Please help me infinding a SAW filter with a special dielectric - Page 1
Forum section: electronics / rf-microwave

author: cat87
author_rank: Regular Contributor
timestamp: March 31, 2017, 04:52:17 pm
content: Hi everyone,This may sound a bit weird, and out of context, but bare with me on this.So, I' trying to get a hold of some cheap Lithium Niobate or Lithium Tantalate crystals. Commercially, they are available for something like 200 $ for a 5mm x 5mm wafer.Now, I've dug around and found that some SAW filters used for high bandwidth (4-10 GHz ?) use Lithium niobate as a substrate.If this is truly accurate, or not, I can;t really say.Therefore, I'm trying to track down some of these filters, so if anyone is knolwdgeable in filter substrates, could anyone help me in getting some part numbers, or at lest some SAW filter series or manufacturers?...any clue is helpfulEven tough some of the parts might be obsolete, it may still be of use...It'll give me something to look for on ebay and such.Thanks.

author: LaserSteve
author_rank: Super Contributor
timestamp: March 31, 2017, 08:28:03 pm
content: Have you tried Crystal Technologies in Palo Alto California? They made some of my favorite Acousto Optic products until Siemans bought them for the Lithium Niobate production line.S.

author: cat87
author_rank: Regular Contributor
timestamp: April 02, 2017, 06:51:00 am
content: Thanks for the replies, guys.For my needs, almost any kind of shape would do, as long as it's one of the materials I mentioned. The reason is, I'm not going to use it in an optical set-up. What I want to do is to use the crystal's pyroelectric effect and try to make a small and low power, low voltage X-ray source.Basically, I want to put the crystal in a vacuum, heat it up (say 50- 100 degrees C) and it should generate some high potentials inside the crystal matrix (i.e. x-rays)I'm going to follow you suggestions ans see what pops us.

author: johansen
author_rank: Super Contributor
timestamp: April 02, 2017, 06:59:54 am
content: Quote from: cat87 on April 02, 2017, 06:51:00 ami'll have to check the scrolls but i don't think that's possible.

author: cat87
author_rank: Regular Contributor
timestamp: April 02, 2017, 11:24:18 am
content: Well, I hope I'm not polluting the RF side of the forum with too much non-RF stuff, but since it seems that some very nice comments are coming out of this thread, please allow me to share some info I've come across.Looks like Amptek have a solid state X-ray generator based on the pyroelectric effect:http://amptek.com/products/cool-x-pyroelectric-x-ray-generator/#4Small size, low power. Also, it looks like the base is a Peltier module, so the heating can't be something like several hundred degrees CWhe I first saw this, I thought it was ... not dooable. But the I started reading some scientific papers about these kinds of crystals and the pyroelectric effect, and it realy seems that it is possible.A similar DIY version to what I want to do, can be found here:http://www.intechopen.com/books/scanning-electron-microscopy/palmtop-epmaYou can have a look on the site, or just download the PDF attachedThis is also another very nice article on how to do things DIY:http://www.rapp-instruments.de/index8.htmClick on the "Pyroelektrische Röntgenquelle" and Voila!What got me going on the SAW filters as a source for the crystals was this:http://www.edn.com/design/wireless-networking/4413442/SAW--BAW-and-the-future-of-wirelesstogether with a german site that unfortunately can not find right now that mentions the same source for getting LiNnO3.Indeed, there is a certain geometry required, for maximum efficiency of generated X-rays, but as far as I understood it, any shape should allow me to generate some (small-er) amount of X-rays.So , basically, right now I'm shooting for a proof-of-concept type of deal, that's why I was scavenging on the net for some cheap sources for the crystals.Curious thing is, that like it was mentioned on this thread, a crystal from an ordinary lighter might also work, with much less efficiency, however. So I think I'm going to try this, as a backup solution.Also, I have to mention that I didn't make much sense in my las post, so let's put things in order. The crystal itself isn't responsible for generating the X-rays. The crystal is put in a small vacuum chamber, together with a metal "target". When heated, the crystal will give off electrons, which will strike the taget, which in turn generates the actual X-rays.

author: cat87
author_rank: Regular Contributor
timestamp: April 11, 2017, 08:17:53 am
content: So, I've been looking around for some SAW filters that have a Lithium Niobate or Lithium Tantalate substrate, but unfortunately no manufacturer seems to mention the type of substrate in their data sheet.I've looked at Mini-Circuits datasheets, Qorvo, Synergy and others and they all take a pass on mentioning this kind of stuff. The few mentions I came across say : "Body: Al2O3" which is most likely referring to the external ceramic case than the dielectric type itself.I'll do some more digging around, but it looks like I'm going to have to bite the bullet on this one and order one of those 200 dollar/piece crystals.

author: ThomasDK
author_rank: Regular Contributor
timestamp: April 11, 2017, 05:47:11 pm
content: Will these do?http://www.rf-microwave.com/en/shop/0/409-140-mhz-filters/4488-FW-312291.htmlThomas

author: daqq
author_rank: Super Contributor
timestamp: April 11, 2017, 06:20:19 pm
content: Try Sawcomtech:https://www.google.sk/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=site:sawcomtech.com/+linbo3Or maybe Thorlabs? They have everything obscure...https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=7101#ad-image-0Or good old ali:https://www.alibaba.com/showroom/lithium-niobate.html

author: cat87
author_rank: Regular Contributor
timestamp: April 12, 2017, 07:11:23 am
content: Thanks for the link ThomasDK. That seems to be exactly the thing I was searching for. The price is OK for me. I'm going to order one of these right awayI've looked at some Alibaba sources, and though some sellers also sell a 1-off quantity, i hadn't had the courage to pull the trigger because I've never dealt with Alibaba stuff before. Call me paranoid, but some of the sources there seemed too good a price to be true.