A millimeter wave filtering power divider based on substrate integrated waveguide

Abstract

The application belongs to the technical field of radio frequency communication, and particularly relates to a millimeter wave filtering power divider based on a substrate integrated waveguide, which comprises a substrate upper metal layer, a substrate dielectric layer and a substrate lower metal layer; the substrate lower metal layer serves as a ground plane and covers the lower surface of the entire substrate dielectric layer, and the substrate upper metal layer is arranged on the upper surface of the substrate dielectric layer; the substrate dielectric layer is provided with a plurality of regularly arranged metal through holes which penetrate through the entire substrate dielectric layer and connect the substrate upper metal layer and the substrate lower metal layer. The filtering power divider proposed in the application is a filtering power division structure coupled by three SIW cavities, in two SIW rectangular cavities at the output end of the structure, the coupling window and the microstrip to SIW transition structure are perpendicular to each other, the structure can introduce a transmission zero point in the S parameter diagram to enhance the out-of-band suppression of the filtering power divider, and further improve the filtering performance of the filtering power divider.

Description

Technical Field

[0001] This invention belongs to the field of radio frequency communication technology, and specifically relates to a millimeter-wave filter power divider based on a substrate integrated waveguide. Background Technology

[0002] In the electromagnetic frequency band, electromagnetic waves in the range of 30 GHz to 300 GHz are defined as the millimeter wave band. Electromagnetic waves in this band are characterized by wide bandwidth, narrow beamwidth, and low atmospheric absorption attenuation at the window frequency. When applied to communication systems, they exhibit significant advantages such as strong anti-attenuation capabilities, strong anti-interference capabilities, large information capacity, and high security. Therefore, millimeter wave technology has immense application value in the field of communication and has been widely researched and applied in both military and civilian sectors.

[0003] In microwave and millimeter-wave radio frequency (RF) circuits, filters and power dividers are typically cascaded to suppress harmonics while achieving power distribution and eliminating noise and interference caused by nonlinear devices. However, cascaded filters and power dividers result in a large circuit size, hindering the miniaturization of RF circuit systems. Furthermore, this structure leads to significant losses and high design costs. Therefore, some researchers have proposed integrating the power divider and filter into a single filtered power divider design to achieve frequency-selective power dividers. This avoids the need for additional cascaded filters at the power divider's input or microstrip-SIW transition structure, thereby reducing the overall size and losses of the RF system. This approach has thus become an important means of achieving miniaturized RF front-ends.

[0004] As the frequencies used in radio frequency systems continue to increase, millimeter-wave bands have become widely used. However, this places higher demands on the precision of circuit fabrication, which in turn increases manufacturing costs and limits the widespread adoption of millimeter-wave applications. Substrate integrated waveguides (SIWs) are a novel microwave and millimeter-wave transmission line structure that can be fabricated using printed circuit board (PCB) technology, a mature and inexpensive process. SIWs achieve a nearly closed waveguide structure on a dielectric substrate, offering advantages such as low loss and high Q-value. Furthermore, they can be easily integrated with planar circuits, making this transmission structure a promising candidate for high-frequency applications in the microwave and millimeter-wave bands.

[0005] Currently, with the increasing scarcity of communication spectrum, microwave and millimeter-wave bands have been widely used due to their abundant spectrum resources. However, the increase in frequency brings difficulties in manufacturing and processing. Currently, the manufacturing processes for commonly used high-frequency devices, such as metal waveguides and LTCC processes, are difficult to process and require consideration of many factors during design, resulting in higher design and production costs.

[0006] Existing filter power dividers, such as bandpass filter power dividers based on SIW coupled cavities, have the following structure: Figure 1 As shown, the dual-mode response (TE) of the SIW triangular cavity is utilized. 101 Model and TE 102 A dual-passband bandpass filter power divider was designed, but its input return loss in the first passband was poor (only better than 10dB). Furthermore, the power divider lacked structures such as cross-coupling, resulting in the absence of transmission zeros in the overall S-parameter plot, leading to limited out-of-band suppression and poor frequency selectivity. Existing technologies utilize a half-mode SIW triangular cavity to construct the power divider output cavity, but the quality factor (Q value) of a half-mode SIW cavity is lower than that of a full-mode SIW cavity, especially in the high-frequency millimeter-wave band. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention proposes a millimeter-wave filter power divider based on a substrate integrated waveguide, comprising: an upper metal layer on the substrate, a substrate dielectric layer, and a lower metal layer on the substrate.

[0008] The lower metal layer of the substrate serves as the ground plane and covers the entire lower surface of the substrate dielectric layer. The upper metal layer of the substrate is disposed on the upper surface of the substrate dielectric layer. The substrate dielectric layer is provided with several regularly arranged metal vias that penetrate the entire substrate dielectric layer and connect the upper metal layer and the lower metal layer of the substrate.

[0009] Preferably, the regularly arranged metal through holes form three rectangular arrays, constituting a SIW rectangular resonant cavity including a first cavity, a second cavity, and a third cavity.

[0010] Furthermore, a microstrip to SIW transition structure is provided at the midpoint of the side of each cavity of the SIW rectangular resonant cavity, corresponding to the first microstrip to SIW transition structure, the second microstrip to SIW transition structure, and the third microstrip to SIW transition structure.

[0011] Furthermore, the third cavity of the SIW rectangular resonant cavity is provided with three metal through holes, and the first cavity and the second cavity are each provided with two metal through holes, and the metal through holes provided in the first cavity and the second cavity are longitudinally symmetrically distributed.

[0012] Furthermore, the SIW rectangular resonant cavity forms a first coupling window and a second coupling window through a metal through-hole array notch.

[0013] Furthermore, the two coupled windows are longitudinally symmetrically distributed.

[0014] Furthermore, the first microstrip to SIW transition structure is perpendicularly orthogonal to the first coupling window, the second microstrip to SIW transition structure is perpendicularly orthogonal to the second coupling window, and the third microstrip to SIW transition structure is located on the longitudinal symmetry line between the first microstrip to SIW transition structure and the second microstrip to SIW transition structure. The first microstrip to SIW transition structure, the second microstrip to SIW transition structure, and the third microstrip to SIW transition structure constitute a symmetrical structure distribution.

[0015] Furthermore, the microstrip-SIW transition structure consists of microstrip lines and coplanar waveguide structures.

[0016] The beneficial effects of this invention are:

[0017] 1. The power divider proposed in this invention is a power divider structure with three SIW cavities coupled together. In the two SIW rectangular cavities at its output end, the coupling window and the microstrip to the SIW transition structure are orthogonal and perpendicular to each other. This structure can introduce a transmission zero in the S-parameter diagram to enhance the out-of-band rejection of the power divider, thereby improving the filtering performance of the power divider.

[0018] 2. The three-cavity coupled filter power divider structure proposed in this invention has the characteristics of simple structure, easy processing and low cost. It introduces a transmission zero point. Its structure is simple and can be manufactured by PCB technology. It is easy to process and has low cost. It is suitable for microwave and millimeter wave high-frequency front-end system applications. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of an existing bandpass filter power divider based on a SIW coupled cavity.

[0020] Figure 2 This is a top view of the substrate dielectric and the stacked metal layers on the upper surface of the substrate of the millimeter-wave filter power divider based on substrate integrated waveguide of the present invention.

[0021] Figure 3 This is a three-dimensional view of the dielectric substrate, the upper surface metal layer of the substrate, and the lower surface metal layer of the substrate stacked in the millimeter-wave filter power divider based on the substrate integrated waveguide of the present invention.

[0022] Figure 4 This is a scaled layout of the substrate dielectric layer of the millimeter-wave filter power divider based on a substrate integrated waveguide according to the present invention.

[0023] Figure 5 This is a layout of the metal layer on the upper surface of the substrate of the millimeter-wave filter power divider based on a substrate integrated waveguide, with scale markings, according to the present invention.

[0024] Figure 6 The figure shows the simulation results of the millimeter-wave filter power divider based on substrate integrated waveguide of the present invention;

[0025] In the figure: 1: First cavity; 2: Microstrip to SIW transition structure; 3: Coupling window; 4, 6: Metal vias; 5: Second cavity; 7: Third cavity; 8: Upper metal layer of substrate; 9: Lower metal layer of substrate; 10: Dielectric layer of substrate; Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] A millimeter-wave filter power divider based on substrate integrated waveguide, such as Figure 2 , Figure 3 As shown, it includes: an upper metal layer (8) of the substrate, a substrate dielectric layer (10) and a lower metal layer (9) of the substrate, wherein the lower metal layer (9) of the substrate serves as a ground plane and covers the entire lower surface of the substrate dielectric layer (10).

[0028] like Figure 4 , Figure 5 As shown, the substrate dielectric layer (10) is provided with several metal vias, which penetrate the entire substrate dielectric layer (10) and connect the upper metal layer (8) and the lower metal layer (9) of the substrate. The regularly arranged metal vias form a rectangular array, which constitutes the first cavity (1), the second cavity (5), and the third cavity (7) of the SIW rectangular resonant cavity. The first cavity (1), the second cavity (5), and the third cavity (7) are coupled through a coupling window (3) formed by the notch of the metal via array, so as to couple the electromagnetic wave energy of the third cavity (7) to the two cascaded cavities, the first cavity (1) and the second cavity (5), and thus form a coupling filter power divider between the cavities. The width of the coupling window (3) can control the coupling amount between the cavities (1) and (7) to adjust the resonant frequency position of the two cavities. There are two coupling windows (3), which are symmetrical along the longitudinal direction.

[0029] Three metal through-holes (4) are provided inside the SIW rectangular resonant cavity (7) to interfere with the TE in the third cavity (7). 101 The three metal through holes (4) suppress the resonance of the fundamental mode, thereby eliminating the first passband.

[0030] The coupling window (3) of the first cavity (1) of the SIW rectangular resonator is set perpendicularly and orthogonally to the microstrip transition structure (2). This arrangement allows the third cavity (7) to couple with the first cavity (1) to excite the TE. 102The microband is placed at the midpoint of the side of the first cavity (1) to form the SIW transition structure. 102 The positive and negative phases cancel each other out at this point, thus obtaining a stable transmission zero point; in order to adjust the resonant frequency of the SIW cavity so that the resonant frequencies of the third cavity (7) and the first cavity (1) are close, thus forming a filter passband, two metal through holes (6) for adjusting the resonant frequency are set; the second cavity (5) and the first cavity (1) are set in the same way, and the two are set symmetrically along the longitudinal direction.

[0031] The microstrip to SIW transition structure (2) is used to convert the TEM mode to the TE mode. The electromagnetic wave transmitted on the microstrip line is in quasi-TEM mode, while the electromagnetic wave transmitted on the SIW is in TE mode. A transition structure is needed to transmit the electromagnetic wave from the microstrip line to the SIW.

[0032] The input and output of the filtering power divider circuit are realized by three microstrip lines and SIW transition structures (2), which are composed of microstrip lines and coplanar waveguide structures; one input transition structure is set in the third cavity (7), and two output transition structures are set in the first cavity (1) and the second cavity (5) respectively.

[0033] The overall circuit is symmetrically distributed along the longitudinal direction, which reduces the influence of phase difference on the filtering effect.

[0034] The working principle of this invention is as follows: The SIW rectangular cavity is connected to two output SIW resonant cavities through two coupling windows. The windows of equal width achieve 3dB power distribution. The coupling windows and output transition structures of the output SIW resonant cavities are orthogonally set. The electromagnetic and magnetic field distribution at the center of the side of the output cavity is very weak. Setting the output transition structure at this position can make the TE102 mode excited in the output cavity cancel each other out at this position, and the TEM mode cannot be excited, thus generating a transmission zero in the stopband.

[0035] Example 1: Simulation of the present invention was performed. The selected dielectric substrate material was Rogers RT5880, with a relative permittivity ε. r =2.2, loss tangent tanθ=0.0009, thickness is 0.508mm.

[0036] The simulation results of the S-parameters are shown below. Figure 6 S 11 S represents the input port return loss. 21 and S 31 The S-parameter plot shows that the center frequency of this example is 35.39 GHz, and the 3 dB bandwidth is 1.16 GHz. From the S-parameter plot... 11 The curve shows that the return loss is generally better than 20dB, indicating good matching; from S 21 and S 31As can be seen from the graph, the two curves almost overlap, and there is a transmission zero on the right side of the passband (at 36.62GHz). The transmission coefficient to the right of this transmission zero is better than 29dB, indicating good out-of-band suppression.

[0037] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A millimeter-wave filter power divider based on a substrate integrated waveguide, characterized in that, include: Upper metal layer of substrate, substrate dielectric layer and lower metal layer of substrate; The lower metal layer of the substrate serves as the ground plane and covers the entire lower surface of the substrate dielectric layer, while the upper metal layer of the substrate is disposed on the upper surface of the substrate dielectric layer. The substrate dielectric layer has several regularly arranged metal vias that penetrate the entire substrate dielectric layer and connect the upper metal layer and the lower metal layer of the substrate. Regularly arranged metal vias form three rectangular arrays, constituting a SIW rectangular resonant cavity containing a first cavity, a second cavity, and a third cavity; A microstrip to SIW transition structure is set at the midpoint of the side of each cavity of the SIW rectangular resonant cavity, corresponding to the first microstrip to SIW transition structure, the second microstrip to SIW transition structure, and the third microstrip to SIW transition structure. The third cavity of the SIW rectangular resonant cavity is provided with three metal through holes, and the first cavity and the second cavity are each provided with two metal through holes, and the metal through holes provided in the first cavity and the second cavity are symmetrically distributed longitudinally. The SIW rectangular resonant cavity forms the first and second coupling windows through the notches of the metal through-hole array. The two coupled windows are symmetrically distributed longitudinally. The first microstrip to SIW transition structure is perpendicularly orthogonal to the first coupling window, the second microstrip to SIW transition structure is perpendicularly orthogonal to the second coupling window, and the third microstrip to SIW transition structure is located on the longitudinal symmetry line between the first microstrip to SIW transition structure and the second microstrip to SIW transition structure. The first microstrip to SIW transition structure, the second microstrip to SIW transition structure, and the third microstrip to SIW transition structure constitute a symmetrical structure distribution. The microstrip-SIW transition structure consists of a microstrip line and a coplanar waveguide structure.

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