TECHNICAL FIELD

[0001] This disclosure relates generally to branchline couplers and more particularly to compact branchline couplers.

BACKGROUND OF THE INVENTION

[0002] As is known in the art, one type of analog phase shifter includes a branchline coupler. One such branchline coupler, sometimes also referred to as a reflective coupler or a shunt hybrid combiner, is shown in FIG. 1 to include a pair of main transmission lines and a pair of shunt transmission lines. One analog phase shifter, (FIG. 2) that includes a branchline coupler is described in a paper entitled "Integral analysis of hybrid coupler semiconductor phase shifters" by Kori et al, IEE Proceedings, vol. 134, Pt.H. No. 2. April 1987.

[0003] One technique used to adjust phase shift of the branchline coupler type phase shifter is to connect a phase adjusting section connected to each one of the pair of shunt transmission lines as described in a paper entitled "A Low-Loss Voltage-Controlled Analog Phase-Shifter Using Branchline Coupler and Varactor Diodes" by Gupta et al, (Gupta, Nishant, Raghuvir Tomar, and Prakash Bhartia. "A low-loss voltage-controlled analog phase-shifter using branchline coupler and varactor diodes." Microwave and Millimeter Wave Technology, 2007. ICMMT07. International Conference on. IEEE, 2007). There a pair of varactor diodes is controlled by voltages to adjust the phase shift provided by the phase shifter. Another branchline coupler type phase shifter having a phase adjusting section connected to each one of the pair of shunt transmission lines is shown in FIG. 3 A. Here the phase adjusting sections each includes a pair of conductors separated one from and the other; one of the conductors being connected to a ground plane conductor on the bottom of a substrate. The two conductors are connected by a series of bridging, spaced bond wires, as shown. With an input signal applied, the phase at the output is measured and the bond wires are removed one at a time, as shown in FIG. 3B, to thereby change the electrical length of the path through the phase adjusting sections to ground until the desired phase shift is obtained; FIG. 3B showing several of the bond wires removed from the branchline coupler type phase shifter of FIG. 3 A.

SUMMARY OF THE INVENTION

[0004] In accordance with the present disclosure a branchline coupler structure is provided, comprising: a support structure; a pair of main transmission lines disposed on different horizontal levels of the support structure; and a pair of shunt transmission lines, vertically disposed and laterally spaced, and disposed in the support structure. A first one of the pair of shunt transmission lines is coupled between: one region of a first one of the pair of main transmission lines and a first end of a second one of the pair of main transmission line. A second one of the pair of shunt transmission lines is coupled between a second region of the first one of the pair of main transmission lines, laterally spaced from the first region, and a second end of the second one of the main transmission lines.

[0005] In one embodiment, the branchline coupler structure includes: a pair of phase adjusting sections, each one of the pair of phase shifting sections being coupled to a corresponding one of a pair of shunt transmission line sections through a corresponding one of pair phase shifter section transmission lines, the pair phase shifter section transmission lines being disposed on an upper surface of the support structure. A ground pad is disposed on an upper surface of the support structure, separate from the signal strip conductors of the phase shifter section transmission lines by gaps; and a plurality of electrical conductors, bridging the gaps, disposed successive along over the gaps, each one of the plurality of electrical conductors having one end to connect the ground pad and a second end connected to the phase shifter transmission line sections.

[0006] In one embodiment, the branchline coupler structure includes: a second ground pad disposed on an upper surface of the support structure, separate from the signal strip conductors of the pair of phase shifter section transmission lines by a pair of gaps; and a second plurality of electrical conductors, bridging the pair of gaps, disposed successive along over the pair of gaps, each one of the second plurality of electrical conductors having one end connect the second ground pad and a second end connected to the corresponding one of the phase shifter transmission line sections. [0007] In one embodiment, the first-mentioned plurality of electrical conductors and the second plurality of electrical conductors are staggered along the first mentioned gap and a corresponding one of the pair of gaps.

[0008] In one embodiment, pair of shunt transmission lines propagate energy with the electric field of such energy being disposed vertically.

[0009] In one embodiment, the pair of main transmission lines propagate energy with the electric field of such energy being disposed horizontally.

[0010] In one embodiment, a branchline coupler structure is proved comprising: a pair of main transmission lines; a pair of shunt transmission lines, a first one of the pair of shunt transmission lines is coupled between: one region of a first one of the pair of main transmission lines and a first end of a second one of the pair of main transmission line, a second one of the pair of shunt transmission lines is coupled between a second region of the first one of the pair of main transmission lines, laterally spaced from the first region, and a second end of the second one of the main transmission lines; a pair of phase adjusting sections, each one of the pair of phase shifting sections being coupled to a corresponding one of a pair of shunt transmission line sections through a corresponding one of pair phase shifter section transmission lines; a ground pad disposed on an upper surface of the support structure, separate from the signal strip conductors of the phase shifter section transmission lines by gaps; and a plurality of electrical conductors, bridging the gaps, disposed successive along over the gaps, each one of the plurality of electrical conductors having one end to connect the ground pad and a second end connected to one of the phase shifter transmission line sections.

[0011] In one embodiment, a second ground pad disposed on an upper surface of the support structure, separate from the signal strip conductors of the pair of phase shifter section transmission lines by a pair of gaps. A second plurality of electrical conductors, bridging the pair of gaps, is disposed successive along over the pair of gaps, each one of the second plurality of electrical conductors having one end connect the second ground pad and a second end connected to the corresponding one of the phase shifter transmission line sections. [0012] In one embodiment the first-mentioned plurality of electrical conductors and the second plurality of electrical conductors are staggered along the first mentioned gap and a corresponding one of the pair of gaps.

[0013] With such an arrangement a compact branchline coupler is provided. Also, the number of phase shifts available is increased by providing the second ground pad.

[0014] The details of one or more embodiments of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 is a schematic diagram of a branchline coupler according to the PRIOR ART;

[0016] FIG. 2 is a schematic diagram of a phase shifter using a branchline coupler according to the PRIOR ART;

[0017] FIGS. 3A and 3B are perspective views of a phase shifter using a branchline coupler according to the PRIOR ART at various stages in the fabrication thereof according to the PRIOR ART ;

[0018] FIG. 4 is a perspective view, partially shown in phantom, of a branchline coupler according to the disclosure;

[0019] FIG. 4 A is the perspective of view, partially shown in phantom, of the branchline coupler of FIG. 4 with a portion thereof removed to show inner layers of the branchline coupler according to the disclosure, such inner portion being encircled by an arrow designated 7-7 and shown in FIG. 7;

[0020] FIG. 4B shows the signal conductors used in the branchline coupler of FIG. 4 according to the disclosure; [0021] FIG. 5 is an exploded, perspective sketch showing each one of a plurality of vertically stacked printed circuit boards of the branchline coupler of FIG. 4 according to the disclosure;

[0022] FIGS. 5A-5M are top views of each one of the printed circuit boards of FIG. 5 used to form the branchline coupler of FIG. 4 according to the disclosure;

[0023] FIG. 6 is a simplified, exploded, diagrammatic schematic sketch of the branchline coupler of FIG. 4 useful in further understanding the arrangement of the printed circuit boards of FIG. 5A-5M of the branchline coupler of FIG. 4 according to the disclosure; and

[0024] FIG. 7 is a cross sectional view of the inner portion designated as 7-7 in FIG. 4A of the branchline coupler of FIG. 4 according to the disclosure.

[0025] Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

[0026] Referring now to FIGS. 4, 4 A, 4B and 5, a branchline coupler structure 10 is shown. The branchline coupler structure 10 incudes: a support structure 12 (FIG. 4A) here a dielectric structure comprising a plurality of, here thirteen, planar printed circuit boards 12i-12i ₃ , vertically stacked along the Z-axis, as shown in FIG. 6, the planar surfaces of the boards 12i-12i ₃ being disposed in horizontal (X-Y) planes, the top view of each one of the plurality of printed circuit boards 12i-12i ₃ being shown in FIGS. 5A-5M, respectively; the top one of the boards 12i-12i ₃ being designated as 12i and the bottom one of the boards 12i-12i ₃ being labelled 12i _3. When the plurality of printed circuits boards 12i-12i ₃ are bonded together with any conventional dielectric bonding material, not shown, the branchline coupler structure 10 forms, as shown diagrammatically in FIG.5; the signal strip conductors 16 ₁ ,16 ₂ , inner signal conductors 26 ₁ ,26 ₂ and signal strip conductors 38I,382, of the branchline coupler 10, to be described in more detail below, being shown in FIG. 4B.

[0027] Referring also to FIGS. 5A-5M, a pair of main transmission lines 14i, 14 ₂ , (FIG.

5) here microstrip transmission lines, each one having a signal strip conductor I6 ₁ , I6 ₂ , respectively, formed on the upper surface of boards 12n and 12i, respectively, as shown in FIGS. 5K and 5 A, respectively, and a corresponding, underlying one a pair of ground plane conductors 18I,182, respectively, formed by conductive sheet portions 12i3me _tai/ground plane and 123me _{tai/ground plane} on boards 12i ₃ and 12 ₃ , respectively, as shown in FIGS. 5M and 5C, respectively, disposed in the X-Y horizontal plane to support an electric field along the vertical Z-axis disposed, each one of the main transmission lines 14i, 14 ₂ being disposed on different horizontal levels of the support structure 12; and a pair of shunt transmission lines, 26i, 26 ₂ , (FIG. 5) here coaxial type transmission lines 22i, 22 ₂ , having: (a) grounded outer conductors formed by conductive sheet 24 ₁ , 24 ₂ , 24 ₃ , respectively, formed by conductive sheet portions 125metal/ground plane, 127metal ground plane, and 129metal ground p _lane on boards 12 _5, 12 ₇ and 12 ₉ , respectively (FIGS. 5E, 5G and 51, respectively, the conductive sheets being spaced vertically less than a quarter wavelength at the nominal operating wavelength of the branchline coupler in order to appear electrically as a continuous conductor; and inner signal conductors 26 ₁ , 26 ₂ , respectively, formed by conductive signal vias 22 ₁ , formed by conductive portions of conductive sheets on boards, respectively, 12 ₂ -12i ₂ as shown in FIGS. 5B through FIG. 5L, the coaxial type transmission lines 22i, 22 ₂ , extending vertically and laterally spaced, and disposed in the support structure 12 to support an electric field along the X-Y horizontal planes.

[0028] A first one of the pair of shunt transmission lines 26i, 26 ₂ , (FIG. 5) here shunt transmission line 26i is coupled between: one region 28i on board 12n (FIG. 5K) of a first one of the pair of main transmission lines 14i, 14 ₂ , here main transmission line 14i and a first end 30i on board 12i (FIG. 5A) of a second one of the pair of main transmission lines 14i, 14 ₂ , here main transmission line 14 _2. A second one of the pair of shunt transmission lines 26i, 26 ₂ , here shunt transmission line 26 is coupled between a second region 28 ₂ on board 12n (FIG. 5K) of the first one of the pair of main transmission lines 14i, 14 ₂ , here main transmission line 14i has a region 28i laterally spaced from a second region 28 ₂ on board 12n _.

[0029] Here the branchline coupler structure 10 includes: a pair of phase adjusting sections, 32 ₁ , 32 ₂ , FIG. 5, each one of the pair of phase shifting sections 32i, 32 ₂ being coupled to a corresponding one of a pair of shunt transmission line sections 26 ₁ ,26 ₂ , respectively and a corresponding one of the second one of the pair of main transmission lines, respectively, at a corresponding one of the regions 28 ₁ ,28 ₂ , respectively, as shown, through a corresponding one of pair phase shifter section transmission lines, 34 _I ,34 ₂ , (FIG. 5) respectively, here microstrip transmission lines, as shown. More particularly, phase shifter section transmission lines, 34 _I ,34 ₂ , each has a corresponding of a pair of signal strip conductors 38 _I ,38 ₂ , respectively, disposed on an upper surface of the support structure 10 (board 12i, FIG. 5A) and extending along the Y-direction. Each one of the pair of signal strip conductors 38 ₁ , 38 ₂ , is disposed above a corresponding one of a pair of ground plane conductors 40 _I ,40 ₂ , respectively, here provided by a common conductor 31 pattern as shown on board 12 ₄ as shown in FIG. 5D) and positioned to support a vertical electric field along the Z-axis.

[0030] A plurality of, here three electrically connected ground pads 42 _I ,42 ₂ , and 42 ₃ , are disposed on an upper surface of the support structure 10 are formed by a patterned electrical conductor 19 formed on board 12i (FIG. 5A), as indicted. The three ground pads 42 _I ,42 ₂ , and 42 ₃ , are separate from one another by gaps 44 ₁ and 44 ₂ , as shown, with signal strip conductors 38 _I ,38 ₂ , respectively, being disposed in gaps 44i, 44 ₂ , respectively, as shown. There are two sets 46ai, 46bi and 46a ₂ , 46b ₂ of electrical conductors, here bond wires, are staggered across gaps 44 _I ,44 ₂ , respectively, as shown. One portion of set 46ai, 46bi _, here set 46ai has one end connected to ground pad 42 ₁ and an opposite end connected to signal strip conductor 38 ₁ and here set 46b ₁ has one end connected to ground pad 42 ₂ and an opposite end connected to signal strip conductor 38 ₁ . It is noted that the electrical conductors in set 46ai and set 46bi are disposed successive along over the gap 44 ₁ with each one the conductors in set 46ai being staggered with respect to the each one of the conductors in set 46b ₁ , as shown. To put it another way, each one of the conductors in set 46bi is disposed between a pair of the conductors in set 46ai ,as shown. Likewise, it is noted that the electrical conductors in set 46a ₂ and set 46b ₂ are disposed successive along over the gap 44 ₂ with each one the conductors in set 46a ₂ being staggered with respect to the each one of the conductors in set 46b ₂ , as shown. To put it another way, each one of the conductors in set 46b ₂ is disposed between a pair of the conductors in set 46a ₂ , as shown.

[0031] The ground plane conductors on printed circuit boards 12i, 12 ₃ , 12s, 12 ₇ , 12 ₉ , 12n and 12i ₃ -(FIGS. 5A, 5C, 5E, 5G, 51, 5K and 5M, respectively), and the three ground pads 42 _I ,42 ₂ , and 42 ₃ on board 12i (FIG. 5A), are connected together with conductive ground vias 21, as shown in FIGS. 5A-5M. Boards 12 ₂ , 12 ₄ , 12 ₆ , 12 ₈ , 12io, 12 _I2 (FIGS. 5B, 5D,

5F, 5H, 5J, and 5L), have conductive vias 21 with boards 12 ₄ , 12 ₆ , 12 ₈ , 12 _IO and 12 _I2 also having portions of the center signal conductor of the coaxial shunt transmission lines 22i, 22 ₂ as shown in FIG. 7 _.

[0032] The boards 12i-12i ₃ are formed as shown above and described above in FIGS. 5A- M except for the ground vias 21 and inner signal conductors 26i, 26 _2. The formed boards 12i-12i ₃ are then stacked and bonded together with any conventional dielectric bonding material, not shown. The ground vias 19 and conductive vias of the inner signal conductors 26i, 26 ₂ are formed by first etching or drilling holes in the bonded structure from the bottom or backside of the bonded structure vertically through such structure starting from the back of board 12i ₃ and then then filling the holes with a suitable electrically conductive material. In order to prevent the conductive material from electrically connecting the inner signal conductors 26 ₁ , 26 _2. To the ground plane conductor on board 12n, the portion of the inner signal conductors 26i, 26 _2. conductive material of the inner signal conductors 26i, 26 ₂ making such connection are removed by back-drilling or by timed etching for example and removed conductive material is replaced with a dielectric material.

[0033] Thus, in FIG. 5A, board 12i : numerical designation 19 is conductive sheet patterned to form pads 42 _I ,42 ₂ and 42 ₃ ; signal strip conductors 38 _I ,38 _2; main transmission line signal 14 ₂ strip conductor 16 ₂ ; top portions of inner signal conductors 26i, 26 ₂ ; a first and second ends of the main transmission line 14 _2I signal strip conductors 30i, 30 ₂ ; exposed portion of the surface of the dielectric portions of board 12i being designed 12is.

[0034] In FIG. 5B, board 12 ₂ : dielectric surface of board 12 ₂ s and conductive vias 12 _2signai for center signal conductors of coaxial shunt transmission 22i, 22 ₂ exposed portions of the dielectric surface being designated 12 ₂ s _.

[0035] In FIG. 5C, board 12 ₃ : patterned conductor serves as a ground plane conductor 18 ₂ for signal strip conductor 16 ₂ of the main transmission line 14 ₂ and as the ground plane conductors 40 ₂ for strip conductors 38 ₂ of the phase shifter transmission line 34 ₂ ; numerical designation 12 ₃ s is the dielectric exposed surface portions of the dielectric board 123; numerical designation 123metai/signai designating an outer portion of the inner signal conductors 26i, 26 _2.

[0036] In FIG. 5D, board 12 ₄ : numerical designation 12 ₄ s is the exposed portions of the surface of board 12 _4.

[0037] In FIG. 5E, board 12s: numerical designation Aground plane is patterned conductor providing a ground plane with exposed dielectric portions of the dielectric board 12s being designated 12ss; numerical designation 125metai/signai designates an outer portion of the inner signal conductors 26i, 262.

[0038] In FIG. 5F, board 12 ₆ : numerical designation 12 ₆ s being portions of the surface of dielectric board 12 _6.

[0039] In FIG. 5G, board 12 ₇ : numerical designation Aground plane is patterned conductor providing a ground plane with exposed dielectric portions of the dielectric board 12 ₇ being designated 127s; numerical designation 127metai/signai designates an outer portion of the inner signal conductors 26i, 262.

[0040] In FIG. 5H, board 12s: numerical designation 12ss being portions of the surface of dielectric board 12s _.

[0041] In FIG. 51, board 129: numerical designation Aground plane designates patterned conductor providing a ground plane with exposed dielectric portions of the dielectric board 129 being designated 129s; numerical designation 129metai/signai designating an outer portion of the inner signal conductors 26i, 262.

[0042] In FIG. 5J, board 12io, numerical designation 12ios being portions of the surface of dielectric board 12io _.

[0043] In FIG. 5K, board 12n _, numerical designation 12ngr ₀ und plane designates patterned conductor providing a ground plane with exposed dielectric portions of the dielectric board 12n being designated 12ns; numerical designation 12i _metai/signai designating the signal strip conductor 16i of the main transmission line 14i _.

[0044] In FIG. 5L, board 12n _, numerical designation 12ns designates portions of the surface of dielectric board 12n _.

[0045] In FIG. 6M, board 12 , numerical designation 12n designating the ground plane conductor 18i of the main transmission line 14i _.

[0046] It should now be appreciated, a branchline coupler structure according to the disclosure includes: a support structure; a pair of main transmission lines disposed on different horizontal levels of the support structure; a pair of shunt transmission lines, vertically disposed and laterally spaced, and disposed in the support structure; wherein a first one of the pair of shunt transmission lines is coupled between: one region of a first one of the pair of main transmission lines and a first end of a second one of the pair of main transmission line; and wherein a second one of the pair of shunt transmission lines is coupled between a second region of the first one of the pair of main transmission lines, laterally spaced from the first region, and a second end of the second one of the main transmission lines. The branchline coupler structure can include one or more of the following features, either individually or in combination, to include: a pair of phase adjusting sections, each one of the pair of phase shifting sections being coupled to a corresponding one of a pair of shunt transmission line sections through a corresponding one of pair phase shifter section transmission lines, the pair phase shifter section transmission lines being disposed on an upper surface of the support structure, a ground pad disposed on an upper surface of the support structure, separate from the signal strip conductors of the phase shifter section transmission lines by gaps, and a plurality of electrical conductors, bridging the gaps, disposed successive along over the gaps, each one of the plurality of electrical conductors having one end to connect the ground pad and a second end connected to one of the phase shifter transmission line sections; a second ground pad disposed on an upper surface of the support structure, separate from the signal strip conductors of the pair of phase shifter section transmission lines by a pair of gaps, and a second plurality of electrical conductors, bridging the pair of gaps, disposed successive along over the pair of gaps, each one of the second plurality of electrical conductors having one end connect the second ground pad and a second end connected to the corresponding one of the phase shifter transmission line sections; wherein the first- mentioned plurality of electrical conductors and the second plurality of electrical conductors are staggered along the first mentioned gap and a corresponding one of the pair of gaps; wherein the pair of shunt transmission lines propagate energy with the electric field of such energy being disposed vertically; or wherein the pair of main transmission lines propagate energy with the electric field of such energy being disposed horizontally.

[0047] It should now also be appreciated, a branchline coupler structure according to the disclosure includes: a pair of main transmission lines; a pair of shunt transmission lines, a first one of the pair of shunt transmission lines is coupled between: one region of a first one of the pair of main transmission lines and a first end of a second one of the pair of main transmission line, a second one of the pair of shunt transmission lines is coupled between a second region of the first one of the pair of main transmission lines, laterally spaced from the first region, and a second end of the second one of the main transmission lines; a pair of phase adjusting sections, each one of the pair of phase shifting sections being coupled to a corresponding one of a pair of shunt transmission line sections through a corresponding one of pair phase shifter section transmission lines; a ground pad disposed on an upper surface of the support structure, separate from the signal strip conductors of the phase shifter section transmission lines by gaps; and a plurality of electrical conductors, bridging the gaps, disposed successive along over the gaps, each one of the plurality of electrical conductors having one end to connect the ground pad and a second end connected to one of the phase shifter transmission line sections. The branchline coupler structure can include one or more of the following features, either individually or in combination, to include: a second ground pad disposed on an upper surface of the support structure, separate from the signal strip conductors of the pair of phase shifter section transmission lines by a pair of gaps, and a second plurality of electrical conductors, bridging the pair of gaps, disposed successive along over the pair of gaps, each one of the second plurality of electrical conductors having one end connect the second ground pad and a second end connected to the corresponding one of the phase shifter transmission line sections; or wherein the first-mentioned plurality of electrical conductors and the second plurality of electrical conductors are staggered along the first mentioned gap and a corresponding one of the pair of gaps. [0048] A number of embodiments of the disclosure have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. For example, the phase shifting section need not use bonding wires but techniques described in U. S. Patent No. 10,243,246 Issued March 26, 2019, entitled “Phase Shifter Including a Branchline Coupler Having Phase Adjusting

Sections Formed By Connectable Conductive Pads”, Inventors Laighton et at., assigned to the same assignee as the present invention may be used. Further, the coaxial, vertical, shunt transmission line may be formed by arranging a plurality of vertical columns of conductor closely spaced circumferentially around a signal center conductor as described in U. S. Patent No. 9,887,195 Issued February 6, 2018, Inventors Drab et al, assigned to the same assignee as the present invention. Accordingly, other embodiments are within the scope of the following claims.