Thin-film monolithic coupled spiral balun transformer

Claim 1

A balun device comprising: a. an electrically insulating substrate with a surface in the x-y plane, b. a first coil formed on said substrate, said first coil comprising a spiral conductor with said spiral conductor beginning at point d 1 in the x-y plane and having a radius increasing from initial radius r, said spiral conductor having at least 1.5 turns with a spacing S between turns, and said spiral conductor having a width W, c. an interlevel dielectric covering said first coil, d. a second coil formed on said substrate, said second coil comprising a spiral conductor/with said spiral conductor having a radius increasing from initial radius r, said spiral conductor having at least 1.5 turns with a spacing S between turns, and said spiral conductor having a width W, and having essentially the same geometry as said first spiral conductor and beginning at a point d 2 in the x-y plane, where point d 2 lies 180° from point d 1 on a circle with initial radius r, e. a third coil formed on said interlevel dielectric, connected to said first coil and overlying said first coil with a geometry in a mirror image of said first coil as reflected in said x-y plane, and f. a fourth coil formed on said interlevel dielectric, connected to said second coil and overlying said second coil with a geometry in a mirror image of said second coil as reflected in said x-y plane.