A four-way filtering power divider

Abstract

This invention discloses a four-way filter power divider. The device includes stacked upper and lower metal surfaces and a middle dielectric substrate. The substrate contains a resonant cavity structure surrounded by an array of metallized vias. Its core feature is a centrally symmetrical cross-shaped layout: a square first SIW resonant cavity is located at the center, and four identical rectangular second to fifth SIW resonant cavities are respectively located at the centers of its four sides and coupled to it through coupling windows. The input port is located at one corner of the first resonant cavity, and the four output ports are located on the four rectangular cavities. The central cavity operates at TE... 201 The mold, with four cavities around it, operates at TE. 101 The filter passband is constructed through mode coupling. By using metallized vias of different diameters to construct the cavity boundary and coupling window, a balance between high performance and ease of fabrication is achieved. This invention has advantages such as excellent output amplitude and phase consistency, low insertion loss, compact structure, and ease of integration and mass production.

Description

Technical Field

[0001] This invention relates to the field of microwave passive device technology, specifically to a four-channel filter power divider. Background Technology

[0002] As modern wireless communication systems evolve towards massive MIMO (Multi-Input Multiple-Output) systems, higher demands are placed on the integration, performance, and channel consistency of filtering and power distribution functions in the RF front-end. Traditional solutions employ cascaded filters and power dividers, resulting in large system size, high insertion loss, and complex design. Filtered power dividers based on substrate integrated waveguide (SIW) technology have become an ideal choice for achieving functional integration due to their low loss, high Q value, and ease of integration. However, existing SIW filtered power dividers that achieve four equal-amplitude and in-phase outputs often employ multi-stage cascaded or complex coupling structures, leading to problems such as large size and difficulty in precisely controlling the amplitude and phase consistency between output ports. Therefore, there is an urgent need for a four-channel filtered power divider with a symmetrical structure, good output consistency, and ease of fabrication. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a four-way filter power divider with symmetrical structure, good output consistency, and low insertion loss. This device adopts a centrally symmetrical cross-shaped resonant cavity layout, integrating bandpass filtering and four-way power distribution functions within a single-layer SIW structure.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A four-way filter power divider includes an upper metal surface, a middle dielectric substrate and a lower metal surface stacked together, wherein the middle dielectric substrate has a resonant cavity structure surrounded by an array of metallized vias.

[0006] The resonant cavity structure includes a first substrate integrated waveguide resonant cavity, a second substrate integrated waveguide resonant cavity, a third substrate integrated waveguide resonant cavity, a fourth substrate integrated waveguide resonant cavity, and a fifth substrate integrated waveguide resonant cavity.

[0007] The first substrate integrated waveguide resonant cavity is square in shape, and the second, third, fourth and fifth substrate integrated waveguide resonant cavities are all rectangular in shape, and the four rectangular resonant cavities are of equal size.

[0008] The second, third, fourth, and fifth substrate integrated waveguide resonant cavities are respectively located at the center of the four sides of the first substrate integrated waveguide resonant cavity, forming a cross-shaped structure. Each of the second, third, fourth, and fifth substrate integrated waveguide resonant cavities is provided with a coupling window between itself and the first substrate integrated waveguide resonant cavity to couple electromagnetic energy and construct a filter passband.

[0009] An input port is provided at a right-angle position of the first substrate integrated waveguide resonant cavity, and an output port is provided on the second, third, fourth and fifth substrate integrated waveguide resonant cavities, respectively. Specifically, the second port, the third port, the fourth port and the fifth port are respectively provided on the first substrate integrated waveguide resonant cavity.

[0010] Furthermore, the electromagnetic field mode operating in the first substrate integrated waveguide resonant cavity is TE. 201 The electromagnetic field mode operating in the second, third, fourth, and fifth substrate integrated waveguide resonant cavities is TE. 101 mold.

[0011] Furthermore, the overall structure of the filter power divider is axially symmetrical along the centerline of the input port.

[0012] Furthermore, the input port receives a signal via a first microstrip line, and each of the output ports outputs a signal via a second microstrip line.

[0013] Furthermore, an input slot extending into the cavity is formed at the connection between the first microstrip line and the first substrate integrated waveguide resonant cavity; and an output slot extending into the corresponding cavity is formed at the connection between each second microstrip line and the second, third, fourth, or fifth substrate integrated waveguide resonant cavity to which it is connected.

[0014] Furthermore, the metallized via array includes a first metallized via and a second metallized via with different diameters, wherein the diameter of the first metallized via is larger than the diameter of the second metallized via.

[0015] Furthermore, the cavity boundary of the first substrate integrated waveguide resonant cavity is enclosed by the first metallized via; the cavity boundaries of the second, third, fourth, and fifth substrate integrated waveguide resonant cavities are jointly enclosed by the first metallized via and the second metallized via.

[0016] Furthermore, the second, third, fourth, and fifth ports output signals with equal amplitude and in phase.

[0017] Furthermore, the second port, the third port, the fourth port, and the fifth port are sequentially located at the center of the four outer edges of the cross-shaped structure.

[0018] The beneficial effects of this invention are as follows:

[0019] 1. High symmetry, excellent consistency, and controllable phase relationship: The cross-shaped symmetrical layout, consisting of a central square cavity and four identical rectangular cavities around it, ensures uniform energy distribution structurally. The four output ports are geometrically and electrically symmetrical, thus achieving excellent amplitude consistency.

[0020] 2. Compact Integration and High Performance: Filtering and four-way power splitting functions are integrated into a single planar resonant structure, avoiding the cascading of multiple components and effectively reducing overall size and insertion loss. Utilizing a square cavity TE... 201 Model and rectangular cavity TE 101 The coupling between modules achieves good bandpass filtering characteristics.

[0021] 3. Flexible design and simple process: The entire structure is realized through standard PCB process. By differentiating the design of the first metallized through hole (large diameter) and the second metallized through hole (small diameter), they are used to construct the low-loss main cavity boundary and the coupling window to realize precise coupling control, respectively. While ensuring performance, the processing difficulty is simplified, which is conducive to mass production. Attached Figure Description

[0022] Figure 1 This is a three-dimensional structural schematic diagram of the four-channel filter power divider of the present invention.

[0023] Figure 2 This is a top view of the four-channel filter power divider of the present invention.

[0024] Figure 3 This is a schematic diagram of the magnetic field distribution at the operating frequency of the four-channel filter power divider of the present invention.

[0025] Figure 4 This is a simulated amplitude-frequency response curve of a specific embodiment of the present invention.

[0026] Explanation of the labels in the diagram:

[0027] 1-Upper metal surface, 2-Middle dielectric substrate, 3-Lower metal surface, 4-First substrate integrated waveguide resonant cavity, 5-Second substrate integrated waveguide resonant cavity, 6-Third substrate integrated waveguide resonant cavity, 7-Fourth substrate integrated waveguide resonant cavity, 8-Fifth substrate integrated waveguide resonant cavity, 9-Coupled window, 10-Input port, 11-Second port, 12-Third port, 13-Fourth port, 14-Fifth port, 15-First metallized via, 16-Second metallized via, 17-Input slot, 18-Output slot. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] Please see Figure 1 and Figure 2 This embodiment provides a four-channel filter power divider, implemented using printed circuit board (PCB) technology. It features a typical three-layer board structure, consisting of an upper metal surface 1, a middle dielectric substrate 2, and a lower metal surface 3, from top to bottom. The upper and lower metal surfaces are typically made of copper foil, serving as grounding and shielding. The core functionality involves drilling and metallizing a series of vias on the middle dielectric substrate 2 to form a metallized via array. This via array is equivalent to metal sidewalls, enclosing the required substrate integrated waveguide (SIW) resonant cavity structure.

[0030] The resonant cavity structure is the core of this invention. It consists of a central resonant cavity and four identical branch resonant cavities coupled in a specific manner, forming a highly symmetrical cross-shaped planar layout.

[0031] Central resonant cavity: The first substrate integrated waveguide resonant cavity 4 is designed as a square. The square geometry gives it complete symmetry in four directions (corresponding to the four sides), which is the basic physical structure for achieving uniform energy distribution to the four output ports.

[0032] Branch resonant cavities: The four branch resonant cavities are the second substrate integrated waveguide resonant cavity 5, the third substrate integrated waveguide resonant cavity 6, the fourth substrate integrated waveguide resonant cavity 7, and the fifth substrate integrated waveguide resonant cavity 8. The second substrate integrated waveguide resonant cavity 5, the third substrate integrated waveguide resonant cavity 6, the fourth substrate integrated waveguide resonant cavity 7, and the fifth substrate integrated waveguide resonant cavity 8 are all rectangular in shape and are completely equal in size, ensuring the consistency of the physical structure of the four output channels.

[0033] Coupling Connections and Layout: The second substrate integrated waveguide resonator 5, the third substrate integrated waveguide resonator 6, the fourth substrate integrated waveguide resonator 7, and the fifth substrate integrated waveguide resonator 8 are precisely positioned at the center of the four sides of the first substrate integrated waveguide resonator 4. One long side of each rectangular resonator is parallel to and adjacent to one side of the square resonator, and the two are connected by an opening (i.e., coupling window 9). These four coupling windows 9 are the core channels for coupling electromagnetic energy from the central cavity to the four branch cavities. Their width is a key design parameter, directly determining the coupling coefficient between the cavities, and thus affecting the bandwidth of the filter.

[0034] Port Setup: Input port 10 feeds the signal through a first microstrip line with a characteristic impedance of 50 ohms. Input port 10 is located at a right-angle vertex of the square first substrate integrated waveguide resonant cavity 4. The four output ports, namely the second port 11, the third port 12, the fourth port 13, and the fifth port 14, output signals through four second microstrip lines with a characteristic impedance of 50 ohms each. These four output ports are preferably located at the geometric center of the long side of the four rectangular resonant cavities away from the central square cavity. The entire filter power divider structure is strictly axially symmetric about the axis connecting input port 10 and the center of the square cavity opposite it. This symmetry, combined with the specific operating mode of the excitation in the central square resonant cavity, is fundamental to ensuring excellent amplitude consistency and a definite phase distribution (i.e., two pairs of in-phase and pairs of out-of-phase) for the four output signals.

[0035] To optimize impedance matching and precisely control the external quality factor (Qe), this embodiment incorporates a fine slot structure at the connection between the microstrip line and the resonant cavity. The external quality factor is a key parameter describing the strength of coupling between the resonator and the external feed network, directly affecting the matching and insertion loss within the passband.

[0036] like Figure 2 As shown, at the connection between the first microstrip line (input feed line) and the first substrate integrated waveguide resonant cavity 4, an input slot 17 extending into the cavity is provided. This slot is used to finely adjust the external coupling strength at the input end.

[0037] At the connection points of the four segments of the second microstrip line (output feed line) and their respective connected resonant cavities, output slots 18 extending into the corresponding cavities are respectively provided. Specifically, an output slot is provided at the connection point between the microstrip line connecting the second port 11 and the second substrate integrated waveguide resonant cavity 5; an output slot is provided at the connection point between the microstrip line connecting the third port 12 and the third substrate integrated waveguide resonant cavity 6; an output slot is provided at the connection point between the microstrip line connecting the fourth port 13 and the fourth substrate integrated waveguide resonant cavity 7; and an output slot is provided at the connection point between the microstrip line connecting the fifth port 14 and the fifth substrate integrated waveguide resonant cavity 8. By adjusting the length and width of these input and output slots, the external coupling of each port can be independently and precisely controlled, thereby achieving optimal global impedance matching and minimizing passband insertion loss.

[0038] This embodiment employs two different diameter metallized through-holes to achieve a balance between performance optimization and machining accuracy. For example... Figure 2 As shown, the metallized via array includes a first metallized via 15 with a larger diameter and a second metallized via 16 with a smaller diameter.

[0039] The first metallized via 15 (large-diameter via): primarily serves to construct the boundary of the low-loss resonant cavity. Using a larger diameter via reduces the number of vias required per unit length while meeting the equivalent sidewall electrical conditions of SIW, thereby significantly reducing conductor losses caused by the via array and improving the cavity's unloaded Q-value. Therefore, the entire square boundary of the first substrate integrated waveguide resonant cavity 4 is completely enclosed by this array of large-diameter first metallized vias 15.

[0040] The second metallized via 16 (small-diameter via): primarily responsible for achieving precise coupling control. Small-diameter vias can be arranged more densely within a limited physical space, thus enabling more precise "characterization" of the equivalent electric walls of fine structures. In this design, the second metallized via 16 works in conjunction with the first metallized via 15 to jointly form the rectangular boundaries of the second, third, fourth, and fifth substrate-integrated waveguide resonant cavities. More importantly, the vias forming the "walls" on both sides of the four coupling windows 9, as well as the sidewalls of all input slots 17 and output slots 18, are all densely arranged from these small-diameter second metallized vias 16. By precisely adjusting the spacing and arrangement of these small-diameter vias forming the coupling windows and slots, the coupling strength can be controlled very precisely, thereby achieving precise control of the filtering response and external matching.

[0041] The working principle of this invention can be combined with Figure 3 The schematic diagram of the magnetic field distribution shown is provided for a deeper understanding. When the radio frequency signal is fed in from the input port 10 through the first microstrip line, the energy enters the square first substrate integrated waveguide resonant cavity 4 and excites the TE 201Resonant mode. In this mode, the magnetic field forms two symmetrical magnetic fields with opposite rotation directions within the square cavity. This provides an ideal field distribution basis for uniform coupling of energy in four directions.

[0042] Subsequently, electromagnetic energy is uniformly transferred from the central cavity to the four surrounding rectangular resonant cavities via four symmetrically distributed coupling windows 9 through magnetic coupling, exciting the electromagnetic field (TE) in these cavities. 101 Fundamental mode. Due to the high geometric and electrical symmetry of the entire cross-shaped structure, the energy transmitted to the four branch cavities naturally maintains a consistent amplitude. However, since the central square resonant cavity is excited by the TE mode... 201 The mode has two symmetrical but oppositely oriented electric field distribution regions. This causes the energy transmitted to the four branch cavities through coupling to naturally split into two groups in phase: the output signals from the second port 11 and the third port 12, located in the same electric field region of the central cavity, are in phase; the output signals from the fourth port 13 and the fifth port 14, located in the opposite electric field region of the central cavity, are in phase, while the output signals from these two groups of ports are out of phase. Ultimately, these four in-phase and equal-amplitude signals are output from the four output ports respectively. The frequency response of the bandpass filter is determined by the resonant frequencies of the central cavity and the branch cavities, the inter-cavity coupling coefficient, and the external coupling adjusted by the slot.

[0043] Based on the aforementioned principles of cross-shaped symmetrical structure, slot matching design, and differentiated metallized vias, this invention is modeled and optimized using three-dimensional electromagnetic simulation software. The specific dimensions of the first substrate integrated waveguide resonant cavity, the second, third, fourth, and fifth substrate integrated waveguide resonant cavities, the width of the coupling window, the length and width of the input / output slots, and the diameter and spacing of the two types of metallized vias, etc., can all be collaboratively designed and optimized according to the target operating frequency, bandwidth, and substrate properties.

[0044] Performance simulation results (combined with) Figure 4 Full-wave electromagnetic simulation was performed on the optimized model, and the resulting amplitude-frequency response curve is shown below. Figure 4 As shown. Simulation results show that the device exhibits good bandpass filtering and four-way power splitting characteristics. Input return loss S 11 The performance is better than -20 dB in the passband, indicating excellent impedance matching optimized by the slot structure, with most of the input energy being transferred rather than reflected. The transfer coefficients (Si) at the four output ports are also shown. 21 S 31 S 41 S 51The curves within the passband almost completely overlap. At the center frequency, the insertion loss is approximately -6.25 dB. Considering the inherent distribution loss of an ideal four-way power divider is -6.02 dB, the additional insertion loss of this invention is extremely low, demonstrating its low-loss characteristics. The amplitude imbalance between the four output ports is better than ±0.15 dB and the phase inconsistency is better than ±2 degrees within the passband, which fully verifies the excellent output consistency achievable through the cross-shaped symmetrical structure combined with precision design. Furthermore, the steep rejection curves on both sides of the passband demonstrate the device's good frequency selectivity.

[0045] In summary, this invention utilizes a central square TE 201 The mode resonator and four TEs around it 101 A high-performance, highly consistent four-channel filter power divider was successfully implemented in a single-layer planar structure by combining a cross-shaped symmetrical layout of cascaded rectangular resonant cavities, a fine slot structure at the feed point, and a metallized via design with differentiated diameters. Simulation results confirm its performance in terms of low insertion loss, high isolation, and excellent channel consistency, making it highly suitable for modern multi-channel wireless communication systems with stringent channel consistency requirements.

Claims

1. A four-channel filter power divider, characterized in that, It includes an upper metal surface (1), a middle dielectric substrate (2) and a lower metal surface (3) stacked together. The middle dielectric substrate (2) is provided with a resonant cavity structure surrounded by an array of metallized through holes. The resonant cavity structure includes a first substrate integrated waveguide resonant cavity (4), a second substrate integrated waveguide resonant cavity (5), a third substrate integrated waveguide resonant cavity (6), a fourth substrate integrated waveguide resonant cavity (7), and a fifth substrate integrated waveguide resonant cavity (8). The first substrate integrated waveguide resonant cavity (4) is square in shape, and the second substrate integrated waveguide resonant cavity (5), the third substrate integrated waveguide resonant cavity (6), the fourth substrate integrated waveguide resonant cavity (7) and the fifth substrate integrated waveguide resonant cavity (8) are all rectangular in shape, and the four rectangular resonant cavities are of equal size. The second substrate integrated waveguide resonant cavity (5), the third substrate integrated waveguide resonant cavity (6), the fourth substrate integrated waveguide resonant cavity (7) and the fifth substrate integrated waveguide resonant cavity (8) are respectively located at the center of the four sides of the first substrate integrated waveguide resonant cavity (4), forming a cross-shaped structure. The second substrate integrated waveguide resonant cavity (5), the third substrate integrated waveguide resonant cavity (6), the fourth substrate integrated waveguide resonant cavity (7) and the fifth substrate integrated waveguide resonant cavity (8) are all provided with coupling windows (9) between the first substrate integrated waveguide resonant cavity (4) and the first substrate integrated waveguide resonant cavity (4) for coupling electromagnetic energy to construct a filter passband. An input port (10) is provided at a right angle position of the first substrate integrated waveguide resonant cavity (4), and an output port is provided on the second substrate integrated waveguide resonant cavity (5), the third substrate integrated waveguide resonant cavity (6), the fourth substrate integrated waveguide resonant cavity (7) and the fifth substrate integrated waveguide resonant cavity (8), specifically the second port (11), the third port (12), the fourth port (13) and the fifth port (14).

2. The four-channel filter power divider according to claim 1, characterized in that, The electromagnetic field mode operating in the first substrate integrated waveguide resonant cavity (4) is TE. 201 The electromagnetic field mode operating in the second substrate integrated waveguide resonator (5), the third substrate integrated waveguide resonator (6), the fourth substrate integrated waveguide resonator (7), and the fifth substrate integrated waveguide resonator (8) is TE. 101 mold.

3. The four-channel filter power divider according to claim 1, characterized in that, The overall structure of the filter power divider is axially symmetrical along the center line of the input port (10).

4. The four-channel filter power divider according to claim 1, characterized in that, The input port (10) receives a signal through the first microstrip line, and each of the output ports outputs a signal through the second microstrip line.

5. The four-channel filter power divider according to claim 4, characterized in that, An input slot (17) extending into the cavity is provided at the connection point between the first microstrip line and the first substrate integrated waveguide resonant cavity (4); an output slot (18) extending into the corresponding cavity is provided at the connection point between each second microstrip line and the second substrate integrated waveguide resonant cavity (5), the third substrate integrated waveguide resonant cavity (6), the fourth substrate integrated waveguide resonant cavity (7) or the fifth substrate integrated waveguide resonant cavity (8) to which it is connected.

6. The four-channel filter power divider according to claim 1, characterized in that, The metallized via array includes a first metallized via (15) and a second metallized via (16) with different diameters, wherein the diameter of the first metallized via (15) is larger than the diameter of the second metallized via (16).

7. The four-channel filter power divider according to claim 6, characterized in that, The cavity boundary of the first substrate integrated waveguide resonant cavity (4) is enclosed by the first metallized via (15); the cavity boundaries of the second substrate integrated waveguide resonant cavity (5), the third substrate integrated waveguide resonant cavity (6), the fourth substrate integrated waveguide resonant cavity (7) and the fifth substrate integrated waveguide resonant cavity (8) are jointly enclosed by the first metallized via (15) and the second metallized via (16).

8. The four-channel filter power divider according to claim 1, characterized in that, The second port (11), the third port (12), the fourth port (13) and the fifth port (14) output signals with equal amplitude and in phase.

9. The four-channel filter power divider according to claim 1, characterized in that, The second port (11), the third port (12), the fourth port (13) and the fifth port (14) are respectively located at the center of the four outer sides of the cross-shaped structure.

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