Help me identify this system - Page 1
Forum section: electronics / projects

author: alexwhittemore
author_rank: Frequent Contributor
timestamp: July 21, 2014, 09:37:35 pm
content: I came across this gorgeous distributed element filter yesterday, but nobody knows exactly what it came out of. My take is that it's probably something along the lines of a radar or a millimeter wave scanner, given that it looks like there's a transmit and receive antenna in each of the cavities, but maybe that's unrelated - both transmit or both receive, but 90* polarization to each other. Maybe the latter makes more sense- all the paths look quite similar, but then I don't know enough about RF that I could likely tell a transmit side from a receive unless Tx was coming straight out of a marked RF power amp IC. Someone DID tell me that given the particular junk drawer it came out of, it's more likely to be civilian than military.Anyway, does anyone with more RF experience than myself know with any confidence what this is actually from? The filters are just gorgeous. The two ICs on the bottom are marked (I think) IX2458/315A and 78F9116A/0447L811EDIT: it looks like the second marked part I listed (78F9116A, closest to the left of the board in the first couple shots) is a generic NEC microcontroller.http://www.datasheet-pdf.com/datasheet/NEC/554121/78F9116A.pdf.html

author: mikerj
author_rank: Super Contributor
timestamp: July 21, 2014, 10:17:17 pm
content: Looks like a dual LNB (low noise block) to me.

author: alexwhittemore
author_rank: Frequent Contributor
timestamp: July 21, 2014, 10:23:54 pm
content: Any idea what the deal is with the paths terminating on one end in the cavities and on the other near those (ceramic?)... studs?

author: mikerj
author_rank: Super Contributor
timestamp: July 21, 2014, 10:44:46 pm
content: The circular holes are where the feedhorns would be placed, i.e. the part that is mounted at the focal point of the dish. The ceramic pucks are possibly dielectric resonators used for bandpass/bandstop filters at microwave frequencies.I'm not exactly an expert on distributed element microwave filters though, it's far too close to witchcraft for my tiny brainWe have an engineer at work who designs this kind of stuff and he has god-like powers IMOEDIT: Here are a couple of similar PCBAs from LNBs which have the same features:http://www.dbstalk.com/uploads/monthly_06_2013/post-417451-0-41266000-1372386294.jpghttp://www.satellites.co.uk/forums/attachments/lnb-1b-jpg.65399/

author: Stonent
author_rank: Super Contributor
timestamp: July 21, 2014, 11:32:10 pm
content: Makes me wonder if they used the guy that designed some of the roads in Dallas.

author: alexwhittemore
author_rank: Frequent Contributor
timestamp: July 21, 2014, 11:45:52 pm
content: @mike: Nice! Thanks!@stonent: JEET SWEESUS!

author: Stonent
author_rank: Super Contributor
timestamp: July 22, 2014, 02:20:57 am
content: And they wonder why so many Texans own guns...

author: Jebnor
author_rank: Regular Contributor
timestamp: July 22, 2014, 02:32:32 am
content: I'm in awe of the serious RF voodoo displayed. Very nice.

author: Hugoneus
author_rank: Frequent Contributor
timestamp: July 22, 2014, 03:01:30 am
content: Scale that down by about a factor of 50 to 100 and I make these in Silicon...

author: alexwhittemore
author_rank: Frequent Contributor
timestamp: July 22, 2014, 03:29:01 am
content: I don't suppose you can show off any layout, but got any microscopy you can share?

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: July 22, 2014, 05:35:02 am
content: I don't suppose anybody could photoshop some (useful) comments onto one of the images.I haven't much idea on how this would work, and or what are the critical parts and what the schematic would look like.

author: amyk
author_rank: Super Contributor
timestamp: July 22, 2014, 06:09:10 am
content: Serious voodoo indeed... I could almost imagine some civilization in the future, to which this technology has been lost, discovering these andthinking they were for some other purpose.

author: lapm
author_rank: Frequent Contributor
timestamp: July 22, 2014, 06:49:50 am
content: Now thats just beatiful design..

author: wiss
author_rank: Frequent Contributor
timestamp: July 22, 2014, 08:45:20 am
content: Quote from: Stonent on July 21, 2014, 11:32:10 pmOakland, California plus photoshop...https://maps.google.com/maps?q=Oakland,+California&hl=sv&ll=37.82487,-122.267189&spn=0.012797,0.02135&sll=32.923042,-97.032623&sspn=0.054395,0.085402&t=k&hnear=Oakland,+Alameda+County,+Kalifornien&z=16

author: miguelvp
author_rank: Super Contributor
timestamp: July 22, 2014, 08:55:43 am
content: Not that but still not Dallas TX, I lived there until 2009 and even if they do have a lot of construction I don't think it would have gotten that much out of hand.183? 635? Not sure what that's supposed to be.Maybe Stonent can give us a couple of intersecting highways like say 635 and 75.

author: wiss
author_rank: Frequent Contributor
timestamp: July 22, 2014, 10:06:32 am
content: Quote from: miguelvp on July 22, 2014, 08:55:43 amNot Oakland you mean? Compare the buildings around the intersection.Quote

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 22, 2014, 11:32:30 am
content: Quote from: wiss on July 22, 2014, 10:06:32 amHe's correct:

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: July 22, 2014, 12:12:31 pm
content: If that was for me, I was kinda hoping for similar on the pcb images.

author: VK5RC
author_rank: Unknown
timestamp: July 22, 2014, 12:49:40 pm
content: I am a bit interested in Amateur microwave stuff and have gear that will tx to 10GHz, it is a rather unusual design, I don't quite get why two sides and apparently two different "feeds" into the 'holes'. These may be direct injector probes into round waveguide clamped onto the board. Perhaps the 'holes' feed into left and right hand circularly polarised antenna structures, so each polarity has a Tx and Rx chain?? Huge guess!The interdigital filters, it is difficult to get the scale, below is a photo of a 10GHz multiplier (put in a freq around 1.2GHz , amplify it with MMICs to distortion then filter the harmonic you want (10.368GHz) and amplify it again). The local Ham Vk3XDK has produced this board and a ruler in mm is at the edge of an unpopulated board. Remember at very high frequency a straight trace has both capacitance and inductance so is a tuned circuit. The high level computer guys have the same problems even worse cause I only have to worry about one channel at a time!