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CPWG Line width and spacings - 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.


ashishbondia
Post subject: CPWG Line width and spacings Posted: Tue Jan 06, 2009 9:18 am

Captain


Joined: Wed Aug 16, 2006 8:20 am
Posts: 23
Location: India
Hi
I am using a CPWG topology for one of my board design. I find that line width of 40 mil with 18 mils spacing from adjoining ground on a 20 mil Rogers 4350 substrate gives a 50 ohm impedance. Similarly a 20 mil wide trace with spacing of 5 mils also yields 50 ohm for same 20 mil thick substrate.

To take advantage of the low loss offered by a 40 mil trace I went for this choice. While the components in the RF portion (3 GHz to 7 GHz) of the design were easily routed with this trace width, the components in Base Band section (DC to 250 MHz) had inputs and output which run parallel to each other. This makes using 40 mil wide trace with 20 mil ground spacing difficult. however I can accommodate the 20 mil wide and 5 mil spacing easily.
Has anyone ever used two different CPWG dimensions on the same PCB. Also would it be a good idea to do so. The main IC creating problem is HMC626LP5 from Hittite. It is a VGA with an Attenuator between two amplifiers. the input and output of each amplifier are on same side separated by a single Ground pin.

_________________
Ashish Bondia,
Design Engineer- RF


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IR
Post subject: Posted: Sat Jan 10, 2009 12:30 pm

Site Admin


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

There should be no problem to route the signal lines in the configuration you mentioned as long as it gives 50-ohm impedance. For the control signal you can use 5mil lines as they require no specific impedance.

Good luck!


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ashishbondia
Post subject: Posted: Mon Jan 12, 2009 2:17 am

Captain


Joined: Wed Aug 16, 2006 8:20 am
Posts: 23
Location: India
Hi IR,

Thanks for your suggestions

_________________
Ashish Bondia,
Design Engineer- RF








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