Broadband planar coupled spiral balun

摘要

A coupled transmission line balun construction employs two pairs of planar interleaved spiral coils (3,5&7,9) formed on an electrically insulating or semi-insulating substrate (11) defining a planar structure. One coil in each pair is connected in series to define the input transmission line of the balun, with one end (8) of that transmission line being open circuit. The balun of the Marchand type provides an ultra-wide bandwidth characteristic in the frequencies of interest for MMIC devices, is fabricated using the same techniques employed with fabrication of MMIC devices, and is of a physical size that lends itself to application within MMIC devices.