Ceramic resonators

Thread Starter

ag-123

Joined Apr 28, 2017
269
I'm reading up a little on ceramic resonators and I stumbled into some rather good resources
https://ecsxtal.com/news-resources/...nical-guides/127-ceramic-resonator-principles
https://www.mouser.com/ds/2/281/p17e14-188039.pdf

then if you search the online open markets
https://www.aliexpress.com/wholesale?SearchText=ceramic+resonator
you would find a variety of 2 pin and 3 pin types

accordingly 3 pin types is equivalent to simply having the caps to gnd at the terminals embedded - possibly the center pin is gnd
https://electronics.stackexchange.com/questions/524429/16mhz-ceramic-resonator-3pin-vs-2-pin

next I looked at some graphs / charts
https://ecsxtal.com/news-resources/...nical-guides/127-ceramic-resonator-principles
imp1.png
imp2.pngI think I've seen such charts (these are the most precise / characteristic yet).

Now I've a question:
If i use a ceramic resonator as a bandpass filter,
- I'd assume it 'resonates' at Fr which is the low impedance point?
- these charts now stirs lots of question in a sense that lets say I've a rf mixer prior this say a sa602 double mixer
https://www.nxp.com/docs/en/data-sheet/SA602A.pdf
and I make target the difference frequency (IF) of 455 khz

do this ceramic resonator in effect *band pass* the IF of 455 khz?
the charts are at least surprising as it implies that some other high frequencies could be present at the output

- the other thing is this is highly non-linear, it would seem that frequencies lower than and higher than Fr would be attenuated by very different levels.
at Fr lowest impedance, it implies this is the highest at the output (band pass), but frequencies lower and higher are attenuated differently, e.g. a frequency closer to Fa would be pretty much supressed, then higher frequencies are let through the filter again (non-linear)
while the lower frequencies are attenuated as well but following very different curves

so if one is trying to decode FM (frequency modulated signnals) centered around Fr, any thing closer to Fa is supressed, then varying signals, higher and lower frequencies still can be seen in the output and attenuated to different extent.

how would this in effect be the demodulated / detected signal?
 
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Thread Starter

ag-123

Joined Apr 28, 2017
269
taking some inspirations from here
https://www.electronics-notes.com/articles/radio/rf-mixer/bipolar-transistor-mixer.php
and here
http://www.crystal-radio.eu/set9/enset9.htm

I'd guess this is a possible feasible attempt, to make AM demodulator, it would at least need a diode and parallel RC small setup at the output. It'd seemed a transistor amplifier would be needed at the output stage as well.
fig1.png

A trouble I'd see is this uses the resonator to remove the much higher RF, LO and RF + (RF-LO) frequencies. But that they are nevertheless present in the output. It seemed as well, the images to be removed are not fully considered.
I'd guess in ordinary radios, the higher spurious frequencies are simply inaudible. But that say in an SDR, possibly an LPF would likely help at the output
 
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