Advice on Planar EM Filters and EDA and PCB houses that offer bang for the buck? - Page 1
Forum section: electronics / rf-microwave

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: July 22, 2016, 05:48:32 pm
content: Ok so as time goes marching on I am starting really need to learn an EDA package, I would also like to start designing some PCB based filters in some cases sticking a piece of PCB with sma connectors on each end is a lot more practical than a bunch of lump elements. It also seems that more and more I need to use QFN only chips.So I have access to Ansoft/Nexim 2.2 and ADS 2011 for EM design. I dont quite know how to use either of these programs but from what I have read ansoft isn't to hard and a lot of hams use it because they get free copy's at conferences. I have checked out ansoft a little and it doesnt seem to be to bad, I haven't even taken a look at ADS though, would I be correct in saying that ADS is one of those over blown bloated programs that isn;t to easy to learn? Basically I just want to design PCB filters and PCB antennas.So I am thinking I would like to use KiCad for EDA, there are a lot of tutorials out there, and I may even sign up for Chris Gammels class. I know Eagle is the gold star hobbyist and small consultant package but from what I understand it's not very intuitive and I don't really like the idea of designing any OSH with it. So how do planar filters work, do you design them in ansoft/ads and then somehow expot/import that design in to your EDA package, this is where I am really confused!? What is the easiest way to get a PCB based BP filter designed and printed for tonter transfer if it were the only thing on the PCB?Lastly are there any PCB houses out there like OSHPark, SeedStudio, etc for doing more exotic designs and get bang for your your buck on a low quantity. Im talking about different substrates used in higher end/frequency RF pcb's than FR4, with 4 layer capability. Im guessing what im talking about is going to get ridiculously expensive for proto spins but im sure some board houses are cheaper with small quantity. Also if you are only doing 1 or 2 layer design for a filter or antenna can you get teflon, PTFE or whatever substrate copper clad for home etching, just like the FR4 boards at RS?

author: KJDS
author_rank: Super Contributor
timestamp: July 22, 2016, 06:06:09 pm
content: I design all my planar filters in excel, then a little tweaking with whichever planar EM software I have available and it works.It should be reasonably straightforwards for anyone with a decent grounding in filter theory to do the same. If you don't have a decent grounding in filter theory then I'd start improving that rather than worry about software packages.For substrates, Taconics, Arlon and Rogers all do reasonably cheap materials.

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: July 22, 2016, 06:48:40 pm
content: So is ansoft, ADS not something like Elsie? Where you basically feed it the parameters and it spits out a filter, or you give it components and it tells you the frequency? Where would you suggest I start out with the theory. I understand how filters, but the only thing I know about a PCB filter is its most likely substrate capacitance fir the C and the L is the inductance of a line. I dont really understand the width inbetween the traces or anything about where the curvature of the traces should be.I know its probably not possible but it would be nice to just type in a center a bandwidth and filter architecture and it just spit something out that works and I can print on for transfer.

author: KJDS
author_rank: Super Contributor
timestamp: July 22, 2016, 07:51:33 pm
content: Quote from: rwgast_lowlevellogicdesin on July 22, 2016, 06:48:40 pmIt's possible, just pay a few 10s of £1000 to AWR and include their filter suite.

author: tec5c
author_rank: Frequent Contributor
timestamp: July 26, 2016, 02:01:53 pm
content: Quote from: rwgast_lowlevellogicdesin on July 22, 2016, 05:48:32 pmI would say yes. I have used AWR all throughout my degree and having to now use ADS to compare results to AWR is taking quite a bit of getting used to.As mentioned, AWR has an iFilter wizard which I think is what you're looking for.Here's a video from AWR demonstrating the wizardI believe ADS has similar capabilities but I wouldn't even know where to begin with that as I have never used it. Keysight Genesys (formally Eagleware) offers something that more closely resembles what AWR's wizard is like. Where you choose your desired filter type (LPF, HPF, BPF etc) along with the filter shape (Bessel, Chebychev, Elliptic...), punch in your frequencies and it spits out the circuit (lumped, microstrip, etc)The problem is that none of these are cheap options, cheapest would be Genesys but that's still not really in the hobbyist price range.Aside from these major players, there are things like NuHertz Filter Solutions (who offer a free package, though I'm not too sure on how restricted it is. It's called NuHertz FilterFree)