Balun

Could anybody help with understanding baluns? So far I know they
transform unbalanced input to balanced output and vice-versa. Say I
have a receiver coil - one that looks like a loop and the ends are
connected to a balun. The voltages on the ends are of the same
magnitude but are 180 degrees out of phase. How do these two voltages
get combined at the output? Or does this not happen? Please let me
know...

sthim

 

transformer

 

From a technologist viewpoint, alot of baluns are also based upon 1:1
transformations (in differing configurations.) It seems like 1:1 transformers
tend to have wider bandwidth than direct 4:1 (impedance) transformers.

So, using a 4:1 balun configuration with a natural 1:1 impedance transformer
as a constituent, it seems to tend to perform better than a 4:1 (impedance) or
2:1 (voltage) transformer.

John

 

I have a PDF on this. Just email me and I will send it.

--

Regards,

Boris Mohar

Got Knock? - see:
Viatrack Printed Circuit Designs http://www3.sympatico.ca/borism/
Aurora, Ontario

 

There is always the Guanella 4:1 balun to consider that has a theoretically
infinite cut off frequency.

 

The best reading I have found on these mystical items is by Jerry Sevick.
There are a few papers by him, unfortunately they are IEEE and therefore
cost an arm and a leg and a good book "Transmission Line Transformers"
published by Noble. It's a bit hard to get but worth the effort.

 

I understand that... Before I 'studied' the subject, I was also confused
(like the original poster) about the real difference between a 'transformer'
and a special configuration called a 'balun.' When I was a kid, and didn't
realize the almost subtile differences, I almost thought that the term
was gratuitious (however incorrectly.) The whole area of transmission line
transformers, traditional transformers and various configurations can be
quite interesting and enlightening !!! .

John

 

There is also a directional coupler that can be formed from two cleverly connected
conventional transformers as shown in US Patent 3,426,298 Figure 10.