Microwave Distribution Network

Abstract

The microwave distribution network comprises a stack of several layers (4), each of the layers (4) comprising a plurality of unit cells (1); - the unit cell (1) includes a coaxial input (2) connected to three transmission lines (3) by an angular subtense of 120 degrees, the coaxial input (2) being oriented on the Z axis of a Cartesian system of axes in which the three transmission lines (3) lie in the XY plane; the layer (4) is constructed as a hexagonal lattice formed by unit cells (1) by periodic replication, the coaxial inputs (2) being located at the corners of the hexagon, so that each unit cell (1) is connected to three adjacent unit cells, and the coaxial inputs (2) of the three adjacent unit cells are oriented on the Z axis of the Cartesian system of axes of the three transmission lines (3) lying in the XY plane, so that this orientation on the Z axis is opposite to the orientation of the coaxial input (2) of the previous unit cell (1) on the same Z axis; - the distance between the coaxial inputs (2) is such that it satisfies the 1 / 4 wavelength condition, - Adjacent layers (4) are interconnected by means of coaxial inputs (2) of unit cells aligned in opposite directions.

Description

[Technical field]

[0001] The present invention relates to microwave distribution networks primarily used in space systems and in satellite applications or in terrestrial or ground segment applications, either as part of a reflector or lens system or as a direct radiating array, and also to antenna arrays, reflector antennas or lens antennas, including such microwave distribution networks. [Background technology]

[0002] An antenna array consists of a set of multiple simple antennas acting together as a single composite antenna.

[0003] There exist multi-beam antennas capable of generating several independent beams that emerge simultaneously from a common antenna aperture. In multi-beam applications, one of the most frequent limitations is the maximum resolving power of the system, which is limited by the size and dimensions of the radiating elements and by the distance between the phase centers of adjacent beams. A useful approach is to implement an effective radiating area with an array of small antennas, opening up the ability to overlap and reduce the distance between adjacent beams. This is particularly relevant for applications with reflector systems (see, for example, the article "Multi-beam applications of CORPS BFN: Reflector antenna feeding system"; D. Betancourt, c. Del Rio Bocio).

[0004] “A novel methodology to feed phased array antennas” (D. Betancourt, c. Del Rio Bocio): This paper introduces a novel methodology for designing beamforming networks (BFNs) that feed antenna arrays. N×N antenna arrays are now being used in place of the traditional N 2Using this approach is feasible to reduce the associated control complexity of phased arrays, since instead of a single BFN, four phase shifters are used to control the beam steering. As a proof of concept, a prototype has been designed, built, and measured. The prototype consists of a 3 × 3 pseudo-Yagi antenna fed by four input ports. Measurements show that the main beam of the antenna array fed by this BFN can be steered in any desired direction.

[0005] “A beamforming network for multibeam antenna arrays based on coherent radiating periodic structures” (D. Betancourt, c. Del Rio) describes practical applications of CORPS-BFN in the field of multibeam systems. It presents analytical studies and a prototype composed of three input ports, three layers, and six output ports. A BFN is a structure capable of distributing different signals in an ingenious way, in that a signal introduced at any input port is driven to a specific set of output ports, the ones closer to the input port throughout the structure.

[0006] “Investigations on the efficiency of array fed coherently radiating periodic structure beam forming networks” (Ferrando N., Fonseca NJG) studies the capabilities and efficiency of C-BFN systems. By introducing a simple matrix composition, it details the losses due to beam steering capabilities as well as the non-orthogonality of the BFN for mono- and multi-beams. The results of the investigation show that the CORPS-BFN has a reasonable limit of 3-4 layers in mono-beam configurations, but 8-10 layers for multi-beams. It also shows how the periodic array structure has applications in annular or cylindrical designs.

[0007] “A new multiple-beam forming network design approach for a planar antenna array using CORPS” (Arce A., Covarrubias DH, Panduro MA, Garza LA) addresses an approach to design and analyze beamforming networks (BFNs) for multiple-beam steerable planar antenna arrays using the Coherently Radiating Periodic Structures (CORPS) technique. It proposes a configuration that alternates input ports in subgroups, where the input ports are reused by more than one signal or beam. A complete multi-beam system is designed to generate nine orthogonal beams simultaneously.

[0008] Another prior art document is “Coherently radiating periodic structures (CORPS): a step towards high resolution imaging systems” (R. Garcia, D. Betancourt, A. Ibanez, c. del Rio).

[0009] The current state of the art offers several proposals for distributed networks or structures, some of which are based on the Coherently Radiating Periodic Structures-Beam Forming Network (CORPS-BFN) technique.

[0010] However, there is a need to further reduce the distance between adjacent beams in a distribution network. Summary of the Invention

[0011] It is therefore an object of the present invention to provide a microwave distribution network that allows a reduction in the distance between adjacent beams.

[0012] The present invention provides a microwave distribution network comprising a stack of several layers, each of the layers comprising a plurality of unit cells, the unit cell includes a coaxial input connected to three transmission lines by an angular subtense of 120 degrees, the coaxial input being oriented on the Z-axis of a Cartesian system of axes in which the three transmission lines lie in an XY plane; the layer is constructed as a hexagonal lattice formed by unit cells by periodic replication and the coaxial inputs are placed at the corners of the hexagon so that each unit cell is connected to three adjacent unit cells, the coaxial inputs of the three adjacent unit cells being oriented on the Z-axis of a Cartesian system of axes of the three transmission lines lying in the XY-plane, so that this orientation on the Z-axis is opposite to the orientation of the coaxial input of the previous unit cell on the same Z-axis; -The distance between the coaxial inputs is such that it satisfies the 1 / 4 wavelength condition, Adjacent layers are interconnected by means of coaxial inputs of unit cells aligned in opposite directions.

[0013] The present invention also provides a microwave distribution network comprising a stack of several layers, each of the layers comprising a plurality of unit cells, the unit cell includes a coaxial input connected to four transmission lines by an angular subtense of 90 degrees, the coaxial input being oriented on the Z-axis of a Cartesian system of axes in which the four transmission lines lie in an XY plane; - the layer is constructed as a square or rectangular lattice formed by unit cells by periodic replication, so that each unit cell is connected to four adjacent unit cells, and the coaxial inputs of the four adjacent unit cells are oriented on the Z axis of a Cartesian system of axes of the four transmission lines lying in the XY plane, so that this orientation on the Z axis is opposite to the orientation of the coaxial input of the previous unit cell on the same Z axis; -The distance between the coaxial inputs is such that it satisfies the 1 / 4 wavelength condition, Adjacent layers are interconnected by means of coaxial inputs of unit cells aligned in opposite directions.

[0014] The present invention also provides antenna arrays, reflector antennas, and lens antennas that include such microwave distribution networks.

[0015] The above configuration of the microwave distribution network results in an effective overlap of the radiating areas.

[0016] Another advantage of the present invention is that the microwave distribution network can be totally passive and reciprocal, it can be used in simultaneous transmission and reception, and it can be part of an active system or include active elements in either reception or transmission or both.

[0017] Other characteristics and advantages of the invention will become apparent from the following detailed description of illustrative and non-limiting embodiments in connection with the accompanying drawings, in which: [Brief description of the drawings]

[0018] [Figure 1] The unit cell is shown. [Diagram 2] 1 shows the hexagonal lattice formed after periodic replication of the unit cell. [Diagram 3] The periodicity conditions and impedance aspects are given. [Figure 4] 1 is a scheme of the shunts present at the intersections between a coaxial port and three transmission lines from the perspective of the transmission lines. [Diagram 5] 1 shows a stack of layers. [Figure 6] FIG. 13 is a diagram of a simulated structure having 121 coaxial inputs. [Figure 7] Reflection of input ports, transmission and isolation between input and output ports are shown. [Figure 8] 13 shows an example of power distribution on a four-layer ODIN with periodic layers for the ideal case. [Figure 9] 13 shows an example of power distribution on a four-layer ODIN with periodic layers for the ideal case. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] A new topology of the structure called Overlapped Distribution Network (ODIN) is proposed. The basic unitary cell of the network is shown in Figure 1. The proposed structure is a four-port network whose dimensions may be tuned to ensure equal power distribution to each branch. The basic structure consists of a transition from a coaxial port or input to three equal transmission lines arranged with an angular subtense of 120 degrees. The transmission lines may be striplines.

[0020] Some vias surrounding the transition may be positioned to provide protection and promotion of field coupling to the transmission line.

[0021] P1 is the coaxial port, Z0 characteristic impedance of the coaxial line, and Z s The input impedance seen by P1 is obtained directly by calculating the parallel of the three transmission line impedances, thus Z in_coax=Z S / 3 (1) It is.

[0022] If perfect matching is desired, then relation (2) can be obtained straightforwardly. Z S =3·Z0(2)

[0023] Now imagine an infinite periodic duplication of the cells, connecting each cell to its three neighbors. After this periodic duplication, all ports of the network are coaxial lines, with transmission lines acting as crossovers between their coaxial ports (Figure 2).

[0024] It is important to note that in this replication, adjacent coaxial ports are at different orientations on the Z axis. That is, if a coaxial port in the original cell is pointing upwards, its three nearest neighbors are pointing downwards. Following this format, they point upwards, and so on. The distance between the ports is now such that it satisfies the quarter wavelength condition. Replication of cells in the above manner implies the creation of a hexagonal lattice, as depicted in FIG. 2. Assuming the periodicity condition, and since the ends of the lattice are not considered, it is assumed that the impedance seen at each transmission line branch of the input is identical, i.e., Z in It is asserted that the impedance is the result of the interaction between adjacent cells. Each cell is loaded by the rest of the network. Under the same assumptions, the impedance seen at the end of each transmission line, i.e., Z A (corresponding to the parallel of the coaxial line and the other two transmission lines connected to the rest of the network) is also identical for each crossing. For a clearer view from an impedance point of view, see Figure 3. Z0 and Z s Let be the characteristic impedance of the coaxial line and the transmission line, respectively. Since the length of the transmission line corresponds to one quarter of a wavelength, the transmission line is governed by the well-known relationship: Z in =Z S 2 / Z A (3) According to the above, it acts as a quarter wave impedance transformer.

[0025] Z A is calculated as the parallel impedance between one coaxial port loaded by the rest of the periodic structure and the two transmission lines. Z A =Z0 / / Z in / / Z in 1 / Z A =1 / Z0+1 / Z in +1 / Z in (4) Z A =Z0 Z in / (2 Z0+Z in )

[0026] To ensure impedance matching at the coaxial port, Z in Assuming = 3·Z0, and substituting (4) in (3), we obtain the following relationship (5) between the characteristic impedance of the coaxial line and the transmission line: Z S =Z0·sqrt(9 / 5) (5)

[0027] Furthermore, Z A =3 / 5·Z0(6) can also be tested.

[0028] At this point, it can be stated that the total power entering the network from only the coaxial input ports is divided equally among the three transmission lines, since the input impedance seen at each branch is identical. Following this assumption, the power delivered to adjacent coaxial ports is Z A From the viewpoint of three parallel impedances: Z0 / / Z in / / Z in For a clearer idea, refer back to FIG. 2 in conjunction with FIG. 4. Here, the auxiliary voltage V Amay be defined from the relationship (7a) between power and voltage. It can then be obtained that the power delivered to the load Z0 corresponds to 3 / 5 of the power available in the input transmission line. Thus, the power delivered to each coaxial port adjacent to the input coaxial is: P=V I=V 2 / Z (7a) P Z0 =V A 2 / Z0=P A Z A / Z0=1 / 3P T 3 / 5=1 / 5P T (7b) It is.

[0029] P T represents the total input power coming from the first coaxial port. Up until now, we have determined the amount of power delivered to each branch from the coaxial port (one third each) and the amount of power delivered to each adjacent port (three fifths of the available power in each branch, i.e. one fifth of the total power). From those results, we can deduce that six fifteenths of the total power (one per transmission line branch) is being delivered to the rest of the network. As stated in (7b), three fifths of the power is delivered to the coaxial ports (one twenty-fifth of the total power, i.e. -14 dB), which is the nominal separation between consecutive coaxial ports in the plane (this means consecutive coaxial ports with the same orientation in the Z axis).

[0030] Up to this point, the main characteristics and behavior of the network have been presented and its properties under periodic conditions have been discussed. The next step involves the deposition of several layers of a hexagonal lattice, as diagrammed in Figure 5. In this regard, it is important to note that it has been stated that the coaxial ports are arranged in alternating directions. This characteristic allows the crossing of layers and the longitudinal propagation of energy across the structure.

[0031] Reference is made to Figures 8 and 9 to see an example representation of the power distribution for the N=4 scenario (which means that one third of the power is delivered to each adjacent port). Here, the dark circles represent the power inputs at each layer and the light circles represent the output ports at each layer. The smaller light circles represent the coaxial lines pointing downwards and the smaller dark circles correspond to the ones pointing upwards at N=1. For N=2, 3... their orientations should be swapped instead at each layer to follow the upward propagation. The power is distributed within each layer, concentrating most of it at a central location relative to the input port at layer 1. As it can be seen, the distance between consecutive radiating elements is less than half a wavelength, since the sides of the hexagon correspond to a quarter of a wavelength.

[0032] To provide an example of the performance of the network as a single, finite layer of the structure has been simulated in the on-circuit simulator software, as shown in FIG. 6. The coaxial ports have been modeled by lumped ports with Z0=50Ω. The L-Band has been selected as the band of operation, and a reference frequency f0 of 1.5 GHz has been selected to design the quarter-wave transformer. The fact that the topology is composed of resonant elements infers the resonant behavior of the network. Since it was not feasible to simulate an infinite number of periodic structures, a reasonably large structure with 121 ports has been simulated. It has been observed that the transmission to adjacent ports (e.g., from port 1 to ports 2, 6, and 10 in FIG. 6) was about -6.5 dB, and the isolation between consecutive ports was roughly -16 dB.

[0033] Concerning the non-contiguous ports, two types of non-contiguous ports can be distinguished: those located on the normal axis in the center of the three symmetry axes (ports 17, 21, 25, 29, 33 and 37) and those that are not (15, 19, 23, 27, 31 and 35). For a clearer illustration, see FIG. 6. It was seen that the separation between port 1 and the first type of ports presents a higher separation (below 35 dB) than the rest (below 20 dB). All their parameters are represented in FIG. 7.

[0034] In Figure 8, it can be seen that a signal incident through one of the inputs, located at one of the six corners of the hexagon, distributes power primarily through the three coaxial outputs closest to the upper layer, then does the same for the next layer, resulting in the signal being distributed over an increasingly larger area. The signal is radiated by all radiating elements that receive a significant portion of the introduced signal.

[0035] Figures 8 and 9 show an example of power distribution on a four-layer ODIN with periodic layers for the ideal case. The dark circles represent the sources on each layer. The light circles with numbers represent the receiving nodes (output ports) on each layer. In this scenario of four layers, the power division provided by the network is used to feed a hexagonal array of 19 radiating elements.

[0036] Several layers of the structure are suitably deposited to increase the number of radiating elements, thus defining a larger radiating area for each of the beams, which are highly overlapping and well separated from each other.

[0037] The transmission line 3 may include a stub or width of the line, or a height of the transmission line or path line. The transmission coaxial input 2 may include a tuning structure or a screw or stub.

[0038] Another possibility is to obtain a square or rectangular lattice after periodic replication of a unit cell 1, which includes a coaxial input 2 connected to four transmission lines 3 by an angular range of 90 degrees, the coaxial input 2 being oriented on the Z axis of a Cartesian system of axes in which the four transmission lines 3 lie in the XY plane.

[0039] Although the present invention has been described in detail in relation to preferred embodiments, it is not intended to be limited thereto, but it is clear that modifications may be made thereto within the scope of the following claims.

Claims

1. a microwave distribution network comprising a stack of several layers (4), each of said layers (4) comprising a plurality of unit cells (1); - said unit cell (1) comprises a coaxial input (2) connected to three transmission lines (3) with an angular extent of 120 degrees, said coaxial input (2) being oriented on the Z-axis of a Cartesian system of axes in which said three transmission lines (3) lie in the XY plane; - said layer (4) is constructed as a hexagonal lattice formed by said unit cells (1) by periodic replication and said coaxial inputs (2) are placed at the corners of a hexagon, so that each unit cell (1) is connected to three adjacent unit cells, and said coaxial inputs (2) of said three adjacent unit cells are oriented on the Z-axis of a Cartesian system of axes of said three transmission lines (3) lying in the XY-plane, so that this orientation on said Z-axis is opposite to the orientation of said coaxial input (2) of the previous unit cell (1) on the same Z-axis; the distance between said coaxial inputs (2) is set to λ / 4, λ being the wavelength of the operating frequency of said microwave distribution network; - adjacent layers (4) are interconnected by means of the coaxial inputs (2) of the unit cells arranged in opposite directions; The microwave distribution network.

2. a microwave distribution network comprising a stack of several layers (4), each of said layers (4) comprising a plurality of unit cells (1); - said unit cell (1) comprises a coaxial input (2) connected to four transmission lines (3) with an angular extent of 90 degrees, said coaxial input (2) being oriented on the Z-axis of a Cartesian system of axes in which said four transmission lines (3) lie in the XY plane; - said layer (4) is constructed as a square or rectangular lattice formed by said unit cells (1) by periodic duplication, so that each unit cell (1) is connected to four adjacent unit cells, and said coaxial inputs (2) of said four adjacent unit cells are oriented on the Z-axis of a Cartesian system of axes of said four transmission lines (3) lying in the XY-plane, so that this orientation on said Z-axis is opposite to the orientation of said coaxial inputs (2) of the previous unit cell (1) on the same Z-axis; the distance between said coaxial inputs (2) is set to λ / 4, λ being the wavelength of the operating frequency of said microwave distribution network; - said adjacent layers (4) are interconnected by means of the coaxial inputs (2) of the unit cells arranged in opposite directions; The microwave distribution network.

3. A microwave distribution network according to claim 1 or 2, wherein the unit cell (1) includes a number of shielding vias (5) surrounding the transition between the coaxial input (2) and the transmission line (3).

4. A microwave distribution network according to any one of the preceding claims, wherein the unit cell (1) comprises a substrate (6) on which the transmission line (3) is arranged and on which the coaxial input (2) enters.

5. The microwave distribution network according to any one of claims 1 to 3, wherein the transmission line (3) comprises a stub or width of a line, or a height of a transmission line or a path line.

6. A microwave distribution network according to any one of the preceding claims, wherein the transmission coaxial input (2) comprises a tuning structure or a screw or a stub.

7. - An antenna array comprising a microwave distribution network according to any one of claims 1 to 6.

8. A reflector antenna system comprising a microwave distribution network according to any one of claims 1 to 6.

9. A lens antenna comprising a microwave distribution network according to any one of claims 1 to 6.

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