A miniature substrate integrated waveguide filter with in-band ripple suppression

Abstract

The application discloses a micro substrate integrated waveguide filter with in-band ripple suppression, a wide-stop-band band-pass filter adopts a single-cavity substrate integrated waveguide structure, four novel complementary open-loop resonant rings with the same shape are etched on the upper layer metal of the resonant cavity and are recorded as wide-stop-band resonant rings, a capacitive slot line is etched on the middle position of the upper layer metal along the longitudinal direction and is recorded as a wide-stop-band capacitive slot line, and the lower layer metal is etched to form a defect ground; a dual-band band-pass filter adopts a single-cavity substrate integrated waveguide structure, four novel complementary open-loop resonant rings are etched on the upper layer metal of the resonant cavity, the four open-loop resonant rings are divided into two groups according to the size and are recorded as large resonant rings and small resonant rings, a capacitive slot line is etched on the middle position of the upper layer metal along the longitudinal direction and is recorded as a dual-band capacitive slot line, a grid-shaped slot line is etched along the transverse direction, a symmetrical slot microstrip line is etched at the tapered interface of the upper layer metal, a metal counterbore is arranged in the resonant cavity, and a slow-wave substrate integrated waveguide structure is formed by connecting a circuit ground plane.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of microwave radio frequency communication technology, and relates to a micro substrate integrated waveguide filter with in-band ripple suppression. BACKGROUND

[0002] With the rapid development of wireless communication technology, radio frequency devices are required to have better performance. As one of the main components of radio frequency devices, bandpass filters are required to have a more compact structure, better filtering performance and the characteristics of easy integration. Substrate integrated waveguide has been widely used in the field of microwave and millimeter wave because of its relatively high quality factor, high power capacity, small size, easy integration and low cost, attracting the attention of a large number of researchers worldwide. The filter using the substrate integrated waveguide structure has the advantages of low insertion loss, low cost, high selectivity and easy integration, which can well meet the requirements of modern wireless communication systems.

[0003] However, most of the current designs of substrate integrated waveguide filters use a structure of multiple waveguide resonant cavities coupled. Although this structure has excellent rectangular coefficients, the more resonant cavities mean that the insertion loss caused by the circuit itself is larger, and the overall size of the circuit also increases. Although the multi-layer dielectric substrate structure used in many designs can alleviate the problem of size increase, the multi-layer circuit board also has the disadvantage of not being easy to integrate.

[0004] In view of the current technical problems, it is necessary to design a substrate integrated waveguide bandpass filter which has good rectangular coefficients and low in-band insertion loss, and can maintain the advantages of small size and easy integration of the substrate integrated waveguide structure without being affected. SUMMARY

[0005] In order to overcome the difficulties in the prior art, the present application proposes a micro substrate integrated waveguide filter with in-band ripple suppression function, including a wide stopband filter and a dual-band filter. The filter is based on a substrate integrated waveguide structure, and four new complementary open resonant rings are formed on the waveguide resonant cavity by etching the metal layer. The resonant rings have capacitive slot lines between them. The defect ground structure is applied in the wide stopband filter; the slow-wave substrate integrated waveguide structure and the symmetric slot line interface structure are used in the dual-band filter.

[0006] To achieve the above purpose, the technical scheme of the present application is as follows:

[0007] A micro substrate integrated waveguide filter with in-band ripple suppression, including a wide stopband bandpass filter and a dual-band bandpass filter, wherein,

[0008] The wide-stop-band band-pass filter adopts a single-cavity substrate integrated waveguide structure, four novel complementary open resonant rings of the same shape are etched on the upper layer of metal of the resonant cavity, recorded as wide-stop-band resonant rings, a capacitive slot line is etched at the middle position of the upper layer of metal in the longitudinal direction, recorded as a wide-stop-band capacitive slot line, and a defect is etched in the lower layer of metal;

[0009] The dual-band band-pass filter adopts a single-cavity substrate integrated waveguide structure, four novel complementary open resonant rings are etched on the upper layer of metal of the resonant cavity, the four open resonant rings are divided into two groups according to different sizes and recorded as large resonant rings and small resonant rings, a capacitive slot line is etched at the middle position of the upper layer of metal in the longitudinal direction and recorded as a dual-band capacitive slot line, a grid-shaped slot line is etched in the transverse direction, a symmetrical slot microstrip line is etched at the tapered interface of the upper layer of metal, and a metal counterbore is arranged inside the resonant cavity to connect the circuit ground plane to form a slow-wave substrate integrated waveguide structure.

[0010] Preferably, the single-cavity substrate integrated waveguide structure is a single-layer dielectric substrate, and the upper and lower layers are covered with metal layers, and a metal through hole is punched at the edge position of the upper metal layer to form a resonant cavity.

[0011] Preferably, the wide-stop-band resonant ring is a double-ring structure, wherein the outer ring is a square complementary open resonant ring, and the inner ring is a circular open resonant ring, the four wide-stop-band resonant rings have the same shape and size, and are uniformly arranged at four positions of the upper metal layer of the resonant cavity in a rectangular distribution.

[0012] Preferably, the wide-stop-band resonant ring is equivalent to a parallel LC resonant circuit, wherein the equivalent inductance L C and the equivalent capacitance C C According to the shape and size of the wide-stop-band resonant ring, the relationship is:

[0013]

[0014]

[0015] B(x)=S0(x)J1(x)-S1(x)J0(x)

[0016] wherein r b , r a are the radii of the inscribed circle of the outer ring and the inner ring respectively, L pul is the inductance per unit length, c is the speed of light in vacuum, ε0 is the dielectric constant of vacuum, εr is the dielectric constant of the dielectric substrate, h is the thickness of the dielectric substrate, S n and J n are n-order Struve and Bessel functions, and the resonant frequency of the resonant ring is calculated as:

[0017]

[0018] Preferably, the wide resistive slot line is a groove line formed by etching metal in the middle of the upper metal layer, and the direction is perpendicular to the direction of the input / output feed line.

[0019] Preferably, the defect is dumbbell-shaped, and four are arranged in the lower metal layer below the input / output feed line and are perpendicular to the input / output feed line.

[0020] Preferably, the grid-shaped slot line is a groove line parallel to the input / output feed line in the middle of the upper metal layer of the resonant cavity.

[0021] Preferably, the slot microstrip line is symmetrically arranged at the input / output interface, and part of the metal is etched, and the remaining part forms a microstrip line structure with a terminal open circuit.

[0022] Preferably, the slow-wave substrate integrated waveguide structure is a uniformly arranged metal sink hole formed in the resonant cavity dielectric substrate by laser technology, one end of the metal sink hole is connected to the bottom surface metal of the resonant cavity, and the other end is in the resonant cavity dielectric substrate.

[0023] Preferably, for the slow-wave substrate integrated waveguide, the equivalent dielectric constant is:

[0024]

[0025] Where h is the total thickness of the dielectric substrate, h2 is the height of the metal sink hole, h=h1+h2, εr is the dielectric constant of the dielectric substrate, and the resonant frequency of the slow-wave substrate integrated waveguide resonant cavity is:

[0026]

[0027] Where W S and L are the equivalent width and length of the resonant cavity, f TEmon-SIW is the resonant frequency of the TE mon mode of the resonant cavity.

[0028] The present application uses the high-pass property of the substrate integrated waveguide and the band-stop property of the complementary split ring resonator to design a band-pass filter. The capacitive slot line between the split ring resonators can reduce the coupling between the resonators and thus suppress the in-band ripple. The defect ground structure in the wide-stop-band band-pass filter has a low-pass characteristic and can expand the stop band of the filter. The slow-wave substrate integrated waveguide structure used in the dual-pass-band filter can reduce the resonant frequency of the resonant cavity, thereby reducing the overall size of the filter. The symmetric slot microstrip line structure can introduce a transmission zero to improve the selectivity of the passband.

[0029] Compared with the prior art, the present application has the following technical effects:

[0030] 1. The single-layer single-cavity substrate integrated waveguide loaded with the complementary open resonant ring structure of the application replaces the traditional multi-cavity substrate integrated waveguide filter, avoids the problems of large size, large insertion loss of the traditional multi-cavity substrate integrated waveguide filter, and the problem of not easy to integrate multi-layer circuit while ensuring the overall characteristics of the filter unchanged;

[0031] 2. The capacitive slot line structure of the application can reduce the coupling between the resonant rings in the form of equivalent capacitance, so that the resonant ring spacing can be smaller while suppressing the in-band ripple caused by strong coupling;

[0032] 3. Because the filter designed by the application includes 5G frequency band below 6G (4.8GHz-5.0GHz), the application can be applied to 5G communication base station, and used as a post-circuit of communication base station power amplifier. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 It is a structure diagram of the prior art multi-cavity substrate integrated waveguide filter;

[0034] Figure 2 It is a structure diagram of the in-band ripple suppression micro-substrate integrated waveguide filter of the embodiment of the application;

[0035] Figure 3 It is a new type of complementary open resonant ring (a) and its equivalent LC circuit diagram (b) of the in-band ripple suppression micro-substrate integrated waveguide filter of the embodiment of the application;

[0036] Figure 4 It is a structure diagram and S parameter simulation curve of the half-mode substrate integrated waveguide filter loaded with the prior art open resonant ring and the half-mode substrate integrated waveguide filter loaded with the new type of open resonant ring of the application;

[0037] Figure 5 It is a graph showing the influence of the capacitive slot line of the in-band ripple suppression micro-substrate integrated waveguide filter of the embodiment of the application on the filter S parameter;

[0038] Figure 6 It is a defect ground structure and its resonant frequency and size relationship graph of the in-band ripple suppression micro-substrate integrated waveguide filter of the embodiment of the application;

[0039] Figure 7 It is a simulation and measured S parameter graph of the wide stopband bandpass filter of the in-band ripple suppression micro-substrate integrated waveguide filter of the embodiment of the application;

[0040] Figure 8 It is a simulation and measured S parameter graph of the dual-band bandpass filter of the in-band ripple suppression micro-substrate integrated waveguide filter of the embodiment of the application; DETAILED DESCRIPTION

[0041] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0042] On the contrary, the present application covers any substitution, modification, equivalent method and scheme made within the essence and scope of the present application defined by the claims. Further, in order to make the public have a better understanding of the present application, some specific details are described in the following detailed description of the present application. The present application can also be completely understood without the description of these details by those skilled in the art.

[0043] Reference is made to Figure 2 The micro-silicon substrate integrated waveguide filter with in-band ripple suppression function shown in the figure includes a wide stopband filter and a dual-passband filter. The two filters are based on a silicon substrate integrated waveguide structure, and four complementary open resonant rings are formed on the resonant cavity of the waveguide by etching the metal layer. There is a capacitive slot line between the resonant rings. The wide stopband filter applies a defect ground structure; the dual-passband filter adopts a slow-wave silicon substrate integrated waveguide structure and a symmetric slot line interface structure. Compared with Figure 1 Compared with the traditional multi-cavity silicon substrate integrated waveguide filter structure shown in the figure, the present application only adopts a single-layer silicon substrate integrated waveguide resonant cavity, which maximally reduces the insertion loss and the disadvantages of large volume and difficulty in integration introduced by the multi-cavity structure or multi-layer structure.

[0044] The wide stopband bandpass filter adopts a single-cavity silicon substrate integrated waveguide structure, four novel complementary open resonant rings with the same shape are etched on the resonant cavity, which are denoted as wide stop resonant rings 11, a capacitive slot line is etched in the middle position of the upper metal layer along the longitudinal direction, which is denoted as wide stop capacitive slot line 12, and a defect ground 13 is etched in the lower metal layer;

[0045] The dual-passband bandpass filter adopts a single-cavity silicon substrate integrated waveguide structure, four novel complementary open resonant rings are etched on the resonant cavity, the four open resonant rings are divided into two groups according to the size, which are denoted as large resonant rings 21 and small resonant rings 22, a capacitive slot line is etched in the middle position of the upper metal layer along the longitudinal direction, which is denoted as dual-passband capacitive slot line 23, a grid-shaped slot line 24 is etched along the transverse direction, a symmetric slot microstrip line 25 is etched at the tapered interface of the upper metal layer, a metal counterbore 26 is arranged inside the resonant cavity to form a slow-wave silicon substrate integrated waveguide structure by connecting the circuit ground plane.

[0046] The single-cavity silicon substrate integrated waveguide structure is a single-layer dielectric substrate, and the upper and lower surfaces are covered with metal layers. A metal through hole 14 is punched at the edge position of the upper metal layer to form a resonant cavity.

[0047] The wide-stop-band resonant ring 11 is a double ring structure, wherein the outer ring is a square complementary open resonant ring, and the inner ring is a circular open resonant ring. The four wide-stop-band resonant rings 11 have the same shape and size, and are uniformly arranged at four positions of the metal layer on the resonant cavity in a rectangular distribution.

[0048] In specific embodiments, Figure 3 The novel complementary open resonant ring of the application is a double ring structure, wherein the outer ring is a square complementary open resonant ring, and the inner ring is a circular open resonant ring. This structure can simultaneously have the characteristics of high selectivity of the square complementary resonant ring and wide-stop-band of the circular resonant ring. Each complementary open resonant ring can be equivalent to a parallel LC resonant circuit. The equivalent inductance L C and the equivalent capacitance C C can be obtained according to the shape and size of the resonant ring, and the relationship is:

[0049]

[0050]

[0051] B(x) = S0(x)J1(x) - S1(x)J0(x)

[0052] wherein r b , r a are the radii of the inscribed circle of the outer ring and the inner ring respectively, L pul is the inductance per unit length, c is the speed of light in vacuum, ε0 is the vacuum permittivity, ε is the dielectric constant of the dielectric substrate, h is the thickness of the dielectric substrate, S n and J n are n-order Struve and Bessel functions. The resonant frequency of the resonant ring can be calculated as:

[0053]

[0054] For a dual-band bandpass filter, the grid-shaped slot line 24 is a slot line parallel to the input / output feed line at the middle position of the upper metal layer of the resonant cavity.

[0055] The slotted microstrip line 25 is symmetrically arranged at the input / output interface, and part of the metal is etched, and the remaining part forms a microstrip line structure with a terminal open circuit.

[0056] The slow-wave substrate integrated waveguide structure is a uniformly arranged metal counterbore 26 inside the dielectric substrate of the resonant cavity by laser technology. One end of the metal counterbore 26 is connected to the bottom surface metal of the resonant cavity, and the other end is inside the dielectric substrate of the resonant cavity. For the slow-wave substrate integrated waveguide, the equivalent permittivity is:

[0057]

[0058] Where h is the total thickness of the dielectric substrate, h2 is the height of the metal countersunk hole 26, and h = h1 + h2, ε r Let be the dielectric constant of the substrate. Then, the resonant frequency of the slow-wave substrate integrated waveguide resonant cavity is:

[0059]

[0060] Among them, W S L and f are the equivalent width and length of the resonant cavity, respectively. TEmon-SIW For the resonant cavity TE mon The resonant frequency of the mode.

[0061] See Figure 4 The structure of a substrate integrated waveguide filter loaded with the novel complementary split-ring resonator of this invention and a substrate integrated waveguide filter loaded with a conventional complementary split-ring resonator are compared, along with their S-parameter simulation results (IV). (II) is a conventional square double-ring complementary split-ring resonator. Although its resonant frequency is lower, resulting in better passband selectivity compared to the other two, it suffers from a narrow stopband and relatively large in-band ripple. Similarly, although the conventional circular double-ring complementary split-ring resonator (I) has relatively small in-band ripple, its stopband is still narrow, and its passband center frequency is significantly higher than the other two, failing to meet the requirements for circuit miniaturization. The novel complementary split-ring resonator (III) of this invention, however, possesses the advantages of small in-band ripple and wide stopband, without a significant increase in passband center frequency, thus meeting the requirements for miniaturization and high performance. Therefore, the novel complementary split-ring resonator of this invention is the best choice among the three complementary split-ring resonators as the resonant unit.

[0062] See Figure 5 To illustrate the impact of capacitive slotted lines on the filter's S-parameters in this embodiment, the S-parameters of a filter without capacitive slotted lines are used for comparison. Figure 5 (I) with Figure 5 (II) is a filter S with the spacing Sg of the complementary open-loop resonators as the variable. 11 Changes, S 11 Smaller fluctuations mean smaller ripples. Figure 5 (III) S is the two filters at the same spacing Sg. 21 and S 11 The two filters are identical in structure except for the presence or absence of slotted lines. In the capacitive slotted line filter of this invention, the ripple in the passband is significantly reduced when the spacing between the complementary open-ring resonators reaches 2.2 mm, while the filter without slotted lines only achieves the same effect when the spacing between the complementary open-ring resonators is around 3.6 mm. Figure 5 (III) indicates that at the same distance, the former has superior performance in terms of both in-band ripple and passband selectivity.

[0063] Referring to Figure 6 For the variation of the resonance frequency of the defect ground 13 with respect to the structure size, it can be seen that the resonance frequency decreases with the increase of the overall size. Figure 6 (I) is a structure diagram of the defect ground 13, Figure 6 (II) and (III) are diagrams of the variation of the resonance frequency of the defect ground 13 with respect to the structure size, in the present application, the length Lg of the dumbbell-shaped defect ground 13 slot line is selected as a combination of 6.8 mm, 6.0 mm, 3.7 mm and 3.3 mm, the width g of the rectangular part is 0.2 mm, and the diameter r of the semicircular part is 1.3 mm. r

[0064] Referring to Figure 7 and Figure 8 are measurement diagrams of the two filters of the present application. From the S parameters, it can be seen that the less than -20 dB stopband range of the wide stopband bandpass filter reaches 3.3 times the center frequency, both filters have good selectivity, and the overall results meet the expectations. The actual size of the two filter circuits is very small, the length of the wide stopband bandpass filter is less than 3 cm, and the length of the dual-band bandpass filter is less than 4 cm, specifically, only 0.43λ g × 0.41λ g and 0.37λ g × 0.32λ g (λ g is the waveguide wavelength corresponding to the first passband), which is much smaller than most filters of the same level on the market. Some deviations between simulation and measurement are caused by machining precision and SMA interface loss. Overall, the similarity between the measurement results and the simulation results is high, which verifies the feasibility of the present application.

[0065] The above only describes the preferred embodiments of the present application and is not intended to limit the present application, any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.​

Claims

1. A micro-slab integrated waveguide filter with in-band ripple suppression, characterized by, The application relates to a wide-band band-pass filter and a double-band band-pass filter. The wide-band band-pass filter adopts a single-cavity substrate integrated waveguide structure, four novel complementary open resonant rings are etched on the upper layer metal of a resonant cavity, the rings are recorded as wide-band resonant rings, a capacitive slot line is etched at the middle position of the upper layer metal in the longitudinal direction and is recorded as a wide-band capacitive slot line, and a defect ground is etched on the lower layer metal. The double-band band-pass filter adopts a single-cavity substrate integrated waveguide structure, four novel complementary open resonant rings are etched on the upper layer metal of a resonant cavity, the four open resonant rings are divided into two groups according to the size and are recorded as large resonant rings and small resonant rings, a capacitive slot line is etched at the middle position of the upper layer metal in the longitudinal direction and is recorded as a double-band capacitive slot line, a grid-shaped slot line is etched in the transverse direction, a symmetrical slot microstrip line is etched at the tapered interface of the upper layer metal, a metal counterbore is arranged in the resonant cavity, and a slow-wave substrate integrated waveguide structure is formed by connecting a circuit ground plane.

2. The micro-slab integrated waveguide filter with in-band ripple suppression according to claim 1, wherein, The single-cavity substrate integrated waveguide structure is a single-layer dielectric substrate, and metal layers are arranged above and below the single-layer dielectric substrate; metal through holes are punched at the edge positions of the upper metal layer to form a resonant cavity.

3. The micro-slab integrated waveguide filter with in-band ripple suppression of claim 1, wherein, The wide-band resonant ring is a double-ring structure, wherein the outer ring is a square complementary open resonant ring, and the inner ring is a circular open resonant ring; the four wide-band resonant rings have the same shape and size and are uniformly arranged at four positions of the upper metal layer of the resonant cavity in a rectangular distribution.

4. The micro-slab integrated waveguide filter with in-band ripple suppression according to claim 3, wherein, The wide-stop-band resonant ring is equivalent to a parallel LC resonant circuit, wherein the equivalent inductance L C and the equivalent capacitance C C According to the shape and size of the wide-stop-band resonant ring, the relationship is: B(x) = S0(x)J1(x) - S1(x)J0(x) where r b and r a are the outer and inner radii of the ring, L pul is the inductance per unit length, c is the speed of light in vacuum, ε0is the vacuum permittivity, ε r is the relative permittivity of the dielectric substrate, h is the dielectric substrate thickness, S n and J n are the n-th order Struve and Bessel functions, respectively, and the resonant frequency of the ring is calculated as 5. The micro-slab integrated waveguide filter with in-band ripple suppression of claim 1, wherein, The wide-band capacitive slot line is a groove line formed by etching metal at the middle position of the upper layer metal, and the direction is perpendicular to the direction of the input / output feed line.

6. The micro-slab integrated waveguide filter with in-band ripple suppression of claim 1, wherein, The defect ground is dumbbell-shaped, and four are arranged in the lower metal layer below the input / output feed line and are perpendicular to the input / output feed line.

7. The micro-slab integrated waveguide filter with in-band ripple suppression of claim 1, wherein, The grid-shaped slot line is a slot line parallel to the input / output feed line at the middle position of the upper layer metal of the resonant cavity.

8. The micro-slab integrated waveguide filter with in-band ripple suppression of claim 1, wherein, The slot microstrip line is symmetrically arranged at the input / output interface, part of the metal is etched, and the remaining part forms a microstrip line structure with a terminal open circuit.

9. The micro-slab integrated waveguide filter with in-band ripple suppression of claim 1, wherein, The slow-wave substrate integrated waveguide structure is that metal counterbores are uniformly arranged in the dielectric substrate of the resonant cavity by laser technology, one end of the metal counterbores is connected to the bottom surface metal of the resonant cavity, and the other end is in the dielectric substrate of the resonant cavity.

10. The micro-slab integrated waveguide filter with in-band ripple suppression according to claim 9, wherein, For the slow-wave substrate integrated waveguide, the equivalent dielectric constant is: Wherein, h is the total thickness of the dielectric substrate, h2 is the height of the metal sink hole, and h = h1 + h2, ε r The relative dielectric constant of the dielectric substrate is ε, and the resonant frequency of the slow-wave substrate integrated waveguide resonant cavity is: where W S and L are the equivalent width and length of the resonator, respectively, and f TEmon-SIW is the resonant frequency of the TE mon mode of the resonator.

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