SISL-based filter and duplexer

Abstract

The invention belongs to the technical field of filters, and particularly relates to an SISL-based filter and a duplexer. Comprising five layers of dielectric substrates which are sequentially arranged from top to bottom, and the five layers of dielectric substrates are sub1-sub5 respectively; the upper surface and the lower surface of each layer of dielectric substrate are covered with metal layers, and the ten metal layers G1-G10 are arranged from top to bottom. Two or three rectangular parts are cut off from the edges of the dielectric substrate sub1 and the dielectric substrate sub2, and the dielectric substrate sub1 and the dielectric substrate sub2 are overlapped; the five layers of dielectric substrates and the ten layers of metal layers are provided with through metal through hole square arrays, and the metal through hole square arrays of the dielectric substrates and the metal through hole square arrays of the metal layers coincide; the metal layer G5 is provided with GCPW transition-to-T-shaped feed structures, wherein the number of the GCPW transition-to-T-shaped feed structures is the same as that of rectangular parts cut off from the edge of the dielectric substrate sub1. The band-pass filter has excellent out-of-band rejection performance, a small circuit size and a wide stop band range.

Description

Technical Field

[0001] The invention belongs to the technical field of filters, and in particular relates to a filter and a duplexer based on SISL. Background Art

[0002] With the rapid development of modern communication systems, the performance requirements for RF transceiver systems are constantly increasing. In this context, RF filters are particularly important as a vital component in wireless communication systems. Its main function is to screen signals in a specific frequency band at the RF front end and remove useless signals, thereby ensuring high-quality signal transmission. In terms of filter design, microstrip line-based filters are favored because of their convenient design, miniaturization, planar circuits, and easy integration with other circuits. Therefore, they are widely used in wireless communication systems. However, microstrip line filters also have some limitations, such as lower Q values ​​and larger radiation losses, which may affect the performance of the filter. In addition, in the design and testing process of the entire RF circuit, additional processing of the shielding box is usually required, which increases the complexity of design and manufacturing.

[0003] With the rapid growth of information in modern society and the increasing demand for portability, communication technology is developing rapidly in the direction of broadband, high capacity and miniaturization. In this context, the traditional single passband filter can no longer meet the rapidly developing information transmission needs. Therefore, the dual-frequency filter has attracted much attention due to its ability to simultaneously select two different frequency bands. Through this technology, the communication system can achieve simultaneous operation of two frequency bands while saving system volume and cost, and make more efficient use of spectrum resources. This is crucial for modern communication systems, especially in the context of increasingly tight spectrum resources. Dual-frequency filters are becoming one of the important trends in the development of modern microwave millimeter-wave front-end circuits with their advantages such as wide stopband, miniaturization, high selectivity, low loss and self-packaging.

[0004] Substrate Integrated Suspension Line (SISL) is a new type of microwave and millimeter wave transmission line structure. This type of transmission line inherits the advantages of both planar circuits and waveguides, and has the advantages of self-packaging, high integration, low loss, and high quality factor. Therefore, wide-stopband dual-band filters based on dielectric integrated suspension lines have attracted the attention of researchers.

[0005] The prior art proposes a dual-passband filter based on SISL, which can achieve dual-passband filtering performance as a whole, but the stopband of the dual-passband filter is not wide enough. In some environments, the filter is required to have a good wide stopband. In addition, the lower stopband of the first passband does not introduce a transmission zero point, which makes the out-of-band suppression effect of the first passband of the filter limited, and the filtering performance needs to be further improved. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention proposes a filter and a duplexer based on SISL, the filter comprising: five dielectric substrates arranged in sequence from top to bottom, namely sub1-sub5; the upper surface and the lower surface of each dielectric substrate are covered with a metal layer, and there are ten metal layers G1-G10 from top to bottom; two rectangular parts are cut off from the edges of the dielectric substrate sub1 and the dielectric substrate sub2, and the dielectric substrate sub1 and the dielectric substrate sub2 overlap; penetrating square arrays of metal through holes are provided on the five dielectric substrates and the ten metal layers, and the square arrays of metal through holes on each dielectric substrate and each metal layer overlap; two GCPW transition to T-shaped feeding structures are provided on the metal layer G5.

[0007] Preferably, a step impedance microstrip resonator with a center-loaded short-circuit branch is provided on the metal layer G2.

[0008] Preferably, a stepped impedance suspended line resonator with a center-loaded short-circuit branch is provided on the metal layer G6.

[0009] Preferably, air cavities are provided in the middle of both the dielectric substrate sub2 and the dielectric substrate sub4. The air cavities are inside the square array of metal through holes, and the air cavity of the dielectric substrate sub4 overlaps with the air cavity of the dielectric substrate sub2.

[0010] Preferably, the GCPW transition to the T-shaped feeding structure includes a GCPW structure, a T-shaped feeding branch, and two rows of parallel metal through holes; the GCPW structure is arranged directly below the rectangular portion cut off from the edge of the dielectric substrate sub1, and the two rows of parallel metal through holes are respectively arranged on both sides of the GCPW structure; the T-shaped feeding branch is connected to the GCPW structure and is located inside the square array of metal through holes.

[0011] Preferably, the five-layer dielectric substrate and the ten-layer metal layer are provided with fixing through holes for fixing the filter.

[0012] A SISL-based duplexer comprises: five dielectric substrates arranged in sequence from top to bottom, namely sub1-sub5; the upper surface and the lower surface of each dielectric substrate are covered with metal layers, and there are ten metal layers G1-G10 from top to bottom; three rectangular parts are cut off from the edges of the dielectric substrate sub1 and the dielectric substrate sub2, and the dielectric substrate sub1 and the dielectric substrate sub2 overlap; penetrating square arrays of metal through holes are arranged on the five dielectric substrates and the ten metal layers, and the square arrays of metal through holes on each dielectric substrate and each metal layer overlap; three GCPW transition to T-shaped feeding structures are arranged on the metal layer G5.

[0013] Preferably, a step impedance microstrip resonator with a center-loaded short-circuit branch is provided on the metal layer G2; a step impedance suspended line resonator with a center-loaded short-circuit branch is provided on the metal layer G6; air cavities are provided in the middle of the dielectric substrate sub2 and the dielectric substrate sub4, and the air cavities are inside the square array of metal through holes, and the air cavity of the dielectric substrate sub4 overlaps with the air cavity of the dielectric substrate sub2.

[0014] Preferably, the GCPW transition to the T-shaped feeding structure includes a GCPW structure, a transition structure and a T-shaped feeding branch; the GCPW structure is arranged directly below the rectangular portion cut off from the edge of the dielectric substrate sub1, the T-shaped feeding branch is connected to the GCPW structure through the transition structure, and the T-shaped feeding branch is located inside the square array of metal through holes.

[0015] Preferably, fixed through holes are provided on the five-layer dielectric substrate and the ten-layer metal layer for fixing the duplexer.

[0016] The beneficial effects of the present invention are as follows: the designed filter uses microstrip resonators and suspension line resonators to achieve dual passbands. Transmission zeros are introduced by source-load coupling, so that the passband has high selectivity and better filtering performance. The center frequency of the first passband can be adjusted by adjusting the size of the microstrip resonator. The center frequency of the second passband can be adjusted by adjusting the size of the suspension line resonator; if designed as a dual-frequency filter, the present invention achieves a dual-passband filtering effect, and five transmission zeros are introduced into the transmission coefficient of the dual passband, which greatly improves the selectivity of the dual passband; if designed as a duplexer, the present invention achieves a wide stopband effect, and three transmission zeros are introduced into the transmission coefficient of each passband, which greatly improves the selectivity of the dual passband; the present invention adopts a 3D stacked resonator structure, so that the filter has a smaller volume under the same performance conditions; simulation results show that the present invention has excellent out-of-band suppression performance, a smaller circuit size and a wider stopband range. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a hierarchical schematic diagram of the filter based on SISL in the present invention;

[0018] Figure 2 It is a top view of the stacking of G1, G2 and sub1 of the dual-frequency filter of the present invention;

[0019] Figure 3 It is a top view of the stacking of G3, G4 and sub2 of the dual-band filter of the present invention;

[0020] Figure 4 A top view of the stack of G5, G6 and sub3 layers of the dual-band filter of the present invention;

[0021] Figure 5A top view of the stack of G7, G8 and sub4 layers of the dual-band filter of the present invention;

[0022] Figure 6 A top view of the stack of G9, G10 and sub5 layers of the dual-band filter of the present invention;

[0023] Figure 7 It is a layered schematic diagram of the duplexer in the present invention;

[0024] Figure 8 It is a top view of the stacking of G1, G2 and sub1 of the duplexer of the present invention;

[0025] Fig. 9 It is a top view of the stacking of G3, G4 and sub2 of the duplexer of the present invention;

[0026] Fig.10 A top view of the stacking of the G5, G6 and sub3 layers of the duplexer of the present invention;

[0027] Fig.11 A top view of the stacking of the G7, G8 and sub4 layers of the duplexer of the present invention;

[0028] Fig.12 A top view of the stacking of the G9, G10 and sub5 layers of the duplexer of the present invention;

[0029] Fig.13 It is a simulation result diagram of the dual-frequency filter in the present invention;

[0030] Fig.14 This is a simulation result diagram of the duplexer in the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The stopband of the filter designed in the prior art is not wide enough, but in some environments, the filter is required to have a good wide stopband. In addition, the lower stopband of the first passband of the existing filter does not introduce a transmission zero, which makes the out-of-band suppression effect of the first passband of the filter limited, and the filtering performance needs to be further improved. To this end, the present invention proposes a filter based on SISL, such as Figure 1As shown, the filter includes: five dielectric substrates arranged in sequence from top to bottom, namely sub1-sub5; the upper surface and the lower surface of each dielectric substrate are covered with a metal layer, and there are ten metal layers G1-G10 from top to bottom, and the metal layers covering the upper and lower surfaces of the dielectric substrates are exactly the same in shape and size as the corresponding dielectric substrates.

[0033] The top view of the stack of each dielectric layer and the metal layer it covers is shown in Figure 2-Figure 6 As shown. Two rectangular parts are cut off from the edges of the dielectric substrate sub1 and the dielectric substrate sub2, and the dielectric substrate sub1 and the dielectric substrate sub2 overlap; the five dielectric substrates and the ten metal layers are provided with penetrating square arrays of metal through holes, and the square arrays of metal through holes in each dielectric substrate and each metal layer overlap; two GCPW transitions to T-shaped feeding structures are provided on the metal layer G5.

[0034] The filter has multiple layers of dielectric substrates that are stacked and assembled to form a dielectric integrated suspension line. The uppermost and lowermost dielectric substrates and metallized through holes that are connected vertically all around form a metal shielding structure, thereby reducing radiation loss.

[0035] Preferably, a step-impedance microstrip resonator with a center-loaded short-circuit branch is provided on the metal layer G2, and a step-impedance suspended line resonator with a center-loaded short-circuit branch is provided on the metal layer G6.

[0036] Preferably, an air cavity is provided in the middle of the dielectric substrate sub2 and the dielectric substrate sub4. The air cavity is inside the square array of metal through holes. The air cavity is formed by removing a rectangular dielectric substrate from the middle of the original dielectric substrate. The air cavity of the dielectric substrate sub4 overlaps with the air cavity of the dielectric substrate sub2.

[0037] Preferably, the GCPW transition to the T-shaped feeding structure includes a GCPW structure, a transition structure and a T-shaped feeding branch; the GCPW structure is arranged directly below the rectangular portion cut off from the edge of the dielectric substrate sub1, the T-shaped feeding branch is connected to the GCPW structure through the transition structure, and the T-shaped feeding branch is located inside the square array of metal through holes.

[0038] like Figure 2-Figure 4 As shown, two rectangular parts are cut off from the edges of the dielectric substrate sub1 and the dielectric substrate sub2, and there are two T-shaped feeding structures corresponding to the GCPW transition set on the corresponding metal layer G5; the metal layer G5 has an input port and an output port, that is, one GCPW structure is used as the input port, and the other GCPW structure is used as the output port, and the input port and the output port are located on the same straight line; at this time, the SISL-based filter is a dual-frequency filter.

[0039] The present invention also provides a SISL-based duplexer, such as Figure 7 As shown, its structure includes: five dielectric substrates arranged in sequence from top to bottom, namely sub1-sub5; the upper surface and the lower surface of each dielectric substrate are covered with a metal layer, and there are ten metal layers G1-G10 from top to bottom.

[0040] The top view of the stack of each dielectric substrate and the metal layer covering it is shown in Figure 1. Figure 8-Figure 12 As shown; three rectangular parts are cut off from the edges of the dielectric substrate sub1 and the dielectric substrate sub2, and the dielectric substrate sub1 and the dielectric substrate sub2 overlap; the five dielectric substrates and the ten metal layers are provided with penetrating square arrays of metal through holes, and the square arrays of metal through holes in each dielectric substrate and each metal layer overlap; three GCPW transitions to T-shaped feeding structures are provided on the metal layer G5.

[0041] A step impedance microstrip resonator with a center-loaded short-circuit branch is provided on the metal layer G2; a step impedance suspended line resonator with a center-loaded short-circuit branch is provided on the metal layer G6; an air cavity is provided in the middle of the dielectric substrate sub2 and the dielectric substrate sub4, and the air cavity is inside the square array of metal through holes, and the air cavity of the dielectric substrate sub4 overlaps with the air cavity of the dielectric substrate sub2. The GCPW transition to T-shaped feeding structure includes a GCPW structure, a transition structure and a T-shaped feeding branch; the GCPW structure is provided directly below the rectangular part cut off from the edge of the dielectric substrate sub1, the T-shaped feeding branch is connected to the GCPW structure through the transition structure, and the T-shaped feeding branch is located inside the square array of metal through holes.

[0042] like Figure 8-Figure 10 As shown, in the duplexer, three rectangular parts are cut off from the edges of the dielectric substrate sub1 and the dielectric substrate sub2, and there are three GCPW transitions to T-shaped feeding structures set on the corresponding metal layer G5; the metal layer G5 has one input port and two output ports, that is, one GCPW structure is used as an input port, and the other two GCPW structures are used as output ports, and the two ports are on the same straight line.

[0043] Preferably, the five-layer dielectric substrate and the ten-layer metal layer of the filter and the duplexer are provided with fixing through holes for fixing the components.

[0044] The working principle of the dual-band filter is as follows: the input signal is transitioned to the T-shaped branch of SSL through the structure GCPW (grounded coplanar waveguide), the T-shaped feeding structure located in the G5 layer couples the energy to the step impedance microstrip resonator of the center-loaded short-circuit branch located in the G2 metal layer through the upper air cavity, the microstrip resonator couples the energy to the T-shaped feeding at the output end through the air cavity, and finally transitions to the GCPW at the output end, the entire transmission forms the first passband, the T-shaped feeding transmits the energy to the step impedance resonator of the center-loaded short-circuit branch of the G6 layer through coupling, the resonator couples the energy to the T-shaped feeding end at the output end, the entire transmission forms the second passband, and two T-shaped feeding structures are used to introduce source load coupling, and transmission zeros are introduced between the first passband and the second passband and on both sides of the passband to achieve higher selectivity. The center frequency of the first passband can be adjusted by the overall length of the microstrip resonator, and the center frequency of the second passband can be adjusted by the overall length of the suspension line resonator.

[0045] The simulation results of the dual-frequency filter are shown in Fig.13 As shown, it can be seen from the simulation results that the first filter passband is 2.27-2.64GHz, the second filter passband is 4.8-5.4GHz, and a transmission zero is introduced in the stopband below the first passband, two transmission zeros are introduced between the first passband and the second passband, and two transmission zeros are introduced in the stopband above the second passband. The input return loss (S11) in the two passbands is better than 20dB, and the insertion loss (S21) of the two passbands is better than 0.22dB and 0.2dB respectively. The overall stopband reaches 11GHz below -20dB (4.5f0, f0 is the center frequency of the first passband) and the overall center circuit size is 11mm*10mm (0.09λ g

[0046] *0.082λ g ) It can be seen that the simulation example of the present invention has excellent out-of-band suppression performance, a smaller circuit size and a wider stopband range. Compared with the simulation effect of the dual-passband filter document "A Self-Packaged Low-Loss and Compact SISL DBBPF With Multiple TZs" which is also a dielectric integrated suspension line, the dual-passband structure proposed in the present invention has better out-of-band suppression effect, smaller size and wider stopband range.

[0047] The working principle of the duplexer: the input signal is transferred to the input T-type branch of SSL through the GCPW structure. The T-shaped feeding structure located in the G5 layer couples the energy to the step impedance microstrip resonator of the center-loaded short-circuit branch located in the G2 metal layer through the upper air cavity. The microstrip resonator couples the energy to the T-type branch of the output end 2 through the air cavity, and finally transitions to the GCPW of the output end 2. The entire transmission forms the first passband. The T-type feeding of the input port 1 transmits the energy to the step impedance resonator of the center-loaded short-circuit branch of the G6 layer through coupling. The resonator couples the energy to the T-shaped feeding end of the output end 3. The entire transmission forms the second passband. Two T-shaped feeding structures are used to introduce source-load coupling, introduce a transmission zero point on the left side of the first passband and the second passband, and introduce two transmission zero points on the right side of the passband to achieve higher selectivity. The center frequency of the first passband can be adjusted by the overall length of the microstrip resonator, and the center frequency of the second passband can be adjusted by the overall length of the suspension line resonator.

[0048] The simulation results of the duplexer are shown in Fig.14 As shown, the simulation results show that the first filter passband is 2.26-2.61GHz, the second filter passband is 4.57-5.87GHz, and a transmission zero is introduced in the lower stopband of the first / second passband, and two transmission zeros are introduced in the upper stopband. The input return loss (S11) in the two passbands is better than 20dB, and the insertion loss (S21) of the two passbands is better than 0.21dB and 0.15dB respectively. The overall stopband reaches 11GHz below -20dB (4.5f0, f0 is the center frequency of the first passband) and the overall center circuit size is 11.5mm*12.4mm (0.094λ g *0.102λ g ), the isolation between output port 2 and output port 3 is also better than 35dB, it can be seen that the simulation example of the present invention has excellent out-of-band suppression performance, smaller circuit size and wider stopband range. Compared with the simulation effect of the duplexer of the same dielectric integrated suspension line document "A High Isolation and Low Loss Duplexer Based on SISL Platform", the structure of the present invention has better out-of-band suppression effect, smaller size and wider stopband range.

[0049] In summary, the filter and duplexer designed by the present invention use microstrip resonators and suspension line resonators to achieve dual passbands. The transmission zero is introduced by source-load coupling, so that the passband has high selectivity and better filtering performance. By adjusting the size of the microstrip resonator, the center frequency of the first passband can be adjusted. By adjusting the size of the suspension line resonator, the center frequency of the second passband can be adjusted; the simulation results show that the present invention has excellent out-of-band suppression performance, a smaller circuit size, and a wider stopband range.

[0050] The above embodiments further illustrate the purpose, technical solutions and advantages of the present invention in detail. It should be understood that the above embodiments are only preferred implementation modes of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made to the present invention within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A filter based on SISL, characterized in that: include: The five dielectric substrates arranged in sequence from top to bottom are sub1-sub5; the upper surface and the lower surface of each dielectric substrate are covered with metal layers, and there are ten metal layers G1-G10 from top to bottom; two rectangular parts are cut off from the edges of the dielectric substrate sub1 and the dielectric substrate sub2, and the dielectric substrate sub1 and the dielectric substrate sub2 overlap; penetrating square arrays of metal through holes are provided on the five dielectric substrates and the ten metal layers, and the square arrays of metal through holes on each dielectric substrate and each metal layer overlap; two GCPW transition to T-shaped feeding structures are provided on the metal layer G5.

2. A filter based on SISL according to claim 1, characterized in that: A step impedance microstrip resonator with a center-loaded short-circuit branch is arranged on the metal layer G2.

3. A SISL-based filter according to claim 1, characterized in that: A step impedance suspended line resonator with a center-loaded short-circuit branch is arranged on the metal layer G6.

4. A SISL-based filter according to claim 1, characterized in that: An air cavity is disposed in the middle of both the dielectric substrate sub2 and the dielectric substrate sub4. The air cavity is inside the square array of metal through holes, and the air cavity of the dielectric substrate sub4 overlaps with the air cavity of the dielectric substrate sub2.

5. A SISL-based filter according to claim 1, characterized in that: The GCPW transition to the T-shaped feeding structure includes a GCPW structure, a transition structure and a T-shaped feeding branch; the GCPW structure is arranged directly below the rectangular part cut off from the edge of the dielectric substrate sub1, the T-shaped feeding branch is connected to the GCPW structure through the transition structure, and the T-shaped feeding branch is located inside the metal through-hole square array.

6. A SISL-based filter according to claim 1, characterized in that: The five-layer dielectric substrate and the ten-layer metal layer are provided with fixing through holes for fixing the filter.

7. A SISL-based duplexer, characterized in that: include: The five dielectric substrates arranged in sequence from top to bottom are sub1-sub5; the upper surface and the lower surface of each dielectric substrate are covered with metal layers, and there are ten metal layers G1-G10 from top to bottom; three rectangular parts are cut off from the edges of the dielectric substrate sub1 and the dielectric substrate sub2, and the dielectric substrate sub1 and the dielectric substrate sub2 overlap; penetrating square arrays of metal through holes are provided on the five dielectric substrates and the ten metal layers, and the square arrays of metal through holes on each dielectric substrate and each metal layer overlap; three GCPW transition to T-shaped feeding structures are provided on the metal layer G5.

8. A SISL-based duplexer according to claim 7, characterized in that: A step impedance microstrip resonator with a center-loaded short-circuit branch is arranged on the metal layer G2; a step impedance suspended line resonator with a center-loaded short-circuit branch is arranged on the metal layer G6; air cavities are arranged in the middle of the dielectric substrate sub2 and the dielectric substrate sub4, and the air cavity is inside the square array of metal through holes, and the air cavity of the dielectric substrate sub4 overlaps with the air cavity of the dielectric substrate sub2.

9. The SISL-based duplexer according to claim 7, characterized in that: The GCPW transition to the T-shaped feeding structure includes a GCPW structure, a transition structure and a T-shaped feeding branch; the GCPW structure is arranged directly below the rectangular part cut off from the edge of the dielectric substrate sub1, the T-shaped feeding branch is connected to the GCPW structure through the transition structure, and the T-shaped feeding branch is located inside the metal through-hole square array.

10. The SISL-based duplexer according to claim 7, characterized in that: Fixed through holes are arranged on the five-layer dielectric substrate and the ten-layer metal layer for fixing the duplexer.

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