Piezo-Electric Filters
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- Опубліковано 30 вер 2024
- #225 In this episode I start looking at piezo-electric based components that can be used in filter circuits. Things like ceramic resonators, quartz crystals and SAW or BAW filter components can all be categorized into a wider class of piezo-electric components. I first look at what are the principles used by such a component and then continue by looking at the equivalent electrical model. Finally I run some basic measurements and also look at how a filter can be built around a crystal type component.
Filter series:
Ep1 - Intro : • Intro to Filters
Ep2 - Passive RC Filters: • Passive RC Filters
Ep3 - Active RC Filters: • Active RC-filter Basics
Ep4 - More Active RC Filters: • MORE Active RC Filters
Ep5 - Introduction to LC Filters: • Introduction to LC Fil...
Ep6 - LC filter limitations: • Limitations of LC Filters
Ep7 - Piezo-Electric Filters: • Piezo-Electric Filters
Ep8 - Crystal Filter Measurements and Design: • Crystal Filter Experim...
Ep9 - Cavity filter Basics: • Cavity Filter Basics
Ep10 - Cavity filter Experiments: • Cavity filter Experiments
Ep11 - Stub filters: • Coax Stub Filters
Measuring and simulating crystals: • Measuring and Simulati...
Further reading:
Handbook of Filter Synthesis; A.I. Zverev, 1967
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I thought to myself when I first saw the case, “That's a delay line from a 1970s TV”. Yep, I'm old.
It took me quite some time to figure out what it was... I remember seeing these in old TV sets in the past, but I never knew what they did.
PAL, SECAM or NTSC? 🤣
Hello fellow old person.
Me 2. Also old person 😂
@0:08 it's a video scan-line delay-line. It contains 1 scan-line (63.5uS long) and its analog contents are used to repeat/replace a scan-line that has a "Drop-Out" in it. The piezo-electrodes are on the corners of the glass, and the Piezo transmit beam enters @ a 45 degree and bounces around diagonally off of all of the edges inside until the signal finally hits the Receiver Piezo. The Seven black-spots on the glass are between the reflection grid to reduce beam path cross-talk and total crystal resonance.
My first "Citizen Band" (27Mhz) radio from the 1970's had 40 channels. When i finally dismantled it out of curiosity, I discovered it had 40 replaceable " tin can" piezo crystals! 🙂
If that was a Philips delay line, I used to make those at the Philips plant in Blackburn UK probably around 30 years ago. I operated the screen printing machines that put the diamonds of damping compound on the glass. I remember a display in the entrance that had with one of all the different generations of the delay line they had made. The very early ones were huge.
Indeed it is a "Philips, DL700, 84701; kh 08010" these are all the markings present on the top side. I think it would be really special if this was one of the components you worked on in the past;
It would think that it would be rather unlikely to be one that I helped produce. We would probably have produced many thousands per week. I think I left in around 1996 but production was ramping down by that point. Didn't think about it when I worked there but looking back it was really quite an interesting process. Thanks for showing it. It's brought back some great memories.
So is that glass or quartz?
Was definitely glass, although if I remember correctly I think some special formula (it's a long time ago).
The crystal model used is called the Butterworth Van Dyke (BVD) model. The model can be extended by adding multiple RLC circuits along with a single parallel capacitor to model the primary and secondary resonant and anti-resonant frequencies. For sonar usage, widening the band between the resonant and anti-resonant frequencies by addition of series and parallel inductance is an underutilized method for achieving better performance...
Anyone else get audio issues? Last couple of vids and this one I get lots of glitch artifacts from my DAC. Make it unwatchable unfortunately
@@joel_mckay
It's optical out to a DAC from TV. My Yamaha RN301 also does the same thing using the internal DAC.
No other videos do it's an odd one, skipping CD type noise
Thank you.
@4:55 how did you get the equivalent component values?
Sorry, I now see it in the Measuring video linked in the description
comprehensive presentation.
Top video, Thanks!
Thank you! 🙏
👍
Now waiting for Andreas, and my Sunday shall be whole :)
Who?
@@MegaCadr Spiess.. Andreas Spiess.
@@AdityaMehendale Oh, right. I'm subscribed to him, too. :)
This is fantastic! Any chance you are going to do one on mechanical filters?
What sort of filters do you have in mind?
@@FesZElectronics The ones that they used to use as IF filters on radios, like the Collins 455khz filters. Very similar in a lot of ways to what you have here. It just find how they model the physical parts in between interesting.
I'm not really sure if the operating principle is different, its just a different material - ceramics vs crystals.
@@FesZElectronics no, same principle, I just find it super cool. I wanted to experiment making my own bad ones by hand and just seeing what I end up with :)