The filter is not "3 resonators and 3 capacitors", but actually 6 resonators: 3 of them (the thin ones) operating at parallel resonance (at the 455kHz), the thick ones are operating at series resonance, their characteristic impedances (given by their thickness and mode of operation - the series ones operate at some overtone mode) so in total the pass band is formed by essentially 6 critically coupled resonators in a ladder configuration. The small patch on the thick ones (the horizontal elements in the kadder) is to make their characteristic impedance as high as needed to ensure the coupling being exactly critical (so reach flat top in the pass vand). On top of that the series resonance of the parallel elements forms a reject notch just below the pass band, the parallel resonance of the horizontal elements forms a reject notch just above the pass band, both effect contributing to the edge steepness. By the way the reject notch just above the pass band is a giveaway the thick horizontal elements are resonators as well and not just capacitors. Plus the side steepness and a suppression around the pass band (for the given bandwidth) could be reached only with 6 resonators, not just by 3.
I was going to say , yep very similar to a crystal in construction. The filter I was familiar with after replacing the noisy ones in my old TS-2000 . I was curious enough to pull one apart but never a 455kc resonator. Thanks for showing us.
3:24 Forgive my ignorance on the subject. If three legs of the second filter are essentially a circuit ground, why does the manufacturer keep them independent instead of connecting them together? I would expect to see three legs instead of five: in, out and ground.
Hi, each ceramic wafer resonates at a certain frequency within the filter's bandwidth and is coupled with the next wafer by a specific value of capacitance (determined by the area of the circular metallisation) for a tighter or little loose coupling to bring about the desired filter plateau. The leads to the ground, as you suggested can very well be connected but it's always better to be grounded then and there; moreover it adds mechanical ruggedness to the whole device for sure. De VU2RZA
The 3 ground leads are needed to actually reach the specified out-of-band suppression (in the 80-ish dB). If there were just one common, its parasitic inductance would severely compromise that. Of course, it works only when the PCB layout uses proper layout (ground plane, signal flow ground routing,...), to not introduce that parasitic back in your design.
when they mine products/elements from the ground, the products R refined. depending on the Mfg's needs/specs! most crystals don't contain a shiny crystal, clear glass like crystal. aka Yogies crystal!! so, some products can be a slury. or a molted mixture of ''conglomerate'' elements! and others, could simply add metals or other chems. by using a basic evaporation chamber, in a vacuum of course.. the great thing about all of this? is, there is still plenty of room 2 expand technology! technology is funny? it twists and turns. creeps around. then bam! it snaps in2 & kills U! then U find ''Yogies Crystal", & the pearly gates!! the end!
