Microwave quadrature coupler having lumped-element capacitors

Claim 2

A microwave quadrature coupler having an input port, an isolated port and two output ports, said coupler being particularly characterized in that it comprises a plurality of thin conductive strips supported coplanar on an insulating substrate, said conductive strips comprising sections of transmission line, each of said sections having a physical length less than one-quarter wavelength at a midband frequency, said sections of transmission line comprising a first series circuit of two of said sections of line connected between said input port and one of said output ports, a second series circuit of two of said sections of line connected between said isolated port and the other of said output ports, and first, second and third branch lines, said first branch line connected between the ends of said first and second series circuits at the input and isolated ports, respectively, said second branch line connected between the junctions formed by the two line lengths in said first and second series circuits, said third branch line connected between the ends of said first and second seriEs circuits at the two output ports, respectively, and said conductive strips further comprising lumped capacitors coupling the ends of said line sections to ground.

Claim 3

The combination of claim 1 wherein said lumped capacitors comprise six fixed capacitors each having a grounded end and an ungrounded end, said ungrounded ends being connected, respectively, to the ends of said three branch lines.

Claim 4

A microwave quadrature coupler having an input port, an isolated port and two output ports, said coupler comprising an insulating substrate, a plurality of thin conductive strips supported coplanar on said substrate, said strips comprising sections of transmission line having distributed parameters, each of said sections of said transmission line having a length less than a quarter wavelength at a midband frequency, and said strips further comprising lumped capacitors coupled to the ends of said line sections, said sections of transmission line comprising a first series circuit comprising two of said sections of said transmission line connected between said input port and one of said output ports, a second series circuit comprising two of said sections of said transmission line connected between said isolated port and the other of said output ports, and first, second and third branch lines, said first branch line connected between the ends of said first and second series circuits at the input and isolated ports, respectively, said second branch line connected between the junctions formed by the two line lengths in said first and second series circuits, said third branch line connected between the ends of said first and second series circuits at the two output ports, respectively.

Claim 5

A microwave quadrature coupler having an input port, an isolated port and two output ports, said coupler comprising an insulating substrate, a plurality of thin conductive strips supported coplanar on said substrate, said strips comprising sections of transmission line having distributed parameters, each of said sections of said transmission line having a length less than a quarter wavelength at a midband frequency, and said strips further comprising lumped capacitors coupled to the ends of said line sections, said sections of transmission line comprising a first series circuit comprising two of said sections of said transmission line connected between said input port and one of said output ports, a second series circuit comprising two of said sections of said transmission line connected between said isolated port and the other of said output ports, and first, second and third branch lines, said first branch line connected between the ends of said first and second series circuits at the input and isolated ports, respectively, said second branch line connected between the junctions formed by the two line lengths in said first and second series circuits, said third branch line connected between the ends of said first and second series circuits at the two output ports, respectively.

Claim 6

The combination of claim 3 wherein said lumped capacitors comprise six fixed capacitors each having a grounded end and an ungrounded end, said ungrounded ends being connected, respectively, to the ends of said three branch lines.

Claim 7

A microwave quadrature coupler comprising: an input port, an isolated port, and two output ports; an insulating substrate; first and second series circuits each comprising at least one section of transmission line having a length less than a quarter wavelength at the midband frequency, each said section comprising a thin conductive strip supported coplanar on said substrate, said first series circuit connecting said input port to one of said output ports, said second series circuit connecting said isolated port to the other of said output ports, said first and second series circuits extending parallel to each other; and a plurality of lumped-element capacitors connected between said first series circuit and said second series circuit at the ends of said sections of transmission line, each of said capacitors comprising thin conductive strips supported coplanar on said substrate.

Claim 8

A microwave quadrature coupler comprising: an input port, an isolated port, and two output ports; an insulating substrate; first and second series circuits each comprising at least one section of transmission line having a length less than a quarter wavelength at the midband frequency, each said section comprising a thin conductive strip supported coplanar on said substrate, said first series circuit connecting said input port to one of said output ports, said second series circuit connecting said isolated port to the other of said output ports, said first and second series circuits extending parallel to each other; and a plurality of lumped-element capacitors connected between said first series circuit and said second series circuit at the ends of said sections of transmission line, each of said capacitors comprising thin conductive strips supported coplanar on said substrate.