Best CAD to build an RF board with? - Page 1
Forum section: electronics / rf-microwave

author: nth_degree
author_rank: Regular Contributor
timestamp: February 17, 2023, 09:17:10 pm
content: What CAD is best for RF work? I want to build a SDR PCB

author: Bud
author_rank: Super Contributor
timestamp: February 18, 2023, 07:43:52 am
content: PCB layout programs are generic software, you use one for any purpose. What features are you looking for?

author: nctnico
author_rank: Super Contributor
timestamp: February 18, 2023, 10:18:50 am
content: Quote from: Bud on February 18, 2023, 07:43:52 amNot at all! Remember that in RF designs, PCB traces often are components. Having support for creating free-form traces or components with pads that can have all kinds of weird shapes can be super helpfull. On top of that, being able to simulate the board in order to check impedances is a big plus.One step further is integrating the RF design flow with the board layout:https://resources.pcb.cadence.com/orcad-datasheets/allegro-pcb-rf-4I have not used this myself but if I need to get really serious with RF layouts, I'd give this a look.

author: tggzzz
author_rank: Super Contributor
timestamp: February 18, 2023, 10:46:31 am
content: Quote from: Bud on February 18, 2023, 07:43:52 amCAD is more than PCB layout, especially at RF.Here are some examples of RF filters. It is challenging to represent the individual components on a schematic!Typically RF CAD will enable design and analysis of such structures, often involving modelling the electromagnetic waves.

author: djsb
author_rank: Super Contributor
timestamp: February 18, 2023, 11:01:17 am
content: tggzzz,Don't keep us in suspense. Which CAD software was used in the picture you posted? Thanks.

author: tggzzz
author_rank: Super Contributor
timestamp: February 18, 2023, 11:17:23 am
content: Quote from: djsb on February 18, 2023, 11:01:17 amNo idea! They are random pictures I googledHowever, googling will reveal several candidates, some free, some requiring one or more limbs.

author: yl3akb
author_rank: Regular Contributor
timestamp: February 18, 2023, 11:29:18 am
content: Quote from: nth_degree on February 17, 2023, 09:17:10 pmI dont beleive You need microstrip EM simulator to design SDR PCB... Instead research the info on general RF layout tecniques, grounding, return paths, clearances, study components manufacturers datasheets for example layouts etc. and use Kicad or other general puprose layout tool.

author: tggzzz
author_rank: Super Contributor
timestamp: February 18, 2023, 11:42:00 am
content: Quote from: yl3akb on February 18, 2023, 11:29:18 amAgreed, with the caveat of not knowing the frequencies involved.My first comment was simply a reaction to the concept that there is nothing a standard PCB layout tool can't do at RF.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: February 18, 2023, 07:21:47 pm
content: We actually use 2 or 3 pieces of software to do this.We design the most complex structures in 3D in HFSS. Simulating 2D structures with transmissionlines is mostly in Keysight ADS/Momentum. We then turn the shapes spit out by these two tools into a GDS, Gerber, or similar file, and import them into a tool like Allegro or Altium.Then, when you are one with the entire design, you export that back into ADS or HFSS (in that case usually HFSS3D Layout) and verify the design for manufacturing.Advantage of HFSS and ADS is that you can parametrize or even script these structures, and iterate the design with EM simulation/run optimizers and so on. So you can for example define the width and length of a patch antenna, and then optimize the design for these variables.

author: Bud
author_rank: Super Contributor
timestamp: February 18, 2023, 07:47:19 pm
content: You guys are talking about very specialized packages that cost tens and hundred thousand dollars. No way OP can afford that and it makes no sense to recommend them to OP.

author: tggzzz
author_rank: Super Contributor
timestamp: February 18, 2023, 08:39:10 pm
content: Quote from: Bud on February 18, 2023, 07:47:19 pmIt is useful in that it answers the OP's question. Whether the answer helps or is relevant is a separate issue, of course.

author: nctnico
author_rank: Super Contributor
timestamp: February 18, 2023, 08:53:22 pm
content: Quote from: Bud on February 18, 2023, 07:47:19 pmHow can you be sure about what the OP is able to afford? There is no mention of any budgetary restrictions. Besides that, it often helps to know what is out there so you can enquire about pricing and decide what makes sense. It is also possible to hire consultants that have access to expensive packages. Last thing I would want is someone else to decide for me what I can afford or not. Maybe the OP is doing a 40GHz SDR design???

author: ejeffrey
author_rank: Super Contributor
timestamp: February 20, 2023, 12:03:32 am
content: Also: many of those tools are available for free or at substantial discount to universities. If you understand the workflow of the professional tools you can also do many of the same things with free tools, but without the workflow automation and design assistant tools. You can trade hours for dollars very effectively in this space.

author: tszaboo
author_rank: Super Contributor
timestamp: February 20, 2023, 09:00:09 am
content: The best CAD tool to do occasional RF design is the one you already know. Unless it's eagle.Otherwise PathWave from Keysight or Cadence tools are probably better, if you can afford it.

author: coppercone2
author_rank: Super Contributor
timestamp: February 20, 2023, 02:12:07 pm
content: the first thing you need is a spec of what you want to build

author: ejeffrey
author_rank: Super Contributor
timestamp: February 21, 2023, 04:51:24 am
content: For things like PCB RF filter design, I also know some people who just use AutoCAD (or something free like qcad). They design the filter using whatever circuit and EM simulators they want, then just draw the polygons with a standard 2D CAD tool. It turns out that a program whose only purpose in life is to draw the polygons you ask for is often better than something that tries to optimize for PCB design where you often end up working against it "helping" you route tracks. This works great if you want to do something like a connectorized filter, and adding a few simple part footprints isn't too onerous, but it will get bad quickly if you want to make a complex PCB with a lot of ICs and also some PCB integrated filters.All that said, for a basic SDR operating up to ~4 GHz you likely won't be doing any of that. The RF signal path is probably pretty simple, PCB trace circuit elements are big, and cheap pooled PCBs aren't really good enough to do fancy stuff anyway. You probably just need 50 ohm traces. For this, pretty much any PCB CAD tool you are familiar with is fine. Use an online PCB trace impedance calculator to find the geometry you need for your preferred stackup, and optionally configure design rules for your RF lines so that they are checked to be the right geometry. Or just check by hand if the number of RF traces is small.

author: Overspeed
author_rank: Frequent Contributor
timestamp: February 21, 2023, 11:25:27 am
content: HelloI use ProgeCAD ( an Autocad clone ) and a soft to convert DXF in Gerber , that works perfectly with one layer Acad for one Gerber file .That allow to adjust / tune every line of the PCBRegardsOS

author: scopeman
author_rank: Frequent Contributor
timestamp: March 03, 2023, 01:35:37 am
content: I use a manual layout software that will allow you to make traces with square ends where needed. When doing things like filters and microstrips and things like that youhave to do your own calculations. Personally I use SprintLayout 6.0 from Abacom. It's easy to learn and use and has many useful features and is very inexpensive.It costs about the same as dinner for 5 at McDonald's. Permanent license, no dongles or strange installation and is not a web based program. I have had excellent results with it and is the most bug free PCB CAD software I have ever used and I have used dozens of packages in my career. I have no financial affiliation with the company I just have been very impressed with their products. Quite a bang for the buck.You can download a free full featured version to try out that does everything but save.https://www.electronic-software-shop.com/lng/en/electronic-software/sprint-layout-60.html?language=enSamW3OHM

author: hanakp
author_rank: Regular Contributor
timestamp: March 05, 2023, 05:03:31 pm
content: Quote from: tszaboo on February 20, 2023, 09:00:09 amActually, even old Eagle 5.x could do it just fine. In my workplace, we've designed RF circuits with Serenade Desktop (later Ansoft Designer) and exported them as Gerber or DXF. Then we used a 3rd party utility that could convert them as polygons into Eagle. In Autodesk-era Eagle, it's even simpler because it has built-in DXF import and there are free scripts (ULP) that can import several other vector formats. Of course, it's nowhere as streamlined and foolproof as with professional CAD packages, but it can be done relatively painlessly.

author: LukeW
author_rank: Frequent Contributor
timestamp: March 06, 2023, 02:53:38 pm
content: Quote from: nth_degree on February 17, 2023, 09:17:10 pmWell, have youdesignedthe SDR first?Will your design have any particularly complex layout-defined parts, like distributed element filters?What frequency are you operating at?Are tools like Ansys HFSS, Comsol, Cadence stuff going to be financially realistic for you?Does your design have any distributed components? Or just stuff like some 50 ohm CPWG lines?You could try free software like Qucs.But I have a gut feeling that youdon't actually needelectrodynamics FEM / simulation software for your application.

author: W2DML
author_rank: Contributor
timestamp: March 08, 2023, 02:20:54 pm
content: If you're trying simulate the effects of each trace, etc. a proper sim like AWR Microwave Office is good. You can define your substrate and run microstrip lines of the dimensions you like. It features loads of models to simulate real components on a PCB and even do EM sims if you like. During my Master's this was the preferred software of all my professors.If you're just trying to lay out a board, any PCB CAD software will work. At my current job I've been using KICAD to do my RF boards, it's not as simple as MWO, but it gets the job done. I just use a rectangle to properly set the dimensions, then fill it by drawing a polygon fill area over it. In the attached board I needed gaps, so I created a gap schematic symbol and basic 3mm gap footprint. Also KICAD is supported by CERN which do loads of RF with their particle accelerators.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: March 09, 2023, 08:37:43 am
content: Quote from: W2DML on March 08, 2023, 02:20:54 pmThis statement always bothers me a bit. Just because CERN is in part behind KICAD does not mean they actually use KICAD for all of their design. From what I'm told, quite the opposite.This is just like Analog Devices owning/developing LTSpice does not mean those people actually use it to design the chips.

author: nctnico
author_rank: Super Contributor
timestamp: March 09, 2023, 03:57:08 pm
content: Quote from: TheUnnamedNewbie on March 09, 2023, 08:37:43 amAgreed. Given the size of CERN, they are likely to use a wide range of electronics CAD packages.

author: Chat GPT
author_rank: Contributor
timestamp: March 10, 2023, 10:33:45 am
content: When it comes to RF design and PCB layout, there are several CAD tools that are commonly used:Altium Designer - This is a popular choice among professional RF designers due to its comprehensive set of tools and features specifically tailored to RF design.Eagle PCB - While Eagle PCB is primarily a general-purpose PCB design tool, it has some useful RF-specific features that make it a popular choice for hobbyists and smaller projects.KiCAD - KiCAD is a free, open-source CAD tool that has been gaining popularity in recent years. It offers a range of features and capabilities that make it a viable option for RF design and layout.ADS (Advanced Design System) - This is a high-end CAD tool specifically designed for RF and microwave design. It offers advanced simulation capabilities, including electromagnetic field simulation, making it a powerful tool for designing SDR circuits.Ultimately, the best CAD tool for your SDR project will depend on your specific needs and budget. If you are a hobbyist or small-scale designer, Eagle PCB or KiCAD may be sufficient. If you are a professional RF designer with a larger budget, Altium Designer or ADS may be more suitable.

author: n4u
author_rank: Contributor
timestamp: March 27, 2023, 10:34:34 am
content: You may use AWR / CST for design or rf planar circuits + mentor expedition for higt speed digital (u dont have to manually calculate impedance for nets etc, they have sim for digital too). Good luck with money collection

author: DenzilPenberthy
author_rank: Frequent Contributor
timestamp: March 27, 2023, 11:56:41 am
content: All of the projects I've worked on there have used either Cadence tools - e.g. DE HDL and Allegro or Altium.As to OP's question - it depends entirely on the scope of your project and your budget.This very capable SDR is on a very basic PCB with no fancy RF stuff.http://websdr.ewi.utwente.nl:8901/Quote from: nctnico on March 09, 2023, 03:57:08 pm

author: stephen_g
author_rank: Newbie
timestamp: March 28, 2023, 03:50:21 am
content: We use Altium. An SDR board shouldn't be super difficult to design though, so you should be able to get away with Kicad or something if you don't have access to Altium.As long as you don't need complex microstrip filters or anything (and you shouldn't - just use Mini-circuits ones if you can because they're well designed and work to spec), it's just a matter of getting your trace impedance right and watching out for parasitics etc. (we try to get our stackup so an 0402 cap or resistor's pads are about the same width of a 50 ohm trace, so we don't have to worry as much. For boards with more layers you can do the same but with 0201 parts).It's when you start having microstrip filters and matching networks and stuff that you do start to need a simulator like ADS, and that's when things get expensive. Once its simulated though we bring the geometry into Altium.