Radio frequency circuit with a multi-layer transmission line assembly having a conductively filled trench surrounding the transmission line

A transmission line assembly comprising:

• a pair of dielectric substrates;
• an electrical conductor at least partially embedded between the pair of dielectric substrates;
• a pair of reference conductors at least partially embedded between the pair of dielectric substrates and positioned to be co-planar with the electrical conductor and spaced apart from the electrical conductor by a respective gap;
• a pair of ground planes, each of the pair of ground planes disposed adjacent to an outer surface of a respective one of the pair of dielectric substrates, each of the pair of ground planes being substantially parallel to each other and to the co-planar arrangement of the electrical conductor and the pair of reference conductors;
• a pair of electromagnetic boundaries formed of an electrically continuous conductor disposed through the pair of dielectric substrates, substantially extending between the pair of ground planes and in electrical communication with the pair of ground planes, wherein the pair of electromagnetic boundaries is in electrical communication with the pair of reference conductors;
• and
• a first electrical component electrically coupled to a first end of the electrical conductor and a second electrical component electrically coupled to a second end of the electrical conductor, the electrical conductor being configured to convey an electromagnetic signal of greater than 24 GHz between the first electrical component and the second electrical component.

A method of fabricating an electromagnetic circuit, the method comprising:

• providing a first dielectric substrate having a conductive cladding disposed upon a first surface thereof;
• machining the conductive cladding to remove a portion of the conductive cladding to form a transmission line, the removed portion forming a respective gap between the transmission line and a remaining portion of the conductive cladding, at least some of the remaining portion of the conductive cladding forming a pair of reference conductors on either side of, and co-planar with, the transmission line;
• providing a second dielectric substrate having a second surface and positioning the second dielectric substrate so that the second surface faces the first surface, thereby at least partially encapsulating the transmission line and the pair of reference conductors between the first dielectric substrate and the second dielectric substrate;
• providing the first dielectric substrate with a first ground plane disposed on a third surface, the third surface being an opposing and substantially parallel surface to the first surface, and providing the second dielectric substrate with a second ground plane disposed on a fourth surface, the fourth surface being an opposing and substantially parallel surface to the second surface, each of the first ground plane and the second ground plane being substantially parallel to each other and to the co-planar arrangement of the transmission line and the pair of reference conductors;
• machining the first dielectric substrate and the second dielectric substrate to form a trench through the first dielectric substrate and the second dielectric substrate, the trench extending between and being substantially perpendicular to the first ground plane and the second ground plane;
• and
• filling the trench with a conductive material, the conductive material arranged to be in electrical contact with each of the first ground plane and the second ground plane.