I'm looking for information on designing what I believe is a microstripdirectional coupler. I don't want to do stripline, since I would like tokeep this to a 2 layer PCB. Google is not turning up anything overly usefulother then typical stripline / microstrip stuff and GHz stuff.Basically it is a largish microstrip which carries the RF energy, and itlinearly couples slightly to two smaller microstips, one on each side of thelargish microstrip. The small microstrip outputs are rectified with a diodeand filtered with a cap. The output is given as a DC voltage dependant onpower. One of the small micostrips is used to measure forward power, and theother is arranged so that the diode is forward biased when the power flowsin the other direction giving the reverse / return power.Here is a website selling such a device as an expensive adaptor for an RFconnector:599c60544bc43b72f8135084c1ac540 Note that they call it a stripline when itis actually a micrpstrip, and I'd love to see the stated 500w or even 1kWflowing 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.

Note that the URL didn't wrap, trying the , it may need to cut and pastedI'm looking for information on designing what I believe is a microstripdirectional coupler. I don't want to do stripline, since I would like tokeep this to a 2 layer PCB. Google is not turning up anything overly usefulother then typical stripline / microstrip stuff and GHz stuff.Basically it is a largish microstrip which carries the RF energy, and itlinearly couples slightly to two smaller microstips, one on each side of thelargish microstrip. The small microstrip outputs are rectified with a diodeand filtered with a cap. The output is given as a DC voltage dependant onpower. One of the small micostrips is used to measure forward power, and theother is arranged so that the diode is forward biased when the power flowsin the other direction giving the reverse / return power. Here is a website selling such a device as an expensive adaptor for an RFconnector:Note that they call it a stripline when it is actually a...

3,75 US$ a pop.AD8312, on the other hand, at 1.09 US$, is in WLCSPThis form factor is a bit less fun to use.SioL

Mircostrip directional coupler???

Apr 29, 2007 22 Replies

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John Larkin 19 years ago

AD8361 comes in a 6-pin SOT-23.

John

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SioL 19 years ago

3,75 US$ a pop.

AD8312, on the other hand, at 1.09 US$, is in WLCSP

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This form factor is a bit less fun to use.

SioL

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Tom Bruhns 19 years ago

Riiigggghhhht. Like I said, there is no need to make it a quarter wave long; it's just that the coupling peaks at 1/4, 3/4, ... all odd quarter waves, and dips to a null at even quarter waves long. You should be able to find info on this online. It's still directional, even though the coupling is less, at 1/25 or 1/50 or 1/100 wavelength long.

Cheers, Tom

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