A small-sized quad-band bandpass filter with independently controllable dual-mode coupling

Abstract

The present invention discloses a small-sized four-band bandpass filter with independently controllable dual-mode coupling, comprising a top metal layer, an intermediate metal layer, a bottom metal layer, a dielectric layer, a first port, a second port, a first metallized through-hole array, a second metallized through-hole array, and a third metallized through-hole. The first and second passbands are constructed by utilizing the first and second modes of an FSIW-like passband resonator, which has the advantages of small size and closedness. The first and second passbands are respectively split into two passbands by utilizing the first and second modes of an FSIW-like stopband resonator, thereby constructing a four-band filter. The coupling between the first modes is independently controlled by changing the length of a coupling window between the passband resonator and the stopband resonator, and the coupling between the second modes is independently controlled by changing the width of a microstrip connecting the passband resonator and the stopband resonator. The filter can independently control the coupling amount of each mode.

Description

Technical Field

[0001] The present invention belongs to the field of microwave technology and relates to a four-band bandpass filter, in particular to a small-sized four-band bandpass filter with dual-mode coupling and independent controllability. Background Art

[0002] The rapid development of modern microwave communication technology has greatly promoted the formation of multi-functional or multi-standard communication formats, and the operating frequency and bandwidth requirements of different communication formats have given rise to the birth of multi-functional transceiver systems capable of processing complex electromagnetic spectra. In order to support the simultaneous operation of multi-functional transceivers in multiple non-contiguous frequency channels, the multi-band filters in multi-functional transceivers must not only have physical properties such as miniaturization, lightweight, planarization, and integration, but also be able to adapt to complex passband frequencies and operating bandwidth requirements. Substrate integrated waveguide (SIW) filters have the advantages of small size, planarization, integration, low loss, and frequency closure. Compared with single-band filters, multi-band filters can realize signal screening in multiple frequency bands and can be applied to more complex working scenarios. At present, there have been many reports on SIW multi-band filters, and known technical solutions include dual-mode resonant coupling technology, passband parallel technology, band splitting technology, and single multi-mode resonator technology.

[0003] Due to the limited design freedom of SIW technology, there are relatively few SIW filters with more than two frequency bands. SIW three-band filters can only be realized by combining passband parallel technology with multi-mode resonator technology, combining dual-mode resonator with passband parallel technology, or combining dual-mode resonator with band splitting technology. SIW four-band filters are even rarer and more difficult to implement. The cavity in the SIW filter usually introduces magnetic coupling and electric coupling respectively by slotting and slits, and the only ways to control the coupling are position and length. Although these methods can also be applied to multi-band filters, the coupling between the passbands will change simultaneously when controlling the coupling, which makes it impossible to achieve independent control of the passbands. Summary of the Invention

[0004] The present invention addresses the existing problems of difficult internal coupling control, limited design freedom, and large size associated with quad-band filters. By combining dual-mode resonators with band-splitting technology, the present invention proposes a compact quad-bandpass filter with independently controllable dual-mode coupling. This filter utilizes an FSIW-like rectangular cavity, resulting in a compact, fully enclosed design. By leveraging the orthogonal characteristics of the dual-mode electric fields within the FSIW-like cavity, an internal coupling scheme combining a coupling window and striplines is proposed, enabling independent adjustment of the coupling between the two modes, reducing the difficulty of controlling the dual-mode coupling.

[0005] The present invention adopts the following technical solutions:

[0006] A small-size four-band bandpass filter with dual-mode coupling and independent controllability, comprising:

[0007] a dielectric layer (4);

[0008] A top metal layer (1) is located on the upper surface of the dielectric layer (4);

[0009] an intermediate metal layer (2) located within the dielectric layer (4);

[0010] A bottom metal layer (3) is located on the lower surface of the dielectric layer (4);

[0011] in:

[0012] A first metallized through-hole array (7) penetrating the dielectric layer (4) is provided in the dielectric layer (4), the first metallized through-hole array (7) comprising a plurality of first metallized through-holes respectively connected to the top metal layer (1), the bottom metal layer (3), and the middle metal layer (2), and enclosing first to fourth rectangular frames distributed in a 2×2 array;

[0013] Adjacent rectangular frames in the first to fourth rectangular frames use a common edge;

[0014] A first window is formed on a common side of the first rectangular frame and the second rectangular frame, and a second window and a third window are formed on outer sides of the first rectangular frame and the second rectangular frame, respectively; the first rectangular frame and the second rectangular frame are symmetrically arranged about the common side axis; a fourth window is formed on a common side of the first rectangular frame and the third rectangular frame, and a fifth window is formed on a common side of the second rectangular frame and the fourth rectangular frame;

[0015] The first window, the second window, the third window, the fourth window, and the fifth window are all provided with no first metallized through-holes; a third metallized through-hole array (9) is provided at the position of the second window; the third metallized through-hole array (9) includes a plurality of third metallized through-holes connecting the bottom metal layer (3) and the middle metal layer (2); a second metallized through-hole array (8) is provided at the position of the third window, and the second metallized through-hole array (8) includes a plurality of second metallized through-holes connecting the top metal layer (1) and the middle metal layer (2);

[0016] Four FSIW-like rectangular cavities (2-a), (2-b), (2-c), and (2-d) are constructed by a top metal layer (1), a bottom metal layer (3), an intermediate metal layer (2), a dielectric layer (4), and first to fourth rectangular frames;

[0017] The first type of FSIW rectangular cavity (2-a) and the second type of FSIW rectangular cavity (2-b) are both passband resonators, and the third type of FSIW rectangular cavity (2-c) and the fourth type of FSIW rectangular cavity (2-d) are both stopband resonators.

[0018] The first window serves as a coupling window q1 between the two passband resonators at the common side wall; the fourth window and the fifth window serve as coupling windows q2 and q3 between each passband resonator and the adjacent stopband resonator at the common side wall, respectively;

[0019] The top metal layer (1) includes a first microstrip line and a first rectangular metal patch; the bottom metal layer (3) includes a second microstrip line and a second rectangular metal patch; the bottom metal layer (3) and the top metal layer (1) have the same shape and size, and the first microstrip line and the second microstrip line are directed in opposite directions;

[0020] The side of the first type FSIW rectangular cavity (2-a) close to the third type FSIW rectangular cavity (2-c), the side of the second type FSIW rectangular cavity (2-b) close to the fourth type FSIW rectangular cavity (2-d), the side of the third type FSIW rectangular cavity (2-c) close to the first type FSIW rectangular cavity (2-a), and the side of the fourth type FSIW rectangular cavity (2-d) close to the second type FSIW rectangular cavity (2-b) each have a notch in the intermediate metal layer (2) that is close to the first metallized through hole, and the notches on both sides of the coupling window q2 are connected, and the notches on both sides of the coupling window q3 are connected; a first stripline is loaded in the two connected notches where the coupling window q2 is located, the first stripline is close to the first metallized through hole array where the second window is located, and is seamlessly connected to the intermediate metal layer (2); the width D of the first stripline is 12 Smaller than the width W of the coupling window q2 12 A second stripline is loaded in the two connected gaps where the coupling window q3 is located. The second stripline is closely attached to the first metallized through-hole array where the third window is located and is seamlessly connected to the intermediate metal layer (2). The width of the second stripline is smaller than the width of the coupling window q3.

[0021] Preferably, the coupling window q2 and the coupling window q3 have the same width, and the first stripline and the second stripline have the same width;

[0022] Preferably, the second metallized through hole array (8) and the third metallized through hole array (9) are arranged in parallel;

[0023] Preferably, the coupling window q1 between the two passband resonators has a coupling window width W that controls the magnitude of the coupling between the passbands, and a coupling window position Dw that controls the ratio of the relative bandwidths of the first virtual wide passband and the second virtual wide passband;

[0024] Preferably, the two coupling windows q2 and q3 for connecting the passband resonator and the stopband resonator are close to the first metallized through hole array (i.e., the outer side wall of the FSIW-like rectangular cavity) where the second and third windows are located, and the width W of the coupling windows q2 and q3 is 12Controlling the coupling between the passband resonator and the second mode of the stopband resonator;

[0025] Preferably, the width D of the first stripline and the second stripline 12 Controlling the coupling magnitude between the passband resonator and the first mode of the stopband resonator;

[0026] Preferably, the first microstrip line is directly connected to the first rectangular metal sheet, and two parallel slot lines are provided at the connection between the first microstrip line and the first rectangular metal sheet; the second microstrip line is directly connected to the second rectangular metal sheet, and two parallel slot lines are provided at the connection between the second microstrip line and the second rectangular metal sheet; the first microstrip line and the slot lines on both sides are located in the second window, and the second microstrip line and the slot lines on both sides are located in the third window;

[0027] Preferably, the positions D of the first and second microstrip lines IN , the length of the trough line L S , the width of the groove line W S Together they determine the coupling between the first and second microstrip lines and the FSIW-like rectangular cavity;

[0028] Preferably, the first and second microstrip lines adopt 50 ohm impedance;

[0029] Preferably, the distances between the middle metal layer (2) and the top metal layer (1) and the bottom metal layer (3) are equal;

[0030] Preferably, the dielectric layer (4) is formed by stacking two dielectric plates with a thickness of H on top of each other, and the intermediate metal layer (2) is located between the two dielectric substrates; more preferably, the dielectric substrate is a Tanconic TLY-5 dielectric substrate with a relative dielectric constant of 2.2, a loss tangent of 0.0009, and a thickness of 0.508 mm;

[0031] More preferably, the four passbands of the filter are set to 10.18 GHz, 10.81 GHz, 11.33 GHz, and 11.86 GHz respectively.

[0032] Specific working principle:

[0033] The signal excites the first and second modes of the passband resonator 2-a connected to it through the input microstrip (first microstrip line). Then it enters the passband resonator 2-b connected to the output microstrip (second microstrip line) through the coupling window q1, forming the first and second virtual wide passbands. A stopband resonator is connected in parallel below each of the two passband resonators, so that the first and second virtual wide passbands are split into two sub-passbands, and two zero points are generated between the two sub-passbands; at the same time, since the first and second modes are coupled through the coupling windows q2 and q3, a 180-degree phase difference is generated between the first and second modes, thereby generating a zero point;

[0034] The first mode of the passband resonator is coupled to the first mode of the stopband resonator through the first stripline and the second stripline, and the coupling amount is determined by the stripline width D 12 Control; the second mode of the passband resonator is coupled to the second mode of the stopband resonator through the coupling windows q2 and q3, and the coupling amount is determined by the coupling window width W 12 Control; Due to the different field distributions of the first and second modes of the FSIW-like rectangular cavity, the above two coupling quantities can be controlled independently. Since the center frequency ratio of the two sub-passbands after the first virtual wide passband is split is only related to the coupling of the first mode of the passband resonator and the stopband resonator, and the center frequency ratio of the two sub-passbands after the second virtual wide passband is split is only related to the coupling of the second mode of the passband resonator and the stopband resonator, changing the stripline width D 12 The frequency ratio between the two sub-passbands after the first virtual wide passband is split can be controlled separately, and the width W of the coupling windows q2 and q3 can be changed. 12 The frequency ratio between the two sub-passbands after the second virtual wide passband is split can be controlled independently.

[0035] The present invention has the following advantages:

[0036] (1) The coupling amount of each mode in the dual-mode resonator can be adjusted independently, which reduces the difficulty of dual-mode coupling control;

[0037] (2) There are multiple zeros in the filter, which improves the passband selectivity;

[0038] (3) The folded structure reduces the size of the filter while maintaining shielding performance;

[0039] (4) The filter structure is symmetrical and the design is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a three-dimensional structural schematic diagram of the technical solution of the present invention;

[0041] Figure 2(a) and (b) are views of the top metal layer and the middle metal layer, respectively;

[0042] Figure 3 A topological diagram of the filter of the present invention;

[0043] Figure 4 (a) and (b) show the changes of W 12 、D 12 When , the variation curve of the coupling coefficient of the first mode and the second mode between the two cavities;

[0044] Figure 5 is the S parameter simulation result of the filter of the present invention;

[0045] Figure 6 (a) and (b) show the changes of W 12 、D12 When , the change curve of filter S21.

[0046] Markings in the figure: 1, top metal layer; 2, middle metal layer; 3, bottom metal layer; 4, dielectric layer; 5, first port; 6, second port; 7, first metallized through hole array; 8, second metallized through hole array; 9, third metallized through hole; DETAILED DESCRIPTION

[0047] The present invention will be further described below with reference to the accompanying drawings.

[0048] Figure 1 A multi-band filter capable of independently controlling frequency ratios comprises a dielectric layer 4, a top metal layer 1 located on the upper surface of the dielectric layer 4, an intermediate metal layer 2 located within the dielectric layer 4, and a bottom metal layer 3 located on the lower surface of the dielectric layer 4.

[0049] A first metallized through-hole array 7 is provided in the dielectric layer 4 and penetrates the dielectric layer 4. The first metallized through-hole array 7 includes a plurality of first metallized through-holes connected to the top metal layer 1, the bottom metal layer 3, and the middle metal layer 2, respectively, and encloses first to fourth rectangular frames distributed in a 2×2 array.

[0050] Adjacent rectangular frames in the first to fourth rectangular frames use a common edge;

[0051] A first window is formed on a common side of the first rectangular frame and the second rectangular frame, and a second window and a third window are formed on outer sides of the first rectangular frame and the second rectangular frame, respectively; the first rectangular frame and the second rectangular frame are symmetrically arranged about the common side axis; a fourth window is formed on a common side of the first rectangular frame and the third rectangular frame, and a fifth window is formed on a common side of the second rectangular frame and the fourth rectangular frame;

[0052] No first metallized through-holes are provided on the first window, the second window, the third window, the fourth window, and the fifth window; a third metallized through-hole array 9 is provided at the position of the second window; the third metallized through-hole array 9 includes a plurality of third metallized through-holes penetrating the lower dielectric layer 4 and connecting the bottom metal layer 3 and the middle metal layer 2; a second metallized through-hole array 8 is provided at the position of the third window, the second metallized through-hole array 8 includes a plurality of second metallized through-holes penetrating the upper dielectric layer 4 and connecting the top metal layer 1 and the middle metal layer 2;

[0053] Four FSIW-like rectangular cavities 2-a, 2-b, 2-c, and 2-d are constructed by the top metal layer 1, the bottom metal layer 3, the middle metal layer 2, the dielectric layer 4, and the first to fourth rectangular frames;

[0054] The first type FSIW rectangular cavity 2-a and the second type FSIW rectangular cavity 2-b are both passband resonators, and the third type FSIW rectangular cavity 2-c and the fourth type FSIW rectangular cavity 2-d are both stopband resonators;

[0055] The first window serves as a coupling window q1 between the two passband resonators at the common side wall; the fourth window and the fifth window serve as coupling windows q2 and q3 between each passband resonator and the adjacent stopband resonator at the common side wall, respectively;

[0056] The top metal layer 1 includes a first microstrip line and a first rectangular metal patch; the bottom metal layer 3 includes a second microstrip line and a second rectangular metal patch; the bottom metal layer 3 has the same shape and size as the top metal layer 1, and the first microstrip line and the second microstrip line are directed in opposite directions;

[0057] The first type FSIW rectangular cavity 2-a close to the third type FSIW rectangular cavity 2-c, the second type FSIW rectangular cavity 2-b close to the fourth type FSIW rectangular cavity 2-d, the third type FSIW rectangular cavity 2-c close to the first type FSIW rectangular cavity 2-a, and the fourth type FSIW rectangular cavity 2-d close to the second type FSIW rectangular cavity 2-b each have a gap in the intermediate metal layer 2 close to the first metallized through hole, and the gaps on both sides of the coupling window q2 are connected, and the gaps on both sides of the coupling window q3 are connected; the two connected gaps where the coupling window q2 is located are loaded with a first stripline, and the first stripline is close to the first metallized through hole array where the second window is located, and is seamlessly connected to the intermediate metal layer 2; the width D of the first stripline 12 Smaller than the width W of the coupling window q2 12 A second stripline is loaded in the two connected gaps where the coupling window q3 is located. The second stripline is closely attached to the first metallized through-hole array where the third window is located and is seamlessly connected to the intermediate metal layer 2. The width of the second stripline is smaller than the width of the coupling window q3.

[0058] The coupling window q2 and the coupling window q3 have the same width, and the first stripline and the second stripline have the same width;

[0059] The second metallized through hole array 8 and the third metallized through hole array 9 are arranged in parallel;

[0060] One end of the first microstrip line is directly connected to the first rectangular metal sheet, and the other end is connected to the first port 5, and two parallel slot lines are provided at the connection between the first microstrip line and the first rectangular metal sheet; one end of the second microstrip line is directly connected to the second rectangular metal sheet, and the other end is connected to the second port 6, and two parallel slot lines are provided at the connection between the second microstrip line and the second rectangular metal sheet; the first microstrip line and the slot lines on both sides are located in the second window, and the second microstrip line and the slot lines on both sides are located in the third window; in actual applications, the microstrip line port can be further converted into other ports such as strip, coplanar waveguide, etc. through other transition structures, but this does not fall within the scope of protection of the present invention.

[0061] The first and second microstrip lines adopt 50 ohm impedance;

[0062] The distances between the middle metal layer 2 and the top metal layer 1 and the bottom metal layer 3 are equal;

[0063] The dielectric layer 4 is formed by stacking two dielectric substrates of thickness H on top of each other, with the intermediate metal layer 2 located between the two dielectric substrates. The dielectric substrate is a Tanconic TLY-5 dielectric substrate with a relative dielectric constant of 2.2, a loss tangent of 0.0009, and a thickness of 0.508 mm.

[0064] Figures 2(a) and (b) are views of the top metal layer and the middle metal layer of the present invention. The main body of the multi-band filter with independently adjustable coupling provided by the present invention is composed of four FSIW-like rectangular cavities. The length L1 and width W1 of the cavity determine the center frequencies of the first and second virtual wide passbands of the filter, and L2 determines the center frequencies after the first and second virtual wide passbands are split; the width W of the two laterally symmetrical coupling windows in the filter is 12 The coupling between the first mode of the passband resonator and the first mode of the stopband resonator can be controlled independently, and the stripline width D in the coupling window 12 The coupling between the second mode of the passband resonator and the second mode of the stopband resonator can be controlled separately; the coupling window width W between the two passband resonators controls the coupling between the first and second virtual wide passbands; the feeding window width of the source and the load is W IN , position D IN , W IN 、D IN Together they determine the coupling strength between the source and the load; two slot lines 1b are provided next to the connection between the input microstrip line 1a and the rectangular metal sheet 1c, and the slot line length L S , width W S Determine enhancements to feeds;

[0065] The final dimensions are shown in the figure below (unit: mm):

[0066] <![CDATA[L S ]]> <![CDATA[W S ]]> <![CDATA[D IN ]]> <![CDATA[W IN ]]> <![CDATA[L1]]> <![CDATA[W1]]> <![CDATA[L2]]> 5.9 0.2 5.55 5.5 12.7 11.7 13.7 <![CDATA[D W ]]> W H D <![CDATA[D 12 ]]> <![CDATA[W 12 ]]> G 6.28 4.75 0.508 0.8 4.4 6.6 2.2

[0067] Figure 3 1a and 1b represent the first mode and the second mode of the passband resonator 2-a, 2a and 2b represent the first mode and the second mode of the passband resonator 2-b, 3a and 3b represent the first mode and the second mode of the stopband resonator 2-c, and 4a and 4b represent the first mode and the second mode of the stopband resonator 2-d.

[0068] Figure 4 (a) and (b) are respectively the present invention in regulating the coupling window width W 12 , stripline width D 12 The coupling coefficient between the passband resonator and the stopband resonator is extracted from the figure. It can be seen from the figure that when W 12 When the diameter increases from 3.5mm to 5mm, the coupling coefficient of the first mode remains basically unchanged, while the coupling coefficient of the second mode increases significantly. 12 When the diameter increases from 2.5 to 4 mm, the coupling coefficient of the second mode remains basically unchanged, while the coupling coefficient of the first mode increases significantly. This shows that the coupling between the first and second modes of the bandpass resonator and the corresponding modes of the bandstop resonator can be independently controlled.

[0069] Figure 5 This is the S-parameter simulation result of the filter of the present invention. As can be seen from the figure, there are five zero points between the four passbands of the filter, of which there are two zero points between the two sub-passbands split from the first virtual wide passband, one zero point between the first and second virtual wide passbands, and two zero points between the two sub-passbands split from the second virtual wide passband;

[0070] Figure 6 (a) and (b) show the changes of W 12 、D 12 The change curve of the filter S21 can be seen from the figure. When the stripline width D 12 When the coupling window width W increases, the higher frequency passband in the two sub-passbands split from the first virtual wide passband will shift to high frequency, and the frequencies of the other three passbands remain unchanged. At this time, the frequency ratio between the two passbands split from the first passband increases. 12 When it increases, the lower frequency passband in the two sub-passbands split from the second virtual wide passband will shift to a higher frequency, while the frequencies of the other three passbands remain unchanged. At this time, the frequency ratio between the two sub-passbands split from the second virtual wide passband decreases.

[0071] 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 principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A small-sized quad-band bandpass filter with independently controllable dual-mode coupling, comprising: a dielectric layer (4); A top metal layer (1) is located on the upper surface of the dielectric layer (4); an intermediate metal layer (2) located within the dielectric layer (4); A bottom metal layer (3) is located on the lower surface of the dielectric layer (4); Its characteristics are: A first metallized through-hole array (7) penetrating the dielectric layer (4) is provided in the dielectric layer (4), the first metallized through-hole array (7) comprising a plurality of first metallized through-holes respectively connected to the top metal layer (1), the bottom metal layer (3), and the middle metal layer (2), and enclosing first to fourth rectangular frames distributed in a 2×2 array; Adjacent rectangular frames in the first to fourth rectangular frames use a common edge; A first window is formed on a common side of the first rectangular frame and the second rectangular frame, and a second window and a third window are formed on outer sides of the first rectangular frame and the second rectangular frame, respectively; the first rectangular frame and the second rectangular frame are symmetrically arranged about the common side axis; a fourth window is formed on a common side of the first rectangular frame and the third rectangular frame, and a fifth window is formed on a common side of the second rectangular frame and the fourth rectangular frame; The first window, the second window, the third window, the fourth window, and the fifth window are all provided with no first metallized through-holes; a third metallized through-hole array (9) is provided at the position of the second window; the third metallized through-hole array (9) includes a plurality of third metallized through-holes connecting the bottom metal layer (3) and the middle metal layer (2); a second metallized through-hole array (8) is provided at the position of the third window, and the second metallized through-hole array (8) includes a plurality of second metallized through-holes connecting the top metal layer (1) and the middle metal layer (2); The top metal layer (1), the bottom metal layer (3), the middle metal layer (2), the dielectric layer (4) and the first to fourth rectangular frames are used to construct the first type FSIW rectangular cavity (2-a), the second type FSIW rectangular cavity (2-b), the third type FSIW rectangular cavity (2-c) and the fourth type FSIW rectangular cavity (2-d); The first type of FSIW rectangular cavity (2-a) and the second type of FSIW rectangular cavity (2-b) are both passband resonators, and the third type of FSIW rectangular cavity (2-c) and the fourth type of FSIW rectangular cavity (2-d) are both stopband resonators; The first window serves as a coupling window q1 between the two passband resonators at the common side wall; the fourth window and the fifth window serve as coupling windows q2 and q3 between each passband resonator and the adjacent stopband resonator at the common side wall, respectively; The side of the first type FSIW rectangular cavity (2-a) close to the third type FSIW rectangular cavity (2-c), the side of the second type FSIW rectangular cavity (2-b) close to the fourth type FSIW rectangular cavity (2-d), the side of the third type FSIW rectangular cavity (2-c) close to the first type FSIW rectangular cavity (2-a), and the side of the fourth type FSIW rectangular cavity (2-d) close to the second type FSIW rectangular cavity (2-b) each have a gap in the intermediate metal layer (2) that is close to the first metallized through hole, and the gaps on both sides of the coupling window q2 are connected, and the gaps on both sides of the coupling window q3 are connected; a first stripline is loaded in the two connected gaps where the coupling window q2 is located, the first stripline is close to the first metallized through hole array where the second window is located, and is seamlessly connected to the intermediate metal layer (2); the width D of the first stripline is 12 Smaller than the width W of the coupling window q2 12 A second stripline is loaded in the two connected gaps where the coupling window q3 is located. The second stripline is closely attached to the first metallized through-hole array where the third window is located and is seamlessly connected to the intermediate metal layer (2). The width of the second stripline is smaller than the width of the coupling window q3.

2. The bandpass filter according to claim 1, characterized in that The top metal layer (1) includes a first microstrip line and a first rectangular metal patch; the bottom metal layer (3) includes a second microstrip line and a second rectangular metal patch; the bottom metal layer (3) and the top metal layer (1) have the same shape and size, and the first microstrip line and the second microstrip line are directed in opposite directions.

3. The bandpass filter according to claim 1, wherein The coupling window q2 and the coupling window q3 have the same width, and the first stripline and the second stripline have the same width.

4. The bandpass filter according to claim 1, wherein The coupling window q1 of the two passband resonators at the common side wall has a coupling window width W that controls the magnitude of the coupling between the passbands, and a coupling window position Dw that controls the ratio of the relative bandwidths of the first virtual wide passband and the second virtual wide passband.

5. The bandpass filter according to claim 1, characterized in that The two coupling windows q2 and q3 used to connect the passband resonator and the stopband resonator are close to the first metallized through-hole array where the second and third windows are located. The width W of the coupling windows q2 and q3 is 12 Control the coupling between the passband resonator and the second mode of the stopband resonator.

6. The bandpass filter according to claim 1, characterized in that The width D of the first stripline and the second stripline 12 Control the coupling between the passband resonator and the first mode of the stopband resonator.

7. The bandpass filter according to claim 1, characterized in that A first microstrip line is directly connected to a first rectangular metal sheet, and two parallel slot lines are provided at the connection between the first microstrip line and the first rectangular metal sheet; a second microstrip line is directly connected to a second rectangular metal sheet, and two parallel slot lines are provided at the connection between the second microstrip line and the second rectangular metal sheet; the first microstrip line and the slot lines on both sides are located in the second window, and the second microstrip line and the slot lines on both sides are located in the third window; The positions D of the first and second microstrip lines IN , the length of the trough line L S , the width of the groove line W S Together they determine the coupling between the first and second microstrip lines and the FSIW-like rectangular cavity.

8. The bandpass filter according to claim 1, wherein The dielectric layer (4) is formed by stacking two dielectric plates with a thickness of H on top of each other, and the middle metal layer (2) is located between the two dielectric substrates; the dielectric substrate adopts a Tanconic TLY-5 dielectric substrate with a relative dielectric constant of 2.2, a loss tangent of 0.0009, and a thickness of 0.508 mm.

9. The bandpass filter according to claim 1, wherein The four passbands of the filter are set to 10.18 GHz, 10.81 GHz, 11.33 GHz, and 11.86 GHz respectively.

10. The bandpass filter according to claim 1, characterized in that The signal, passing through the first microstrip line, excites the first and second modes of the passband resonator connected to it. The signal then passes through the coupling window q1 and enters the passband resonator connected to the second microstrip line, forming the first and second virtual wide passbands. A stopband resonator is connected in parallel below each of the two passband resonators, splitting the first and second virtual wide passbands into two sub-passbands and generating two zeros between them. Simultaneously, because both the first and second modes are coupled through the coupling windows q2 and q3, a 180-degree phase difference is generated between the first and second modes, resulting in a zero. The first mode of the passband resonator is coupled to the first mode of the stopband resonator through the first stripline and the second stripline, and the coupling amount is determined by the stripline width D 12 Control; the second mode of the passband resonator is coupled to the second mode of the stopband resonator through the coupling windows q2 and q3, and the coupling amount is determined by the coupling window width W 12 Control; Since the first mode and the second mode field distribution of the FSIW-like rectangular cavity are different, the above two coupling quantities can be controlled independently; Since the center frequency ratio of the two sub-passbands after the first virtual wide passband is split is only related to the coupling of the first mode of the passband resonator and the stopband resonator, and the center frequency ratio of the two sub-passbands after the second virtual wide passband is split is only related to the coupling of the second mode of the passband resonator and the stopband resonator, changing the stripline width D 12 The frequency ratio between the two sub-passbands after the first virtual wide passband is split can be controlled separately, and the width W of the coupling windows q2 and q3 can be changed. 12 The frequency ratio between the two sub-passbands after the second virtual wide passband is split can be controlled independently.

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