Low-pass filter
By setting through holes of different depths on the dielectric base and connecting them with metal transmission lines, combined with multiple bent metal microstrip lines, the problem of insufficient coupling capacitance and equivalent inductance in the miniaturization process of filters in the existing technology is solved, a wider suppression bandwidth and higher suppression degree are achieved, and the product size is reduced.
Patent Information
- Application Number
- CN202422798823.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-18
- Publication Date
- 2025-09-05
- Estimated Expiration
- 2034-11-18
AI Technical Summary
Existing miniaturized low-pass filters are difficult to achieve a wide range of coupling capacitance and equivalent inductance while maintaining the overall size, resulting in insufficient suppression bandwidth and suppression degree of the filter.
By setting through holes of different depths on the dielectric base and connecting these through holes with metal transmission lines, combined with metal microstrip lines with multiple bends, a larger range of coupling capacitance and equivalent inductance can be achieved, reducing the product size.
Without increasing the overall size, a wider suppression bandwidth and higher suppression degree are achieved, and the size of the product is further reduced.
Smart Images
Figure CN223309187U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to a low-pass filter. Background Art
[0002] RF filters are commonly used components in communication equipment and come in many types and forms. Among them, metal duplexers and multiplexers are used in the RF front-end of high-power wireless communication base stations.
[0003] With the increasing development of wireless communication technology, wireless communication base stations are distributed more and more densely, and the volume requirements for base stations are getting smaller and smaller. As a result, the volume requirements for filters are also getting smaller and smaller.
[0004] Currently, a miniaturized low-pass filter uses a body made of solid dielectric material, metallized on the surface of the dielectric body, and multiple through-holes with consistent depth, resulting in the same capacitance value. This makes it impossible to achieve a wide range of coupling capacitance while maintaining the overall size. The through-holes are connected by straight or stepped metal transmission lines, resulting in a small equivalent inductance. Utility Model Content
[0005] The purpose of the utility model is to address the above-mentioned problems in the existing technology and propose a low-pass filter, which changes the size of the coupling capacitance by arranging first through holes, second through holes and third through holes of different depths on a base. Without changing the overall size of the low-pass filter, a larger range of ground capacitance can be achieved with a smaller size, thereby realizing a wider suppression bandwidth and a higher suppression degree of the filter. The tops of the through holes are connected by metal transmission lines, and the metal transmission lines connecting adjacent through holes are bent once or multiple times, so that a larger equivalent inductance can be achieved with a smaller size, thereby further reducing the size of the product.
[0006] The objectives of the present invention can be achieved through the following technical solutions: A low-pass filter comprises a dielectric base, a transmission line body, a base shell, and a metal shell, wherein the dielectric base is provided with a first through hole, a second through hole, and a third through hole, the dielectric base having a top surface, a front surface, two side surfaces, a back surface, and a bottom surface, the transmission line body being arranged on the top surface, the bottom surface, and the first through hole, the second through hole, and the third through hole of the dielectric base, the base shell being covered on the dielectric base and not in contact with the transmission line body, the metal shell being mounted on the base shell and located on the back surface of the dielectric base, the upper end of the metal shell being located above the top surface of the dielectric base, characterized in that:
[0007] The first through hole, the second through hole and the third through hole all pass through the dielectric base, the upper end thereof is located on the top surface of the dielectric base, and the lower end thereof is located on the bottom surface of the dielectric base, and the depth of the first through hole and the third through hole is less than the depth of the second through hole;
[0008] The transmission line body is provided with two electrodes which are respectively mounted on the corners where the top surface and the front surface of the dielectric base intersect.
[0009] Furthermore, the transmission line body includes an inductor body and a through-hole body, and the through-hole body includes a first top surface capacitor corresponding to the first through-hole, a first through-hole capacitor, a first bottom surface capacitor, a second top surface capacitor corresponding to the second through-hole, a second through-hole capacitor, a second bottom surface capacitor, a third top surface capacitor corresponding to the third through-hole, a third through-hole capacitor, and a third bottom surface capacitor. The first top surface capacitor, the second top surface capacitor, and the third top surface capacitor are respectively arranged at the upper ports of the first through-hole, the second through-hole, and the third through-hole and contact the top surface of the dielectric base. The first through-hole capacitor, the second through-hole capacitor, and the third through-hole capacitor are respectively arranged on the inner walls of the first through-hole, the second through-hole, and the third through-hole. The first bottom surface capacitor, the second bottom surface capacitor, and the third bottom surface capacitor are respectively arranged at the lower ports of the first through-hole, the second through-hole, and the third through-hole and contact the bottom surface of the dielectric base. The inductor body is connected to the first top surface capacitor, the second top surface capacitor, the third top surface capacitor, and the electrode.
[0010] Furthermore, the inductor line includes a first inductor, a second inductor, a third inductor, a fourth inductor, a fifth inductor, a sixth inductor and a seventh inductor. The first inductor, the second inductor, the third inductor, the fourth inductor, the fifth inductor, the sixth inductor and the seventh inductor are all metal microstrip lines. One end of the first inductor is connected to one of the electrodes and the other end is connected to one end of the third inductor. One end of the seventh inductor is connected to another electrode and the other end is connected to one end of the fifth inductor. One end of the second inductor is connected to the first top surface capacitor and the other end is connected to the third inductor. One end of the sixth inductor is connected to the third top surface capacitor and the other end is connected to the fifth inductor. The fourth inductor is connected to the second top surface capacitor, and its two ends are connected to the other ends of the third inductor and the fifth inductor respectively.
[0011] Furthermore, the first inductor and the seventh inductor are linear metal microstrip lines.
[0012] Furthermore, the second inductor and the sixth inductor have the same shape and are metal microstrip lines with three bends, and the bend angle is 90°.
[0013] Furthermore, the third inductor and the fifth inductor have the same shape and are metal microstrip lines with six bends, and the bend angle is 90°.
[0014] Furthermore, the fourth inductor is a metal microstrip line with a relatively large width and a relatively short length.
[0015] Furthermore, the line width of the metal microstrip line is in the range of 0.1-1.5 mm.
[0016] Furthermore, the areas of the first bottom capacitor and the third bottom capacitor are smaller than that of the second bottom capacitor.
[0017] Compared with the prior art, the advantages of the present application are as follows: by providing first through holes, second through holes, and third through holes of different depths on the dielectric base to change the coupling capacitance, and without changing its overall size, it is possible to achieve a larger range of coupling capacitance with a smaller size, thereby achieving a higher out-of-band suppression index and a larger out-of-band suppression bandwidth range; the tops of the through holes are connected by metal transmission lines, and the metal transmission lines connecting adjacent through holes are bent once or multiple times, so that a larger equivalent inductance can be achieved with a smaller size, thereby achieving the purpose of further reducing the product size. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 It is a schematic diagram of a low-pass filter;
[0019] Figure 2 It is a schematic diagram of the dielectric base and the transmission line body;
[0020] Figure 3 is a schematic diagram of a transmission line;
[0021] Figure 4 It is a schematic diagram of the dielectric base and the bottom of the transmission line body;
[0022] Figure 5 is a schematic diagram of the top surface of the transmission line body;
[0023] Figure 6 1 is a side view of a low-pass filter;
[0024] Figure 7 This is a schematic diagram of the other side of the low-pass filter;
[0025] Figure 8 This is the front diagram of the low-pass filter;
[0026] Figure 9 This is a schematic diagram of the back of the low-pass filter;
[0027] Figure 10 This is a schematic diagram of the back of the metal housing where the low-pass filter is assembled;
[0028] Figure 11 This is a schematic diagram of the low-pass filter simulation curve;
[0029] Figure 12 This is the schematic diagram of the low-pass filter circuit;
[0030] In the figure, 1. base shell; 2. metal shell; 3. dielectric base; 4. transmission line body; 41. first through hole; 411. first top surface capacitor; 412. first through hole capacitor; 413. first bottom surface capacitor; 42. second through hole; 421. first top surface capacitor; 422. second through hole capacitor; 423. second bottom surface capacitor; 43. third through hole; 431. third top surface capacitor; 432. third through hole capacitor; 433. third bottom surface capacitor; 44. electrode; 441. first inductor; 442. second inductor; 443. third inductor; 444. fourth inductor; 445. fifth inductor; 446. sixth inductor; 447. seventh inductor. DETAILED DESCRIPTION
[0031] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention.
[0032] like Figure 1-12 As shown, a low-pass filter includes a dielectric base 3, a transmission line body 4, a base shell 1, and a metal shell 2. The dielectric base 3 is provided with a first through hole 41, a second through hole 42, and a third through hole 43. The dielectric base 3 has a top surface, a front surface, two side surfaces, a back surface, and a bottom surface. The transmission line body 4 is disposed on the top surface and bottom surface of the dielectric base 3 and within the first through hole 41, the second through hole 42, and the third through hole 43. The base shell 1 is coated on the dielectric base 3 and does not contact the transmission line body 4. The metal shell 2 is mounted on the base shell 1 and is located on the back surface of the dielectric base 3. The upper end of the metal shell 2 is located above the top surface of the dielectric base 3. The filter is characterized in that:
[0033] The first through hole 41, the second through hole 42 and the third through hole 43 all pass through the dielectric base 3, with their upper ports located on the top surface of the dielectric base 3 and their lower ports located on the bottom surface of the dielectric base 3. The depths of the first through hole 41 and the third through hole 43 are less than the depth of the second through hole 42. By providing through holes, a larger coupling capacitance is achieved, and the depth of each through hole is different. By using a smaller size, a larger range of coupling capacitance is achieved. In addition, the dielectric base 3 (dielectric body) of the present application can select dielectric bodies with different dielectric constants according to actual size requirements and the passband resonant frequency of the filter. The larger the dielectric constant, the smaller the overall size of the product will be and the lower the resonator frequency will be.
[0034] The transmission line body 4 is provided with two electrodes 44 which are respectively mounted on the corners where the top surface and the front surface of the dielectric base 3 intersect.
[0035] like Figure 3 、 5As shown, further, the transmission line body 4 includes an inductor body and a through-hole body, and the through-hole body includes a first top surface capacitor corresponding to the first through-hole 41, a first through-hole capacitor 412, a first bottom surface capacitor 413, a second top surface capacitor 421 corresponding to the second through-hole 42, a second through-hole capacitor 422, a second bottom surface capacitor 423, a third top surface capacitor 431 corresponding to the third through-hole 43, a third through-hole capacitor 432, and a third bottom surface capacitor 433, the first top surface capacitor, the second top surface capacitor 421 and the third top surface capacitor 431 are respectively arranged in the first through-hole 41, the second through-hole 42 and the third through-hole 43. The upper port of the three through holes 43 is in contact with the top surface of the dielectric base 3. The first through hole capacitor 412, the second through hole capacitor 422 and the third through hole capacitor 432 are respectively arranged on the inner walls of the first through hole 41, the second through hole 42 and the third through hole 43. The first bottom surface capacitor 413, the second bottom surface capacitor 423 and the third bottom surface capacitor 433 are respectively arranged at the lower ports of the first through hole 41, the second through hole 42 and the third through hole 43 and in contact with the bottom surface of the dielectric base 3. The inductor is connected to the first top surface capacitor, the second top surface capacitor 421, the third top surface capacitor 431 and the electrode 44.
[0036] like Figure 3 、 5 As shown, further, the inductor body includes a first inductor 441, a second inductor 442, a third inductor 443, a fourth inductor 444, a fifth inductor 445, a sixth inductor 446 and a seventh inductor 447. The first inductor 441, the second inductor 442, the third inductor 443, the fourth inductor 444, the fifth inductor 445, the sixth inductor 446 and the seventh inductor 447 are all metal microstrip lines. One end of the first inductor 441 is connected to one of the electrodes 44 and the other end is connected to the third inductor 44 3, one end of the seventh inductor 447 is connected to another electrode 44 and the other end is connected to one end of the fifth inductor 445, one end of the second inductor 442 is connected to the first top surface capacitor and the other end is connected to the third inductor 443, one end of the sixth inductor 446 is connected to the third top surface capacitor 431 and the other end is connected to the fifth inductor 445, the middle part of the fourth inductor 444 is connected to the second top surface capacitor 421, and two ends thereof are connected to the other ends of the third inductor 443 and the fifth inductor 445 respectively.
[0037] like Figure 5 As shown, further, the first inductor 441 and the seventh inductor 447 are linear metal microstrip lines.
[0038] like Figure 5 As shown, further, the second inductor 442 and the sixth inductor 446 have the same shape and are metal microstrip lines with three bends, and the bend angle is 90°.
[0039] Furthermore, the third inductor 443 and the fifth inductor 445 have the same shape and are metal microstrip lines with six bends, and the bend angle is 90°.
[0040] like Figure 5 As shown, further, the fourth inductor 444 is a metal microstrip line with a shorter length, and the width of the fourth inductor 444 is greater than that of the third inductor 443.
[0041] In the above description, the loading layer is connected by a multi-bend metal microstrip line, thereby further reducing the size of the product while maintaining the required inductance value. Furthermore, the width of the metal microstrip line is in the range of 0.1-1.5 mm.
[0042] like Figure 4 As shown, further, the areas of the first bottom capacitor 413 and the third bottom capacitor 433 are smaller than the second bottom capacitor 423 .
[0043] The low-pass filter has a first through hole 41, a second through hole 42 and a third through hole 43 on a dielectric base 3, and performs metallization treatment on the through holes (i.e., a first through hole capacitor 412, a second through hole capacitor 422 and a third through hole capacitor 432). Loading layers are provided at both ends of the through holes (i.e., a first top surface capacitor, a second top surface capacitor 421 and a third top surface, a first bottom surface capacitor 413, a second bottom surface capacitor 423 and a third bottom surface capacitor 433). This allows not only coupling capacitance to be achieved by the loading layers at the upper and lower ends of the through holes, but also a larger coupling capacitance to be achieved on the surface of the through holes, thereby achieving a larger coupling capacitance with a smaller size. In addition, the tunability of the filter can be achieved later by changing the size of the loading layer area at both ends of the through holes.
[0044] The conventional stripline low-pass filter only realizes the coupling capacitance by coupling the loading layer with the ground plane. When the passband frequency of the filter is low, a larger coupling capacitance is required. The stripline low-pass can only increase the length and width of the loading layer (X / Y axis direction) to increase the coupling capacitance. However, the structure of the present low-pass filter can increase the coupling capacitance by increasing the longitudinal dimension (Z axis direction, i.e., the depth of the through hole) without changing the length and width of the loading layer (X / Y axis direction). In some application scenarios where the length and width (X / Y axis direction) are required to be relatively small but there is still space in the longitudinal direction (Z axis direction), the structural advantages of the present low-pass filter are obvious. The low-pass filter is only slightly increased in height direction, while the length direction is significantly reduced compared with the conventional stripline low-pass, and the overall size is significantly reduced.
[0045] The invention achieves coupling capacitances of varying sizes by providing first through-holes 41, second through-holes 42, and third through-holes 43 of varying depths on the dielectric base 3. The coupling capacitance is larger than that of conventional low-pass filters, thereby reducing the size of the product. Metal end faces are connected at both the upper and lower ends of the through-holes, which not only increases the overall coupling capacitance but also enables the tunability of the filter. The varying depths of the through-holes allow for a wider range of coupling capacitances without changing the overall size of the product, thereby increasing the filter's out-of-band suppression range. The tops of the through-holes are connected by metal transmission lines, and the metal transmission lines connecting adjacent through-holes are bent once or multiple times, thereby achieving a larger equivalent inductance with a smaller size, further reducing the product size.
[0046] The technical solution of the above-mentioned utility model provides a solution that is significantly different from the existing technology to address the technical problem that the existing technology solution is too single. The parts not involved in the technical solution of this application are the same as the existing technology or can be implemented by using the existing technology, and will not be repeated here.
[0047] The technical solutions in the above embodiments have clearly and completely described the contents of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.
Claims
1. A low-pass filter comprising a dielectric base, a transmission line, a base shell, and a metal shell, wherein the dielectric base is provided with a first through hole, a second through hole, and a third through hole, the dielectric base having a top surface, a front surface, two side surfaces, a back surface, and a bottom surface, the transmission line being disposed on the top surface, the bottom surface, and within the first through hole, the second through hole, and the third through hole, the base shell being disposed over the dielectric base without contacting the transmission line, the metal shell being mounted on the base shell and located on the back surface of the dielectric base, with the upper end of the metal shell being located above the top surface of the dielectric base, characterized in that: The first through hole, the second through hole and the third through hole all pass through the dielectric base, the upper end thereof is located on the top surface of the dielectric base, and the lower end thereof is located on the bottom surface of the dielectric base, and the depth of the first through hole and the third through hole is less than the depth of the second through hole; The transmission line body is provided with two electrodes which are respectively mounted on the corners where the top surface and the front surface of the dielectric base intersect.
2. A low-pass filter according to claim 1, characterized in that: The transmission line body includes an inductor body and a through-hole body, and the through-hole body includes a first top surface capacitor corresponding to the first through-hole, a first through-hole capacitor, a first bottom surface capacitor, a second top surface capacitor corresponding to the second through-hole, a second through-hole capacitor, a second bottom surface capacitor, a third top surface capacitor corresponding to the third through-hole, a third through-hole capacitor, and a third bottom surface capacitor. The first top surface capacitor, the second top surface capacitor, and the third top surface capacitor are respectively arranged at the upper ports of the first through-hole, the second through-hole, and the third through-hole and contact the top surface of the dielectric base. The first through-hole capacitor, the second through-hole capacitor, and the third through-hole capacitor are respectively arranged on the inner walls of the first through-hole, the second through-hole, and the third through-hole. The first bottom surface capacitor, the second bottom surface capacitor, and the third bottom surface capacitor are respectively arranged at the lower ports of the first through-hole, the second through-hole, and the third through-hole and contact the bottom surface of the dielectric base. The inductor body is connected to the first top surface capacitor, the second top surface capacitor, the third top surface capacitor, and the electrode.
3. A low-pass filter according to claim 2, characterized in that: The inductor line includes a first inductor, a second inductor, a third inductor, a fourth inductor, a fifth inductor, a sixth inductor and a seventh inductor. The first inductor, the second inductor, the third inductor, the fourth inductor, the fifth inductor, the sixth inductor and the seventh inductor are all metal microstrip lines. One end of the first inductor is connected to one of the electrodes and the other end is connected to one end of the third inductor. One end of the seventh inductor is connected to another electrode and the other end is connected to one end of the fifth inductor. One end of the second inductor is connected to the first top surface capacitor and the other end is connected to the third inductor. One end of the sixth inductor is connected to the third top surface capacitor and the other end is connected to the fifth inductor. The fourth inductor is connected to the second top surface capacitor, and its two ends are respectively connected to the other ends of the third inductor and the fifth inductor.
4. A low-pass filter according to claim 3, characterized in that: The first inductor and the seventh inductor are linear metal microstrip lines.
5. A low-pass filter according to claim 4, characterized in that: The second inductor and the sixth inductor have the same shape and are metal microstrip lines with three bends, and the bend angle is 90°.
6. A low-pass filter according to claim 5, characterized in that: The third inductor and the fifth inductor have the same shape and are metal microstrip lines with six bends, and the bend angle is 90°.
7. A low-pass filter according to claim 6, characterized in that: The fourth inductor is a metal microstrip line with a shorter length, and the width of the fourth inductor is greater than that of the third inductor.
8. A low-pass filter according to claim 3, characterized in that: The line width of the metal microstrip line is in the range of 0.1-1.5 mm.
9. A low-pass filter according to claim 2, characterized in that: The first bottom capacitor and the third bottom capacitor have smaller areas than the second bottom capacitor.