How To Make A If Filter Using 455 Khz Ceramic Resonators?

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Some slap-up research from 'UOS!
I've never used ceramics either so I but guessed at some likely motional parameters; my guesses were some way from reality.

I think there's a typo though; a Cm of 385uH seems to give resonance most 4MHz with 4.4pF.

http://www3.telus.net/chemelec/Calculators/LC-Calculator.htm

Co is particularly high; on reflection, I suppose that ceramic has a high dielectric constant (we utilise ceramic capacitors, don't nosotros ) and it'southward spring to be high.

Re my design in AADE; well, that'due south what information technology produced.

As the human said; "I just do it, I don't explicate it".

I've had the "double-hump" problem in crystal filters earlier; information technology'due south sometimes caused past mis-alignment of the sections but I call up it can also effect from insufficient Q.

Comments?

I did a similar blueprint in AADE using 'UOS parameters (with 385uH) for the 4MHz ceramics;

It was not possible to design a narrower filter; AADE advised" insufficient Q".
Ok anybody. It might be a little while before I pick this back up. I really will get back here and dive in to the mathematics and mechanics of this. Id similar to follow through with all the information, and know why I have implement the algebraic methods usedin this filter blueprint stuff.
Be aware that I will need help in discussing each gene along the way. I feel that my fellow hams wont let usa down. Remainder assured I will exist dorsum. Its the season to work here. Olfactory organ to the grindstone!

The Apprentice's Creed:
Just, if we do err, in that location is e'er the prayer in the Volume;
We have left undone those things which we ought to have done; and we take done those things which we ought not to have done.

I thought some years ago that I had at least some grasp of crystal filters; subsequently trying to design some precision filters for a measurement application I realised that I knew null.

I've been studying hard since then and I now know at to the lowest degree 10 times as much as I did then.

It'south a fascinating subject that has led me to acquire or build some interesting examination gear.

Beware; filter building is addictive!
OK, Im back and hopefully tin hang in hither for a few rounds. Id like to examine some properties of a resonator, be it crystal or ceramic. Id assume that our give-and-take could also be applied to mechanical filters?
Theres some hams in hither that accept a lot more than experience than I, so if you can, please share your knowledge!

Not sure where to start hither.Basically, we are "ringing" the element(s) at its resonant frequency, and via the capcitors and terminations we can "clench" downwardly on the vibration, like a drummer when he hits a cymbal and "snuffs" information technology out with his paw? Is this whats called motional inductance or did I simply brand up a discussion?

Id like to know exactly why Ill be juggling these numbers around. Which equation should nosotros outset with? Lets swoop in here and piece of work this field of study to death.
You have a lot of reading to exercise!
This is how a crystal or ceramic resonator is modelled;

Lm is motional inductance; Cm is motional capacitance; Rm is motional resistance and Co is shunt or holder capacitance.

Ignoring Co for the moment, the circuit is simply the aforementioned as a serial-resonant circuit made from a capacitor and an inductor; the resistance comes mainly from wire resistance in the inductor and dielectric loss in the capacitor.

The L & C values are somewhat dissimilar to those commonly found in an Fifty/C circuit; L is very high and C is tiny for crystals, less-so for ceramics. Hither are some parameters for a fairly-average crystal;

Parameters for ceramics are a fiddling dissimilar as discussed before in this thread.

Co is a PITA; it'due south the inevitable result of the two plates that connect wires to the crystal/ceramic "piece". It causes a parallel-resonance near the series-resonance that we want to utilize;

Series resonance is the peak on the left; parallel resonance is the trough on the right.

I think that this newspaper is excellent, at kickoff glance for describing measurement methods only, if you lot written report it closely, information technology tells a lot about crystals generally;

http://www.cliftonlaboratories.com/Documents/Crystal Motional Parameters.pdf

I oasis't studied ceramics at all but the principles should be the aforementioned as for crystals; information technology's the much lower Q that makes ceramics perform poorly compared to crystals.

Once y'all accept the "feel" for motional parameters, try some filter designs with ELSIE or the AADE programme.