Balun: Difference between revisions

To operate at even higher frequencies, magnetic loading becomes ineffective. Nathan Marchand proposed a 'conversion transformer' that was capable of operation over a 1:3 bandwidth ratio in 1944.<ref>{{Cite journal |last=Marchand |first=Nathan |date=December 1944 |title=Transmission-Line Conversion |url=https://www.worldradiohistory.com/Archive-Electronics/40s/Electronics-1944-12.pdf |journal=Electronics |pages=142-145}}</ref> This basic circuit has been widely adapted and modified for use in planar structures (such as MMICs and RFICs) at frequencies up to at least 100 GHz.<ref>{{Cite journal |last=Weerathunge |first=Nethini |last2=Chakraborty |first2=Sudipta |date=2023-07-23 |title=A W-Band Marchand Balun in 0.1 μm GaAs pHEMT Process |url=https://ieeexplore.ieee.org/document/10289414/ |publisher=IEEE |pages=75–76 |doi=10.23919/USNC-URSI54200.2023.10289414 |isbn=979-8-3503-7020-1 |journal=EEE Xplore}}</ref>

These types of planar baluns work exciting a mode in a ground plane or shield, which is then 'floated' away from the main ground. This allows extraction of the negative signal in addition to the main transmission line, creating positive and negative signal pairs. By connecting the positive and negative signal paths in various configurations dozens of balun configurations have been proposed and published in the electronics literature.