A miniaturized filter combining SIW cavity and stripline resonator

Abstract

The present invention discloses a miniaturized filter that is a hybrid of a SIW cavity and a stripline resonator, which mainly includes a SIW cavity, an intermediate metal layer composed of two striplines, a blind hole connecting the stripline and the lower surface metal layer, and a feeding microstrip line. The SIW cavity, the secondary mode of the full-wavelength stripline resonator, and the primary mode of the half-wavelength stripline are used to construct the transmission poles of the filter. The primary mode of the full-wavelength stripline is used as a non-resonant node to construct an additional transmission zero point, and the filter generates two transmission zero points with adjustable positions. The two striplines introduce electrical coupling into the two SIW cavities, and an inductive window can be opened on the common metal sidewalls of the adjacent SIW cavities to construct an electromagnetic hybrid coupling, thereby adding an additional transmission zero point to the right side of the passband. Compared with the traditional fourth-order SIW filter, the size of the present invention is reduced by 50%, while maintaining a high frequency selectivity.

Description

Technical Field

[0001] The invention belongs to the field of microwave technology and relates to a highly selective substrate integrated waveguide (SIW) filter, in particular to a highly selective miniaturized filter which is a mixture of an SIW cavity and a stripline resonant structure. Background Art

[0002] Contemporary wireless communication systems require microwave filters to have high selectivity, wide stopband, low loss, easy processing and miniaturization. Substrate integrated waveguide (SIW) filters have been widely studied and applied in the microwave field due to their advantages such as low loss, easy processing and easy integration with other planar circuits. However, traditional SIWs are large in size and cannot meet the requirements of modern microwave circuits for miniaturization. To address this shortcoming, semi-open SIW structures such as half-mode SIW (HMSIW) and quarter-mode SIW (QMSIW) have emerged one after another. Although such structures have a size much smaller than that of ordinary SIW cavities, the traditional HMSIW and QMSIW filters lack sufficient transmission zeros in their responses. In addition, their semi-open structures result in unsatisfactory frequency selectivity and radiation loss of such filters.

[0003] In recent years, researchers have begun to combine different transmission line structures with SIW cavities to construct Box-Like topology structures, hoping to reduce the size of the filter while introducing transmission zeros to improve the selectivity of the filter. One method is to etch semi-open transmission line structures such as coplanar integrated waveguides (CPW) or microstrip lines on the metal surface of the SIW cavity. Such structures can be used as additional resonators in the filter in addition to the SIW cavity through special design, but because such structures are semi-open and their existence destroys the integrity of the SIW cavity, the insertion loss of such filters is often large; another method does not destroy the integrity of the SIW cavity, and uses externally etched microstrip lines or CPW as additional resonant structures while establishing direct coupling with the SIW cavity, but such overall structures are often more complex and occupy additional area, so they are not conducive to the miniaturization and integration of filters.

[0004] In view of the above problems, the present invention proposes a method for embedding a stripline inside a SIW cavity by using a three-layer metal structure, using the secondary mode of the stripline with an electrical length of a full wavelength and the primary mode of the stripline with a length of half a wavelength as resonators of the filter, and constructing a Box-Like filter topology structure in combination with the SIW cavity; using the primary mode of the full-wavelength stripline as a non-resonant node (NRN), introducing two transmission zeros with controllable positions near the passband, and the two transmission zeros can be located on both sides of the passband respectively or on one side of the passband at the same time; at the same time, the structure proposed by the present invention can conveniently introduce an inductive window between the SIW cavities, and then introduce electromagnetic hybrid coupling, and additionally increase transmission zeros, while ensuring the closedness of the overall structure of the filter, minimizing the volume of the filter and improving the selectivity of the filter. Summary of the invention

[0005] The purpose of the present invention is to address the deficiencies of the prior art and to propose a miniaturized filter that combines a SIW cavity with a stripline resonator.

[0006] The present invention adopts the following technical solution:

[0007] A miniaturized filter hybrid of a SIW cavity and a stripline resonator, comprising:

[0008] Intermediate dielectric layer (2);

[0009] An upper surface metal layer (1) and a lower surface metal layer (5) are respectively located on the upper and lower surfaces of the intermediate dielectric layer (2);

[0010] An intermediate metal layer, arranged in the middle of the intermediate dielectric layer (2);

[0011] A metallized through-hole array (6) penetrating the intermediate dielectric layer (2) and used to connect the upper surface metal layer (1) and the lower surface metal layer (5);

[0012] A first metallized blind hole (7) and a second metallized blind hole (8), used to connect the middle metal layer and the lower surface metal layer (5);

[0013] Feed microstrip line (9);

[0014] in:

[0015] The metallized through hole array (6), the upper surface metal layer (1) and the lower surface metal layer (5) form two adjacent SIW cavities; one of the metal walls of the two SIW cavities is shared;

[0016] The intermediate metal layer comprises a full-wavelength stripline (3) and a half-wavelength stripline (4); the electrical lengths of the full-wavelength stripline (3) and the half-wavelength stripline (4) are respectively a full wavelength and a half wavelength, and the physical length L p1 and Lp2 The resonant frequencies of the corresponding modes are respectively satisfied to be near the center frequency of the filter; first metallized blind holes (7) are arranged at both ends of the full-wavelength stripline (3), so that it forms a full-wavelength stripline resonator with a short-circuit terminal; second metallized blind holes (8) are arranged at both ends of the half-wavelength stripline (4), so that it forms a half-wavelength stripline resonator with a short-circuit terminal; wherein the secondary mode of the full-wavelength stripline resonator, the primary mode of the half-wavelength stripline resonator and the two SIW cavities constitute four transmission poles of the filter, and their resonant frequencies are all near the center frequency; the primary mode of the full-wavelength stripline resonator serves as a non-resonant node (NRN) in the filter structure, realizing the introduction of an additional transmission zero point on the basis of the traditional Box-Like structure;

[0017] A feeding window is provided at the outer end of the metallized through hole arrays (6) of the two SIW cavities, and the feeding window position of the upper surface metal layer (1) is connected to a feeding microstrip line (9) as an input and output feeding port;

[0018] Preferably, the feeding microstrip line (9) is arranged in parallel with the full-wavelength stripline (3) and the half-wavelength stripline (4).

[0019] Preferably, both sides of the feeding microstrip line (9) and the upper surface metal layer (1) are provided with L-shaped feeding slots (10);

[0020] As a preference, the two SIW cavities have the same size and the length L is adjusted. c and width W c Make the cavity resonance frequency located at the center frequency of the filter;

[0021] Preferably, the characteristic impedance of the feeding microstrip line (9) is 50 ohms;

[0022] Preferably, the first metallized blind holes (7) on both sides of the full-wavelength stripline (3) have the same diameter, and the second metallized blind holes (8) on both sides of the half-wavelength stripline (4) have the same diameter;

[0023] As a preferred method, by adjusting the horizontal offset D between the full-wavelength stripline (3) and the center line of the SIW cavity p1 , the horizontal offset D between the half-wavelength stripline (4) and the centerline of the SIW cavity p2 , thereby controlling the coupling amount between the SIW cavity and the stripline resonator.

[0024] Preferably, the filter may further include an inductive window (11) for constructing electromagnetic hybrid coupling, wherein the inductive window (11) is arranged on a common metal wall of adjacent SIW cavities, and there is no metallized through hole at the location of the inductive window (11), and its width W w Adjust the size of electromagnetic hybrid coupling;

[0025] Preferably, the center of the inductive window (11) coincides with the center of a common metal wall of the two SIW cavities.

[0026] The transmission poles of the filter are constructed by using the secondary mode of the resonator of the full-wavelength stripline (3), the primary mode of the half-wavelength stripline (4) and two SIW cavities. By adjusting the physical length L of the two striplines, p1 and L p2 The resonant frequency of the corresponding mode is made near the center frequency of the filter; at the same time, the first mode of the full-wavelength stripline (3) is used as the NRN to introduce an additional transmission zero point; by adjusting the offset D between the full-wavelength stripline (3), the half-wavelength stripline (4) and the center line of the SIW cavity p1 and D p2 , line width W p1 and W p2 , the diameter D of the first metallized blind hole (7) and the second metallized blind hole (8) v1 and D v2 Control the size of the internal coupling amount; by controlling the length and width L of the L-shaped feeding slot (10) s1 With L s2 , line width W s and the horizontal offset D of the feed microstrip line (9) relative to the filter center. f The size of the external quality factor can be adjusted. A width of W is constructed between adjacent SIW cavities. w By opening the inductive window and introducing electromagnetic hybrid coupling, an additional transmission zero point can be added to the right side of the passband. The size of the hybrid coupling is adjusted by the width of the inductive window (11).

[0027] The present invention utilizes two resonant modes of a stripline with an electrical length of a full wavelength, wherein the secondary mode is used as a resonator to construct the transmission pole of the filter, and the primary mode is used as an NRN structure to introduce an additional transmission zero in the stopband of the filter; the primary mode resonant frequency of the stripline with an electrical length of half a wavelength is located near the center frequency and is used to construct the transmission pole of the filter. Two SIW cavities are defined as resonator 1 and resonator 4, the secondary mode of the full-wavelength stripline (3) is resonator 2, and the primary mode of the half-wavelength stripline (4) is resonator 3; the coupling coefficient between resonator 1 and resonators 2 and 3 is defined as M 12 、M 13 , the coupling coefficient between resonator 4 and resonators 2 and 3 is M 24 、M 34 From the electric field distribution of the stripline resonator, we can see that the secondary mode of the full-wavelength stripline (3) is an even mode, and the primary mode of the half-wavelength stripline (4) is an odd mode. At the same time, the filter structure is symmetrical, so M 13 =M 34 , M 12 =-M24 The resonant frequency of the second mode of the full-wavelength resonator is denoted by f even The first mode resonant frequency of the half-wavelength resonator is denoted by f odd By fine-tuning the length L of the two strip lines p1 and L p2 The resonant frequency of the stripline resonator, f even With f odd Size; by adjusting the stripline offset D p1 With D p2 , Stripline width W p1 With W p2 And the blind hole diameter D v1 With D v2 The internal coupling amount M can be adjusted 12 、M 13 When f even <f odd When M 12 >M 13 , the filter will produce two transmission zeros on the right side of the passband; if M 12 <M 13 , the filter will produce two transmission zeros on the left side of the passband; when f even >f odd When , the filter will generate a transmission zero point in the upper and lower stop bands. In summary, the present invention can flexibly adjust the positions of the two transmission zero points of the filter according to actual needs.

[0028] The width W is constructed between adjacent SIW cavities. w The inductive windowing introduces magnetic coupling between the two SIW cavities. In addition, the stripline located in the middle metal layer acts as a resonator and also introduces electrical coupling between the two SIW cavities. The amount of electrical coupling depends on the diameter D of the blind holes terminated at both ends of the stripline. v1 , D v2 and the stripline width W p1 , W p2 The electromagnetic hybrid coupling constructed by combining the two can introduce an additional transmission zero point to the right side of the passband, further increasing the selectivity of the filter.

[0029] The stripline resonator is embedded in the SIW cavity. This hybrid structure reduces the size of the filter and reduces radiation loss. At the same time, it introduces a transmission zero with adjustable position for the filter, making the filter design more flexible and improving the stopband frequency selection characteristics of the filter.

[0030] The present invention has the following advantages:

[0031] (1) The structural size of the proposed invention is only half of that of the traditional fourth-order SIW filter, which greatly reduces the volume of the filter;

[0032] (2) The present invention has two transmission zeros with adjustable positions, which can be located on both sides of the passband or on one side of the passband at the same time, making the filter design more flexible;

[0033] (3) The present invention can also realize electromagnetic hybrid coupling by introducing the inductive window (11), add an additional transmission zero point in the upper stop band, and further optimize the stop band performance;

[0034] (4) The filter structure is completely closed, which reduces radiation loss and interference with other circuits; at the same time, the circuit structure is symmetrical, which simplifies the design process. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of Example 1 of the present invention;

[0036] Figure 2 It is a schematic diagram of the dimensions of Example 1 of the present invention;

[0037] Figure 3 is a schematic diagram of the structure of the stripline resonator in the present invention;

[0038] Figure 4 This is the topological structure diagram of Example 1;

[0039] Figure 5 is the electric field distribution diagram of the stripline resonator;

[0040] Figure 6 is the filter response curve of Example 1 when adjusting the transmission zero positions located on both sides of the passband;

[0041] Figure 7 This is the filter response curve of Example 1 when adjusting the positions of the two transmission zeros that are simultaneously located on the left side of the passband;

[0042] Figure 8 This is the filter response curve of Example 1 when adjusting the two transmission zero positions that are simultaneously located on the right side of the passband;

[0043] Fig. 9 is a schematic diagram of the structure of Example 2;

[0044] Fig.10 This is the topological structure diagram of instance 2;

[0045] Fig.11 In Example 1, even >f odd The response curve of Example 2 designed based on this.

[0046] Markings in the figure: upper surface metal layer 1, intermediate dielectric layer 2, full-wavelength stripline 3, half-wavelength stripline 4, lower surface metal layer 5, metallized through-hole array 6, first metallized blind hole 7, second metallized blind hole 8, 50 ohm feeding microstrip line 9, L-shaped feeding slot 10, inductive window 11. DETAILED DESCRIPTION

[0047] The present invention is further described below in conjunction with the accompanying drawings.

[0048] Example 1 uses the SIW cavity and two sets of stripline resonators inside the cavity to construct a fourth-order Box-Like bandpass response, and uses the first mode of the stripline with an electrical length of a full wavelength as the NRN to introduce two position-controllable transmission zeros near the passband; Example 2 combines the inductive windowing between the SIW cavities on the basis of Example 1 to construct electromagnetic hybrid coupling, introduces additional transmission zeros on the right side of the passband, and improves the frequency selectivity while reducing the size of the filter. At the same time, the structure is simple and fully enclosed.

[0049] Example 1: A miniaturized filter that combines a SIW cavity and a stripline resonator

[0050] like Figure 1-3 As shown, the present invention provides a hybrid filter structure of SIW and stripline resonators, including an upper surface metal layer 1, an intermediate dielectric layer 2, a full-wavelength stripline 3, a half-wavelength stripline 4, a lower surface metal layer 5, a metallized through-hole array 6, a first metallized blind hole 7 connecting the full-wavelength stripline and the lower surface metal layer, a second metallized blind hole 8 connecting the half-wavelength stripline and the lower surface metal layer, a 50-ohm feeding microstrip line 9, an L-shaped feeding slot 10, and an inductive window 11.

[0051] Two strip lines with electrical lengths of full wavelength and half wavelength are constructed between the two SIW resonant cavities. Metallized blind holes are provided on both sides of the strip lines to connect to the metal layer on the lower surface. The strip line resonator with short-circuited terminals is constructed. Its physical lengths are L p1 and L p2 , the widths are W p1 and W p2 , the blind hole diameters are D v1 and D v2 In addition, the two strip lines are D p1 and D p2 The SIW cavity surrounded by periodically arranged metallized through holes has a length and width of L c and W c .

[0052] The 50 ohm microstrip line 9 connects the input and output ports and is fed through the L-shaped feed slot 10. The width of the L-shaped feed slot is W. s, the horizontal length is L s1 , the vertical length is L s2 The feeding microstrip line and the filter center line are set with a size of D f Adjusting the above parameters can change the external quality factor of the filter and thus adjust the bandwidth of the filter.

[0053] like Figure 4 , 5 As shown, in the topological structure diagram of the present invention, resonators 1 and 4 represent the main mode of the SIW cavity, resonator 2 represents the secondary mode of the full-wavelength resonator, resonator 3 represents the primary mode of the half-wavelength resonator, and N represents the non-resonant node introduced by the primary mode of the full-wavelength resonator. Since the secondary mode of the full-wavelength stripline is an even mode, the primary mode of the half-wavelength stripline is an odd mode, and the filter structure is symmetrical, there is M 13 =M 34 , M 12 =-M 24 .

[0054] like Figure 6-8 As shown, the positions of the two transmission zero points of Example 1 of the present invention can be flexibly adjusted. Figure 6 Medium p1 =19.59mm, L p2 =10.1mm, L p1 <L p2 , so f even >f odd , the two transmission zeros of the filter are located on both sides of the passband. p1 =4.85mm, the center frequency of the filter is 10GHz, the insertion loss is -1.15dB, the relative bandwidth is 10.02%, and the two transmission zeros of the filter are located at 8.58GHz and 11.28GHz respectively; at the same time, it can be seen from the figure that by adjusting D p1 The size of the two transmission zero points can be shifted to the left or to the right at the same time. Figure 7 Medium p1 =20.92mm, L p2 =9.85mm, L p1 >L p2 , so f even <f odd , and M 12 <M 13 , the two transmission zeros of the filter are located on the left side of the passband at the same time. p1 =4.85mm, the center frequency of the filter is 10GHz, the insertion loss is -1.09dB, the relative bandwidth is 9.98%, and the two transmission zeros of the filter are located at 6.23GHz and 9.37GHz respectively; it can be seen from the figure that by adjusting Dp1 The size of the two transmission zero points can be close to or far away from each other at the same time. Figure 8 Medium p1 =20.36mm, L p2 =9.68mm, L p1 >L p2 , so f even <f odd , the two transmission zeros of the filter are located on the right side of the passband at the same time. p1 =4.85mm, the center frequency of the filter is 10GHz, the insertion loss is -1.29dB, the relative bandwidth is 10%, and the two transmission zeros of the filter are located at 10.74GHz and 11.68GHz respectively; it can be seen from the figure that by adjusting D p1 The size of the two transmission zero points can be close to or far away from each other at the same time.

[0055] Example 2: A miniaturized filter with a hybrid SIW cavity and stripline resonator (in Example 1, f even >f odd Set the width to W based on w Sensual window opening

[0056] Fig. 9 Schematic diagram of the structure of Example 2 of the present invention. Example 2 adds a width W between SIW cavities based on the structure of Example 1. w The inductive window introduces magnetic coupling into the filter, which, combined with the electric coupling introduced by the stripline inside the cavity, constitutes electromagnetic hybrid coupling.

[0057] Fig.10 The topology diagram of the filter of Example 2 is shown in FIG. The direct coupling M between resonator 1 and resonator 4 is added to the topology diagram. 14 , combined with the above, M 14 It is the electromagnetic hybrid coupling between the two SIW cavities. It is worth mentioning that in order to embed the stripline inside the SIW cavity, the adjacent metal walls between the cavities are provided with a window slightly larger than the width of the stripline, which will inevitably introduce a weak magnetic coupling. However, compared with the electrical coupling introduced by the stripline, the magnitude of the magnetic coupling is negligible, and thus the magnitude of the electromagnetic hybrid coupling is also negligible. Figure 4 In the topology diagram of Example 1 shown, this weak electromagnetic hybrid coupling is not marked.

[0058] Fig.11 In Example 1, even >f odd The response curve of Example 2 designed based on . It can be seen from the figure that when W w=1.52mm Example 2 The center frequency of the filter is 10GHz, the insertion loss is -1.18dB, and the relative bandwidth is 10.02%. The filter introduces a transmission zero on the left side of the passband and two transmission zeros on the right side of the passband. The three transmission zeros are located at 8.44GHz, 11.74GHz, and 12.04GHz. The positions of the newly added zeros introduced by electromagnetic hybrid coupling have been marked. The remaining two transmission zeros are introduced by negative coupling in the NRN and Box-Like structures, respectively. By adjusting the inductive window width W w The size of electromagnetic hybrid coupling can be controlled, and thus the zero point position can be controlled. It can be seen that the structure proposed by the present invention greatly improves the frequency selectivity of the filter while reducing the size of the filter.

[0059] The final dimensions are shown in the following table (unit: mm):

[0060] <![CDATA[L c ]]> <![CDATA[W c ]]> <![CDATA[L s1 ]]> <![CDATA[L s2 ]]> <![CDATA[W s ]]> <![CDATA[W f ]]> <![CDATA[D f ]]> <![CDATA[L p1 ]]> 14.25 14.25 5 1.2 0.4 1.53 0.1 19.61 <![CDATA[L p2 ]]> <![CDATA[D p1 ]]> <![CDATA[D p2 ]]> <![CDATA[W p1 ]]> <![CDATA[W p2 ]]> <![CDATA[D v1 ]]> <![CDATA[D v2 ]]> <![CDATA[W w ]]> 10.11 4.41 5.28 0.28 0.3 0.6 0.42 1.49

[0061] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A miniaturized filter hybrid of a substrate integrated waveguide (SIW) cavity and a stripline resonator, comprising: Intermediate dielectric layer (2); An upper surface metal layer (1) and a lower surface metal layer (5) are respectively located on the upper and lower surfaces of the intermediate dielectric layer (2); An intermediate metal layer, arranged in the middle of the intermediate dielectric layer (2); A metallized through-hole array (6) penetrating the intermediate dielectric layer (2) and used to connect the upper surface metal layer (1) and the lower surface metal layer (5); A first metallized blind hole (7) and a second metallized blind hole (8), used to connect the middle metal layer and the lower surface metal layer (5); Feed microstrip line (9); Features: The metallized through hole array (6), the upper surface metal layer (1) and the lower surface metal layer (5) form two adjacent SIW cavities; one of the metal walls of the two SIW cavities is shared; The intermediate metal layer comprises a full-wavelength stripline (3) and a half-wavelength stripline (4); the electrical lengths of the full-wavelength stripline (3) and the half-wavelength stripline (4) are respectively a full wavelength and a half wavelength, and the physical length L p1 and L p2 The resonant frequency of the corresponding mode is respectively satisfied to be near the center frequency of the filter; the two ends of the full-wavelength stripline (3) are provided with a first metallized blind hole (7), so that it forms a full-wavelength stripline resonator with a short-circuit terminal; the two ends of the half-wavelength stripline (4) are provided with a second metallized blind hole (8), so that it forms a half-wavelength stripline resonator with a short-circuit terminal; The secondary mode of the full-wavelength stripline resonator, the primary mode of the half-wavelength stripline resonator and the two SIW cavities constitute the four transmission poles of the filter, and their resonant frequencies are all located near the center frequency; the primary mode of the full-wavelength stripline resonator serves as a non-resonant node in the filter structure, realizing the introduction of an additional transmission zero point on the basis of the traditional Box-Like structure; A feeding window is provided at the outer end of the metallized through hole arrays (6) of the two SIW cavities, and the feeding window position of the upper surface metal layer (1) is connected to a feeding microstrip line (9) as an input and output feeding port.

2. The miniaturized filter according to claim 1, characterized in that: The feeding microstrip line (9) is arranged in parallel with the full-wavelength strip line (3) and the half-wavelength strip line (4).

3. The miniaturized filter according to claim 1, characterized in that: L-shaped feeding slots (10) are provided on both sides of the feeding microstrip line (9) and the upper surface metal layer (1).

4. The miniaturized filter according to claim 1, characterized in that: The first metallized blind holes (7) on both sides of the full-wavelength stripline (3) have the same diameter, and the second metallized blind holes (8) on both sides of the half-wavelength stripline (4) have the same diameter.

5. The miniaturized filter according to claim 1, characterized in that: By adjusting the horizontal offset D between the full-wavelength stripline (3) and the center line of the SIW cavity p1 , the horizontal offset D between the half-wavelength stripline (4) and the centerline of the SIW cavity p2 , thereby controlling the coupling amount between the SIW cavity and the stripline resonator.

6. The miniaturized filter according to claim 1, characterized in that: The filter also includes an inductive window (11) for constructing electromagnetic hybrid coupling. The inductive window (11) is arranged on a common metal wall of adjacent SIW cavities. There is no metallized through hole at the location of the inductive window (11). The width W w Adjust the size of electromagnetic hybrid coupling.

7. The miniaturized filter according to claim 6, characterized in that: The center of the inductive window (11) coincides with the center of a common metal wall of the two SIW cavities.

8. The miniaturized filter according to any one of claims 1 to 7, characterized in that: Define two SIW cavities as resonator 1 and resonator 4, the secondary mode of the full-wavelength stripline (3) as resonator 2, and the primary mode of the half-wavelength stripline (4) as resonator 3; define the coupling coefficient between resonator 1 and resonators 2 and 3 as M 12 、M 13 , the coupling coefficient between resonator 4 and resonators 2 and 3 is M 24 、M 34 ; From the electric field distribution of the stripline resonator, we can see that the secondary mode of the full-wavelength stripline (3) is an even mode, and the primary mode of the half-wavelength stripline (4) is an odd mode. At the same time, the filter structure is symmetrical, so M 13 =M 34 , M 12 =-M 24 ; The resonant frequency of the second mode of the full-wavelength resonator is denoted by f even The first mode resonant frequency of the half-wavelength resonator is denoted by f odd ; By fine-tuning the length L of the full-wavelength stripline (3) and the half-wavelength stripline (4) p1 and L p2 Changing the resonant frequency of the stripline resonator, i.e. f even With f odd size; By adjusting the offset D between the full-wavelength stripline (3), the half-wavelength stripline (4) and the center line of the SIW cavity p1 With D p2 , Stripline width W p1 With W p2 And the blind hole diameter D v1 With D v2 Adjust the internal coupling amount M 12 、M 13 size; When f even <f odd When M 12 >M 13 , the filter will produce two transmission zeros on the right side of the passband; if M 12 <M 13 , the filter will produce two transmission zeros on the left side of the passband; When f even >f odd When , the filter will produce a transmission zero in the upper and lower stop bands.

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