Designing PCB's at GHz

eeka chu · 28th January 2007, 10:18 PM

I got bored and went googling when I found some pictures of PCBs designed for GHz signals.

I knew before I saw the pictures roughly the amount of voodoo design effort it takes to produce these, but some of the boards looked literally as if they'd been pulled from a UFO. The traces had crop circle and aztec writing style elements to them. 'Random' traces start and stop and seem to connect to nothing, or curve around and come to a dead end, or fan out in a cone shape with nothing on them.

Does anyone know any good books that cover what the superstar jive powered funk is going on with these things? They're just unbelievable.

pinkmouse · 28th January 2007, 10:33 PM

I was recommended this one, but I didn't have the money to purchase at the time.

I_Forgot · 28th January 2007, 10:47 PM

All those shapes are about controlling impedances. If you put a short at the end of a 1/4 wavelength stub, the other end of the stub looks like infinite Z, for example.

Those boards are usually some expensive materials- ordinary G7 isn't manufactured under tight enough tolerances to get controlled impedance lines. Teflon and other high dielectric constant materials are used to keep tolerances tight and line widths narrow, and to minimize thickness of the substrate (this minimizes ground inductance).

I have a couple books in boxes somewhere from back when I used to design RFICs... let me see if I can find them and get the titles..

I_F

BWRX · 28th January 2007, 10:52 PM

Lots of good reading on the web. Search for microwave or high frequency amplifier design.

http://web.syr.edu/~nkkunder/Nisha%20Projects/LNA.pdf

http://scholar.lib.vt.edu/theses/ava...cted/chap3.PDF

http://home.sandiego.edu/~ekim/e194rfs01/rfamp.pdf

28th January 2007, 10:18 PM	#1
eeka chu diyAudio Member Join Date: Nov 2003 Location: England	Designing PCB's at GHz I got bored and went googling when I found some pictures of PCBs designed for GHz signals. I knew before I saw the pictures roughly the amount of voodoo design effort it takes to produce these, but some of the boards looked literally as if they'd been pulled from a UFO. The traces had crop circle and aztec writing style elements to them. 'Random' traces start and stop and seem to connect to nothing, or curve around and come to a dead end, or fan out in a cone shape with nothing on them. Does anyone know any good books that cover what the superstar jive powered funk is going on with these things? They're just unbelievable.

28th January 2007, 10:33 PM	#2
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	I was recommended this one, but I didn't have the money to purchase at the time. __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

28th January 2007, 10:52 PM	#4
BWRX diyAudio Moderator Emeritus Join Date: Jan 2005 Location: Pennsylvania	Lots of good reading on the web. Search for microwave or high frequency amplifier design. http://web.syr.edu/~nkkunder/Nisha%20Projects/LNA.pdf http://scholar.lib.vt.edu/theses/ava...cted/chap3.PDF http://home.sandiego.edu/~ekim/e194rfs01/rfamp.pdf __________________ Brian

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28th January 2007, 10:47 PM	#3
I_Forgot diyAudio Member Join Date: Jan 2005 Location: Phoenix, Az.	All those shapes are about controlling impedances. If you put a short at the end of a 1/4 wavelength stub, the other end of the stub looks like infinite Z, for example. Those boards are usually some expensive materials- ordinary G7 isn't manufactured under tight enough tolerances to get controlled impedance lines. Teflon and other high dielectric constant materials are used to keep tolerances tight and line widths narrow, and to minimize thickness of the substrate (this minimizes ground inductance). I have a couple books in boxes somewhere from back when I used to design RFICs... let me see if I can find them and get the titles.. I_F

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