[time-nuts] Galvanic decoupling of GPS antenna

[Bob Camp]

Hi

The DC isolation part should be pretty simple. There are off the shelf RF
transformers that are rated for the frequencies you are looking at. Weather
they are rated for 250 volts or not I don't know. MA-Com is one source:

http://www.macomtech.com/Transformers?partNum=&searchType=Contains&filter=20
%7C343&page=1&pageSize=20&sortType=PartNumber&sortFieldID=0&sortOrder=asc&ca
tID=25

Alternately winding your own is pretty easy, there's not much to them.

Bob 

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Yuri Ostry
Sent: Wednesday, June 16, 2010 5:10 PM
To: time-nuts at febo.com
Subject: [time-nuts] Galvanic decoupling of GPS antenna

Hello,

I'm trying to put gps (for a coarse timing sync and RTC
auto-setting) to a small controller that must be completely
galvanically decoupled from outside world. Antenna power must be
supplied from separate power source (ground potential of isolated part
of circuit can slowly float up to +/- 250 volts referenced to ground
of antenna power supply).

First thinked about using some choke to inject power, then DC-blocking
capacitor around 20-30 pf and then smt 1:1 wideband transformer, but
looks like Mini-Circuits don't make standard models for frequencies
over 1200 MHz, their search engine give me some part numbers that looks
like special order ones, and cannot be found in their catalog.

Is there any chances to get decent performance if I'll simply split
stripline (both ground and signal traces) by dc-blocking caps? Idea
looks not very good to me, of course, I suspect that i'll get all
sorts of interference right to GPS LNA input...

Maybe there is some well proven solution with easily obtainable parts?

-- 
Sincerely,
 Yuri                          mailto:yuri at ostry.ru



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