Design of a simple coupled-line microstrip balun?

Hello everyone,

I need to design and fabricate a simple coupled-line microstrip balun, but don't know where to start. The best reference I've found is here: Baluns - Microwave Encyclopedia - Microwaves101.com Are there good references for how to do this? I have HFSS but not ADS, but I think HFSS will work for this job.

One other thing: If I can design the balun to operate at a few hundred watts, that is a huge plus.

A bit of background: What I'm trying to do is characterize an antenna array that has a single balanced input. It should have an impedance of 200 ohms; I need to verify this. The idea is to design, fabricate, and measure the balun, then the antenna with the balun, and remove the effects of the balun in software afterwards to get the response of the antenna.

The balun input and output will be coax so I can test the balun with a VNA. The center conductors of the coax at the balanced end will connect to an antenna via a short piece of metal wire.

Any advice is greatly appreciated!

All the successful broadband baluns I have seen are suspended stripline with defected ground planes. I have been looking for a good microstrip design for years, but never found one!

Fortunately this balun doesn't need to be broadband. I only need about 5% bandwidth, max. 2% will probably suffice. Broader bandwidth is good, but not a necessity for this application.

There is a thing called a Marchand balun that probably will get you 5%