Microstrip-to-microstrip RF transition including co-planar waveguide

An RF circuit comprising:

• a substrate including a first surface and a second surface;
• a first microstrip line deposited on the first surface of the substrate, said first microstrip line including a narrow portion, a widened portion and a tapered transition therebetween;
• and
• a first ground plane deposited on the first surface of the substrate, said first ground plane including a first extended section and a second extended section positioned adjacent to the widened portion of the first microstrip line and defining a slot therebetween, wherein the first and second extended sections of the first ground plane, the widened portion of the first microstrip line and the slot therebetween define a co-planar waveguide having a characteristic impedance, and wherein the characteristic impedance of the co-planar waveguide is substantially the same as the characteristic impedance of the narrow portion of the first microstrip line.

An RF circuit comprising:

• a substrate including a first surface and a second surface;
• a first microstrip line deposited on the first surface of the substrate, said first microstrip line including a narrow portion, a widened portion and a tapered transition therebetween;
• a second microstrip line deposited on the first surface of the substrate, said second microstrip line including a narrow portion, a widened portion and a tapered transition therebetween;
• a third microstrip line deposited on the second surface of the substrate, said third microstrip line including a first end and a second end, said first end of the third microstrip line including a narrow portion, a widened portion and a tapered transition therebetween and said second end of said third microstrip line including a narrow portion, a widened portion and a tapered transition therebetween;
• a first ground plane deposited on the first surface of the substrate, said first ground plane including a first end and a second end, said first end of the first ground plane including a first extended section and a second extended section positioned adjacent to the widened portion of the first microstrip line and defining a slot therebetween, wherein the first and second extended sections of the first end of the first ground plane, the widened portion of the first microstrip line and the slot therebetween define a first co-planar waveguide having a characteristic impedance, said second end of the first ground plane including a first extended section and a second extended section positioned adjacent to the widened portion of the second end of the second microstrip line and defining a slot therebetween, wherein the first and second extended sections of the second end of the first ground plane, the widened portion of the second microstrip line and the slot therebetween define a second co-planarwaveguide having a characteristic impedance;
• a second ground plane deposited on the second surface of the substrate, said second ground plane including a first extended section and a second extended section positioned adjacent to the widened portion of the first end of the third microstrip line and defining a slot therebetween, wherein the first and second extended sections of the second ground plane, the widened portion of the first end of the third microstrip line and the slot therebetween define a third co-planar waveguide having a characteristic impedance;
• a third ground plane deposited on the second surface of the substrate, said third ground plane including a first extended section and a second extended section positioned adjacent to the widened portion of the second end of the third microstrip line and defining a slot therebetween, wherein the first and second extended sections of the third ground plane, the widened portion of the second end of the third microstrip line and the slot therebetween define a fourth co-planar waveguide having a characteristic impedance;
• a first signal via extending through the substrate and being electrically coupled to the widened portion of the first microstrip line and the widened portion of the first end of the third microstrip line;
• a second signal via extending through the substrate and being electrically coupled to the widened portion of the second microstrip line and the widened portion of the second end of the third microstrip line;
• and
• at least one ground via extending through the substrate and being electrically coupled to the first ground plane and the second ground plane and at least one ground via extending through the substrate and being electrically coupled to the first ground plane and the third ground plane, wherein the characteristic impedance of the first, second, third and fourth co-planar waveguide provide a substantially constant characteristic impedance between the first, second and third microstrip lines.