Ultra broadband planar via-less crossover with high isolation

A via-less crossover for use in broadband microwave/mm-wave circuitry, comprising:

• a dielectric substrate;
• a top layer disposed on one side of the substrate and including a top microstrip line with an input and an output and a co-planar waveguide (CPW) central line of reduced width, two tapered sections which are placed around the top microstrip line such that a tapered section is disposed adjacent to and along each side of the CPW central line of reduced width to allow gradual impedance transformation, one microstrip portion having an input and which connects to one top layer stub disposed adjacent to one of the two tapered sections, and another microstrip portion having an output and which connects to another top layer stub disposed adjacent to the other of the two tapered sections;
• and
• a ground layer disposed on an opposite side of the substrate and including a bottom layer CPW central line situated in a central cutout and which connects between a bottom layer stub on one side and another bottom layer stub on the other side situated in ground cutouts, respectively.