wideband directional coupler
frequency bandwidth : 100KHz ~ 3GHz, 100KHz ~ 6GHz
coupling value : 3, 10, 20dB
directivity : min 20dB
Is it possible?
Please, help me.
It's really wideband.
"RF and Microwave Coupled-line Circuits" by Rajesh Mongia might triger some idea.
"Nonuniform Line Microstrip Directional Couplers and Filters" by Sener Uysal may also help.
Personally I think the 100KHz to 6GHz is almost impossible.
Soon
Look into using diplexers to combine two or more couplers each for a different frequency range. The diplexers are on all four external ports of the combined coupler.
I have opened once the directional bridge from our HP8753 network analyzer, frequency range from 300 KHz to 3 GHz.
It is very complicated and seems that the tuning is hand made .
If you need a picture I will open it again.
If you need a coupler with coupled lines the best is the old HP 778 D ( 100 MHz to 2 GHz ).
Going to a lower frequency the phisical dimension of the coupler is becoming larger and so the losses.
Better is something like a bridge, but the attenuation is fixed.
Mandi
If you do not mind the coupling to change with frequency, ordinary parallel transmission line ones have a coupling coefficient which is proportional to the sine of the line length at the frequency you are using.
Hi FANT,
I'd appreciate if you could post (perhaps PM, not to overload the list) a few photographs from different angles on the directional bridge of the 8753 VNA.
One can always learn a lot, knowing how HP realize things that are difficult to do.
Thanks in advance
g579
Hi, FANT
Thank you for your reply.
I want to see the pictures.
If you show the pictures, possible, please show me.
Thank you.
The instrumantal directional couplers are easy in the schematic topology but difficult to replicate and require very accurate mechanics and very good operative skilness.
If not... why only few high cost companies like Agilent, Rhode-Schwarz sell it?
Taken the pictures today; tomorrow or saturday afternoon I will post them.
Due to the fact the pictures are quite large ( about 1,3 M each ) can anybody explain me how to post more pictures in a post ?
Mandi
If you compress them as .rar or .zip you can put four per post.
Are the wideband components designed with very different theories?
Here the pictures; sorry but my winrar program won't compresso, so only Winzip.
If necessary anything else just ask.
Mandi
Hi FANT,
Thanks for the photos. I'll try to understand how this directional bridge details work.
I'll ask perhaps 2 or 3 more photos on some details.
Thanks anyway. As usual I always learns from HP.
g579
I hope this application note guide to understand how this directional bridge details work. The extra broadband ballun realization is the preferred section in the bridge.
I hope this application note guide to understand how this directional bridge details work. The extra broadband ballun realization is the preferred section in the bridge.
Here's another intersting article on directional bridges. Probably similar to 8753 coupler.
Hi,All
Thanks very much for your sharing of the photo and the app notes
i have a question , how can i make a directional coupler wideband?
Added after 3 minutes:
i meant tell me the method for making a wideband directional coupler.
Woahh the pictures of the internal bridge in the 85044A are really impressives. Thank's for sharing