Substrate integrated duplexer with independently controllable cut-off frequency

Abstract

The invention discloses a substrate integrated duplexer with independently controllable cut-off frequency, and belongs to the technical field of microwave communication. Wherein the substrate integrated waveguide comprises a top-layer dielectric substrate, a bottom-layer dielectric substrate and a multi-layer filtering structure arranged between the top-layer dielectric substrate and the bottom-layer dielectric substrate, and the multi-layer filtering structure sequentially comprises a first dielectric layer, a first metal column layer, a second dielectric layer, a second metal column layer, a third dielectric layer and a copper-clad layer from bottom to top; each layer is provided with two rows of cylindrical through holes, the inner walls of the cylindrical through holes are coated with copper to form side electric walls, and the side electric walls are fixed through positioning screws; the passband and stopband cut-off frequency is independently controlled by adjusting the width of each layer of cylindrical through hole. According to the invention, the upper and lower cut-off frequencies and the high-stop-band frequency of two passbands of the duplexer are independently regulated and controlled under a compact structure; by introducing the multi-layer through hole structure and the metal column layer, the selectivity, isolation and out-of-band rejection performance of the device are effectively improved; and meanwhile, low insertion loss, good electromagnetic compatibility and manufacturing process consistency are ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave communications, and in particular relates to a substrate integrated duplexer with independently controllable cutoff frequency. Background Art

[0002] The continuous advancement of wireless communication technology has placed higher demands on the performance of devices in the microwave and millimeter wave bands, especially in terms of miniaturization, improved transmission efficiency, and suppression of out-of-band interference. As a key component for separating transmit and receive signals, duplexers are widely used in radar communications, satellite communications, 5G base stations, and other fields. Their performance has a significant impact on the reliability and stability of the entire system.

[0003] Currently, duplexers based on substrate integrated waveguide (SIW) technology have attracted widespread attention due to their advantages of low insertion loss, good compatibility, and ease of integration. However, existing duplexers based on resonant cavity structures or electromagnetic perturbation designs have the following problems when achieving bandpass characteristics: (1) Limited freedom of control of the passband boundary: In most designs, the upper and lower cutoff frequencies of the passband are highly coupled, making it difficult to achieve independent adjustment, which affects the optimization of filter performance; (2) Structural size limits compact development: When traditional planar duplexers are expanded to multiple channels, the overall size is difficult to control, which restricts their application in highly integrated systems; (3) Insufficient out-of-band suppression performance: Some structures fail to fully suppress out-of-band parasitic responses, resulting in insufficient anti-interference capabilities; (4) It is difficult to balance insertion loss and isolation: Insertion loss performance is often sacrificed in high isolation designs, resulting in a performance trade-off problem.

[0004] To address these issues, surface plasmon-like (ESSPP) structures have been gradually introduced in recent years. Their engineered dispersion properties enable precise control of the transmission passband. These structures utilize a combination of periodic metal units and dielectrics to mimic the transmission characteristics of electromagnetic modes on metal surfaces. They offer excellent cutoff frequency tunability and compact structure, making them a key research direction for improving duplexer performance.

[0005] Although existing research has explored the integration of ESSPP structure and SIW technology to a certain extent, there is still a lack of a duplexer design solution with a compact structure, independently controllable cutoff frequency, high isolation and low insertion loss characteristics.

[0006] In view of this, this application is hereby filed. Summary of the Invention

[0007] The purpose of the present invention is to provide a substrate integrated duplexer with independently controllable cutoff frequency, so as to solve the problems in the prior art that the passband cutoff frequency and the out-of-band cutoff frequency cannot be independently controlled, the insertion loss is high, and the stability of the stopband needs to be enhanced.

[0008] Technical solution: A substrate-integrated duplexer with independently controllable cutoff frequency, comprising a substrate-integrated waveguide, the substrate-integrated waveguide comprising a top dielectric substrate, a bottom dielectric substrate, and a multilayer filter structure disposed therebetween. The multilayer filter structure comprises, from bottom to top, a dielectric layer 1, a metal pillar layer 1, a dielectric layer 2, a metal pillar layer 2, a dielectric layer 3, and a copper cladding layer.

[0009] Each layer is provided with two rows of cylindrical through holes, the inner wall of which is covered with copper to form the side electrical wall and fixed by positioning screws;

[0010] A first microstrip line and a second microstrip line are provided on the top of the bottom dielectric substrate, and a third microstrip line is provided on the top of the top dielectric substrate;

[0011] One end of the first microstrip line is a feeding port connected to the first microwave high-frequency connector, and the other end is connected to the second microwave high-frequency connector via the second microstrip line;

[0012] The third microstrip line is connected to the third microwave high-frequency connector as an output port;

[0013] The passband and stopband cutoff frequencies can be independently controlled by adjusting the width of the cylindrical through holes in each layer.

[0014] In a further embodiment, the dielectric layer 1 includes a dielectric substrate 1 and a surface copper sheet 1, and the widths of the two rows of cylindrical through holes are adjusted to adjust the cutoff frequency in the first passband.

[0015] In a further embodiment, the metal column layer 1 has a "V" structure, including a dielectric 1, a plurality of air gaps 1 are spaced apart on the dielectric 1, the sidewalls of the air gaps 1 are covered with a copper sheet 1, the copper sheet 1 and the dielectric 1 constitute a metal column 1, and the metal column 1 is spaced apart between two rows of cylindrical through holes, and the width of the two rows of cylindrical through holes adjusts the cutoff frequency on the first passband.

[0016] In a further embodiment, the second dielectric layer includes a second dielectric substrate, a second surface copper sheet, and second rectangular air slots clad with copper at both ends of the second dielectric substrate, wherein the width of the two rows of cylindrical through holes adjusts the cutoff frequency in the second passband.

[0017] In a further embodiment, the metal column layer 2 has a "V" structure, including a dielectric 2, a plurality of air gaps 2 are spaced apart on the dielectric 2, the sidewalls of the air gaps 2 are covered with a copper sheet 2, the copper sheet 2 and the dielectric 2 constitute metal columns 2, and the metal columns 2 are spaced apart between two rows of cylindrical through holes, and the width of the two rows of cylindrical through holes adjusts the cutoff frequency on the second passband.

[0018] In a further embodiment, the dielectric layer three includes a dielectric substrate three, a surface copper sheet three and a fourth rectangular air slot, and the width of the two rows of cylindrical through holes thereof adjusts the cutoff frequency of the high resistance band.

[0019] In a further embodiment, the copper cladding layer covers the entire top layer of the structure and has a thickness less than or equal to 0.1 mm.

[0020] In a further embodiment, the first microstrip line and the second microstrip line are a combination structure of a long strip and a trumpet-shaped gradient microstrip line;

[0021] The third microstrip line is a combination structure of an L-shaped strip and a trumpet-shaped gradient microstrip line.

[0022] In a further embodiment, the regulation relationship between the width of the cylindrical through-holes in each layer and the cutoff frequency satisfies: when the width of the through-hole in the dielectric layer increases, the cutoff frequency in the first passband decreases;

[0023] When the width of the through hole in the metal pillar layer increases, the cutoff frequency in the first passband decreases;

[0024] When the width of the second through hole in the dielectric layer increases, the cutoff frequency in the second passband decreases;

[0025] When the width of the second through hole in the metal pillar layer increases, the cutoff frequency in the second passband decreases;

[0026] When the width of the three-way hole in the dielectric layer increases, the cutoff frequency in the high-resistance band decreases.

[0027] In a further embodiment, the duplexer operates in frequency bands of 7.7–11.6 GHz and 14.7–17.6 GHz, has an insertion loss of ≤0.9 dB, and an isolation of ≥35 dB.

[0028] Beneficial effects: The present invention constructs a multi-layer stacked dielectric layer-metal pillar layer-dielectric layer structure and introduces a surface plasmon-like polariton (ESSPP) excitation mechanism to achieve independent regulation of the upper and lower cutoff frequencies and high stopband frequencies of the two passbands of the duplexer in a compact structure; by introducing a multi-layer through-hole structure and metal pillar layer, the selectivity, isolation and out-of-band suppression performance of the device are effectively improved; at the same time, all structures are integrated into the SIW system to ensure low insertion loss, good electromagnetic compatibility and manufacturing process consistency; the overall structure of the present invention is compact and suitable for a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the front structure of the present invention;

[0030] Figure 2 It is a schematic diagram of the back structure of the present invention;

[0031] Figures 3 to 8 This is a schematic diagram of the decomposition structure of the present invention from bottom to top;

[0032] Figure 9 is the width W of the two rows of cylindrical through holes in the dielectric layer 1 in the embodiment of the present invention Ⅴ Schematic diagram of the effect of dispersion on the lower cutoff frequency of the first passband;

[0033] Figure 10 is the width W of the two rows of cylindrical through holes in the metal column layer 1 in the embodiment of the present invention Ⅳ Schematic diagram of the effect of dispersion on the upper cutoff frequency of the first passband;

[0034] Figure 11 is the width W of the two rows of cylindrical through holes in the dielectric layer 2 in the embodiment of the present invention Ⅲ Schematic diagram of the dispersion effect on the upper cutoff frequency of the second passband;

[0035] Figure 12 is the width W of the two rows of cylindrical through holes in the metal column layer 2 in the embodiment of the present invention Ⅱ Schematic diagram of the dispersion effect on the upper cutoff frequency of the second passband;

[0036] Figure 13 is the width W of the two rows of cylindrical through holes in the dielectric layer 3 in the embodiment of the present invention Ⅰ Schematic diagram of the effect of dispersion on the upper cutoff frequency of the high stop band;

[0037] Figure 14 Schematic diagram of S parameters simulated at 7.7-11.6 GHz and 14.7-17.6 GHz in an embodiment of the present invention;

[0038] Figure 15 Schematic diagram of simulated isolation in an embodiment of the present invention.

[0039] Reference numerals: 1, substrate integrated waveguide; 2, first microstrip line; 3, second microstrip line; 4, third microstrip line; 5, positioning screw; 6, cylindrical through hole; 7, first microwave high-frequency connector joint; 8, second microwave high-frequency connector joint; 9, third microwave high-frequency connector joint; 10, copper cladding layer;

[0040] 61. Dielectric layer 1; 611. Dielectric substrate 1; 612. Surface copper sheet 1;

[0041] 62. Metal pillar layer 1; 621. First rectangular air slot; 622. Dielectric 1; 623. Copper sheet 1; 624. Air gap 1;

[0042] 63, dielectric layer 2; 631, dielectric substrate 2; 632, surface copper sheet 2; 633, second rectangular air slot;

[0043] 64, metal pillar layer 2; 641, dielectric layer 2; 642, air gap 2; 643, third rectangular air slot; 644, copper sheet 2;

[0044] 65. Dielectric layer three; 651. Dielectric substrate three; 652. Fourth rectangular air slot; 653. Surface copper sheet three. DETAILED DESCRIPTION

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0046] like Figure 1 and Figure 2 As shown, the present application provides a substrate-integrated duplexer with independently controllable cutoff frequency, comprising a substrate-integrated waveguide 1. The substrate-integrated waveguide 1 comprises a top dielectric substrate, a bottom dielectric substrate, and a multilayer filter structure disposed therebetween. From bottom to top, the multilayer filter structure comprises, in order, dielectric layer 1 61, metal pillar layer 1 62, dielectric layer 2 63, metal pillar layer 2 64, dielectric layer 3 65, and a copper cladding layer 10. Each layer is mechanically secured by a number of positioning screws 5 to ensure overall compactness and interlayer alignment accuracy.

[0047] Two rows of cylindrical through holes 6 extending along the transmission direction are provided in both the dielectric layer and the metal column layer. The inner walls of the through holes are all covered with copper to form equivalent electromagnetic side walls for limiting the diffusion of electromagnetic waves.

[0048] 11. A first microstrip line 2 and a second microstrip line 3 are provided on the top of the bottom dielectric substrate, and a third microstrip line 4 is provided on the top of the top dielectric substrate. One end of the first microstrip line 2 is connected to the first microwave high-frequency connector joint 7 as a feed port, and the other end is connected to the second microwave high-frequency connector joint 8 via the second microstrip line 3. The third microstrip line 4 is connected to the third microwave high-frequency connector joint 9 as an output port. The first and second microstrip lines 2 and 3 are a combination of a long strip and a trumpet-shaped tapered microstrip line structure, and the third microstrip line 4 is a combination of an L-shaped long strip and a trumpet-shaped tapered microstrip line structure, to ensure good impedance matching and low-reflection feeding performance.

[0049] like Figures 3 to 9As shown, metal pillar layer 1 62 has a V-shaped structure, consisting of dielectric layer 1 622, with several air slots 1 624 defined within it, its inner walls covered with copper sheet 1 623. The air slots 1 624 and dielectric layer 1 622 together form metal pillar 1, which is spaced apart between the through-holes. Similarly, metal pillar layer 2 64 also has air slots 2 642 and copper sheet 2 644, forming metal pillar 2. This structure can excite equivalent surface plasmon polaritons (ESSPPs) within the microwave frequency range, thereby achieving a frequency-tunable bandpass effect. Specifically, the upper cutoff frequency of the first passband can be independently controlled by controlling the width of the two rows of cylindrical through-holes 6 in metal pillar layer 1 62, while the upper cutoff frequency of the second passband can be independently controlled by controlling the width of the two rows of cylindrical through-holes 6 in metal pillar layer 2 64.

[0050] The dielectric layer 161 includes a dielectric substrate 1611 and a surface copper sheet 1612. The lower cutoff frequency of the first passband is independently controlled by controlling the width of the two rows of cylindrical through holes 6 in the dielectric layer 161. Specifically, both sides of the dielectric layer 161 have microstrips transitioning to the substrate integrated waveguide 1, namely the first microstrip line 2 and the second microstrip line 3, which are used to achieve good feeding, reduce losses, and obtain a good S 11 parameter.

[0051] Dielectric layer 2 63 includes a second dielectric substrate 631, a second surface copper sheet 632, and a second rectangular air slot 633, copper-clad at both ends of dielectric substrate 631. The width of its two rows of cylindrical through holes 6 adjusts the lower cutoff frequency of the second passband. Similarly, dielectric layer 3 65 includes a third dielectric substrate 651, a third surface copper sheet 653, and a fourth rectangular air slot 652. The width of its two rows of cylindrical through holes 6 adjusts the upper cutoff frequency of the high-stop band.

[0052] The copper cladding layer 10 covers the entire top layer of the structure and has a thickness of less than or equal to 0.1 mm to prevent leakage of electromagnetic waves.

[0053] The specific working process of the above-mentioned embodiment of the present application is as follows: the signal is fed into the first microwave high-frequency connector joint 7, and then passes through the first microstrip line 2, the second microstrip line 3, the dielectric layer 1 61, the metal column layer 1 62, the dielectric layer 2 63, the metal column layer 2 64 and the dielectric layer 3 65 to realize the filtering of the signal in the filtering structure, and then passes through the third microstrip line 4 and the second microwave high-frequency connector joint 8 and the third microwave high-frequency connector joint 9 to extract the filtered signal to realize the entire filtering process.

[0054] In this embodiment, the regulation relationship between the width of the cylindrical through holes 6 in each layer and the cutoff frequency is as follows:

[0055] The lower cutoff frequency of the first passband is controlled by controlling the width of the two rows of cylindrical through holes 6 in the dielectric layer 1 61 , that is, as the width of the two rows of cylindrical through holes 6 in the dielectric layer 1 61 increases, the lower cutoff frequency of the first passband decreases.

[0056] The upper cutoff frequency of the first passband is independently controlled by controlling the width of the two rows of cylindrical through holes 6 in the metal pillar layer 1 62 , that is, as the width of the two rows of cylindrical through holes 6 in the metal pillar layer 1 62 increases, the upper cutoff frequency of the first passband decreases.

[0057] The lower cutoff frequency of the second passband is controlled by controlling the width of the two rows of cylindrical through holes 6 in the second dielectric layer 63. That is, as the width of the two rows of cylindrical through holes 6 in the second dielectric layer 63 increases, the lower cutoff frequency of the second passband decreases.

[0058] The upper cutoff frequency of the second passband is independently controlled by controlling the width of the two rows of cylindrical through holes 6 of the second metal pillar layer 64. That is, as the width of the two rows of cylindrical through holes 6 of the second metal pillar layer 64 increases, the upper cutoff frequency of the second passband decreases.

[0059] The upper cutoff frequency of the high resistance band is controlled by controlling the width of the two rows of cylindrical through holes 6 in the dielectric layer three 65 , that is, as the width of the two rows of cylindrical through holes 6 in the dielectric layer three 65 increases, the upper cutoff frequency of the high resistance band decreases.

[0060] This application reveals the operating mechanism of ESSPPs modes supported on a transmission line through the dispersion relation. To obtain the dispersion relation, the structure is divided into five layers: dielectric layer 1 61, metal pillar layer 1 62, dielectric layer 2 63, metal pillar layer 2 64, and dielectric layer 3 65. In the first frequency range, the substrate-integrated waveguide 1 and all dielectric cavities have negative effective permittivity, resulting in no propagation. In the second and fourth frequency ranges, ESSPPs modes are supported and exhibit behavior similar to true SPPs, going to infinity at specific frequencies known as surface plasmon frequencies fSP1 and fSP2. In the second frequency range, ESSPPs propagate along the metal pillars of metal pillar layer 1 62. Similarly, in the third frequency range, ESSPPs propagate along the metal pillars of metal pillar layer 2 64. Because the proposed structure can support SPP-like propagation in two different frequency ranges, it opens the possibility of designing dual-band filters.

[0061] Compared with the ESPP duplexer, the proposed filter power splitter can be extended to design dual-band or even multi-band due to the completely independent and controllable cutoff frequencies, in each layer of the present application, each cutoff frequency is determined, ensuring independent passband and out-of-band control.

[0062] The five-layer filter structure of the present invention has an inherent equivalent dielectric constant for each layer, which depends on its width and the dielectric material filling it. The independent selection of the geometric parameters of each layer or the corresponding dielectric material provides a large degree of freedom to arbitrarily position the passband in the spectrum.

[0063] This embodiment conducts simulation experiments, and the simulation verification results are as follows:

[0064] Figures 9 to 13 The dielectric layer 1 61, the metal column layer 1 62, the dielectric layer 2 63,

[0065] The corresponding widths of the second metal pillar layer 64 and the third dielectric layer 65 correspond to the change in the cutoff frequency.

[0066] Figure 9 is the width W of the two rows of cylindrical through holes 6 in the dielectric layer 1 61 in the embodiment Ⅴ The width W of the two rows of cylindrical through holes 6 Ⅴ From the schematic diagram of the influence on the lower cutoff frequency of the first passband, it can be seen that as the width of the two rows of cylindrical through holes 6 in the dielectric layer 1 61 increases, the lower cutoff frequency of the first passband decreases.

[0067] Figure 10 is the width W of the two rows of cylindrical through holes 6 in the metal column layer 1 62 in the embodiment. Ⅳ The schematic diagram of the influence on the upper cutoff frequency of the first passband shows that, as the width of the two rows of cylindrical through holes 6 of the metal column layer 1 62 increases, the upper cutoff frequency of the first passband decreases.

[0068] Figure 11 is the width W of the two rows of cylindrical through holes 6 in the dielectric layer 2 63 in the embodiment Ⅲ From the schematic diagram of the influence on the lower cutoff frequency of the second passband, it can be seen that as the widths of the two rows of cylindrical through holes 6 in the second dielectric layer 63 continue to increase, the lower cutoff frequency of the second passband continues to decrease.

[0069] Figure 12 is the width W of the two rows of cylindrical through holes 6 in the metal column layer 2 64 in the embodiment. Ⅱ The schematic diagram of the influence on the upper cutoff frequency of the first passband shows that, as the width of the two rows of cylindrical through holes 6 of the second metal pillar layer 64 increases, the upper cutoff frequency of the first passband decreases.

[0070] Figure 13 is the width W of the two rows of cylindrical through holes 6 in the dielectric layer 3 65 in the embodiment Ⅰ The schematic diagram of the influence on the upper cutoff frequency of the high-stop band shows that, as the widths of the two rows of cylindrical through holes 6 in the air cavity layer continue to change, the cutoff frequencies of the first passband and the second passband are not affected.

[0071] Figure 14 Figure 3 is a schematic diagram of the simulated and measured S parameters of the embodiment at 7.7-11.6 GHz and 14.7-17.6 GHz. It can be seen that the simulation results show selectivity within the passbands of 7.7-11.6 GHz and 14.7-17.6 GHz and the stable stopbands of 11.7-14.6 GHz and 17.7-20 GHz, with low insertion losses of 0.6 dB and 0.9 dB respectively. Theoretical analysis and simulation have proved that it has the ability of independently controllable cutoff frequency, low insertion loss, stable stopband, good in-band flatness and deep out-of-band suppression.

[0072] Figure 15 It is a schematic diagram of the isolation of the embodiment. It can be seen that the present application has a good isolation effect, can reduce signal interference and improve signal transmission quality.

[0073] The above content is a detailed description of the present invention in conjunction with specific embodiments, and it cannot be considered that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A substrate-integrated duplexer with independently controllable cutoff frequency, comprising a substrate-integrated waveguide, wherein the substrate-integrated waveguide comprises a top dielectric substrate, a bottom dielectric substrate, and a multilayer filtering structure disposed therebetween, characterized in that: The multi-layer filter structure comprises, from bottom to top, a dielectric layer 1, a metal column layer 1, a dielectric layer 2, a metal column layer 2, a dielectric layer 3 and a copper cladding layer; Each layer is provided with two rows of cylindrical through holes, the inner wall of which is covered with copper to form the side electrical wall and fixed by positioning screws; A first microstrip line and a second microstrip line are provided on the top of the bottom dielectric substrate, and a third microstrip line is provided on the top of the top dielectric substrate; One end of the first microstrip line is a feeding port connected to the first microwave high-frequency connector, and the other end is connected to the second microwave high-frequency connector via the second microstrip line; The third microstrip line is connected to the third microwave high-frequency connector as an output port; The passband and stopband cutoff frequencies can be independently controlled by adjusting the width of the cylindrical through holes in each layer.

2. The substrate integrated duplexer with independently controllable cutoff frequency according to claim 1, characterized in that: The dielectric layer 1 includes a dielectric substrate 1 and a surface copper sheet 1, and the width of the two rows of cylindrical through holes is adjusted to adjust the cutoff frequency in the first passband.

3. The substrate integrated duplexer with independently controllable cutoff frequency according to claim 1, characterized in that: The metal pillar layer 1 has a "V" structure and includes a dielectric 1. A plurality of air slots 1 are spaced apart on the dielectric 1. The sidewalls of the air slots 1 are covered with a copper sheet 1. The copper sheet 1 and the dielectric 1 constitute a metal pillar 1. The metal pillar 1 is spaced apart and arranged between two rows of cylindrical through holes. The width of the two rows of cylindrical through holes adjusts the cutoff frequency of the first passband.

4. The substrate integrated duplexer with independently controllable cutoff frequency according to claim 1, characterized in that: The second dielectric layer includes a second dielectric substrate, a second surface copper sheet, and second rectangular air slots clad in copper at both ends of the second dielectric substrate. The width of the two rows of cylindrical through holes adjusts the cutoff frequency in the second passband.

5. The substrate integrated duplexer with independently controllable cutoff frequency according to claim 1, characterized in that: The second metal pillar layer has a "V" structure and includes a second dielectric. A plurality of second air slots are spaced apart on the second dielectric. The sidewalls of the second air slots are covered with a second copper sheet. The second copper sheet and the second dielectric constitute a second metal pillar. The second metal pillar is spaced apart and arranged between two rows of cylindrical through holes. The width of the two rows of cylindrical through holes adjusts the cutoff frequency of the second passband.

6. The substrate integrated duplexer with independently controllable cutoff frequency according to claim 1, characterized in that: The dielectric layer three includes a dielectric substrate three, a surface copper sheet three and a fourth rectangular air slot, and the width of the two rows of cylindrical through holes thereof is used to adjust the cutoff frequency of the high resistance band.

7. The substrate integrated duplexer with independently controllable cutoff frequency according to claim 1, characterized in that: The copper cladding layer covers the entire top layer of the structure and has a thickness less than or equal to 0.1 mm.

8. The substrate integrated duplexer with independently controllable cutoff frequency according to claim 1, characterized in that: The first microstrip line and the second microstrip line are a combination structure of a long strip and a trumpet-shaped gradient microstrip line; The third microstrip line is a combination structure of an L-shaped strip and a trumpet-shaped gradient microstrip line.

9. The substrate integrated duplexer with independently controllable cutoff frequency according to claim 1, characterized in that: The regulation relationship between the width of cylindrical through holes in each layer and the cutoff frequency is satisfied; When the width of the through hole in the dielectric layer increases, the cutoff frequency in the first passband decreases; When the width of the through hole in the metal pillar layer increases, the cutoff frequency in the first passband decreases; When the width of the second through hole in the dielectric layer increases, the cutoff frequency in the second passband decreases; When the width of the second through hole in the metal pillar layer increases, the cutoff frequency in the second passband decreases; When the width of the three-way hole in the dielectric layer increases, the cutoff frequency in the high-resistance band decreases.

10. The substrate integrated duplexer with independently controllable cutoff frequency according to claim 1, characterized in that: The duplexer operates in frequency bands of 7.7–11.6 GHz and 14.7–17.6 GHz, with an insertion loss of ≤0.9 dB and an isolation of ≥35 dB.

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