A compact metal sheet low pass filter

Abstract

The utility model relates to a compact metal sheet low pass filter, including casing and straight piece metal body, and the straight piece metal body includes series branch, first T type branch, second T type branch, third T type branch, first trapezoidal branch, second trapezoidal branch and third trapezoidal branch, the casing has through cavity, first interval cavity, second interval cavity and third interval cavity, and the through cavity extends along the length direction of series branch and communicates with three interval cavities, and the first T type branch stretches into first interval cavity, and the second T type branch, first trapezoidal branch, third T type branch stretch into second interval cavity, and the second trapezoidal branch and third trapezoidal branch stretch into third interval cavity. The utility model discloses the small size of straight piece metal body, and current distribution is even, realizes 500W high -power bearing demand, through the design of composite branch and triple transmission zero point, realizes the coverage of 4.5 10GHz ultra -wide band rejection suppression, and signal is stable.

Description

Technical Field

[0001] This utility model relates to the field of communication technology, and in particular to a compact metal sheet low-pass filter. Background Technology

[0002] With the development of modern wireless communication and related industries, the demand for low insertion loss, high suppression filters, and duplexers is increasing. For 5G macro base station filters, it is necessary to achieve 500W high power handling (traditional solutions ≤100W), 4.5-10GHz ultra-wide stopband suppression (traditional solutions only cover 6-8GHz), and stability under operating conditions of -55℃~125℃ (traditional solutions have temperature drift >±12MHz) within a ≤80mm size. There is a physical limit conflict between power, size, and bandwidth: power handling capacity is positively correlated with heat dissipation area. According to Fourier's law, when the size is compressed to <80mm, the heat dissipation path of traditional PCB substrates is shortened, leading to heat accumulation. For example, 500W power in an 80mm... 2 Under such conditions, if only air cooling is used, the temperature rise will exceed 200°C, far exceeding the junction temperature limit of semiconductor devices (typically ≤150°C). Ultra-wide stopband suppression relies on multi-band resonant units, and the resonator size is proportional to the operating wavelength λ. In traditional solutions, at least two sizes of resonators are required to cover 4.5GHz and 10GHz, and the lateral layout will inevitably exceed the 80mm limit.

[0003] Chinese patent CN109786905B discloses a stripline low-pass filter, comprising a first-stage fifth-order elliptic function filter unit consisting of Y-shaped trapezoidal stripline stubs S1, S2, and S3, and two connected high-impedance U-shaped coupled series stubs W1 and W2; and Y-shaped trapezoidal stripline stubs S4, S5, and S6, and two connected U-shaped high-impedance coupled series stubs W3 and W2. The second-stage fifth-order elliptic function filter unit is composed of series stubs W4; the tenth-order Chebyshev filter unit is composed of series stubs L1, L2, L3, L4, and L5 on the same plane, as well as T-shaped open-circuit stubs T1, T2, T3, T4, and T5 that are perpendicular to each other in the same direction; the input step impedance unit is composed of the stripline step impedance P1; and the output step impedance unit is composed of the stripline step impedance P2. This achieves the technical effects of low passband attenuation, steep near-end stopband attenuation, and far-end stopband suppression. However, the lateral dimensions of the above structure are relatively large.

[0004] Therefore, a new filter needs to be designed to avoid the above problems. Utility Model Content

[0005] The main objective of this invention is to provide a compact metal sheet low-pass filter that can achieve ultra-wide stopband suppression and high power handling requirements within a small size.

[0006] The present invention achieves the above objectives through the following technical solution: a compact metal sheet low-pass filter, comprising a housing and a straight sheet metal body located within the housing, wherein the housing and the straight sheet metal body are not directly connected; The straight sheet metal body includes a series of branches, a first T-shaped branch, a second T-shaped branch, a third T-shaped branch, a first trapezoidal branch, a second trapezoidal branch, and a third trapezoidal branch. The series of branches are strip-shaped. The first T-shaped branch, the second T-shaped branch, the first trapezoidal branch, the third T-shaped branch, the second trapezoidal branch, and the third trapezoidal branch have different structures and are arranged sequentially along the length direction of the series of branches. The housing has a through cavity, a first spacer cavity, a second spacer cavity, and a third spacer cavity. The through cavity extends along the length of the series of branches and communicates with the three spacer cavities. The first T-shaped branch extends into the first spacer cavity, the second T-shaped branch, the first trapezoidal branch, and the third T-shaped branch extend into the second spacer cavity, and the second trapezoidal branch and the third trapezoidal branch extend into the third spacer cavity.

[0007] Specifically, the dimensions of the straight sheet metal body are within 80.0mm × 15.0mm × 1.0mm.

[0008] Specifically, the series of branches has a middle section with a uniform width and two ends located at the beginning and end of the middle section, respectively. The width of the ends is greater than the width of the middle section. The first T-shaped branch, the second T-shaped branch, the first trapezoidal branch, the third T-shaped branch, the second trapezoidal branch, and the third trapezoidal branch are located on the middle section.

[0009] Furthermore, it also includes a first PTFE support column and a second PTFE support column, which are located inside the through cavity and have their two ends fixed respectively.

[0010] Furthermore, it also includes a third PTFE support column and a fourth PTFE support column, the third PTFE support column surrounding the second T-shaped branch, the fourth PTFE support column surrounding the third T-shaped branch, and the third PTFE support column and the fourth PTFE support column being fixed to the bottom of the second spacer cavity.

[0011] Specifically, the surface of the straight sheet metal body is electroplated with silver material with a thickness of 0.3 μm.

[0012] The beneficial effects of this utility model's technical solution are: 1. The straight sheet metal body has a smaller size, which is 28% smaller than the traditional solution.

[0013] 2. The straight sheet metal body has a straight sheet structure, and the current distribution is uniform, which can meet the requirements of 500W high power carrying capacity.

[0014] 3. Overcoming the limitations of equidistant stubs, the composite stub and triple transmission zero design enable signals below 3GHz to pass through without loss. The trapezoidal stubs form parallel capacitive reactances to reflect signals from 4.5-6.4GHz, while the T-shaped stubs generate series resonances to absorb signals from 6.4-10GHz, thus achieving coverage of ultra-wide stopband suppression from 4.5-10GHz.

[0015] 4. PTFE material has very little thermal expansion in the range of -55℃ to 125℃, which can ensure signal stability. Attached Figure Description

[0016] Figure 1 This is a cross-sectional view of the compact sheet metal low-pass filter of the embodiment; Figure 2 This is a diagram showing the positional relationship between the straight sheet metal body and the four PTFE support columns.

[0017] The numbers in the diagram represent: 1-Shell, 11-Through cavity, 12-First spacer cavity, 13-Second spacer cavity, 14-Spacer cavity; 2-Straight sheet metal body, 21-Serial branch, 211-Middle section, 212-End, 22a-First T-shaped branch, 22b-Second T-shaped branch, 22c-Third T-shaped branch, 23a-First trapezoidal branch, 23b-Second trapezoidal branch, 23c-Third trapezoidal branch; 3a - First PTFE support column, 3b - Second PTFE support column, 3c - Third PTFE support column, 3d - Fourth PTFE support column. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to specific embodiments.

[0019] Example: like Figure 1 and Figure 2 As shown, a compact metal sheet low-pass filter of this utility model includes a housing 1, a straight sheet metal body 2, a first PTFE support column 3a, a second PTFE support column 3b, a third PTFE support column 3c, and a fourth PTFE support column 3d.

[0020] Both the housing 1 and the straight sheet metal body 2 are made of conductive materials, acting as independent wires. The first PTFE support column 3a, the second PTFE support column 3b, the third PTFE support column 3c, and the fourth PTFE support column 3d are made of non-conductive PTFE (polytetrafluoroethylene), used to fix the relative positions of the housing 1 and the straight sheet metal body 2, preventing them from being directly conductive. This forms several capacitive structures between the housing 1 and the straight sheet metal body 2, thus achieving a filtering function.

[0021] like Figure 1 and Figure 2 As shown, the straight sheet metal body 2 includes a series of branches 21, a first T-shaped branch 22a, a second T-shaped branch 22b, a third T-shaped branch 22c, a first trapezoidal branch 23a, a second trapezoidal branch 23b, and a third trapezoidal branch 23c. The series of branches 21 are strip-shaped and have a middle section 211 of uniform width and two end sections 212 located at the beginning and end of the middle section 211, respectively. The width of the end sections 212 is greater than the width of the middle section 211. The first T-shaped branch 22a, the second T-shaped branch 22b, the first trapezoidal branch 23a, the third T-shaped branch 22c, the second trapezoidal branch 23b, and the third trapezoidal branch 23c have different structures and are arranged sequentially on the middle section 211 along the length direction of the series of branches 21.

[0022] The straight sheet metal body 2 has a planar structure with no height difference in the thickness direction. It only occupies 1mm of thickness space, and its flatness is ≤0.05mm, eliminating current distortion. It can be fixed by snap-fit, and does not require long fixing screws to increase the thickness of the filter.

[0023] Each branch forms a capacitor with the casing 1. Because the structures of the six branches are different, each branch has a good filtering capability for signals of a certain frequency. The more branches there are, the wider the frequency distribution.

[0024] T-shaped stubs, named for their resemblance to the letter "T," are commonly used in the design of microstrip or stripline filters. Their main functions include: ① Frequency selectivity: T-shaped stubs can provide specific frequency selectivity. By adjusting the length and width of the stub, the cutoff frequency of the filter can be changed, thereby achieving precise control of the signal frequency.

[0025] ② Impedance matching: T-stubs at the input and output of the filter can help achieve impedance matching, reduce signal reflection, and improve the transmission efficiency of the filter.

[0026] ③Size Reduction: Compared to traditional filter structures, T-shaped stubs can reduce the physical size of the filter while maintaining performance, which is especially important for the miniaturization design of modern electronic devices.

[0027] Trapezoidal stubs are characterized by their trapezoidal shape. Their role in filter design primarily includes: ①Bandwidth adjustment: Trapezoidal stubs can be used to adjust the bandwidth of the filter. By changing the length and width ratio of the stubs, precise control of the filter bandwidth can be achieved.

[0028] ② Insertion loss optimization: Trapezoidal stubs can help optimize the insertion loss of the filter. With proper design, the insertion loss of the filter in the passband can be minimized.

[0029] ③ Smoothing of frequency response: Trapezoidal stubs can make the frequency response of the filter smoother, reduce frequency response fluctuations, and improve the performance of the filter.

[0030] In summary, T-shaped and trapezoidal stubs optimize filter performance in filter design by providing frequency selectivity, impedance matching, size reduction, bandwidth adjustment, insertion loss optimization, and frequency response improvement, respectively. In practical design, the appropriate stub structure and parameters need to be selected based on the specific requirements and application scenario of the filter. This filter forms a 6-stub array in a specific order. The dimensions of the straight sheet metal body 2 are within 80.0mm × 15.0mm × 1.0mm, making it small enough for use in confined spaces. The straight sheet metal body 2 has a straight structure, resulting in uniform current distribution and meeting the 500W high-power requirement. Breaking through the limitations of equidistant stubs, a composite stub and triple transmission zero design allow signals below 3GHz to pass without loss. The trapezoidal stubs form parallel capacitive reactance, reflecting signals from 4.5-6.4GHz, while the T-shaped stubs generate series resonance, absorbing signals from 6.4-10GHz, thus achieving stopband suppression coverage of the 4.5-10GHz range. Compared to traditional solutions, the size is reduced by 28% while high-frequency suppression is improved by 8dB, solving the problem of high power density integration in communication base stations.

[0031] like Figure 1 and Figure 2 As shown, the housing 1 has a through cavity 11, a first spacer cavity 12, a second spacer cavity 13, and a third spacer cavity 14. The through cavity 11 extends along the length of the series spurs 21 and communicates with the three spacer cavities. A first T-shaped spur 22 extends into the first spacer cavity 12, a second T-shaped spur 23, a first trapezoidal spur 24, and a third T-shaped spur 25 extend into the second spacer cavity 13, and a second trapezoidal spur 26 and a third trapezoidal spur 27 extend into the third spacer cavity 14.

[0032] The housing 1 is grounded, thus establishing a zero potential. End 212 serves as the input / output terminal for current, and the middle section 211 acts as a conductor between the two ends. The sidewalls between the partition cavities act as one pole of a capacitor, and the various T-shaped and trapezoidal stubs can form capacitors between each other or adjacent sidewalls.

[0033] like Figure 1 and Figure 2 As shown, the first PTFE support column 3a and the second PTFE support column 3b are located in the through cavity 11 and their two ends 212 are fixed respectively. The third PTFE support column 3c surrounds the second T-shaped branch 22b, and the fourth PTFE support column 3d surrounds the third T-shaped branch 22c. The third PTFE support column 3c and the fourth PTFE support column 3d are fixed to the bottom of the second spacer cavity 13.

[0034] The first PTFE support column 3a and the second PTFE support column 3b support the two ends of the straight sheet metal body 2, making the straight sheet metal body 2 suspended in the air. The third PTFE support column 3c and the fourth PTFE support column 3d establish a non-conductive physical connection between the middle of the straight sheet metal body 2 and the second spacer cavity 13, preventing signal instability caused by shaking of the second T-shaped branch 22b, the first trapezoidal branch 23a, and the third T-shaped branch 22c. The contact area between the PTFE support columns and the straight sheet metal body 2 is 1.77 mm². 2 Therefore, the straight sheet metal body 2 still has a large exposed area, which facilitates heat dissipation. The PTFE material has very little thermal expansion in the range of -55℃ to 125℃, which can ensure signal stability.

[0035] The surface of the straight sheet metal body 2 is electroplated with silver material with a thickness of 0.3um.

[0036] The electroplating process for silver plating involves immersing a sheet metal body 2 in an electrolyte containing silver ions, and then using an electric current to reduce the silver ions to metallic silver on the surface of the object, forming a thin silver layer. This silver layer not only has a bright appearance but also gives the sheet metal body 2 good electrical conductivity and corrosion resistance.

[0037] The above descriptions are merely some embodiments of this utility model. For those skilled in the art, various modifications and improvements can be made without departing from the inventive concept of this utility model, and all such modifications and improvements fall within the protection scope of this utility model.

Claims

1. A compact metal sheet low-pass filter, comprising a housing and a straight sheet metal body located within the housing, wherein the housing and the straight sheet metal body are not directly conductive; characterized in that: The straight sheet metal body includes a series of branches, a first T-shaped branch, a second T-shaped branch, a third T-shaped branch, a first trapezoidal branch, a second trapezoidal branch, and a third trapezoidal branch. The series of branches are strip-shaped. The first T-shaped branch, the second T-shaped branch, the first trapezoidal branch, the third T-shaped branch, the second trapezoidal branch, and the third trapezoidal branch have different structures and are arranged sequentially along the length direction of the series of branches. The housing has a through cavity, a first spacer cavity, a second spacer cavity, and a third spacer cavity. The through cavity extends along the length of the series of branches and communicates with the three spacer cavities. The first T-shaped branch extends into the first spacer cavity, the second T-shaped branch, the first trapezoidal branch, and the third T-shaped branch extend into the second spacer cavity, and the second trapezoidal branch and the third trapezoidal branch extend into the third spacer cavity.

2. The compact metal sheet low pass filter according to claim 1, characterized in that: The dimensions of the straight sheet metal body are within 80.0mm × 15.0mm × 1.0mm.

3. The compact metal sheet low pass filter of claim 1, wherein: The series of branches has a middle section of uniform width and two ends located at the beginning and end of the middle section, respectively. The width of the ends is greater than the width of the middle section. The first T-shaped branch, the second T-shaped branch, the first trapezoidal branch, the third T-shaped branch, the second trapezoidal branch, and the third trapezoidal branch are located on the middle section.

4. The compact metal sheet low pass filter according to claim 3, characterized in that: It also includes a first PTFE support column and a second PTFE support column, which are located inside the through cavity and have their two ends fixed respectively.

5. The compact metal sheet low pass filter according to claim 1 or 4, characterized in that: It also includes a third PTFE support column and a fourth PTFE support column, the third PTFE support column surrounding the second T-shaped branch, the fourth PTFE support column surrounding the third T-shaped branch, and the third PTFE support column and the fourth PTFE support column being fixed to the bottom of the second spacer cavity.

6. The compact metal sheet low pass filter of claim 1, wherein: The surface of the straight sheet metal body is electroplated with silver material with a thickness of 0.3 μm.

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