Re: Mircostrip directional coupler???
- From: Fred Bloggs <nospam@xxxxxxxxxx>
- Date: Sun, 29 Apr 2007 21:51:10 GMT
John Larkin wrote:
On Sun, 29 Apr 2007 21:26:34 GMT, "Jeff L" <levy_jeff@xxxxxxxxxxx>
wrote:
I'm looking for information on designing what I believe is a microstrip
directional coupler. I don't want to do stripline, since I would like to
keep this to a 2 layer PCB. Google is not turning up anything overly useful
other then typical stripline / microstrip stuff and GHz stuff.
Basically it is a largish microstrip which carries the RF energy, and it
linearly couples slightly to two smaller microstips, one on each side of the
largish microstrip. The small microstrip outputs are rectified with a diode
and filtered with a cap. The output is given as a DC voltage dependant on
power. One of the small micostrips is used to measure forward power, and the
other is arranged so that the diode is forward biased when the power flows
in the other direction giving the reverse / return power.
Here is a website selling such a device as an expensive adaptor for an RF
connector:
www.pcs-electronics.com/output-board-with-swrpwr-pickup-p-1116.html?osCsid=8
599c60544bc43b72f8135084c1ac540 Note that they call it a stripline when it
is actually a micrpstrip, and I'd love to see the stated 500w or even 1kW
flowing through it continuously.
Application:
Forward and reverse (return / SWR) power indicator.
Hobbyist use low power (fractional watt) ~100 MHz personal FM transmitter.
The material will be standard FR4 with solder mask.
The dielectric constant of the FR4 will not be held to tight tolerance
like some more exotic RF materials.
The purpose is more of an educational one then the actual use.
There are lots of articles, in books and on the web, about microstrip
couplers. But MiniCircuits makes some small, cheap surface-mount
ferrite-transformer directional couplers that might be less hassle.
You can use a single coupler for fwd/rev measurement if you can keep
both ends terminated properly.
John
There is the issue of bandwidth, the fL, fM, and fH ranges for MCL, and then the OP says 1KW thru-power rating which is 1e6mW or 60dBm, seems a bit high for the ones you're talking 'bout.
.
- References:
- Mircostrip directional coupler???
- From: Jeff L
- Re: Mircostrip directional coupler???
- From: John Larkin
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