A miniaturized differential filter

Abstract

The utility model discloses a miniaturized differential filter, include: circuit board and set up on the circuit board circuit structure, the circuit structure includes input, two output and set up in input and output between balun unit, direct current isolation unit and filter unit, balun unit is magnetic transformer balun, balun unit with input connection, direct current isolation unit includes electric capacity C1 and electric capacity C7, electric capacity C1 is connected with input, electric capacity C7 with balun unit is connected, filter unit sets up between electric capacity C1 and electric capacity C7, the utility model discloses balun, direct current isolation electric capacity, filter three devices are integrated to a circuit structure, has reduced the volume of filter, has realized miniaturization. Through integrating direct current isolation electric capacity and magnetic transformer balun in the filter, realize filter integration, miniaturization, improve the inhibition ratio through the optimization circuit structure, and optimize the center insertion loss.

Description

Technical Field

[0001] This utility model relates to the field of filters, and in particular to a miniaturized differential filter. Background Technology

[0002] Differential LC filters are key components used to suppress common-mode interference and extract differential signals, primarily applied in high-speed digital circuits and communication systems. Their sales channels are mainly electronic component distribution platforms, and core parameters include cutoff frequency, insertion loss, and common-mode rejection ratio (CMRR). Differential LC filters are a highly efficient filter design, possessing excellent CMRR and anti-interference capabilities.

[0003] In the existing technology, the differential filter originally required three separate components—a balun, a DC blocking capacitor, and a filter—to be connected in the customer module. Integrating them into one device resulted in a large size. Utility Model Content

[0004] This utility model overcomes the shortcomings of large size of differential filters in the prior art and provides a miniaturized differential filter. To achieve the above objective, the technical solution adopted by this utility model is as follows: a miniaturized differential filter, which includes: a circuit board and a circuit structure disposed on the circuit board. The circuit structure includes an input terminal, two output terminals, and a balun unit, a DC blocking unit, and a filter unit disposed between the input terminal and the output terminal.

[0005] The balun unit is a magnetic transformer balun, and the balun unit is connected to the output terminal;

[0006] The DC blocking unit includes capacitor C1 and capacitor C7. Capacitor C1 is connected to the input terminal, and capacitor C7 is connected to the balun unit.

[0007] The filter unit is positioned between capacitor C1 and capacitor C7.

[0008] In a preferred embodiment of this utility model, the balun unit includes a first output interface, a second output interface, a third output interface, and a fourth output interface;

[0009] The first output interface is connected to the capacitor C7, the second output interface is grounded, and the third and fourth output interfaces are respectively connected to the two output terminals of the circuit structure.

[0010] In a preferred embodiment of this invention, the winding of the magnetic transformer balun adopts a double-strand parallel winding structure of fine enameled wire.

[0011] In a preferred embodiment of this utility model, the capacitor in the circuit structure is a chip capacitor, and the inductor in the circuit structure is a chip inductor.

[0012] In a preferred embodiment of this invention, the filter unit includes three high-frequency transmission zeros and two low-frequency transmission zeros.

[0013] In a preferred embodiment of this invention, the high-frequency transmission zero point includes a capacitor and an inductor connected in parallel, and the low-frequency transmission zero point includes a capacitor and an inductor connected in series.

[0014] In a preferred embodiment of this utility model, two high-frequency transmission zeros, two low-frequency transmission zeros are connected in series, and one high-frequency transmission zero is connected in series sequentially.

[0015] In a preferred embodiment of this invention, an impedance matching network is further provided between the capacitor C1 and the filter unit.

[0016] In a preferred embodiment of this utility model, the impedance matching network includes a capacitor and an inductor connected in parallel, one end of the impedance matching network is connected to the capacitor C1, and the other end is grounded.

[0017] This utility model solves the defects existing in the background technology, and has the following beneficial effects:

[0018] This invention integrates a balun, a DC blocking capacitor, and a filter into a single circuit structure, reducing the filter's size and achieving miniaturization. The filter is integrated and miniaturized by integrating a DC blocking capacitor and a magnetic transformer balun inside the filter. Furthermore, the suppression ratio is improved and the center insertion loss is optimized through circuit structure optimization. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other embodiments can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a circuit diagram of a miniaturized differential filter according to one embodiment of the present invention;

[0021] Figure 2 This is a winding method for a miniaturized differential filter balun structure as described in one embodiment of the present invention;

[0022] Figure 3 This is a simulation curve of the amplitude-frequency response of a miniaturized differential filter according to one embodiment of the present invention;

[0023] Figure 4This is a simulation curve of the phase frequency characteristic of a miniaturized differential filter described in one embodiment of this utility model. Detailed Implementation

[0024] To better understand the above-mentioned objectives, features, and advantages of this utility model, the present utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments. These drawings are simplified schematic diagrams, which only illustrate the basic structure of the present utility model in a schematic manner. Therefore, they only show the components related to the present utility model. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0025] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the scope of protection of this application. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0026] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art will understand the specific meaning of the above terms in this application based on the specific circumstances.

[0027] To facilitate understanding of this utility model, a more complete description will be given below with reference to the accompanying drawings. The drawings illustrate preferred embodiments of this utility model. However, this utility model can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this utility model.

[0028] A miniaturized differential filter includes: a circuit board and a circuit structure disposed on the circuit board, the circuit structure including an input terminal, two output terminals, and a balun unit, a DC blocking unit, and a filter unit disposed between the input terminal and the output terminals.

[0029] Simply put, such as Figure 1 As shown, the balun unit is a magnetic transformer balun, connected to the output terminal. The DC blocking unit includes capacitors C1 and C7; that is, C1 and C7 are DC blocking capacitors. Capacitor C1 is connected to the input terminal, and capacitor C7 is connected to the balun unit. The filter unit is positioned between capacitors C1 and C7.

[0030] refer to Figure 1 The filter input is connected to the input of capacitor C1. The output of capacitor C1 is connected to the inputs of inductors LP1, CP1, L1, and C2. The outputs of inductors LP1 and CP1 are grounded. The outputs of inductors L1 and C2 are connected to the inputs of inductors L2, C3, and CP2. The output of CP2 is grounded. The outputs of inductors L2 and C3 are connected to the input of capacitor C4. The output of C4 is connected to the inputs of capacitors CP3, CP4, and C5. The output of CP3 is connected to the input of inductor LP2. The output of LP2 is grounded. CP4 is grounded. The output of C5 is connected to the inputs of capacitors CP5, LP3, L3, and L6. The output of LP3 is connected to the input of capacitor CP6. The output of LP6 is grounded. Inductor L3 and capacitor C6 are connected in parallel. Their outputs are connected to the inputs of capacitors CP7 and C7. The output of CP7 is grounded. The output of C7 is connected to the input of the balun.

[0031] It should be noted that the capacitor in the circuit structure of this utility model is a chip capacitor, and the inductor in the circuit structure is a chip inductor.

[0032] The overall circuit of the filter unit adopts a multi-zero (five-zero) structure, including three high-frequency transmission zeros and two low-frequency transmission zeros.

[0033] A high-frequency transmission zero consists of a capacitor and an inductor connected in parallel, while a low-frequency transmission zero consists of a capacitor and an inductor connected in series. Two high-frequency transmission zeros, two low-frequency transmission zeros connected in series, and one high-frequency transmission zero are then connected in series sequentially. (Reference) Figure 1 Capacitor C2 and inductor L1, capacitor C3 and inductor L2, and capacitor C6 and inductor L3 form three high-frequency transmission zeros on the high end, improving high-frequency rejection. Capacitor CP6 and inductor LP3, and capacitor CP3 and inductor LP2 form two low-frequency transmission zeros on the low end, enhancing low-frequency rejection capability. This five-zero coordinated layout gives the filter superior selectivity and high rejection ratio over a wide frequency range compared to conventional filter structures.

[0034] Specifically, the balun unit includes a first output interface, a second output interface, a third output interface, and a fourth output interface; the first output interface is connected to capacitor C7, the second output interface is grounded, and the third and fourth output interfaces are respectively connected to the two output terminals of the circuit structure.

[0035] Furthermore, combined Figure 2 As shown, the magnetic transformer balun employs a double-strand parallel winding structure of fine enameled wire. The balun unit achieves a differential input of 200Ω and a single-ended output of 50Ω, enabling 180° phase conversion between filters. Magnetic transformer baluns are chosen to reduce height, keeping the overall height below 2.5mm. The overall circuit utilizes a multi-zero (five-zero) structure to reduce inductance while achieving high rejection. Magnetic rings are selected for this purpose, as they possess high permeability and low loss characteristics. The magnetic material of the balun effectively improves coupling efficiency and suppresses high-frequency interference. Optimized winding structure and turn count matching ensure 180° phase reversal accuracy while meeting impedance transformation requirements. The five-zero filter structure, combined with the magnetic ring inductor and chip capacitor layout, precisely controls the positions of multiple transmission zeros, enhancing out-of-band attenuation capability. The overall design achieves high performance while miniaturizing components and low-profile integration, making it suitable for high-density PCB layouts.

[0036] The left port has a 50Ω impedance, while the right port has a differential impedance of 200Ω (100Ω per port), meeting the requirements for differential signal transmission. Through a compact winding design of the magnetic transformer balun, the design achieves a 180° phase difference and impedance transformation. The winding uses a micro-fine enameled wire double-strand parallel winding process to ensure symmetry and coupling accuracy, further optimizing the common-mode rejection ratio. The overall structure integrates a magnetic ring, chip capacitors, and chip inductors on a multilayer ceramic substrate, reducing lead length, stray inductance, and improving device reliability.

[0037] Combination Figure 1 As shown, an impedance matching network is also provided between capacitor C1 and the filter unit. The impedance matching network consists of a capacitor and an inductor connected in parallel. One end of the impedance matching network is connected to capacitor C1, and the other end is grounded. Specifically, inductor LP1 and capacitor CP1 constitute the impedance matching network to improve the passband loss. By synergistically optimizing the balun unit and the multi-zero filter structure, the contradiction between miniaturization and high performance is effectively balanced, achieving the design goal of a flat passband and suppression of steep peaks.

[0038] like Figure 3 and Figure 4As shown, the circuit structure adopts a five-zero point structure, featuring high suppression ratio and excellent center loss, which is clearly evident in its amplitude-frequency response curve and phase-frequency response curve. This invention integrates a balun, a DC blocking capacitor, and a filter into a single circuit structure, reducing the filter's size and achieving miniaturization. The filter is integrated and miniaturized by integrating a DC blocking capacitor and a magnetic transformer balun inside the filter. The suppression ratio is improved and the center insertion loss is optimized by optimizing the circuit structure.

[0039] The above embodiments only illustrate several implementation methods of this utility model, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.

Claims

1. A miniaturized differential filter, characterized in that, include: The circuit board and the circuit structure disposed on the circuit board, the circuit structure including an input terminal, two output terminals, and a balun unit, a DC blocking unit, and a filter unit disposed between the input terminal and the output terminal; The balun unit is a magnetic transformer balun, and the balun unit is connected to the output terminal; The DC blocking unit includes capacitor C1 and capacitor C7. Capacitor C1 is connected to the input terminal, and capacitor C7 is connected to the balun unit. The filter unit is positioned between capacitor C1 and capacitor C7.

2. The miniaturized differential filter according to claim 1, characterized in that: The balun unit includes a first output interface, a second output interface, a third output interface, and a fourth output interface; The first output interface is connected to the capacitor C7, the second output interface is grounded, and the third and fourth output interfaces are respectively connected to the two output terminals of the circuit structure.

3. A miniaturized differential filter according to claim 1, characterized in that: The winding of the magnetic transformer balun adopts a double-strand parallel winding structure of fine enameled wire.

4. A miniaturized differential filter according to claim 1, characterized in that: The capacitors in the circuit structure are surface-mount capacitors, and the inductors in the circuit structure are surface-mount inductors.

5. A miniaturized differential filter according to claim 1, characterized in that: The filter unit includes three high-frequency transmission zeros and two low-frequency transmission zeros.

6. A miniaturized differential filter according to claim 5, characterized in that: The high-frequency transmission zero includes a capacitor and an inductor connected in parallel, and the low-frequency transmission zero includes a capacitor and an inductor connected in series.

7. A miniaturized differential filter according to claim 5, characterized in that: Two high-frequency transmission zeros, two low-frequency transmission zeros, and one high-frequency transmission zero are connected in series.

8. A miniaturized differential filter according to claim 1, characterized in that: An impedance matching network is also provided between the capacitor C1 and the filter unit.

9. A miniaturized differential filter according to claim 8, characterized in that: The impedance matching network includes a capacitor and an inductor connected in parallel. One end of the impedance matching network is connected to the capacitor C1, and the other end is grounded.

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