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Design >> RF Design >> RFIC ground:
https://designers-guide.org/forum/YaBB.pl?num=1192636716

Message started by novice_designer on Oct 17^th, 2007, 8:58am

Title: RFIC ground:
Post by novice_designer on Oct 17^th, 2007, 8:58am

Hello all,
I have a few questions regarding RF IC design, mainly with respect to ground issues.

1. In an IC, not having a dedicated ground plane causes problem to the RF circuits. Is there anyway we can have a IC ground plane? Is there some way we can show that there is an improvement in RF circuit performance when there is such a ground plane. I have recently looked at some papers that talk about this:

"A sub-surface metallizatiob post-process IC module for RF technology" by Kia T.Nag et al. from Delft Univ, Netherlands

The paper only talks about measurement results. But I would like to know if this study can be done in simulations. And if so, what simulators can I use?

Thanks a lot!

Title: Re: RFIC ground:
Post by didac on Oct 22^nd, 2007, 10:10am

Hi,
In MMIC circuits I think that it's usual to provide a ground plane under the substrate. After they implant active devices,passives and interconnections they polish the backside of the substrate to make it thin,then they make vias to from side to side and add a metallization. Foundries like ommic,winfoundry,macom and other provide design kits basically for ADS with layout options for Cadence, so it's possible to simulate this things. If you don't have an GaAs kit or similar I suppose you can pick a GDS of a CMOS LNA made with CADENCE pick it with momentum and define a substrate with a backside metallization and add vias by yourself, so you can compare the behaviour of the same circuit with and without ground plane.
Hope it helps,

Title: Re: RFIC ground:
Post by loose-electron on Nov 2^nd, 2007, 9:57am

simply stated - every connection has impedance (every wire, every bond wire, every metal trace inside a chip) - consequently the simplification of "its at ground" only applies when the impedance is insignificant.

Start working out some of these impedances, and you will start to get a better feel for when you have to pay attention to them, and at what frequencies (or currents) they become an issue.