I had posted some questions on baluns earlier. Thank you very much for all then information. I should have been more specific. I have done some more reading, and the baluns I'm talking uses lumped components - the Lumped-constant 180 degrees splitter. I found it on the IEEE site in a paper by Tetsuo Hirota and Masahiro Muraguchi. I was wondering how the signals get split by 180 degrees, equations etc.
sthim
Transformers are the easiest way to get 180 splits. But you can't always use a transformer. Generally 180 splitting is only occurring over a range of frequencies with lumped components. At a single freq a single lumped capacitor or inductor can give you 90 degrees of shift between voltage and current. Together you can create 180, but only at one frequency aka a resonance. Expanding the number and spacing resonant frequencies gives a broaden response and range of *nearly*
180 splitting. A perfectly distributed (non-lumped) implementation can give the best implementation because you can create transformer-like circuit without strictly using a transformer as they are familiarly known - the limit is that there is a (low end) cut-off frequency.You'd need to look at the particular paper (most likely it focuses on economizing lumped component counts, which in quantity look distributed, against bandwidth of splitting given a desired error level with (fanatically) not using a wire-wound transformer), or look into filter design techniques, especially all-pass filters and impedance design. Since a balun is about matching impedances, and filters have input and output impedances, then one way to think of impedance matching circuits is as filter design problem. There isn't a simple or single equation for filter design but if you look at filter design you'll find the answer.
MM
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