46.5 MHz small-size band-pass filter

Abstract

The utility model discloses a 46.5 MHz small-size band-pass filter, which comprises a metal shell and a PCB (printed circuit board) covering the opening end of the shell, components of the band-pass filter are arranged on the surface, facing the inner cavity of the shell, of the PCB, an input end is arranged on the upper left side of the PCB, an output end is arranged on the lower right side of the PCB, and a left notch and a right notch are arranged at the positions, opposite to the input end and the output end, of the shell. The left notch and the right notch are respectively kept a certain distance away from the pads at the input end and the output end, two clamping pieces which are staggered left and right are arranged on the front side wall and the rear side wall of the shell, the two clamping pieces are inserted into through holes in the PCB and then are welded and fixed, and the shell is filled with sealant. According to the utility model, the metal shell is adopted to play a shielding role and a protection role; a gap is arranged to avoid short circuit between the metal shell and the bonding pad; the clamping piece is arranged, so that the connection reliability of the shell and the PCB can be ensured; and the filled sealant is thick, so that fixation and elastic buffering of internal components can be realized, and the connection reliability is higher.

Description

Technical Field

[0001] The utility model relates to a 46.5MHz small-size bandpass filter, belonging to the technical field of bandpass filters. Background Art

[0002] The 46.5MHz filter has low insertion loss, high suppression and small size. Conventional bandpass filters such as Butterworth and Chebychev models require more orders, and more orders require sufficient size to meet the requirements. For the assembly of the 46.5MHz filter, the conventional method is to directly install the components on the PCB board. This method is used in places with strong magnetic fields and is easily affected by electromagnetic interference. In addition, it is also easy to cause the components to loosen under long-term vibration conditions. Summary of the invention

[0003] The technical problem to be solved by the utility model is to provide a 46.5MHz small-size bandpass filter to solve the problems existing in the above-mentioned prior art.

[0004] The technical scheme adopted by the utility model is: a 46.5MHz small-size bandpass filter, comprising a metal shell and a PCB board covering the open end of the shell, the PCB board is provided with components of the bandpass filter on the surface facing the inner cavity of the shell, the input end is provided on the upper left side of the PCB board and the output end is provided on the lower right side of the PCB board, a left notch and a right notch are provided at the shell facing the input end and the output end, the left notch and the right notch are respectively kept at a distance from the pads at the input end and the output end, two left and right staggered card connecting pieces are provided on the front and rear side walls of the shell, the two card connecting pieces are inserted into the through holes on the PCB board and then welded and fixed, and the shell is filled with sealant.

[0005] The circuit structure of the bandpass filter includes a capacitor C2, a capacitor C4, a capacitor C7, a capacitor C9, a capacitor C11, a capacitor C14 and a capacitor C16 connected in series from the input end to the output end, an inductor L1, an inductor L3 and an inductor L5 are connected in parallel at both ends of the capacitor C2, the capacitor C7 and the capacitor C16, the input end is also connected to one end of the capacitor C1, the end where the capacitor C2 and the capacitor C4 are connected to each other is also connected to one end of the capacitor C3, the end where the capacitor C4 and the capacitor C7 are connected to each other is also connected to one end of the inductor L2 and one end of the capacitor C6, and the other end of the inductor L2 is connected to one end of the capacitor C5. The interconnected end of capacitor C7 and capacitor C9 is also connected to one end of capacitor C8, the interconnected end of capacitor C9 and capacitor C11 is also connected to one end of capacitor C10, the interconnected end of capacitor C11 and capacitor C14 is also connected to one end of capacitor C12 and one end of inductor L4, the other end of inductor L4 is connected to one end of capacitor C13, the interconnected end of capacitor C14 and capacitor C16 is also connected to one end of capacitor C15, and the other ends of capacitor C1, capacitor C3, capacitor C5, capacitor C6, capacitor C8, capacitor C10, capacitor C12, capacitor C13 and capacitor C15 are grounded.

[0006] Furthermore, the capacitors C1 to C16 are 0402 packaged capacitors; and the inductors L1 to L5 are T12-10 magnetic rings.

[0007] Beneficial effects of the utility model: compared with the prior art, the utility model adopts metal shell packaging, which plays a shielding role on the one hand and a protective role on the other hand; a notch is provided to avoid short circuit between the metal shell and the pad; a card connector is provided to ensure the connection reliability between the shell and the PCB board; the thick filling sealant can realize the fixation of internal components and elastic buffering, and the connection reliability is higher;

[0008] The circuit is transformed from the low-pass prototype of the LC filter. The resonant circuit composed of L2, C5, C6 and L4, C12, C3 is the operating frequency of the bandpass filter; L2, C5 and L4, C13 are connected in series to the ground to increase the out-of-band suppression on the left side of the filter, and L3, C7, C8 and L5, C15, C16 are connected in parallel to increase the out-of-band suppression on the right side of the filter; L1, C1, C2, C3 can increase the far-end suppression of the filter. The utility model realizes low insertion loss, high suppression and small size design. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a three-dimensional structural diagram of a 46.5MHz small-size bandpass filter;

[0010] Figure 2 It is a schematic diagram of the cross-sectional structure of a 46.5MHz small-size bandpass filter;

[0011] Figure 3This is a top view of the structure of a 46.5MHz small-size bandpass filter;

[0012] Figure 4 It is a schematic diagram of the three-dimensional structure of the shell;

[0013] Figure 5 It is a schematic diagram of the layout structure on the PCB board;

[0014] Figure 6 It is a schematic diagram of the PCB pad layout structure;

[0015] Figure 7 It is the circuit schematic;

[0016] Figure 8 It is a simulation circuit diagram;

[0017] Fig. 9 is the simulation variable parameter diagram;

[0018] Fig.10 is the simulation curve. DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0020] Example 1: Figure 1-10 As shown, a 46.5MHz small-size bandpass filter comprises a metal shell 1 and a PCB board covering the open end of the shell, a bandpass filter component 3 is arranged on the surface of the PCB board 2 facing the inner cavity of the shell, an input terminal 4 is arranged on the upper left side and an output terminal 5 is arranged on the lower right side of the PCB board 2, a left notch 6 and a right notch 7 are arranged at the shell 1 opposite to the input terminal 4 and the output terminal 5, and the left notch 6 and the right notch 7 are arranged in a staggered manner to avoid mutual influence, and the left notch 6 and the right notch 7 are respectively kept at a distance from the pads at the input terminal 4 and the output terminal 5 to avoid short circuit between the metal shell and the pads, and the front and rear sides of the shell 1 Two left-right staggered card plates 8 are arranged on the wall, and the two card plates 8 are inserted into the through holes 9 on the PCB board 2 and then fixed by welding, which can ensure the connection reliability between the shell and the PCB board, and the length of the card plates is greater than the length of the through holes 9. The long section is bent and fits on the PCB board and is fixed by soldering, which further improves the connection reliability. The shell 1 is filled with sealant. The thickness of the filled sealant can realize the fixation of internal components and elastic buffering, and the connection reliability is higher. The shell 1 adopts metal plates to obtain four side walls by shearing and bending. This structure can reduce costs.

[0021] The product size requirement is 13.3*6.6*3.8 (max) mm. The length and width of the circuit board are 13.3 mm and 6.6 mm, and the thickness is 0.6 mm. This layout can complete the layout of components while meeting the size requirements.

[0022] The shell thickness is 3.0mm and the circuit board thickness is 0.6mm, which can meet the overall thickness of 3.8mm.

[0023] The circuit structure of the 46.5MHz small-size bandpass filter includes capacitors C2, C4, C7, C9, C11, C14 and C16 connected in series from the input end to the output end, inductors L1, L3 and L5 are connected in parallel at both ends of the capacitors C2, C7 and C16, the input end is also connected to one end of the capacitor C1, the end where the capacitors C2 and C4 are connected to each other is also connected to one end of the capacitor C3, the end where the capacitors C4 and C7 are connected to each other is also connected to one end of the inductor L2 and one end of the capacitor C6, and the other end of the inductor L2 is connected to the inductor L3. The interconnected end of capacitor C7 and capacitor C9 is also connected to one end of capacitor C8, the interconnected end of capacitor C9 and capacitor C11 is also connected to one end of capacitor C10, the interconnected end of capacitor C11 and capacitor C14 is also connected to one end of capacitor C12 and one end of inductor L4, the other end of inductor L4 is connected to one end of capacitor C13, the interconnected end of capacitor C14 and capacitor C16 is also connected to one end of capacitor C15, and the other ends of capacitor C1, capacitor C3, capacitor C5, capacitor C6, capacitor C8, capacitor C10, capacitor C12, capacitor C13 and capacitor C15 are grounded.

[0024] In order to meet the design size, the capacitors C1 to C16 used are 0402 package capacitors; the inductors L1 to L5 are made of T12-10 magnetic rings, which can ensure the inductor Q value and meet the size requirements.

[0025] The circuit of the utility model is transformed from the low-pass prototype of the LC filter. The resonant circuit composed of L2, C5, C6 and L4, C12, C3 is the working frequency of the bandpass filter; L2, C5 and L4, C13 are connected in series to the ground to increase the out-of-band suppression on the left side of the filter, and L3, C7, C8 and L5, C15, C16 are connected in parallel to increase the out-of-band suppression on the right side of the filter; L1, C1, C2, C3 can increase the far-end suppression of the filter; C4, C9, C10, C11, C14 are coupling capacitors.

[0026] The circuit has the following advantages:

[0027] Small insertion loss: The selected inductor has a smaller Q value, and the inductor used is less, which can reduce the filter insertion loss;

[0028] High suppression: The zero points generated by L2, C5, L4, C13 can increase the out-of-band suppression on the left side of the filter, and the zero points generated by L3, C7, C8, L5, C15, C16 can increase the out-of-band suppression on the right side of the filter;

[0029] Small size: The 0402 package capacitors and T12-10 magnetic ring-wrapped inductors used can meet the small size requirements.

[0030] The following simulation is carried out taking the main index requirements of the filter as an example.

[0031] Center frequency 46.5MHz;

[0032] Insertion loss 1.2dB;

[0033] 3dB relative bandwidth 21~22.5MHz;

[0034] Out-of-band suppression ≥60dBc@Fo±23M.

[0035] Simulation schematic diagram Figure 8 By setting the bandpass filter operating bandwidth and stopband suppression requirements, the corresponding parameters and simulation results can be generated, such as Fig. 9 , Fig.10 .

[0036] It can be seen from the simulation results that this solution can meet the product index requirements.

[0037] The above description is only a specific implementation method of the present utility model, but the protection scope of the present utility model is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present utility model, which should be included in the protection scope of the present utility model. Therefore, the protection scope of the present utility model should be based on the protection scope of the claims.

Claims

1. A 46.5MHz small size bandpass filter, characterized in that: The invention comprises a metal shell (1) and a PCB board (2) covering the open end of the shell (1); a bandpass filter component (3) is arranged on the surface of the PCB board (2) facing the inner cavity of the shell; an input end (4) is arranged on the upper left side of the PCB board (2) and an output end (5) is arranged on the lower right side; a left notch (6) and a right notch (7) are arranged on the shell (1) directly opposite the input end (4) and the output end (5); the left notch (6) and the right notch (7) are respectively kept at a distance from the soldering pads at the input end (4) and the output end (5); two left and right staggered card plates (8) are arranged on the front and rear side walls of the shell (1); the two card plates (8) are inserted into through holes (9) on the PCB board (2) and then fixed by welding; and the shell (1) is filled with sealing glue.

2. A 46.5MHz small size bandpass filter according to claim 1, characterized in that: The circuit structure of the bandpass filter includes a capacitor C2, a capacitor C4, a capacitor C7, a capacitor C9, a capacitor C11, a capacitor C14 and a capacitor C16 connected in series from the input end to the output end, an inductor L1, an inductor L3 and an inductor L5 are connected in parallel at both ends of the capacitor C2, the capacitor C7 and the capacitor C16, the input end is also connected to one end of the capacitor C1, the end where the capacitor C2 and the capacitor C4 are connected to each other is also connected to one end of the capacitor C3, the end where the capacitor C4 and the capacitor C7 are connected to each other is also connected to one end of the inductor L2 and one end of the capacitor C6, and the other end of the inductor L2 is connected to one end of the capacitor C5. The interconnected end of capacitor C7 and capacitor C9 is also connected to one end of capacitor C8, the interconnected end of capacitor C9 and capacitor C11 is also connected to one end of capacitor C10, the interconnected end of capacitor C11 and capacitor C14 is also connected to one end of capacitor C12 and one end of inductor L4, the other end of inductor L4 is connected to one end of capacitor C13, the interconnected end of capacitor C14 and capacitor C16 is also connected to one end of capacitor C15, and the other ends of capacitor C1, capacitor C3, capacitor C5, capacitor C6, capacitor C8, capacitor C10, capacitor C12, capacitor C13 and capacitor C15 are grounded.

3. A 46.5MHz small size bandpass filter according to claim 2, characterized in that: Capacitors C1 to C16 are made of 0402 package capacitors; inductors L1 to L5 are made of T12-10 magnetic rings.

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