F0: 175 MHz high-suppression low-bandwidth passive band-pass filter

Abstract

The utility model discloses an F0: 175MHz high-suppression low-bandwidth passive band-pass filter, which comprises a PCB (printed circuit board) and a metal shell, electrical components of the band-pass filter are arranged on the PCB, the metal shell is fixedly covered on the PCB, four T0-0 magnet rings are arranged in the electrical components, three T0-0 magnet rings are wound in an overlapped manner, and the other two T0-0 magnet rings are wound in an overlapped manner. And the layout of the filter in the PCB is bilaterally symmetrical. The magnetic ring inductor of the filter is formed by stacking and winding three T0-0 magnetic ring inductors, so that the number of turns is smaller than that of conventional inductors, the size is greatly reduced, the Q value is higher than that of conventional inductors, the magnetic ring inductor has great advantages in a small-package band-pass filter, the loss of the band-pass filter can be reduced, and meanwhile, the influence of a sealing cover on the indexes of the band-pass filter is greatly reduced; the layout of the filter in the PCB adopts bilateral symmetry, so that parasitic capacitance and inductance generated by the left and right bonding pads are equal, and later product manufacturing is facilitated.

Description

Technical Field

[0001] The utility model relates to a F0: 175MHz high rejection low bandwidth passive band-pass filter, belonging to the technical field of passive band-pass filters. Background Technique

[0002] As Figures 7-8 The shown band-pass filter includes a housing, a coil encapsulated in the housing, and pins arranged at the bottom of the housing. The pins include left and right radio frequency input and output and a large-area ground at the bottom.

[0003] The existing band-pass filters cannot meet the requirements that the insertion loss is less than or equal to 7dB, the rejection outside F0±25MHz is greater than or equal to 60dBc, and the 3dB bandwidth is 4±1MHz under the same size.

[0004] The existing band-pass filters adopt conventional elliptical or Chebyshev models, and the number of inductors is large, which is inconvenient to miniaturize for this small-package band-pass filter. Summary of the Invention

[0005] The technical problem to be solved by the utility model is: to provide a F0: 175MHz high rejection low bandwidth passive band-pass filter to solve the problems existing in the above-mentioned prior art.

[0006] The technical solution adopted by the utility model is: a F0: 175MHz high rejection low bandwidth passive band-pass filter, including a PCB circuit board and a metal housing. Electrical components of the band-pass filter are arranged on the PCB circuit board, and the metal housing is fixedly covered on the PCB circuit board. The magnetic rings in the electrical components use a 4 T0-0 layout, and 3 of them are wound by superimposing. The layout of the filter in the PCB circuit board is symmetric left and right.

[0007] Further, the circuit structure of the band-pass filter arranged on the above-mentioned PCB circuit board (1) includes capacitor C1, capacitor C2, capacitor C3, capacitor C4, capacitor C5, capacitor C6, capacitor C7, capacitor C8, capacitor C9, inductor L1, inductor L2, inductor L3, and inductor L4. One end of capacitor C1 is connected to the input end and one end of inductor L1. The other end of inductor L1 is connected to one ends of capacitor C2 and capacitor C3. The other end of capacitor C3 is connected to one ends of capacitor C4, inductor L2, and capacitor C5. The other end of capacitor C5 is connected to one ends of capacitor C6, inductor L3, and capacitor C7. The other end of capacitor C7 is connected to one ends of capacitor C8 and inductor L4. The other end of inductor L4 is connected to the output end and capacitor C9. The other ends of capacitor C1, capacitor C2, capacitor C4, capacitor C6, capacitor C8, capacitor C9, inductor L2, and inductor L3 are connected to the ground end.

[0008] Further, the above PCB circuit board is provided with two layers. The bottom layer of the PCB circuit board is grounded over a large area, and the top layer is grounded in the space outside the component pads and traces.

[0009] Advantages of the present utility model: Compared with the prior art, the effects of the present utility model are as follows:

[0010] 1) The filter magnetic ring inductor is formed by stacking 3 T0-0 coils, which reduces the number of turns compared to the conventional one, greatly reduces the volume, has a higher Q value than the conventional inductor, and has great advantages in a small package band-pass filter, can reduce the loss of the band-pass filter, and at the same time greatly reduce the influence of the cover on the performance indicators of the band-pass filter; The layout of the filter in the PCB circuit board is symmetric left and right, making the parasitic capacitance and inductance generated by the left and right pads equal, which is convenient for the later production of the product;

[0011] 2) The product has a small size of 20×10×5 (±0.2) mm. By optimizing the circuit and reducing the number of inductors, it is smaller than the conventional 25×15×5 (±0.2) mm;

[0012] 3) There are only 4 inductors, greatly reducing the difficulty of debugging and layout;

[0013] 4) The inductor is formed by stacking 3 T0-0 coils, increasing the inductance under the same number of turns;

[0014] 5) The circuit structure adopts a symmetric left and right design, which can make the input and output matching better and is convenient for debugging. The whole product is welded to the circuit board through a metal shell, with a simple and compact appearance, having a certain anti-interference ability, and the metal shell is convenient for marking and printing. Description of the Drawings

[0015] Figure 1 It is a schematic top-layer layout diagram of the PCB circuit board;

[0016] Figure 2 It is a schematic bottom-layer layout diagram of the PCB circuit board;

[0017] Figure 3 It is a layout diagram of the surface mount components on the PCB circuit board;

[0018] Figure 4 It is a layout diagram of the inductors on the PCB circuit board;

[0019] Figure 5 It is a schematic structural diagram of the test fixture for the band-pass filter;

[0020] Figure 6 It is a left-view structural diagram of the test fixture;

[0021] Figure 7 It is a three-dimensional structural diagram of the band-pass filter;

[0022] Figure 8 It is a schematic diagram of the upward view structure of a band-pass filter;

[0023] Figure 9 It is a schematic circuit diagram of a band-pass filter. Specific implementation manners

[0024] The following further introduces the present utility model in conjunction with the accompanying drawings and specific embodiments.

[0025] Embodiment 1: As Figures 1-9 shown, a high-rejection and low-bandwidth passive band-pass filter with F0: 175 MHz includes a PCB circuit board 1 and a metal shell 2. Electrical components of the band-pass filter are arranged on the PCB circuit board 1, and the metal shell 2 is fixedly covered on the PCB circuit board 1. Four T0-0 layouts are used for the magnetic rings in the electrical components, and 3 of the T0-0 are wound in an overlapping manner. The layout of the filter in the PCB circuit board 1 is symmetric left and right. The layout of the filter in the PCB circuit board is symmetric left and right, making the parasitic capacitance and inductance generated by the left and right pads equal, which is convenient for the later production of the product; the RF input and output pins of the product are made symmetric and consistent to ensure the correct transmission and reception of RF signals; Four inserts 3 are provided at the bottom of the metal shell 2. The lower ends of the inserts 3 pass through the rectangular holes 4 on the PCB circuit board 1 and are bent to fit against the bottom of the PCB circuit board 1, locking the metal shell only on the PCB circuit board 1. The middle parts of both ends of the PCB circuit board 1 are respectively set as the input end 5 and the output end 6, and the input end 5 and the output end 6 are of U-shaped card slot structure;

[0026] As Figure 9 shown, the circuit structure of the band-pass filter arranged on the PCB circuit board 1 includes a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a capacitor C6, a capacitor C7, a capacitor C8, a capacitor C9, an inductor L1, an inductor L2, an inductor L3, and an inductor L4. One end of the capacitor C1 is connected to the input end and one end of the inductor L1. The other end of the inductor L1 is connected to one ends of the capacitor C2 and the capacitor C3. The other end of the capacitor C3 is connected to one ends of the capacitor C4, the inductor L2, and the capacitor C5. The other end of the capacitor C5 is connected to one ends of the capacitor C6, the inductor L3, and the capacitor C7. The other end of the capacitor C7 is connected to one ends of the capacitor C8 and the inductor L4. The other end of the inductor L4 is connected to the output end and the capacitor C9. The other ends of the capacitor C1, the capacitor C2, the capacitor C4, the capacitor C6, the capacitor C8, the capacitor C9, the inductor L2, and the inductor L3 are connected to the ground end.

[0027] The PCB circuit board is provided with two layers. The bottom layer of the PCB circuit board is grounded on a large area, and the space outside the component pads and traces on the top layer is also grounded. By grounding on a large area, the grounding effect is increased.

[0028] The circuit structure adopts a symmetric left-right design, which can make the input-output matching degree better and is convenient for debugging.

[0029] The whole product is welded to the circuit board through a metal shell. It has a simple and compact appearance, has a certain anti-interference ability, and the metal shell is convenient for label printing.

[0030] Embodiment 2: As Figures 1-9 shown, a manufacturing method of a high suppression and low bandwidth passive band-pass filter of F0:F0:175MHz, the method comprising the following steps:

[0031] Step 1. PCB circuit board layout: The PCB circuit board is provided with two layers. The bottom layer of the PCB circuit board is grounded over a large area (as Figure 1 ), and the top layer is covered with a large ground in the space outside the component pads and traces (as Figure 2 ). The grounding effect is increased through a large number of grounding vias. The layout of the filter in the PCB circuit board is symmetric left and right, so that the parasitic capacitance and inductance generated by the left and right pads are equal, which is convenient for the later production of the product; the RF input and output pins of the product are made symmetric and consistent to ensure the correct transmission and reception of RF signals.

[0032] Step 2. The manufacturing method comprises the following steps:

[0033] 2.1) After preparing the chip capacitors, patch them according to the circuit diagram of the band-pass filter ( Figure 3 ), and use lead-free solder paste S-SnAg 3.0 Cu 0.5 for SMT machine patching and reflow soldering to obtain a patched semi-finished product;

[0034] 2.2) Prepare the corresponding inductors according to the parameter table in Table 1;

[0035]

[0036] 2.3) Use lead-free solder paste S-SnAg 3.0 Cu 0.5 and 0.5mm to weld the inductors to the corresponding positions on the PCB circuit board according to the pad diagram;

[0037] 2.4) Assemble the assembled semi-finished product onto the test fixture, debug the filter inductor to achieve the optimal performance, and then fix it with Nanda 704 silicone;

[0038] 2.5) Use a metal shell and lead-free solder paste S-SnAg 3.0 Cu 0.5 and 0.5mm for capping;

[0039] 2.6) After capping, conduct tests and electrical performance index tests to form a data report, and then clean, externally inspect, and package the product to form a finished product.

[0040] Table 2 Circuit Performance Parameters

[0041]

[0042] When the conventional passive band - pass filter cannot meet the requirements that the insertion loss is less than or equal to 7 dB, the out - of - band rejection is greater than or equal to 60 dBc outside F0±25 MHz, and the 3 - dB bandwidth is 4±1 MHz under the same size.

[0043] The inductor of the filter magnetic ring is made by stacking 3 T0 - 0 windings, which makes the number of turns smaller than that of the conventional one, and the volume is greatly reduced. The Q value is higher than that of the conventional inductor, which has great advantages in the small - package band - pass filter. It can reduce the loss of the band - pass filter and greatly reduce the influence of the cover on the performance indicators of the band - pass filter.

[0044] The prepared filter has the following effects:

[0045] 1) The product size is small, which is 20×10×5(±0.2) mm. By optimizing the circuit and reducing the number of inductors, it is smaller than the conventional 25×15×5(±0.2) mm.

[0046] 2) There are only 4 inductors, which greatly reduces the difficulty of debugging and layout.

[0047] 3) The inductor is wound by stacking 3 T0 - 0 windings, which increases the inductance under the same number of turns.

[0048] 3) It can be used in conjunction with a test fixture. During the debugging and testing process, there is no need to weld the product pins, avoiding secondary welding at the client side.

[0049] Among them, for the test of this band - pass filter, such as Figures 5-6The shown test fixture includes two RF probes 201, RF connectors 202, a first portal frame 203, a second portal frame 204, and a base 205. The base 205 is a horizontal F-shaped structure, that is, it includes a bottom plate and a middle vertical plate 206 and a right-end vertical plate 207 fixedly connected to the middle and the right end of the bottom plate respectively. The middle vertical plate 206 and the right-end vertical plate 207 are in a portal shape, and four guide posts 208 are fixedly connected to the four corners. The first portal frame 203 and the second portal frame 204 are movably sleeved on the four guide posts 208 at the four corners, and compression springs 209 are sleeved on the four guide posts 208 on the right-side section of the second portal frame 204. The compression springs 209 can make the first portal frame 203 and the second portal frame 204 fit together. The two RF probes 201 are respectively fixedly connected to the tops of the first portal frame 203 and the second portal frame 204 and are respectively kept in electrical connection with the two RF connectors 202. The two RF connectors 202 are respectively fixedly connected to the bottoms of the top crossbeams of the first portal frame 203 and the second portal frame 204 through screws. The input end and the output end of the arc-shaped U-shaped grooves at both ends of the band-pass filter can be clamped onto the two RF probes 201. The first portal frame 203 and the second portal frame 204 are made of copper material and are grounded over a large area. The two RF connectors are respectively connected with an input cable 210 and an output cable 211. The two left-right arranged RF probes can firmly clamp the band-pass filter through the elastic force of the compression springs. The grounded part at the bottom of the band-pass filter is closely attached to the grounded first portal frame 203 and the second portal frame 204. The input RF pins and the output RF pins of the band-pass filter are connected to a network analyzer through the RF probes, the input cable, and the output cable for index testing. A groove 214 is arranged on the left side of the base 205 to facilitate placing the detection device.

[0050] With this test fixture, there is no need to weld the product pins during the debugging and testing of the band-pass filter, avoiding secondary soldering at the client side.

[0051] Both ends of each guide post 208 are fixedly connected to the middle vertical plate 206 and the right-end vertical plate 207 through two locking screws 212, and the connection is stable and reliable. Metal sleeves 213 are arranged at the places where the screws pass through the middle vertical plate 206 and the right-end vertical plate 207, which can improve the support stability.

[0052] Principle of using the test fixture:

[0053] 1. Connect two RF cables to the two RF connectors, and the RF connectors are respectively connected to the "RFin" and "RFout" of the two first portal frames 203 and the second portal frame;

[0054] 2. Separate the first portal frame 203 and the second portal frame, align the RF input end and the RF output end of the measured band-pass filter with the two RF probes of the test fixture, clamp the band-pass filter with the test fixture, and make the grounding end at the bottom of the band-pass filter closely attached to the grounded first portal frame 203 and the second portal frame 204;

[0055] 3. Connect the "RFin" RF cable to the output port of the network analyzer, and connect the "RFout" RF cable to the input port of the network analyzer for measurement to test the center insertion loss, 3dB bandwidth, rectangularity coefficient, and voltage standing wave ratio of the band-pass filter.

[0056] As mentioned above, it is only the specific implementation manner of the present utility model, but the protection scope of the present utility model is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present utility model can easily think of changes or substitutions, which should all be covered within the protection scope of the present utility model. Therefore, the protection scope of the present utility model shall be subject to the protection scope of the claimed rights.

Claims

1. A F0: 175 MHz high rejection and low bandwidth passive band-pass filter, characterized in that: It includes a PCB circuit board (1) and a metal housing (2). Electrical components of a band-pass filter are arranged on the PCB circuit board (1). The metal housing (2) is fixedly covered on the PCB circuit board (1). The magnetic rings in the electrical components use a 4 T0-0 layout, where 3 of the T0-0 are wound in an overlapping manner. The layout of the filter on the PCB circuit board (1) is symmetric left and right.

2. A kind of F0: 175MHz high suppression and low bandwidth passive band-pass filter according to claim 1, characterized in that: The circuit structure of the band-pass filter arranged on the PCB circuit board (1) includes capacitor C1, capacitor C2, capacitor C3, capacitor C4, capacitor C5, capacitor C6, capacitor C7, capacitor C8, capacitor C9, inductor L1, inductor L2, inductor L3, and inductor L4. One end of capacitor C1 is connected to the input terminal and one end of inductor L1. The other end of inductor L1 is connected to one end of capacitor C2 and capacitor C3. The other end of capacitor C3 is connected to one end of capacitor C4, inductor L2, and capacitor C5. The other end of capacitor C5 is connected to one end of capacitor C6, inductor L3, and capacitor C7. The other end of capacitor C7 is connected to one end of capacitor C8 and inductor L4. The other end of inductor L4 is connected to the output terminal and capacitor C9. The other ends of capacitor C1, capacitor C2, capacitor C4, capacitor C6, capacitor C8, capacitor C9, inductor L2, and inductor L3 are connected to the ground terminal.

3. A F0: 175 MHz high rejection low bandwidth passive bandpass filter according to claim 1, characterized in that: The PCB circuit board has two layers. The bottom layer of the PCB circuit board is grounded over a large area, and the top layer is grounded in the space outside the component pads and traces.

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