Patent Description:
Antenna feed assemblies couple radiofrequency transmitters or receivers with respective antennas and often include feed networks comprising waveguides, circulators or isolators, diplexers, polarization forming networks, etc. Weight and volume are critical constraints in many contexts involving the use of antenna feed assemblies, with satellite communication systems being one such context. A typical satellite may carry a plurality of antenna feed assemblies, corresponding to antenna systems used for communicatively coupling to terrestrial ground stations, such as gateways and user terminals.

Volume and weight savings multiply over the plurality of antenna feed systems included in the satellite. However, certain design requirements create tension in the context of size and weight reductions. For example, antenna feed assemblies used onboard satellites must exhibit high shock and vibration resistance and, in general, offer robust, reliable performance over multiple frequency ranges.

<CIT> discloses an antenna front end including at least two diplexers.

<CIT> discloses an image rejection filter comprising a waveguide-type <NUM>-degree hybrid coupler.

<CIT> discloses a submillimeter wave heterodyne receiver including a finline ortho-mode transducer.

<CIT> discloses a waveguide correlation unit.

A multi-layer, highly-integrated antenna feed assembly and a method of manufacturing a multi-layer, highly-integrated antenna feed assembly are described herein. The antenna feed assembly includes multiple polarization forming networks operable over different frequency bands. In examples herein, the antenna feed assembly includes five layers of conductive material. Alternatively, the number of layers may be different than five.

One embodiment comprises an antenna feed assembly that includes a first layer having a top surface and a bottom surface. The bottom surface of the first layer includes recesses that define portions of a first polarization-forming network. The first polarization-forming network includes a first pair of individual waveguides, a first hybrid including a first pair of ports coupled to the first pair of individual waveguides and further including a second pair of ports, a first filter of a first diplexer coupled to one of the second pair of ports, and a first filter of a second diplexer coupled to another of the second pair of ports.

The antenna feed assembly further includes a second layer having a top surface and a bottom surface. The top surface of the second layer extends across the recesses of the bottom surface of the first layer to form remaining surfaces of the first polarization-forming network. The bottom surface of the second layer includes recesses that define portions of a second polarization-forming network. The second polarization-forming network includes a second pair of individual waveguides, a second hybrid underlying the first hybrid and including a third pair of ports coupled to the second pair of individual waveguides and further including a fourth pair of ports, a second filter of the first diplexer coupled to one of the fourth pair of ports and underlying the first filter of the first diplexer, and a second filter of the second diplexer coupled to another of the fourth pair of ports and underlying the first filter of the second diplexer.

A method of manufacturing an antenna feed assembly is described. The method includes forming a first layer having a top surface and a bottom surface. The bottom surface of the first layer includes recesses that define portions of a first polarization-forming network. The first polarization-forming network includes a first pair of individual waveguides, a first hybrid comprising a first pair of ports coupled to the first pair of individual waveguides and further comprising a second pair of ports, a first filter of a first diplexer coupled to one of the second pair of ports, and a first filter of a second diplexer coupled to another of the second pair of ports. The method further includes forming a second layer having a top surface and a bottom surface. The bottom surface of the second layer including recesses that define portions of a second polarization-forming network. The second polarization-forming network includes a second pair of individual waveguides, a second hybrid underlying the first hybrid and comprising a third pair of ports coupled to the second pair of individual waveguides and further comprising a fourth pair of ports, a second filter of the first diplexer coupled to one of the fourth pair of ports and underlying the first filter of the first diplexer, and a second filter of the second diplexer coupled to another of the fourth pair of ports and underlying the first filter of the second diplexer.

Of course, the present invention is not limited to the above features and advantages. Indeed, those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings.

<FIG> is a perspective-view of an "air model" view that depicts an example arrangement <NUM> of electrical elements provided by a multi-layer antenna feed assembly. The interplay between layer features formed through and in the respective layers in a stack of layers forms an antenna feed assembly comprising the depicted electrical elements. Here, the term "layer features" refers to any one or more of opposing surfaces, recesses, grooves, furrows, or apertures. Layer features present in the abutting surfaces of adjacent layers in the stack are complementary. For example, an opposing surface provided by one layer "covers" a recess or groove formed in the abutting surface of the adjacent layer to form a cavity or channel, e.g., a waveguide, while apertures provide inter-layer pathways.

Among the electrical elements, a first polarization-forming network includes a first pair of individual waveguides 12A and 12B, a first hybrid <NUM> including a first pair of ports 16A and 16B coupled to the first pair of individual waveguides 12A and 12B, and further including a second pair of ports 18A and 18B, a first filter 20A of a first diplexer <NUM> coupled to one of the second pair of ports 18A and 18B, and a first filter 24A of a second diplexer <NUM> coupled to another of the second pair of ports 18A and 18B.

Further among the electrical elements are a second polarization-forming network including a second pair of individual waveguides 28A and 28B, a second hybrid <NUM> underlying the first hybrid <NUM> and including a third pair of ports 32A and 32B coupled to the second pair of individual waveguides 28A and 28B, and further including a fourth pair of ports 34A and 34B, a second filter 20B of the first diplexer <NUM> coupled to one of the fourth pair of ports 34A and 34B and underlying the first filter 20A of the first diplexer <NUM>, and a second filter 24B of the second diplexer <NUM> coupled to another of the fourth pair of ports 34A and 34B and underlying the first filter 24A of the second diplexer <NUM>.

<FIG> also depicts a pair of TEE junctions 40A and 40B and selected ones of the overall set of assembly ports representing connection points (inputs and outputs) of the electrical arrangement <NUM>. Illustrated ports include ports P1a, P2a, P2b, P1c, P2c, P3, and P4. Although port P1b is not visible in <FIG>, its position in relation to P1a is like that shown for P2b in relation to P2a. <FIG> offers an alternate perspective of the air-model introduced in <FIG> and illustrates selected additional example details regarding implementation of the ports P1a, P2a, P2b, P1c, P2c, P3, and P4.

<FIG>, which is a side view of air model shown in <FIG> and <FIG>, also depicts the TEE junctions 40A and 40B and the ports P3, P4, P1a/P1b/P1c and P2a/P2b/P2c. <FIG> illustrates a turnstile junction <NUM>, which may be referred to as a waveguide orthomode transducer. The turnstile junction <NUM> includes multiple ports, including a circular port <NUM>.

Example layers going from the "top" of the example layer stack to the "bottom" of the example layer stack include a first layer <NUM>, a second layer <NUM>, a third layer <NUM>, and a fourth layer <NUM>. In one or more embodiments, the layer stack includes a fifth layer <NUM>, positioned between the second layer <NUM> and the third layer <NUM>. Each of the layers provides layer features or opposing surfaces or both, that are stack-wise complementary such that the aligned stack of layers <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> form the cavities or passageways that comprise the electrical arrangement(s) described herein-i.e., the air-model representation depicted in <FIG>/B and <FIG> correspond to the assembled stack.

<FIG> is a schematic diagram corresponding with the electrical arrangement <NUM> depicted in <FIG>. The schematic illustrates the couplings between the TEE junctions 40A and 40B and the rectangular ports 1a, 1b, 2a, and 2b of the turnstile junction <NUM>. <FIG> provides a corresponding perspective view of the turnstile junction <NUM>, showing the circular port <NUM> and the respective rectangular ports 1a, 1b, 2a, and 2b. <FIG> further depicts a tuning stub <NUM> formed in or otherwise included in the turnstile junction <NUM>.

<FIG> illustrates a multi-layer antenna feed assembly <NUM> in an example installation, where the antenna feed assembly <NUM> is implemented as a highly-integrated assembly by virtue of its fabrication as a multi-layer stack that implements the electrical arrangement <NUM>, according to the example details of <FIG> and <FIG> and <FIG>. The overall arrangement depicted in <FIG> includes the antenna feed assembly <NUM> having the circular port <NUM> coupled to a coupler <NUM>, which in turn couples to a feed horn <NUM> through a circular waveguide <NUM>.

In a ground-based antenna of a satellite communication system, the antenna feed assembly <NUM> may be configured for transmission in the Ka band and reception in the K band. The Ka/K frequency configuration may be reversed for use of the antenna feed assembly <NUM> onboard a satellite in the same satellite communication system.

<FIG> illustrates connectivity with respect to the ports shown in <FIG>, e.g., where ports P3 and P4 are transmission inputs to the antenna feed assembly <NUM>. Ports P1a and P2a are reception outputs corresponding to received traffic signals, while ports P1c and P2c are reception ports tracking-signal reception, with ports P1b and P2b being related coaxial ports used for tracking-signal injection. Here, "tracking" refers to antenna tracking, and it shall be understood that additional circuitry and connections may be involved for implementation of an overall tracking system.

<FIG> illustrates the stack layers <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> corresponding to <FIG> and <FIG>, with the understanding that the assembled set of layers <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> forms the antenna feed assembly <NUM>. Each layer has a top and bottom surface, and respective ones of the layers include layer features that match with complementary layer features in an adjacent layer within the stack or are otherwise complemented by an opposing surface in the adjacent layer. For example, grooves, furrows, or other channels formed in the surface of one layer become waveguides, cavities, etc., when covered by the opposing surface of the adjacent layer. Similarly, apertures formed or machined through one layer provide signal passageways into adjacent layers above or below the layer. Thus, bringing the layers together in stack order forms the electrical arrangement <NUM> as a highly integrated arrangement that is compact and robust.

The perspective view of <FIG> shows the top surfaces of the respective layers in the stack. In more detail, the first stack layer <NUM> has a top surface <NUM>, the second stack layer <NUM> has a top surface <NUM>, the third stack layer <NUM> has a top surface <NUM>, the fourth stack layer <NUM> has a top surface <NUM>, and the fifth stack layer <NUM> has a top surface <NUM>. As noted previously, the fifth stack layer <NUM> may be positioned between the second stack layer <NUM> and the third stack layer <NUM>.

<FIG> illustrates the same layers <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, but shows the bottom surfaces of the respective layers. The first stack layer <NUM> has a bottom surface <NUM>, the second stack layer <NUM> has a bottom surface <NUM>, the third stack layer <NUM> has a bottom surface <NUM>, the fourth stack layer <NUM> has a bottom surface <NUM>, and the fifth stack layer <NUM> has a bottom surface <NUM>. The bottom perspective view of <FIG> also shows a portion of the turnstile junction <NUM>, and depicts the tuning stub <NUM>, according to the exploded view arrangement.

<FIG> illustrate the first layer <NUM> in more detail. In particular, <FIG> illustrates a set of layer features <NUM> formed in the bottom surface <NUM> of the first layer <NUM>, which form a portion of the first polarization-forming network. The layer features <NUM> include a mix of channels or recesses, along with selected apertures.

<FIG> illustrate the second layer <NUM> in more detail. In particular, <FIG> illustrates the top surface <NUM> of the second layer <NUM>, which has layer features <NUM> complementary with the bottom surface <NUM> of the first layer <NUM>. <FIG> illustrates the bottom surface <NUM> of the second layer <NUM>, which includes layer features <NUM> that define portions of the second polarization-forming network of the electrical arrangement <NUM>.

<FIG> illustrate the third layer <NUM> in more detail. The top surface <NUM> of the third layer <NUM> has layer features <NUM>, while the bottom surface <NUM> of the third layer <NUM> has layer features <NUM>.

<FIG> illustrate the fourth layer <NUM> in more detail. The top surface <NUM> of the fourth layer <NUM> has layer features <NUM>.

<FIG> illustrate the fifth layer <NUM> in more detail. As noted, in stack order going from top to bottom, the fifth layer <NUM> may be positioned between the second layer <NUM> and the third layer <NUM>. As such, the layer features <NUM> of the top surface <NUM> of the fifth layer <NUM> are complementary with respect to the layer features <NUM> on the bottom surface <NUM> of the second layer <NUM>, and the layer features <NUM> on the bottom surface <NUM> of the fifth layer <NUM> are complementary with respect to the layer features <NUM> of the top surface <NUM> of the third layer <NUM>.

With the above in mind and in an example embodiment, a multi-layer antenna feed assembly <NUM> comprises a plurality of layers that include layer features that are complementary when the layers are stacked in stack order, where the overall collection of layer features implements the electrical arrangement <NUM>. Particularly, an example antenna feed assembly <NUM> includes a first layer <NUM> having a top surface <NUM> and a bottom surface <NUM>. Layer features <NUM> of the bottom surface <NUM> of the first layer <NUM> includes recesses that define portions of a first polarization-forming network.

The first polarization-forming network includes a first pair of individual waveguides 12A and 12B, and a first hybrid <NUM>. The first hybrid <NUM> comprises a first pair of ports 16A and 16B coupled to the first pair of individual waveguides 12A and 12B, and further comprises a second pair of ports 18A and 18B. The first polarization forming network further includes a first filter <NUM> of a first diplexer <NUM> coupled to one of the second pair of ports 18A and 18B, and a first filter 24A of a second diplexer <NUM> coupled to another of the second pair of ports 18A and 18B.

A second layer <NUM> of the antenna feed assembly <NUM> has a top surface <NUM> and a bottom surface <NUM>. The top surface <NUM> of the second layer <NUM> extends across the recesses of the bottom surface <NUM> of the first layer <NUM> to form remaining surfaces of the first polarization-forming network. Further, layer features <NUM> of the bottom surface <NUM> of the second layer <NUM> include recesses that define portions of a second polarization-forming network.

The second polarization-forming network includes a second pair of individual waveguides 28A and 28B, and a second hybrid <NUM> underlying the first hybrid <NUM>. The second hybrid <NUM> comprises a third pair of ports 32A and 32B coupled to the second pair of individual waveguides 28A and 28B, and further comprises a fourth pair of ports 34A and 34B.

The second polarization-forming network further includes a second filter 20B of the first diplexer <NUM> coupled to one of the fourth pair of ports 34A and 34B and underlying the first filter 20A of the first diplexer <NUM>. Further, a second filter 24B of the second diplexer <NUM> is coupled to another of the fourth pair of ports 34A and 34B and underlies the first filter 24A of the second diplexer <NUM>.

In some embodiments, a first individual waveguide of each of the first and second pairs of individual waveguides 12A/12B and 28A/28B is associated with a first circular polarization, a second individual waveguide of each of the first and second pairs of individual waveguides 12A/12B and 28A/28B is associated with a second circular polarization, a first port of each of the first and third pairs of ports 16A/16B and 32A/32B of the first and second hybrids <NUM> and <NUM> is associated with a first linear polarization, and a second port of each of the first and third pairs of ports 16A/16B and 32A/32B of the first and second hybrids <NUM> and <NUM> is associated with a second linear polarization.

In some embodiments, the antenna feed assembly <NUM> further includes a turnstile junction <NUM> including four side ports 1a, 1b, 2a, 2b and a circular port <NUM>, a first waveguide junction having a first common port coupled to a common waveguide 120A-see <FIG> and <FIG>-of the first diplexer <NUM> and a first pair of divided ports coupled to a first two of the four side ports 1a, 1b, 2a, 2b, and a second waveguide junction having a second common port coupled to a common waveguide 120B-see <FIG> and <FIG>-of the second diplexer <NUM> and a second pair of divided ports coupled to a second two of the four side ports 1a, 1b, 2a, 2b. See the TEE junctions 40A and 40B of <FIG> and <FIG>.

In some embodiments, the antenna feed assembly <NUM> further includes a first E-plane bend 122A-see <FIG> and <FIG>-extending between the first layer <NUM> and the second layer <NUM> and coupled between the first filter 20A of the first diplexer <NUM> and the common port of the first diplexer <NUM>, and a second E-plane bend 122B-see <FIG> and <FIG>-extending between the first layer <NUM> and the second layer <NUM> and coupled between the first filter 24A of the second diplexer <NUM> and the common port of the second diplexer <NUM>.

In some embodiments, the recesses of the second layer <NUM> define portions of the common waveguides of the first and second diplexers <NUM> and <NUM>.

In some embodiments, the common waveguide 120A of the first diplexer <NUM> includes a bend-twist transition section 124A-see <FIG> and <FIG>-coupled between a first waveguide section and a second waveguide section oriented <NUM>-degrees relative to the first waveguide section. A similar arrangement of a bend-twist transition section 124B and first and second waveguide sections applies with respect to the common waveguide 120B of the second diplexer <NUM>.

In some embodiments, the first waveguide sections are defined by the recesses of the second layer <NUM>, and the bend-twist sections 124A/B and the second waveguide sections are defined by the recesses of the second layer <NUM> and the recesses of the first layer <NUM>.

In some embodiments, the antenna feed assembly <NUM> further includes a third layer <NUM> and a fourth layer <NUM>, the third layer <NUM> and the fourth layer <NUM> having respective recesses that define portions of the turnstile junction <NUM> and the first and second waveguide junctions.

In some embodiments, the antenna feed assembly <NUM> further includes a fifth layer <NUM> between the second layer <NUM> and the third layer <NUM>. The fifth layer <NUM> has a top surface <NUM> extending across some of the recesses of the second layer <NUM> and having a bottom surface <NUM> extending across some of the recesses of the third layer <NUM>.

In some embodiments, the third layer <NUM> has a bottom surface <NUM> extending across some of the recesses of the top surface <NUM> of the fourth layer <NUM>.

In some embodiments, the recesses of the third layer <NUM> and the recesses of the fourth layer <NUM> define first waveguides 126A and 126B-see <FIG> and <FIG>-between the first pair of divided ports and the first two of the four side ports 1a, 1b, 2a, 2b and second waveguides 126C and 126D-see <FIG> and <FIG>-between the second pair of divided ports and the second two of the four side ports 1a, 1b, 2a, 2b.

In some embodiments, each of the first waveguides 126A/B and each of the second waveguides 126C/D comprise the same plurality of waveguide sections-i.e., they are formed or built from like waveguide sections. However, an order of the plurality of waveguide sections of the first waveguides 126A/B is different than an order of the plurality of waveguide sections of the second waveguides 126C/D.

In some embodiments, the first waveguides 126A/B cross over the second waveguides 126C/D at a single location.

In some embodiments, the first waveguides 126A/B and the second waveguides 126C/D are in different ones of the third of fourth layers <NUM> and <NUM> at the single location.

In some embodiments, the first waveguides 126A/B and the second waveguides 126C/D extend in orthogonal directions at the single location.

<FIG> illustrates another embodiment, which comprises a method <NUM> of manufacturing an antenna feed assembly as shown herein. The method <NUM> includes forming (Block <NUM>) a first layer <NUM> having a top surface <NUM> and a bottom surface <NUM>. The bottom surface <NUM> of the first layer <NUM> includes recesses that define portions of a first polarization-forming network. The first polarization-forming network includes a first pair of individual waveguides 12A and 12B, a first hybrid <NUM> comprising a first pair of ports 16A and 16B coupled to the first pair of individual waveguides 12A and 12B and further comprising a second pair of ports 18A and 18B, a first filter 20A of a first diplexer <NUM> coupled to one of the second pair of ports 18A and 18B, and a first filter 24A of a second diplexer <NUM> coupled to another of the second pair of ports 18A and 18B.

The method <NUM> further includes forming (Block <NUM>) a second layer <NUM> having a top surface <NUM> and a bottom surface <NUM>. The bottom surface <NUM> of the second layer <NUM> includes recesses that define portions of a second polarization-forming network. The second polarization-forming network includes a second pair of individual waveguides 28A and 28B, a second hybrid <NUM> underlying the first hybrid <NUM> and comprising a third pair of ports 32A and 32B coupled to the second pair of individual waveguides 28A and 28B and further comprising a fourth pair of ports 34A and 34B, a second filter 20B of the first diplexer <NUM> coupled to one of the fourth pair of ports 34A and 34B and underlying the first filter 20A of the first diplexer <NUM>, and a second filter 24B of the second diplexer <NUM> coupled to another of the fourth pair of ports 34A and 34B and underlying the first filter 24A of the second diplexer <NUM>.

The method <NUM> further includes attaching (Block <NUM>) the first layer <NUM> to the second layer <NUM> such that the top surface <NUM> of the second layer <NUM> extends across the recesses of the bottom surface <NUM> of the first layer <NUM> to form remaining surfaces of the first polarization-forming network.

In some embodiments, a first individual waveguide of each of the first and second pairs of individual waveguides is associated with a first circular polarization, a second individual waveguide of each of the first and second pair of individual waveguides is associated with a second circular polarization, a first port of each of the first and third pairs of ports of the first and second hybrids is associated with a first linear polarization, and a second port of each of the first and third pairs of ports of the first and second hybrids is associated with a second linear polarization.

In some embodiments, the method <NUM> further includes providing a turnstile junction <NUM> comprising four side ports 1a, 1b, 2a, and 2b, and a circular port <NUM>. The method <NUM> further comprises providing a first waveguide junction having a first common port coupled to a common waveguide of the first diplexer <NUM> and a first pair of divided ports coupled to a first two of the four side ports 1a, 1b, 2a, 2b, and providing a second waveguide junction having a second common port coupled to a common waveguide of the second diplexer <NUM>, and a second pair of divided ports coupled to a second two of the four side ports.

In some embodiments, the method <NUM> further includes providing a first E-plane bend extending between the first layer <NUM> and the second layer <NUM> and coupled between the first filter 20A of the first diplexer <NUM> and the common port of the first diplexer <NUM> and providing a second E-plane bend extending between the first layer <NUM> and the second layer <NUM> and coupled between the first filter 24A of the second diplexer <NUM> and the common port of the second diplexer <NUM>.

In some embodiments, the common waveguide of the first diplexer <NUM> includes a bend-twist transition section coupled between a first waveguide section and a second waveguide section oriented <NUM>-degrees relative to the first waveguide section.

In some embodiments, the first waveguide section is defined by the recesses of the second layer <NUM>, and the bend-twist section and the second waveguide section is defined by the recesses of the second layer <NUM> and the recesses of the first layer <NUM>.

In some embodiments, the method <NUM> further includes forming a third layer <NUM> and a fourth layer <NUM>, the third layer <NUM> and the fourth layer <NUM> having respective recesses that define portions of the turnstile junction <NUM> and the first and second waveguide junctions.

In some embodiments, the method <NUM> further includes forming a fifth layer <NUM> between the second layer <NUM> and the third layer <NUM>, the fifth layer <NUM> having a top surface <NUM> extending across some of the recesses of the bottom surface <NUM> of the second layer <NUM> and having a bottom surface <NUM> extending across some of the recesses of the top surface <NUM> of the third layer <NUM>.

In some embodiments, the recesses of the bottom surface <NUM> of the third layer <NUM> and the recesses of the top surface <NUM> of the fourth layer <NUM> define first waveguides between the first pair of divided ports and the first two of the four side ports 1a, 1b, 2a, 2b, and second waveguides between the second pair of divided ports and the second two of the four side ports 1a, 1b, 2a, 2b.

In some embodiments, each of the first and second waveguides comprise the same plurality of waveguide sections-i.e., they are formed from like sections-and an order of the plurality of waveguide sections of the first waveguides is different than an order of the plurality of waveguide sections of the second waveguides.

In some embodiments, the first waveguides cross over the second waveguides at a single location.

In some embodiments, the first waveguides and the second waveguides are in different ones of the third of fourth layers at the single location.

In some embodiments, the first waveguides and the second waveguides extend in orthogonal directions at the single location.

Claim 1:
An antenna feed assembly (<NUM>), comprising:
a first layer (<NUM>) having a top surface (<NUM>) and a bottom surface (<NUM>), the bottom surface of the first layer comprising recesses that define portions of a first polarization-forming network, the first polarization-forming network comprising:
a first pair of individual waveguides (12A, 12B);
a first hybrid (<NUM>) comprising a first pair of ports (16A, 16B) coupled to the first pair of individual waveguides and further comprising a second pair of ports (18A, 18B);
a first filter (20A) of a first diplexer (<NUM>) coupled to one of the second pair of ports; and
a first filter (24A) of a second diplexer (<NUM>) coupled to another of the second pair of ports;
a second layer (<NUM>) having a top surface (<NUM>) and a bottom surface (<NUM>), the top surface of the second layer extending across the recesses of the bottom surface of the first layer to form remaining surfaces of the first polarization-forming network, the bottom surface of the second layer comprising recesses that define portions of a second polarization-forming network, the second polarization-forming network comprising:
a second pair of individual waveguides (28A, 28B);
a second hybrid (<NUM>) underlying the first hybrid and comprising a third pair of ports (32A, 32B) coupled to the second pair of individual waveguides and further comprising a fourth pair of ports (34A, 34B);
a second filter (20B) of the first diplexer coupled to one of the fourth pair of ports and underlying the first filter of the first diplexer; and
a second filter (24B) of the second diplexer coupled to another of the fourth pair of ports and underlying the first filter of the second diplexer.