Miniaturized broadband SIW filter for satellite communications

Abstract

The application discloses a miniaturized broadband SIW filter for satellite communication. The SIW structure is adopted as a design basis, and the quarter-mode substrate integrated waveguide and the composite left-hand / right-hand structure are adopted to realize miniaturization of the radio frequency filter. In addition, the electromagnetic bandgap structure is adopted to realize strong suppression effect, high selection characteristic and wideband characteristic on the stop band. Main modules of the filter include a feed port of an electromagnetic bandgap (EBG) structure, a SIW resonant cavity, an inductive coupling window module and a CRLH structure. A tapered line is adopted for impedance matching of input / output ports, and in addition, a gap structure is etched on the input / output ports to realize EBG loading. The QMSIW cavity part is cut according to the symmetry of electromagnetic wave distribution, and the volume of the QMSIW is reduced to one fourth of the whole SIW structure. The CRLH structure loading is realized by using the interdigital structure, and the EBG structure is loaded on the interdigital metal.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication, and particularly relates to a miniaturized broadband SIW filter for satellite communication. Background Technology

[0002] Satellite communication, as a complement to 5G mobile communication, holds great promise, significance, and challenges. It can achieve global communication coverage, providing stable communication services across land, sea, and remote areas. Furthermore, satellite communication can effectively extend and enhance existing terrestrial wireless communication networks, offering broader, faster, and more reliable communication services. More importantly, satellite communication can provide timely communication support in situations such as natural disasters and emergency rescue, helping rescue workers and affected populations to communicate and coordinate effectively. These advantages are precisely what traditional wireless communication systems cannot achieve.

[0003] The satellite communications field is booming. From the launch of the first communications satellite by the Soviet Union in 1957, to the commercial launch of communications satellites by the United States in 1965, and now to the establishment of satellite internet and constellation networks, the field has always been full of unlimited development prospects and momentum. However, the development of satellite communications also faces a series of problems, the most fundamental of which is the allocation of spectrum resources. Satellite communications require specific spectrum resources, which are limited, and how to rationally manage and allocate these resources is a challenge. Currently, the commonly used frequency bands for satellite communications are the C, Ku, and Ka bands. In addition, the stability and security of satellite communications have also attracted widespread attention, such as how to resist communication quality problems caused by severe weather conditions and how to encrypt and protect transmitted information. The most important challenge facing the development of satellite communications is how to control costs. The construction and maintenance of satellite communication systems require huge investments, including the costs of satellite research and development, launch, orbit maintenance, and ground receiving equipment. How to reduce the cost of satellite communications is currently the most important research focus in satellite communications.

[0004] Reducing the cost of satellite communication can be achieved through the miniaturization and broadbanding of radio frequency (RF) devices in satellite communication systems. Miniaturization means a significant reduction in the overall mass and size of the satellite, which plays a crucial role in reducing launch and maintenance costs. Broadbanding is also an important characteristic of satellite communication devices. Broadband characteristics can meet the requirements of different communication frequency bands, enabling communication satellites to receive signals from various communication modes without the need for additional components. The current technical challenge is how to achieve both miniaturization and broadbanding in satellite communication. Summary of the Invention

[0005] The purpose of this invention is to provide a miniaturized broadband SIW filter for satellite communication, thereby reducing the size and weight of satellite communication devices while meeting the requirements of multiple communication modes in satellite communication. This filter, based on the SIW structure, features high power capacity and a high Q value, reducing the cost of satellite communication while improving communication quality.

[0006] To solve the above-mentioned technical problems, the specific technical solution of the present invention is as follows:

[0007] A miniaturized broadband SIW filter for satellite communication comprises a feed port with an electromagnetic bandgap (EBG) structure, a substrate integrated waveguide (SIW) resonant cavity surrounded by a via, an inductive coupling window module, and a composite right-handed / left-handed structure (CRLH).

[0008] EBG-loaded feed ports: Traditional feed port values ​​only focus on impedance matching, using tapered lines, finned lines, or exponentially tapered lines for impedance matching. In this invention, in addition to using tapered lines for impedance matching, EBG loading is achieved by etching slot structures at the input and output ports, thereby meeting the requirements of satellite communication filters for stopband suppression, selectivity, and bandwidth.

[0009] Substrate Integrated Waveguide (SIW) Resonant Cavity Surrounded by Holes: In this invention, the SIW resonant cavity is cut using the symmetry of electromagnetic wave distribution. The cut cavity still retains similar resonant characteristics, such as resonant frequency, resonant mode, and number of resonant points. By cutting along the x-axis and y-axis symmetry directions, the volume of the QMSIW is reduced to one-quarter of the entire SIW structure, significantly reducing its size.

[0010] Inductive Coupling Window Module: A single resonant cavity is only the basic structure for filter design; to achieve the filtering effect, a series of resonant cavities need to be coupled. This invention uses the most common and easiest-to-implement SIW structure—the inductive resonant window structure—for magnetic coupling. The SIW structure suppresses electromagnetic wave leakage by surrounding the cavity with circular metal vias. The inductive coupling window module extracts a certain number of metal vias from a tightly packed array of metal vias, creating a metal-free region of a certain width. Electromagnetic waves can then be coupled through these gaps, and the strength of the magnetic coupling effect is positively correlated with the width of the opening.

[0011] Composite Right-Handed / Left-Handed CRLH Structure: To further improve the integration and reduce the size of this filter, this invention further loads a CRLH structure on top of the QMSIW to form a slow-wave propagation pattern, thereby further reducing the filter size by changing the propagation phase velocity. The most classic and easily implemented CRLH structure is the tilted interdigital structure, which is used in this invention to achieve miniaturized filter design. Furthermore, an EBG structure can also be loaded onto this tilted interdigital structure to achieve bandwidth expansion and suppression of stopband and clutter. This invention employs a circular aperture loading method, etching a circular aperture notch again on the already etched tilted interdigital structure to achieve circular aperture EBG loading.

[0012] The aforementioned miniaturized broadband SIW filter can be applied to satellite communications. Its broadband characteristics enable satellite communication systems to receive signals from multiple communication frequency bands using only a single filter, significantly reducing system complexity. Furthermore, the use of the QMSIW structure and the addition of a CRLH structure greatly reduces the filter's size, further improving integration, which is of great significance for reducing the cost of satellite communications. To achieve broadband characteristics and suppress spurious passbands, an EBG structure is loaded onto the input / output ports and the CRLH structure, resulting in higher filter selectivity.

[0013] Furthermore, the miniaturized broadband SIW filter fully utilizes the symmetry of the electromagnetic distribution of the SIW resonant cavity and adopts a QMSIW structure, that is, the SIW cavity is cut in half along the axis of symmetry. Since the electromagnetic field distribution is symmetrical along the x-axis and y-axis, cutting the SIW cavity in half along the axis of symmetry reduces the volume to one-quarter of the original cavity.

[0014] Furthermore, the miniaturized broadband SIW filter also incorporates a slow-wave effect by loading a CRLH (Continuous Lamp Helix) to reduce the filter size. The slow-wave effect involves loading certain special periodic structures to disturb the electromagnetic field distribution of microwave devices, thereby altering their transmission characteristics. The most significant characteristic is a decrease in the phase velocity of the electromagnetic wave, hence the name "slow-wave effect."

[0015] The most typical structure for realizing the slow-wave effect is the tilted interdigitated structure, which includes several finger-shaped metal strips (this invention uses a 7th-order tilted interdigitated structure) and non-metallic spacing between them. The length and width of the metal strips affect the resonant frequency of the resonant cavity. Furthermore, the non-metallic gaps between the metal strips determine the coupling strength; by changing the spacing, the resonant response can also be adjusted.

[0016] Furthermore, the miniaturized broadband SIW filter is fed using a microstrip transmission line. Due to the inconsistency in the transmission line structure, discontinuities in the transmission mode occur, leading to electromagnetic wave reflection and loss. To reduce the adverse effects of impedance mismatch while considering fabrication feasibility, a linearly tapered microstrip transmission line structure is used for feeding. Common impedance matching methods include exponential tapering and finned tapering, but these have high design complexity and require high fabrication precision. This invention, considering both performance and cost, adopts the easiest to implement and highest-performing linearly tapered impedance matching structure. Simultaneously, the design focus is placed on miniaturization and broadband design. While the linearly tapered impedance matching structure achieves the conversion from a microstrip transmission line to a SIW transmission line structure, its suppression of parasitic passbands and stopbands is poor. This invention uses an electromagnetic bandgap (EBG) structure, i.e., by loading a slot structure at the input and output ports to achieve stopband suppression and spurious passband suppression, thereby giving the designed filter broadband characteristics. The number of slots, the spacing between slots, and the width of the slots all affect the suppression effect.

[0017] Furthermore, the miniaturized broadband SIW filter not only uses a 7th-order tilted interdigital structure as the CRLH structure, but also employs a 2nd-order coupled cavity for filter design. The QMSIW structure with the CRLH structure is reduced in size to a quarter or even less than that of a traditional SIW. However, this only achieves miniaturization of the resonant cavity, enabling a small resonant cavity to achieve the resonant response of a large-volume resonant cavity. Further, at least two resonant cavities are electro- / magnetically coupled through electromagnetic coupling, causing their respective resonant points to mutually attract each other, thus achieving the filtering effect.

[0018] Furthermore, the miniaturized broadband SIW filter is fabricated using a gold-to-gold thermocompression bonding method. A QMSIW device is split into upper and lower pieces and fabricated separately, then finally bonded together into a unified whole structure via thermocompression bonding. The temperature, pressure, and duration of this bonding process significantly affect the final performance of the filter. Excessive thermocompression time can cause metal diffusion into the substrate material, leading to increased substrate loss; furthermore, the dimensional parameters resulting from thermocompression deviate considerably from design standards. Therefore, this invention represents a significant innovation and breakthrough in both design and fabrication.

[0019] Furthermore, the QMSIW resonant cavity includes an all-metal circular via, an inductive coupling window, and a resonant cavity body. Regardless of whether a traditional SIW or QMSIW structure is used, there are very strict requirements for the radius of the metal vias, the spacing between the vias, and the width of the SIW structure. Otherwise, excessively small vias and large spacing will cause electromagnetic wave leakage, leading to increased losses. Specific dimensional requirements are as follows: s / d < 2, d / w < 0.1, where s is the spacing between the centers of the metal vias, d is the diameter of the metal vias, and w is the width of the SIW structure.

[0020] Furthermore, the inductive coupling window refers to a non-metallic enclosed area, similar to a "window," formed by partially removing metal through-holes and not completely isolating the two cavities. The length of this area, as well as the radius and spacing of the metal through-holes on both sides of the window, all affect the coupling effect. Among these, the length of the window has the most significant impact on electromagnetic coupling.

[0021] Furthermore, the loaded CRLH structure adopts an inclined interdigital structure, which includes several finger-shaped metal strips (this invention uses a 7th-order inclined interdigital structure) and non-metallic spacing between them. The length and width of the metal strips affect the resonant frequency of the resonant cavity. In addition, the non-metallic gaps between the metal strips determine the coupling strength; the resonant response can be adjusted by changing the spacing.

[0022] Furthermore, the tilted interdigitated structure is also improved by loading EBG (Extended Enlargement Gel) to enhance stopband suppression characteristics and increase bandwidth. Different shaped circular holes are further etched into the already etched metal interdigitated strip. The size and position of these holes are adjusted to control the suppression effect of the stopband and stray passband.

[0023] Furthermore, to reduce its radiation characteristics and thus electromagnetic loss, the loaded CRLH structure is etched into the middle layer of the QMSIW structure, rather than being etched into the top metal layer in the traditional way. If etched into the top metal layer, the cavity would act like a slot antenna, with electromagnetic waves propagating to the far field through the slots, causing electromagnetic loss. This invention innovatively places it in the middle metal layer, reducing the volume while avoiding losses caused by electromagnetic radiation.

[0024] The miniaturized broadband SIW filter for satellite communication of the present invention has the following advantages:

[0025] Unlike the microstrip or stripline structures used in traditional communications, this invention employs a SIW structure with higher power capacity and a higher quality factor (Q value) as its design basis. It utilizes quarter-mode substrate integrated waveguide (QMSIW) and composite left-handed / right-handed structure (CRLH) techniques to achieve miniaturization of the RF filter. Furthermore, by loading an electromagnetic bandgap structure (EBG), it achieves high selectivity, wide bandwidth, and strong stopband suppression.

[0026] The main modules of the filter include the feed port of the electromagnetic bandgap (EBG) structure, the SIW resonant cavity, the inductive coupling window module, and the CRLH structure. The input / output ports use tapered lines for impedance matching, and EBG loading is achieved by etching slot structures at the input and output ports. The QMSIW cavity portion utilizes the symmetry of electromagnetic wave distribution to cut the SIW resonant cavity, reducing the QMSIW volume to one-quarter of the entire SIW structure. The CRLH structure is loaded using a tilted interdigital structure, and the EBG structure is loaded onto the interdigital metal to further suppress clutter. This invention reduces the size and weight of satellite communication devices while meeting the requirements of multiple communication modes in satellite communication. Based on the SIW structure, this filter features high power capacity and high Q value, reducing satellite communication costs while improving communication quality. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the three-dimensional structure of the filter in an embodiment of the present invention;

[0028] Figure 2 (a) is a cross-sectional view of the three-dimensional structure of the filter along line A-A' in an embodiment of the present invention;

[0029] Figure 2 (b) is an exploded cross-sectional view of the three-dimensional structure of the filter along line A-A' in an embodiment of the present invention;

[0030] Figure 3 (a) is a diagram showing the application scenarios of traditional filters;

[0031] Figure 3 (b) is a diagram showing the application scenario of the miniaturized broadband filter of the present invention;

[0032] Figure 4 (a) is a diagram of the filter structure as a traditional SIW;

[0033] Figure 4 (b) is a diagram showing the symmetrical cropping of the SIW structure using the half-mode method for the filter;

[0034] Figure 4 (c) is a structural diagram of the QMSIW used in this invention;

[0035] Figure 4(d) is Figure 4 (a)- Figure 4 (c) Comparison of the resonant responses of the three filter structures;

[0036] Figure 5 (a) is a diagram of a traditional QMSIW resonant cavity;

[0037] Figure 5 (b) is Figure 5 (a) The CRLH structure diagram was loaded onto the structure;

[0038] Figure 5 (c) is Figure 5 (b) Based on the tilted interdigitated structure, the loading diagram of the electromagnetic bandgap structure (EBG) is continued;

[0039] Figure 5 (d) is Figure 5 (c) A linearly gradient input / output port diagram was used;

[0040] Figure 6 (a) is a three-dimensional schematic diagram of the QMSIW resonant cavity of the present invention;

[0041] Figure 6 (b) is a planar schematic diagram of the QMSIW resonant cavity of the present invention;

[0042] Figure 7 This is a schematic diagram of the gap coupling structure of the present invention;

[0043] Figure 8 This is a schematic diagram of the invention having a top-layer metal gap coupling structure;

[0044] Figure 9 This is a schematic diagram of the present invention with a CRLH coupling structure;

[0045] Figure 10 This is the electromagnetic performance curve of the single-cavity filter of the present invention.

[0046] The markings in the diagram are as follows: 1. Air environment; 2. Lower substrate; 3. First input microstrip line structure; 4. First tilted interdigital structure; 5. Metal strip; 6. Inductive coupling window; 7. Second input microstrip line structure; 8. Hole; 9. Metal film; 10. Upper substrate; 11. Upper metal layer; 12. Intermediate metal layer; 13. Slot coupling structure; 14. Slot coupling structure of upper metal layer; 15. Second tilted interdigital structure. Detailed Implementation

[0047] To better understand the purpose, structure, and function of this invention, a miniaturized broadband SIW filter for satellite communication will be described in further detail below with reference to the accompanying drawings.

[0048] The terminology used in this article in the fields of radio frequency communication and semiconductors are technical terms commonly used by those skilled in the art. For example, in radio frequency communication, IL represents insertion loss, and RL represents return loss due to impedance mismatch. Furthermore, standard processes involved in MEMS fabrication, such as positive / negative photoresist, deep silicon etching, metal stripping, and quasi-LIGA processes, are consistent with the general understanding of those skilled in the art.

[0049] This application proposes a miniaturized broadband microwave filter for satellite communication. By utilizing a quarter-mode SIW (QMSIW) structure and a loaded composite right-hand / left-handed structure (CRLH), the filter size is significantly reduced, achieving miniaturization and weight reduction of the radio frequency communication system. Furthermore, to suppress out-of-band parasitic passbands, this invention also employs electromagnetic bandgap (EBG) loading.

[0050] This invention includes: a feed port with an electromagnetic bandgap (EBG) structure, comprising an input port and an output port, located at the front end of the filter and responsible for signal input and output, with enhanced spurious suppression capability through the EBG structure; a substrate integrated waveguide (SIW) resonant cavity surrounded by vias, closely connected to the input and output ports, realizing electromagnetic wave resonance; the resonant cavity is loaded with a composite right-hand / left-handed CRLH structure to form a slow wave effect, and the use of a tilted interdigitated structure achieves perturbation and modulation of electromagnetic waves, realizing coupling between different modes of electromagnetic waves in the same SIW cavity; and an inductive coupling window module located between different SIW resonant cavities, realizing coupling between different resonant cavities.

[0051] Through holes can be made of all metal or have a gold-plated surface;

[0052] Figure 1 This is one embodiment of the present application, which includes an air environment 1, a lower substrate 2, an input microstrip line structure 3, and a first tilted interdigital structure 4, which is commonly used in CRLH structures. The first tilted interdigital structure 4 contains multiple metal strips 5 to generate perturbations to the electromagnetic field. The air environment 1 surrounds the entire SIW structure filter to simulate the atmospheric environment in a real environment to ensure the accuracy of the simulation design. The lower substrate 2 is the foundation of the entire SIW filter, on which the microstrip line input structure 3 and the CRLH first tilted interdigital structure 4 are etched.

[0053] Inductive coupling window 6 couples the two SIW resonant cavities, enabling electromagnetic wave transmission and frequency selection. Furthermore, the coupling window determines the coupling strength and coupling coefficient between the two resonant cavities; adjusting the length of the coupling window controls the filter's effectiveness. The resonant cavity, encompassed by the all-metal aperture 8, effectively confines electromagnetic waves, preventing leakage. This is why the SIW structure boasts a high quality factor.

[0054] Figure 1 The filter-loaded CRLH structure shown employs an EBG-loaded tilted interdigital structure. As can be seen in Figure 5, circular holes are etched into the metal strip 5. Meanwhile, Figure 1 The input and output ports, namely the first input microstrip line structure 3 and the second input microstrip line structure 7, also exhibit rectangular slot loading, achieving the same EBG loading effect and suppressing parasitic passbands in the stopband. The first input microstrip line structure 3 refers to the input port, and the second input microstrip line structure 7 is the output port. The input port is located at the filter input and connects to the signal source; the output port is located at the filter output and is responsible for transmitting the filtered signal to the load.

[0055] Figure 2 It is along Figure 1 Please also refer to the sectional view of line A-A'. Figure 1 and Figure 2 In one embodiment of the present invention, a metal film 9 sputtered beneath the lower substrate 2 serves as a GND, i.e., a zero-potential plane. Besides the metal film 9, the filter also includes an intermediate metal layer 12 and an upper metal layer 11. The intermediate metal layer 12 is located between the lower substrate 2 and the upper substrate 10, and is mainly used for etching the input / output ports and the tilted interdigitated structure. The upper metal layer 11 is located on top of the upper substrate 10 and is formed by sputtering metal. They are interconnected through all-metal vias 8, which are electrically equivalent to inductive elements, a characteristic of SIW structures. Furthermore, both traditional SIW and QMSIW structures have very strict requirements regarding the radius of the metal vias, the spacing between vias, and the width of the SIW structure. Otherwise, excessively small vias and large spacing will cause electromagnetic wave leakage, leading to increased losses. The specific dimensional requirements are as follows: s / d < 2, d / w < 0.1, where s is the spacing between the centers of the metal vias, d is the diameter of the metal vias, and w is the width of the SIW structure. The upper substrate 10, located on the top layer of the filter, covers the tilted interdigital structure. It covers the middle metal layer, preventing electromagnetic wave radiation loss, which is a key difference between this filter and traditional SIW structure filters.

[0056] Figure 3This is the application scenario for this miniaturized broadband filter. In traditional radio frequency communication systems, namely... Figure 3 In (a), to enable the system to support multiple communication standards, a large number of filter banks in different frequency bands are required. Therefore, this communication system is not only structurally complex and bulky, but the numerous matching networks also degrade the overall communication quality. For example... Figure 3 As shown in (b), by using a novel miniaturized broadband filter, not only is the size reduced, but the number of filters used is also reduced, avoiding complex matching networks. Especially in energy- and space-constrained applications such as satellite communications, miniaturization and broadband of RF devices are key to cost savings.

[0057] Figure 4 This is the basic resonant cavity structure of the filter. Figure 4 (a) is the most basic traditional SIW structure. Figure 4 (b) uses a half-mold method to symmetrically cut the SIW structure, and accordingly... Figure 4 (c) is the QMSIW structure used in this invention, which is further symmetrically modified and trimmed based on the half-molding method. Therefore, QMSIW has the most streamlined structure. From Figure 4 As can be seen from the S11 curve in (d), the resonant responses of the three structures have similar resonant points, with only a very small frequency deviation. This further illustrates that the QMSIW structure can achieve a resonant effect and can be used for filter design to achieve filter miniaturization.

[0058] Figure 5 It is the process of the evolution of the QMSIW structure resonant cavity. Figure 5 (a) is a traditional QMSIW resonant cavity. To further reduce the size, a CRLH structure was added. Figure 5 (b) is Figure 5 (a) The CRLH structure is loaded onto the structure; the loading of the CRLH structure enables slow wave transmission of electromagnetic waves, which reduces the phase velocity of electromagnetic waves. Figure 5 (c) involves further loading an electromagnetic bandgap (EBG) structure onto the tilted interdigitated structure. By etching circular holes, spurious passbands in the filter's stopband can be suppressed. Ultimately... Figure 5 (d) Linearly gradient input / output ports are used, and EBG gaps are applied to the input / output ports, which also aims to improve the suppression effect on the stopband. Figure 5 The lower layer represents the electric field distribution diagram corresponding to each structure. It can be seen that the loading of the CRLH structure plays a regulatory role in the electric field distribution.

[0059] Figure 6This refers to a QMSIW resonant cavity with an added upper substrate, which forms the basis of miniaturized broadband filter structures. Adding an upper substrate structure prevents electromagnetic wave radiation loss; otherwise, electromagnetic waves would propagate to the far field through metal gaps. Figure 6 (a) shows a three-dimensional schematic diagram of the resonant cavity. Figure 6 (b) shows the key dimensions of the structure, including the length and width of the resonant cavity, the length of the interdigitated fingers of the tilted interdigitated structure, the coupling spacing between the interdigitated fingers, and the gap width of the EBG loading at the input and output ports. The specific value range is shown in Table 1. When the dimensions are within this range, a relatively ideal resonance curve can be obtained.

[0060] Table 1. Critical Dimension Range of Resonant Cavities

[0061]

[0062] In one embodiment of this application, gap coupling with an intermediate metal layer is employed, as shown in the schematic diagram below. Figure 7 As shown in the figure, the slot coupling structure 13 couples the electromagnetic waves in the first cavity to the inclined interdigital structure of the second cavity, thereby realizing the transmission of electromagnetic waves. The slot coupling structure 13 is located between the two QMSIW resonant cavities, and the slots extend into both resonant cavities to achieve coupling.

[0063] The length and width of the coupling slot in this structure have a significant impact on the electromagnetic performance of the filter. The frequency selectivity of the filter can be achieved by selecting appropriate size parameters.

[0064] In one embodiment of this application, gap coupling of the upper metal layer is employed, as shown in the schematic diagram below. Figure 8 As shown. The upper metal has a slot coupling structure 14, which is located on the top metal layer between the two QMSIW resonant cavities, with the slots extending into both cavities to achieve coupling. It is... Figure 7 An evolution, the basis of which is still Figure 1 The second-order inductively coupled QMSIW filter is described. By etching coupling gaps in the upper metal layer, it is possible to avoid conflict with the intermediate CRLH structure, thereby opening the coupling gaps to the point where the electric field strength of the tilted interdigital structure is maximum.

[0065] In one embodiment of this application, CRLH coupling with an intermediate metal layer is employed, as shown in the schematic diagram below. Figure 9 As shown, a second tilted interdigital structure 15 is further etched at the center of the inductive coupling window to regulate and couple the electromagnetic field, thereby achieving a better filtering effect.

[0066] Figure 10This is the filtering effect curve of a single-cavity resonant cavity. Due to the presence of the tilted interdigital structure, electromagnetic waves of different propagation modes resonate, enabling a single cavity to achieve a filtering effect. As shown in the figure, the filter's center frequency is 6GHz, covering the uplink channel frequency of C-band satellite communication, and the loss at this frequency is only 0.04dB, while the return loss is close to 20dB.

[0067] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A miniaturized broadband SIW filter for satellite communication, characterized in that, include: The feed port, which incorporates an electromagnetic bandgap (EBG) structure, includes both an input and an output port. Located at the front end of the filter, this port handles both signal input and output, enhancing spurious suppression capabilities through the EBG structure. A substrate integrated waveguide (SIW) resonant cavity, surrounded by vias and connected to the input and output ports, enables electromagnetic wave resonance. This resonant cavity incorporates a composite right-handed / left-handed CRLH structure to create a slow-wave effect. The use of a tilted interdigitated structure allows for perturbation and modulation of the electromagnetic waves, achieving coupling between different modes of electromagnetic waves within the same SIW cavity. An inductive coupling window module is located between different SIW resonant cavities, facilitating coupling between them. Through holes can be made of all metal or have a gold-plated surface.

2. The miniaturized broadband SIW filter for satellite communication according to claim 1, characterized in that, The symmetry of the electromagnetic distribution of the SIW resonant cavity was utilized to adopt a quarter-mode SIW (QMSIW). A quarter-mode SIW (QMSIW) means that the SIW cavity is cut in half along the axis of symmetry. Since the electromagnetic field distribution is symmetrical along both the x-axis and y-axis, the volume of the resonant cavity is reduced to one-quarter of the original cavity volume.

3. The miniaturized broadband SIW filter for satellite communication according to claim 2, characterized in that, The tilted interdigital structure consists of several finger-shaped metal strips and non-metallic spacing that couples with each other; the length and width of the metal strips affect the resonant frequency of the resonant cavity; the non-metallic gaps between the metal strips determine the magnitude of the coupling strength, and the resonant response can be adjusted by changing the size of the spacing.

4. The miniaturized broadband SIW filter for satellite communication according to claim 3, characterized in that, The quarter-mode SIW (QMSIW) uses a linearly tapered microstrip transmission line structure for power feeding.

5. The miniaturized broadband SIW filter for satellite communication according to claim 4, characterized in that, The linearly gradient microstrip transmission line structure realizes the transformation from microstrip transmission line to SIW transmission line structure. The methods to improve stopband suppression characteristics include step impedance structure (SIR), source-load coupling, and electromagnetic bandgap structure (EBG). The EBG structure achieves stopband suppression and spurious passband suppression by loading slot structures on the input and output ports, thereby giving the designed filter broadband characteristics. The number, spacing, and width of the slots all affect the suppression effect.

6. The miniaturized broadband SIW filter for satellite communication according to claim 5, characterized in that, The SIW resonant cavity loaded with tilted interdigital fingers is coupled in second order; at least two resonant cavities are coupled electro-magnetically by means of electromagnetic coupling, so that the resonant points of the resonant cavities attract each other, thereby achieving the filtering effect; The coupling design adopts the magnetic window coupling method in SIW filters; instead of completely isolating the two cavities with through holes, a portion of the through holes is extracted to form a non-metallic surrounding area similar to a "window"; the length of this area and the radius and spacing of the through holes on both sides of the window all affect the coupling effect.

7. The miniaturized broadband SIW filter for satellite communication according to claim 6, characterized in that, To reduce its radiation characteristics and thus electromagnetic loss, the CRLH structure is etched onto the intermediate metal layer of the QMSIW structure; this reduces the volume while also avoiding losses caused by electromagnetic radiation.

8. The miniaturized broadband SIW filter for satellite communication according to claim 7, characterized in that, To enhance stopband suppression characteristics and increase bandwidth, the CRLH structure is improved by loading EBG. Different shaped circular holes are further etched on the already etched metal interdigitated strip. This structure controls the suppression effect on stopband and stray emissions by adjusting the size and position of the circular holes.

9. The miniaturized broadband SIW filter for satellite communication according to claim 8, characterized in that, The SIW filter is fabricated using a gold-gold thermocompression bonding method. A QMSIW device is split into two parts, which are fabricated separately and then bonded together to form a unified whole structure.

10. The miniaturized broadband SIW filter for satellite communication according to claim 9, characterized in that, The specific dimensional requirements for the SIW cavity regarding the radius of the vias, the spacing between vias, and the width of the SIW structure are as follows: s / d < 2, d / w < 0.1 Where s is the distance between the centers of the through holes, d is the diameter of the through holes, and w is the width of the SIW structure.

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