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CPWG Line width and spacings - RF Cafe Forums

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


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


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!


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


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

Thanks for your suggestions

Ashish Bondia,
Design Engineer- RF

Posted  11/12/2012
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