Abstract:
A new technique to implement wideband 90° hybrid coupling profiles
on non-optimal substrate configurations is presented. The technique
uses an impedance taper over the whole length of the hybrid to remove
the restriction of a substrate defined maximum coupling coefficient at
crossover, thus resulting in much more flexibility for the implementation
of hybrids on integrated printed circuit boards. The choice of board
thicknesses and material type no longer needs to be dominated by the
hybrid, but can be optimized for other components or priorities. The
flexibility provided by the technique is shown in the implementation of
a 2–18 GHz hybrid on a large range of substrate thicknesses as well
as on a non-optimal substrate material, for which acceptable measured
performance is still obtained.
