Tunable multilayer substrate integrated waveguide filter with broadband external suppression

Abstract

The invention discloses a tunable multi-layer substrate integrated waveguide filter with broadband external suppression, which is characterized in that a common multi-layer substrate integrated waveguide structure is expanded into a multi-layer air-filled substrate integrated waveguide structure; a specific geometric structure is cleverly excavated from a dielectric substrate through a cutting process in a classic multilayer substrate integrated waveguide structure, so that the loss of electromagnetic waves in penetrating through the dielectric substrate is reduced, and a plurality of rows of non-metal via holes are introduced into the multilayer substrate integrated waveguide structure. And the size of the resonant cavity of the multi-layer substrate integrated waveguide is adjusted in a mode that the metal probe is tuned to enter the non-metal via hole through a mechanical structure, so that a high-quality factor is kept in a tuning process.

Description

Technical Field

[0001] The present application relates to the field of radio frequency microwave circuits and devices, and in particular to a broadband externally suppressed tunable multi-layer substrate integrated waveguide filter. Background Art

[0002] Highly selective, wideband external suppression and tunable microwave filters are one of the key components of modern wireless communications. High selectivity and wideband external suppression characteristics mean that the filter can achieve better anti-interference characteristics and enhance the frequency selectivity and sensitivity of the receiver; the tunable characteristics mean that the filter can achieve compatibility with signals in multiple frequency bands, reducing the complexity of the receiver system.

[0003] Traditional high-selectivity and tunable microwave filters generally use mechanically tuned cavity filters, which adjust the length of the metal screws loaded in the metal resonant cavity to achieve adjustable filter operating frequency. They have the advantages of high Q value, large power capacity, low insertion loss and wide tuning range, but they also have problems of heavy weight and low integration. Other scholars use varactor diodes to tune planar filters, which have a wide tuning range and high integration, but have problems such as large insertion loss. Therefore, maintaining high quality factors during the tuning process has become a difficult point in the design of tuned filters.

[0004] In recent years, filters based on substrate integrated waveguide structures have been widely welcomed. The substrate integrated waveguide structure uses a double-sided copper-clad circuit board to simulate the cavity filter structure, which has the advantages of high quality factor, small size, low cost and high integration. However, the tuning structure design of traditional substrate integrated waveguide filters is difficult. Common tuning methods include varactor diode tuning, liquid metal tuning and ferrite tuning, but there is a problem of quality factor degradation during the tuning process. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention provides a broadband external suppression tunable multilayer substrate integrated waveguide filter to solve the problems of large insertion loss and inability to tune in the current multilayer substrate integrated waveguide filter.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is: a broadband external suppression tunable multi-layer substrate integrated waveguide filter, comprising: a first metal plate, a second metal plate, a third metal plate and a fourth metal plate stacked in sequence from top to bottom;

[0007] A first dielectric plate is attached between the first metal plate and the second metal plate, a second dielectric plate is attached between the second metal plate and the third metal plate, and a third dielectric plate is attached between the third metal plate and the fourth metal plate;

[0008] The tunable multi-layer substrate integrated waveguide filter also includes a rectangular structure surrounded by metal vias, and the metal vias and all the metal plates and dielectric plates together form a resonant cavity;

[0009] The central parts of the first dielectric plate, the second dielectric plate and the third dielectric plate are hollow rectangular grooves, and YIG ferrites parallel to the input port and the output port are arranged on the opposite sides of the rectangular grooves.

[0010] Further: the first metal plate is provided with an input port, and the fourth metal plate is provided with an output port;

[0011] The input port is an input microstrip line with an impedance of 50 ohms, and the input microstrip line is also connected to the first coplanar waveguide line on the surface of the first metal plate;

[0012] The output port is an output microstrip line with an impedance of 50 ohms, and the output microstrip line is also connected to the second coplanar waveguide line on the surface of the fourth metal plate.

[0013] Further: the metal vias include a first type of metal vias, a second type of metal vias and a third type of metal vias;

[0014] The second type of metal via is located directly below the input port, and passes through the second metal plate, the first dielectric plate, the second metal plate, the second dielectric plate, the third metal plate, the third dielectric plate, and the fourth metal plate from top to bottom;

[0015] The third type of metal via is located directly above the output port, and passes through the first metal plate, the first dielectric plate, the second metal plate, the second dielectric plate, and the third metal plate from top to bottom;

[0016] All metal vias except the second-type metal vias and the third-type metal vias are first-type metal vias, which pass through the first metal plate, the first dielectric plate, the second metal plate, the second dielectric plate, the third metal plate, the third dielectric plate and the fourth metal plate from top to bottom.

[0017] Furthermore: the tunable multi-layer substrate integrated waveguide filter is provided with an external magnetic field, and the dielectric constant of the ferrite is adjusted by adjusting the magnetic field strength of the external magnetic field.

[0018] Furthermore: the input port and the output port are symmetrical along the center of the tunable multi-layer substrate integrated waveguide filter.

[0019] Furthermore: the second metal plate is etched with a pair of first-type slot lines symmetrical along the straight line where the input port or output port is located, and the third metal plate is etched with two pairs of second-type slot lines symmetrical along the perpendicular line where the input port or output port is located, for achieving maximum in-band return loss.

[0020] Furthermore: all metal plates and dielectric plates are provided with an axially symmetrical through-hole array along the straight line where the input port or the output port is located, and the through-hole array passes through the first metal plate, the first dielectric plate, the second metal plate, the second dielectric plate, the third metal plate, the third dielectric plate and the fourth metal plate from top to bottom.

[0021] Furthermore: the through hole array is composed of non-metal vias, a suspended metal probe array is arranged above the through hole array, and the metal probe array is driven by a three-dimensional linear displacement driver.

[0022] The beneficial effects of the present invention are:

[0023] 1. The three-layer dielectric plates of the tunable multi-layer substrate integrated waveguide filter with broadband external suppression all adopt the air-filled substrate integrated waveguide structure, which reduces the dielectric loss of electromagnetic waves and effectively reduces the insertion loss of the filter. At the same time, the multi-layer substrate integrated waveguide structure adopted can effectively suppress stray waves and improve the out-of-band suppression width and depth of the filter;

[0024] 2. The broadband external suppression tunable multilayer substrate integrated waveguide filter has a two-dimensional tuning structure. First, a large range of fixed frequency tuning is achieved through a movable array metal probe, and secondly, a small range of continuous tuning is achieved through YIG ferrite. The two tuning methods together achieve a large range of center frequency tuning. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Explosion diagram of a tunable multilayer substrate integrated waveguide filter with broadband external suppression;

[0026] Figure 2 is a schematic diagram of the first layer of metal plate;

[0027] Figure 3 is a schematic diagram of the second dielectric plate;

[0028] Figure 4 is a schematic diagram of the second layer of metal plate;

[0029] Figure 5 is a schematic diagram of the third layer of metal plate;

[0030] Figure 6 is a schematic diagram of the fourth layer of metal plate;

[0031] Figure 7 The simulation diagram of the tunable multilayer substrate integrated waveguide filter with broadband external suppression;

[0032] Figure 8 Simulated out-of-band suppression diagram for a tunable multilayer substrate integrated waveguide filter with broadband out-of-band suppression;

[0033] Fig. 9The wide tuning effect diagram of the tunable multilayer substrate integrated waveguide filter with broadband external suppression;

[0034] Among them: 1. The first layer of metal plate; 2. The first layer of dielectric plate; 3. The second layer of metal plate; 4. The second layer of dielectric plate; 5. The third layer of metal plate; 6. The third layer of dielectric plate; 7. The fourth layer of metal plate; 8. Input port; 9. Output port; 10. Through-hole array; 11. The first coplanar waveguide line; 12. The first type of metal via; 13. The second type of metal via; 14. The third type of metal via; 15. YIG ferrite; 16. The first type of slot line; 17. The second type of slot line; 18. The second coplanar waveguide line. DETAILED DESCRIPTION

[0035] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0036] like Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 As shown, in one embodiment of the present invention, a tunable multilayer substrate integrated waveguide filter with broadband external suppression is provided, comprising: a first metal plate 1, a second metal plate 3, a third metal plate 5 and a fourth metal plate 7 stacked in sequence from top to bottom;

[0037] A first dielectric plate 2 is attached between the first metal plate 1 and the second metal plate 3, a second dielectric plate 4 is attached between the second metal plate 3 and the third metal plate 5, and a third dielectric plate 6 is attached between the third metal plate 5 and the fourth metal plate 7;

[0038] The tunable multi-layer substrate integrated waveguide filter also includes a rectangular structure surrounded by metal vias, and the metal vias and all the metal plates and dielectric plates together form a resonant cavity;

[0039] The central parts of the first dielectric plate 2, the second dielectric plate 3 and the third dielectric plate 6 are hollow rectangular grooves, and YIG ferrites 15 parallel to the input port and the output port are arranged on the opposite sides of the rectangular grooves.

[0040] In this implementation case, the horizontal direction parallel to the paper is called the X direction, the vertical direction parallel to the paper is called the Y direction, and the direction perpendicular to the paper is called the Z direction. The dielectric substrate of the filter adopts Rogers 5880 design with a thickness of 0.508 and a dielectric constant of 2.2, and the thickness of the metal plate is 18 microns. The length of the circuit board is 30 mm and the width is 28 mm.

[0041] Specifically, Figure 3 As shown, two YIG ferrites 15 are installed in the hollow rectangular groove by conductive glue. The ferrite is in the shape of a cuboid, with the same length as the length cut off in the X direction, a height of 0.508 mm, and a width of 1.0 mm. The two YIG ferrites are installed along the X direction, and the installation positions are close to the two sides of the middle cut-off part. The saturation magnetization of the YIG ferrite 15 is 1780G, accompanied by a line width △H≤17Oe, and a relative dielectric constant of 15.

[0042] Optionally, the hollow rectangular grooves of each dielectric plate in the X and Y directions may be different, and the geometric parameters of the hollow rectangular grooves may be adjusted according to the optimization target.

[0043] The input port is an input microstrip line with an impedance of 50 ohms, and the input microstrip line is also connected to the first coplanar waveguide line 11 on the surface of the first metal plate 1;

[0044] The output port is an output microstrip line with an impedance of 50 ohms, and the output microstrip line is also connected to the second coplanar waveguide line 18 on the surface of the fourth metal plate 7 .

[0045] Furthermore, the resonant cavity is defined by a rectangle surrounded by metal vias, the diameter of the metal vias is 0.4 mm, and the center distance between two metal vias is 1.0 mm.

[0046] Furthermore, the first metal plate 1 is provided with an input port 8, and the fourth metal plate 7 is provided with an output port 9;

[0047] The input port 1 is an input microstrip line with an impedance of 50 ohms, and the input microstrip line is also connected to the first coplanar waveguide line 11 on the surface of the first metal plate 1;

[0048] The output port 9 is an output microstrip line with an impedance of 50 ohms, and the output microstrip line is also connected to the second coplanar waveguide line 18 on the surface of the fourth metal plate 7 .

[0049] Specifically, the width of the 50-ohm microstrip line in the first metal plate 1 is 1.58 mm; the width of the first coplanar waveguide line 11 is 1.58 mm, the length is 4.55 mm, the width of the slot lines on both sides of the first coplanar waveguide line 11 is 0.4 mm, and the distance from the slot lines on both sides of the first coplanar waveguide line 11 to the metal vias is 4.55 mm.

[0050] Considering the influence of the input port 8 and the output port 9, the first, second and third types of metal vias are designed.

[0051] like Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 As shown, the second type of metal via 13 is located directly below the input port, and passes through the first metal plate 1, the first dielectric plate 2, the second metal plate 3, the second dielectric plate 4, the third metal plate 5, the third dielectric plate 6 and the fourth metal plate 7 from top to bottom;

[0052] The third type of metal via 14 is located directly above the output port 9, and passes through the first metal plate 1, the first dielectric plate 2, the second metal plate 3, the second dielectric plate 4 and the third metal plate 5 from top to bottom;

[0053] All metal vias except the second-type metal vias 13 and the third-type metal vias 14 are first-type metal vias 12, which pass through the first metal plate 1, the first dielectric plate 2, the second metal plate 3, the second dielectric plate 4, the third metal plate 5, the third dielectric plate 6 and the fourth metal plate 7 from top to bottom.

[0054] Furthermore, the tunable multi-layer substrate integrated waveguide filter is provided with an external magnetic field, and the magnetic field strength of the external magnetic field is adjusted to adjust the dielectric constant of the ferrite to achieve tuning of the center frequency of the filter, and the direction of the external magnetic field is the Y direction.

[0055] Furthermore, if Figure 4 and Figure 5 As shown, the second metal plate 3 is etched with a pair of first-type slot lines 16 symmetrical along the axis of the straight line where the input port 8 or the output port 9 is located, and the third metal plate 5 is etched with two pairs of second-type slot lines 17 symmetrical along the perpendicular axis of the straight line where the input port 8 or the output port 9 is located, for achieving maximum in-band return loss.

[0056] Specifically, the second metal plate 3 is etched with two first-type grooves 16 in the Y direction, the width of the first-type groove 16 is 0.3 mm, the length is 3.6 mm, and the distance between the bottom of the first-type groove 16 and the X axis is 8.65 mm. The first-type grooves 16 are symmetrical about the Y axis and are respectively arranged in the +Y direction and the -Y direction.

[0057] The third metal layer 5 is etched with four second-type grooves 17 on the X-direction plate, the width of the second-type grooves 17 is 0.3mm, the length is 3.6mm, the right side of the second-type grooves 17 is 8.65mm from the Y axis, and the interval between the two second-type grooves 17 on the left side of the X axis is 5.9mm.

[0058] Furthermore, if Figure 1 and Figure 6 As shown, the input port 8 and the output port 9 are symmetrical along the center of the tunable multilayer substrate integrated waveguide filter.

[0059] Furthermore, all metal plates and dielectric plates are provided with an axially symmetrical through-hole array 10 along the straight line where the input port 8 or the output port 9 is located, and the through-hole array passes through the first metal plate 1, the first dielectric plate 2, the second metal plate 3, the second dielectric plate 4, the third metal plate 5, the third dielectric plate 6 and the fourth metal plate 7 from top to bottom.

[0060] Specifically, in this embodiment, three rows of through hole arrays 10 are arranged in the +Y direction and the -Y direction, the diameter of the through holes in each row of through hole array 10 is 0.4 mm, and the center distance between the through holes is 1.0 mm; the number of through hole arrays is not limited to 3 rows and can be adjusted according to actual use.

[0061] The through hole array 10 is composed of non-metallic vias, and a suspended metal probe array is arranged above the through hole array 10. The metal probe array is driven by a three-dimensional linear displacement driver. In this embodiment, the linear driver selected is a three-axis linear driver of model LS65-13C3P, which can achieve a maximum displacement of 13mm in the three directions of XYZ; when the tuning state is not entered, the linear driver controls the metal probe array to be suspended above the filter; when tuning is required, the metal probe array is inserted into the corresponding through hole array.

[0062] like Figure 7 , Figure 8 and Fig. 9 As shown, the operating frequency of the entire filter is 7.114 GHz, the bandwidth is 93 MHz, the quality factor is 76.7, and the relative bandwidth is 1.3%; the simulation shows that the minimum insertion loss is 1.48 dB, and the out-of-band suppression depth in the range of 7.4-22 GHz is higher than 18 dB.

[0063] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A tunable multilayer substrate integrated waveguide filter with broadband external suppression, characterized in that: include: A first metal plate, a second metal plate, a third metal plate, and a fourth metal plate are stacked in sequence from top to bottom; A first dielectric plate is attached between the first metal plate and the second metal plate, a second dielectric plate is attached between the second metal plate and the third metal plate, and a third dielectric plate is attached between the third metal plate and the fourth metal plate; The tunable multi-layer substrate integrated waveguide filter also includes a rectangular structure surrounded by metal vias, and the metal vias and all the metal plates and dielectric plates together form a resonant cavity; The central parts of the first dielectric plate, the second dielectric plate and the third dielectric plate are hollow rectangular grooves, and YIG ferrites parallel to the input port and the output port are arranged on the opposite sides of the rectangular grooves.

2. The broadband external suppression tunable multilayer substrate integrated waveguide filter according to claim 1, characterized in that: The first metal plate is provided with an input port, and the fourth metal plate is provided with an output port; The input port is an input microstrip line with an impedance of 50 ohms, and the input microstrip line is also connected to the first coplanar waveguide line on the surface of the first metal plate; The output port is an output microstrip line with an impedance of 50 ohms, and the output microstrip line is also connected to the second coplanar waveguide line on the surface of the fourth metal plate.

3. The broadband external suppression tunable multilayer substrate integrated waveguide filter according to claim 1, characterized in that: The metal vias include first-type metal vias, second-type metal vias and third-type metal vias; The second type of metal via is located directly below the input port, and passes through the second metal plate, the first dielectric plate, the second metal plate, the second dielectric plate, the third metal plate, the third dielectric plate, and the fourth metal plate from top to bottom; The third type of metal via is located directly above the output port, and passes through the first metal plate, the first dielectric plate, the second metal plate, the second dielectric plate, and the third metal plate from top to bottom; All metal vias except the second-type metal vias and the third-type metal vias are first-type metal vias, which pass through the first metal plate, the first dielectric plate, the second metal plate, the second dielectric plate, the third metal plate, the third dielectric plate and the fourth metal plate from top to bottom.

4. The broadband external suppression tunable multilayer substrate integrated waveguide filter according to claim 1, characterized in that: The tunable multi-layer substrate integrated waveguide filter is provided with an external magnetic field, and the dielectric constant of the ferrite is adjusted by adjusting the magnetic field strength of the external magnetic field.

5. The broadband external suppression tunable multilayer substrate integrated waveguide filter according to claim 1, characterized in that: The input port and the output port are symmetrical along the center of the tunable multi-layer substrate integrated waveguide filter.

6. The broadband external suppression tunable multi-layer substrate integrated waveguide filter according to claim 5, characterized in that: The second metal plate is etched with a pair of first-type slot lines symmetrical along the straight line where the input port or output port is located, and the third metal plate is etched with two pairs of second-type slot lines symmetrical along the perpendicular line where the input port or output port is located, for achieving maximum in-band return loss.

7. The broadband external suppression tunable multilayer substrate integrated waveguide filter according to claim 5, characterized in that: All metal plates and dielectric plates are provided with an axially symmetrical through-hole array along the straight line where the input port or the output port is located, and the through-hole array passes through the first metal plate, the first dielectric plate, the second metal plate, the second dielectric plate, the third metal plate, the third dielectric plate and the fourth metal plate from top to bottom.

8. The broadband external suppression tunable multi-layer substrate integrated waveguide filter according to claim 7, characterized in that: The through hole array is composed of non-metal vias, and a suspended metal probe array is arranged above the through hole array. The metal probe array is driven by a three-dimensional linear displacement driver.

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