Homepage - RF Cafe
Webmaster: Kirt Blattenberger | KB3UON | Sitemap | ©1996-2014     Visit RF Cafe on
      Menu below is just a small sample of what is here!          Visit RF Cafe on Facebook Visit RF Cafe on Twitter Visit RF Cafe on LinkedIn
Custom Search
More than 10,000 searchable pages indexed.
•−•  ••−•    −•−•  •−  ••−•  •
RF Cafe Morse Code >Hear It<

Ground Planes? - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.


RFGuest
Post subject: Ground Planes? Posted: Mon Jan 23, 2006 5:15 pm
Hi all! I was reading about ground planes and it seems like the majority of the advice points to a design where two ground planes are created for analog and digital signals and only connect them at one point near the power supply. But I was reading some more articles and noticed, this:

"A number of different ground plane strategies can be adopted for a radio product PCB. There is no unique answer to the best strategy for a given type of product. Some people are great advocates of split ground planes for analogue, digital, radio or audio circuits. Experience on a number of radio products at Plextek has shown that a single low impedance ground plane for all parts of the circuit is usually a good starting point. Often attempts to split the ground planes causes more problems than it solves. Careful consideration of the flow of currents throughout the product is essential to minimise digital interference with audio and radio circuits. Given the proliferation in the use of DSP and microprocessors in radio products this is a very significant issue."

Can anyone comment from experience? Thanks!


Top

Guest
Post subject: Ground planesPosted: Tue Jan 24, 2006 3:30 pm
The major issue is how much non-DC current flows in the ground region.

I've had good results both ways, but there are a couple of non-obvious (to most people) things to watch out for:

1. Ground loops. If using separate ground planes, proper ("star") grounding becomes more significant. Ground loops can be hard to avoid anyway, but can be critical for small-signal applications requiring low noise pickup.

2. Proper bypassing. This reduces the difference between the two configurations. There need to be both small, high-self-resonant-frequency capacitors at the point of power use, the power plane/ground plane capacitance, and a bulk capacitor as well. There's a lot of material about this on the web - unfortunately, not all of it is correct. Watch out for unwanted resonances.

Basically, keep an eye on where the current is flowing.

Good Luck!


Top

IR
Post subject: Posted: Wed Jan 25, 2006 3:05 pm

Site Admin


Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
Hello guest,

The issue that you raised is a very acute one. I had the same concerns on my last PCB layout, which was for a large Mixed-Signal board with close to 2000 components and included high-speed Digital sections and RF sections up to 400MHz. What I did is using separate ground planes for the Analogue/RF sections and digital sections and added optional resistors at the schematic to connect between these planes. I connected via holes from the different GND planes to the top layer and making an option for connection between the planes through these resistors if neccessary.

Eventually I connected between the planes through the resistors. Indeed, there is no one-way solution to this issue as the 2nd guest mentioned in his reply. Therefore, you should make an option in your layout to cover both options.

Good luck!

_________________
Best regards,

- IR


Top

RFGuest
Post subject: Posted: Wed Jan 25, 2006 5:37 pm
Thanks for the info!

I've seen that term star grounding before. Is that similar to starpoint ground? If so, can someone kindly explain this? I am not familiar. Thanks!


Top

IR
Post subject: Posted: Wed Jan 25, 2006 5:57 pm

Site Admin


Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
Hello RFGUest,

Here is a link for you with relevant information:

http://www.aikenamps.com/StarGround.html

Additional information can be found by Google!

_________________
Best regards,

- IR


Top

itsfrigid
Post subject: Posted: Sat Apr 01, 2006 5:13 pm

Lieutenant

Joined: Thu Mar 23, 2006 4:18 am
Posts: 2
you might wanna have a look at the high speed PCB layout seminar by analog devices -

http://www.analog.com/en/content/0%2C28 ... %2C00.html

scroll down for this seminar.



Posted  11/12/2012
A Disruptive Web Presence

Custom Search
Over 10,000 pages indexed! (none duped or pirated)

Read About RF Cafe
Webmaster: Kirt Blattenberger
    KB3UON

RF Cafe Software

RF Cascade Workbook
RF Cascade Workbook is a very extensive system cascaded component Excel workbook that includes the standard Gain, NF, IP2, IP3, Psat calculations, input & output VSWR, noise BW, min/max tolerance, DC power cauculations, graphing of all RF parameters, and has a graphical block diagram tool. An extensive User's Guide is also included. - Only $35.
RF system analysis including
frequency conversion & filters

RF & EE Symbols Word
RF Stencils for Visio

Product & Service Directory
Personally Selected Manufacturers
RF Cafe T-Shirts & Mugs

RF Cafe Software

Calculator Workbook
RF Workbench
Smith Chart™ for Visio
Smith Chart™ for Excel
Your RF Cafe Progenitor & Webmaster
Click here to read about RF CafeKirt Blattenberger... single-handedly redefining what an
                                 engineering website should be.

View the YouTube RF Cafe Intro Video Carpe Diem! (Seize the Day!)

5CCG (5th MOB): My USAF radar shop

Airplanes and Rockets: My personal hobby website

Equine Kingdom: My daughter Sally's horse riding website