anatol I. Zverev John Wiley & Sons

Reply to
Mark

Thanks for the detailed info... I will let you know how the filter works once completed. If you had to pick one of the three books mentioned above, which would you chose?

Reply to
Stephen

theres some interesting stuff on the net if you look up 'crystal ladder filter networks'

Colin =^.^=

Reply to
colin

Probably Introduction to RF Design by Hayward... and then I'd ask if someone were willing to scan in a couple of relevant pages from Experimental Methods in RF Design and e-mail them to you. :-)

Reply to
Joel Kolstad

Thanks.. I've been doing just that on PSpice (I have to order some crystals as well). I've noticed that people typically use crystals that are ever so slightly above there desitred center frequency. Should I start with the 60.002 khz or 60.003 khz crystals instead of the 60.000 Hz ones? Again, I really want to learn this stuff (not just cook-book it) but I haven't acquired any references yet. Thanks for the help.

Stephen

Joerg wrote:

the

side

be

10k.
Reply to
Stephen

Hello Stephen,

While waiting for the books I'd just whip one up. Drive one side of the crystal with the output of your first RF stage, terminate the other side with a resistor and look at the response curve. The resistor needs to be experimented with, it probably will end up somewhere between 2k and 10k. That's pretty much it. The real thing would be with a bifilar transformer at the driving end and a phasing cap but for many atomic clock receivers that's already too much cost.

Regards, Joerg

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Reply to
Joerg

You need to understand the difference between the series and parallel resonance of a crystal.

Read up on that.

That will answer your question.

Mark

Reply to
Mark

Hello Mark,

Yes. Crystals can be pulled a bit even in filter applications. Spice is ok but it doesn't replace experimenting here. Stephen, until your 60kHz crystals arrive just take any low frequency crystal you have, like a

32.768kHz crystal pried out of a worn-out watch. Make a filter with that and probe around.

Regards, Joerg

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Reply to
Joerg

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