Coupling networks having broader bandwidth than included phase shifters

Claim 2

A network, having an all-pass transmission characteristic over a specified frequency band of interest Delta F comprising: two substantially identical hybrid couplers, each having two pairs of conjugate branches; one branch of one pair of conjugate branches of one coupler being the input port of said network; one branch of one pair of conjugate branches of the other coupler being the output port of said network; first and second wavepaths, each of which connects one branch of the other pair of branches of said one coupler to one branch of the other pair of branches of said other coupler; transmission between said network ports and said first and second wavepaths being defined, respectively, by a pair of coupling coefficients t and k, each of which varies as a function of frequency; and means for introducing an additional 180* of relative phase shift located in one of said wavepaths; characterized in that: the coupling coefficient t is significant over the lower portion of said band of interest and is negligibly small at the higher end of said band of interest; the coupling coefficient k is significant over the upper portion of said band of interest and is negligibly small at the lower end of said band of interest; and in that said phase shift means introduces 180* of relative phase shift over a portion of said band of interest that is at least coextensive with the portion of said band for which the coupling between the wavepath wherein said means is located and said input and output ports is significant, but less than said band of interest.

Claim 3

The network in accordance with claim 1 wherein said phase shift means is a 1:1 turns ratio transformer located in said first wavepath; and wherein said transformer provides 180* of phase shift over the portion of said band for which coupling coefficieNt t is significant.

Claim 4

The network according to claim 1 wherein said phase shift means is a 1:1 turns ratio transformer located in said second wavepath; and wherein said transformer provides 180* of phase shift over the portion of said band for which coupling coefficient k is significant.

Claim 5

A phase shifter, for introducing 180* of relative phase shift between signals in two transmission paths comprising: a first all-pass network in accordance with claim 1 disposed in one of said transmission paths wherein said phase shift means is a 1:1 turns ratio transformer located in said first wavepath for providing 180* of phase shift over the portion of said band for which coupling coefficient t is significant; and a second all-pass network in accordance with claim 1 disposed in the other of said transmission paths wherein said phase shift means is a 1:1 turns ratio transformer located in said second wavepath for providing 180* of phase shift over the portion of said band for which coupling coefficient k is significant.

Claim 6

A circuit, having an all-pass transmission characteristic over a specified frequency band of interest Delta F comprising: two substantially identical hybrid couplers, each having two pairs of conjugate branches; one branch of one pair of conjugate branches of one coupler being the input port of said circuit; one branch of one pair of conjugate branches of the other coupler being the output port of said circuit; first and second signal paths, each of which connects one branch of the other pair of branches of said one coupler to one branch of the other pair of branches of said other coupler; transmission between said circuit ports and said first and second signal paths being defined, respectively, by a pair of coupling coefficients t'' and k'', each of which varies as a function of frequency; said coefficient t'' being significant over the lower portion of said band of interest Delta F, and negligibly small at the upper end of said band of interest Delta F; said coefficient k'' being significant over the upper portion of said band of interest Delta F, and negligibly small at the lower end of said band of interest Delta F; and means for introducing 180* of relative phase shift between signals in said two signal path comprising: a first all-pass network in accordance with claim 1 located in one of said signal paths wherein said phase shift means is located in said first wavepath and provides 180* of phase over a portion of said band for which coupling coefficient t is significant; and a second all-pass network in accordance with claim 1 located in the other of said signal paths wherein said phase shift means is located in said second wavepath and provides 180* of phase shift over a portion of said band for which coupling coefficient k is significant.

Claim 7

The circuit according to claim 5 wherein said first network has an all-pass characteristic over a frequency band that is at least coextensive with the portion of said band of interest Delta F for which the coupling between the signal paths wherein said first network is located and said input and output ports is significant, but less than said band of interest Delta F; and wherein said second network has an all-pass characteristic over a frequency band of interest that is at least coextensive with the portion of said band of interest Delta F for which the coupling between the signal path wherein said second network is located and said input and output ports is significant, but less than said band of interest Delta F.

Claim 8

A broadband transformer comprising: two hybrid couplers, each having two pairs of conjugate branches; one branch of one pair of conjugate branches of one coupler being the input port of said transformer; one branch of one pair oF conjugate branches of the other coupler being the output port of said transformer; the other branch of said one pair of branches of each of said couplers being resistively terminated; first and second wavepaths, each of which connects one branch of the other pair of branches of said one coupler to one branch of the other pair of branches of said other coupler; transmission between said input port and said first and second wavepaths, and between said first and second wavepaths and said output port being defined, respectively, by a pair of coupling coefficients t and k, each of which varies as a function of frequency; said coefficient t being significant over the lower portion of a frequency band of interest, and negligibly small at the upper end of said band of interest; said coefficient k being significant over the upper portion of said band of interest, and negligibly small at the lower end of said band of interest; a first 1:N turns ratio transformer located in said first wavepath and designed to operate over at least that portion of said band of interest for which t is significant, but less than said band of interest; and a second 1:N turns ratio transformer located in said second wavepath and designed to operate over at least that portion of said band of interest for which k is significant, but less than said band of interest.

Claim 9

A broadband transformer comprising: two hybrid couplers, each having two pairs of conjugate branches; one branch of one pair of conjugate branches of one coupler being the input port of said transformer; one branch of one pair oF conjugate branches of the other coupler being the output port of said transformer; the other branch of said one pair of branches of each of said couplers being resistively terminated; first and second wavepaths, each of which connects one branch of the other pair of branches of said one coupler to one branch of the other pair of branches of said other coupler; transmission between said input port and said first and second wavepaths, and between said first and second wavepaths and said output port being defined, respectively, by a pair of coupling coefficients t and k, each of which varies as a function of frequency; said coefficient t being significant over the lower portion of a frequency band of interest, and negligibly small at the upper end of said band of interest; said coefficient k being significant over the upper portion of said band of interest, and negligibly small at the lower end of said band of interest; a first 1:N turns ratio transformer located in said first wavepath and designed to operate over at least that portion of said band of interest for which t is significant, but less than said band of interest; and a second 1:N turns ratio transformer located in said second wavepath and designed to operate over at least that portion of said band of interest for which k is significant, but less than said band of interest.

Claim 10

The transformer in accordance with claim 7 wherein one of said transformers is connected so as to introduce 180* of phase shift relative to the phase shift introduced by the other of said transformers.

Claim 11

The transformer in accordance with claim 7 wherein said couplers have substantially the same frequency characteristics, but different characteristic impedances.