LC band-pass filter
By optimizing the circuit design of the LC bandpass filter, combining the ground series resonance and cross-coupling zero point, the problems of large loss of small volume filters and high process difficulty are solved, and the filter effect with high rejection ability and low loss is achieved.
Patent Information
- Application Number
- CN202422646458.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-31
- Publication Date
- 2025-08-22
- Estimated Expiration
- 2034-10-31
AI Technical Summary
The existing small-volume 3-order narrowband bandpass filter has large losses, poor suppression, high process production difficulty and cost, and high accuracy requirements for capacitive inductor components at high frequencies, resulting in increased filter volume and cost increase.
The circuit design on the circuit board is adopted, including ground series resonance, cross-coupled zero point and coupling capacitor. The circuit includes multiple capacitors and inductors. By optimizing the circuit structure, it realizes a third-order bandpass filter network, reducing losses and improving suppression capabilities.
It realizes high out-of-band rejection, low loss, small size and narrow bandwidth, which reduces debugging difficulty and production costs, and is suitable for application scenarios with small volume requirements.
Smart Images
Figure CN223261510U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the field of filters, in particular to an LC bandpass filter. Background Art
[0002] As the signal transmission distance requirements in current wireless communication technologies become increasingly higher and signal interference increases, the requirements for the squareness ratio and transmission rate of the filter are becoming increasingly higher.
[0003] LC filters are widely used in fields such as wireless communications and electronic countermeasures due to their simple structure, low equipment investment, high operational reliability, and low operating costs.
[0004] Conventional third-order narrowband bandpass filters, while maintaining a similarly small size, suffer from high losses, poor suppression, and weak noise filtering capabilities. At high frequencies, LC filters use smaller capacitor and inductor components and require higher precision, increasing manufacturing complexity and costs. High squareness ratios require increased circuit order, which increases filter size, further increasing manufacturing complexity and costs. Utility Model Content
[0005] The present invention overcomes the shortcomings of the prior art in that the manufacturing process of small-volume filters is more difficult and the cost is further increased, and provides an LC bandpass filter. To achieve the above-mentioned purpose, the present invention adopts the following technical solution: an LC bandpass filter, which includes: a circuit board and a housing arranged on the circuit board, wherein the circuit board is provided with a circuit;
[0006] The circuit includes a series resonance to ground, a cross-coupling zero point and a coupling capacitor. The input end of the circuit is connected to the coupling capacitor, and the output end of the bandpass filter is connected to the output end of the cross-coupling zero point.
[0007] In a preferred embodiment of the present invention, the circuit includes multiple capacitors and multiple inductors.
[0008] In a preferred embodiment of the present invention, the suspended node in the circuit is connected to a capacitor, one end of the capacitor is connected to the suspended node, and the other end is grounded.
[0009] In a preferred embodiment of the present invention, a capacitor C2 is provided at the input end of the circuit, and a capacitor C13 is provided at the output end of the circuit.
[0010] In a preferred embodiment of the present invention, one end of the capacitor C1 is connected to the input end of the circuit, and the other end is grounded; the band-pass filter group includes a capacitor C2, a capacitor C4, an inductor L2, a capacitor C9, an inductor L3, and a capacitor C13 connected in series in sequence, the input end of the capacitor C2 is the input end of a single channel of the band-pass filter group, and the output end of the capacitor C13 is the output end of a single channel of the band-pass filter group; the input end of the capacitor C2 is connected to the ground with a capacitor, and the output ends of the capacitor C2, the capacitor C4, the inductor L2, the capacitor C9, the inductor L3, and the capacitor C13 are connected to the ground with a capacitor; one end of the capacitor C3 is connected to the output end of the capacitor C2, and the other end is grounded.
[0011] In a preferred embodiment of the present invention, the output end of the capacitor C4 is connected in series with the capacitor C5, the inductor L1 and the capacitor C6 to the ground, and the inductor L1 and the capacitor C6 are connected in parallel to the ground.
[0012] In a preferred embodiment of the present invention, the input end of the capacitor C10 is connected to the input end of the capacitor C9, and the output end of the capacitor C10 is connected to the output end of the capacitor C13.
[0013] In a preferred embodiment of the present invention, one end of capacitor C7 is connected to the input end of inductor L2, and the other end is grounded; one end of capacitor C8 is connected to the output end of inductor L2, and the other end is grounded; one end of capacitor C11 is connected to the input end of inductor L3, and the other end is grounded; one end of capacitor C12 is connected to the output end of inductor L3, and the other end is grounded; one end of capacitor C14 is connected to the output end of capacitor C13, and the other end is grounded.
[0014] In a preferred embodiment of the present invention, the low-frequency zero point of the bandpass filter group is a series zero point to ground composed of capacitor C5, adjustable inductor L1 and capacitor C6; the high-frequency zero point is a cross-coupling zero point controlled by capacitor C10.
[0015] The present invention solves the defects in the background technology and has the following beneficial effects:
[0016] This utility model provides a third-order LC bandpass filter network module with high out-of-band rejection and low loss, effectively resisting signal interference. The LC bandpass filter group has a relatively narrow bandwidth, low in-band loss, and a compact size. In practical applications, it can achieve better loss while maintaining a small footprint, showing promising application prospects. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying any creative work, they can also obtain drawings of other embodiments based on these drawings.
[0018] Figure 1 Schematic diagram of an LC bandpass filter group circuit in the prior art;
[0019] Figure 2 Schematic diagram of an LC bandpass filter according to an embodiment of the present invention;
[0020] Figure 3 This is a schematic diagram of a six-way circuit board of an LC bandpass filter according to one embodiment of the present invention;
[0021] Figure 4 This is a circuit diagram of a single path in an LC bandpass filter according to an embodiment of the present invention;
[0022] Figure 5 This is an original simulation waveform diagram of an LC bandpass filter at a center frequency of 231 MHz described in one embodiment of the present invention;
[0023] Figure 6 This is a simulation diagram of an LC bandpass filter described in one embodiment of the present invention compared with a conventional circuit.
[0024] The reference numerals are as follows:
[0025] 10-housing; 20-circuit board; 201-capacitor; 202-inductor. DETAILED DESCRIPTION
[0026] In order to more clearly understand the above-mentioned purposes, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. These drawings are all simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner. Therefore, they only show the structures related to the present invention. It should be noted that, unless there is a conflict, the embodiments in this application and the features in the embodiments can be combined with each other.
[0027] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present utility model, unless otherwise specified, "multiple" means two or more.
[0028] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. 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 internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.
[0029] To facilitate understanding of the present invention, a more comprehensive description of the present invention will be provided below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present invention. However, the present invention 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 comprehensive understanding of the disclosure of the present invention.
[0030] like Figure 2 As shown, the utility model discloses an LC bandpass filter, wherein, as Figure 1 As shown, it includes: a circuit board 20 and a housing 10 arranged on the circuit board 20, and a circuit is arranged on the circuit board.
[0031] Specifically, if Figure 3 As shown, the circuit includes a 6-way band-pass filter group. The 6-way band-pass filters each have a single input and a single output.
[0032] Reference Figure 4 As shown, the circuit includes a series resonance to ground, a cross-coupling zero point and a coupling capacitor. The input end of the circuit is connected to the coupling capacitor, and the output end of the bandpass filter is connected to the output end of the cross-coupling zero point.
[0033] The circuit includes a plurality of capacitors 201 and a plurality of inductors 202. A suspended node in the circuit is connected to the capacitor 201, one end of the capacitor 201 is connected to the suspended node, and the other end is grounded.
[0034] Continue to refer to Figure 4 As shown, one end of capacitor C1 is connected to the input end of the circuit and the other end is grounded. The bandpass filter group includes capacitor C2, capacitor C4, inductor L2, capacitor C9, inductor L3, and capacitor C13, which are connected in series in sequence. The input end of capacitor C2 serves as the input end of the single-channel bandpass filter group, and the output end of capacitor C13 serves as the output end of the single-channel bandpass filter group. The input end of capacitor C2 is connected to ground via a capacitor, and the output ends of capacitors C2, C4, inductor L2, C9, inductor L3, and C13 are connected to ground via capacitors. The output end of capacitor C4 is connected to ground via capacitor C5, inductor L1, and capacitor C6, which are connected in series in sequence. One end of capacitor C3 is connected to the output end of capacitor C2, and the other end is grounded.
[0035] Inductor L1 and capacitor C6 are connected in parallel to ground; the input of capacitor C10 is connected to the input of capacitor C9, and the output of capacitor C10 is connected to the output of capacitor C13. In the prior art, to achieve the same electrical performance, an additional section is required, and conventional zero points reduce component values, making this difficult to implement in engineering. The circuit of the present invention reduces one order, improves the Q value of the entire filter, reduces filter loss, and achieves low loss and a high squareness ratio.
[0036] One end of capacitor C7 is connected to the input end of inductor L2, and the other end is grounded; one end of capacitor C8 is connected to the output end of inductor L2, and the other end is grounded; one end of capacitor C11 is connected to the input end of inductor L3, and the other end is grounded; one end of capacitor C12 is connected to the output end of inductor L3, and the other end is grounded; one end of capacitor C14 is connected to the output end of capacitor C13, and the other end is grounded.
[0037] The low-frequency zero of the bandpass filter group is the series zero to ground composed of capacitor C5, adjustable inductor L1 and capacitor C6; the high-frequency zero is the cross-coupling zero controlled by capacitor C10.
[0038] An LC bandpass filter in the utility model is simulated. Figure 5 and Figure 6 , Figure 6 The loss of a conventional third-order LC bandpass filter is 4.9dB. After using the circuit inductor used in the present invention, the loss can be reduced to 3.5dB.
[0039] This third-order LC bandpass filter network has high out-of-band rejection and can effectively resist signal interference. This LC bandpass filter has a relatively narrow bandwidth, but has good in-band ripple and in-band loss.
[0040] In other words, a single channel of the bandpass filter network is third-order. The six-channel filter group is composed of six third-order filters. In the third-order bandpass filter network, the capacitors can accurately adjust the capacitance parameters to achieve high precision and miniaturization. Conventional third-order narrowband filters have poor loss and low suppression. Since the capacitor 201 and inductor 202 used in the filter have small component values, a small error can double the difficulty of debugging the filter. Improving the return loss can effectively reduce the dependence on the accuracy of the component values, reduce the difficulty of debugging, and improve production efficiency. When debugging this filter, the L2 inductor needs to be rotated 40° to 60°, and the inductor L3 needs to be close to the bottom of the shielding cover of each channel, with a distance of approximately 0.2mm to 0.3mm. This is conducive to offsetting the spatial coupling between the inductors, and the difficulty of debugging is greatly reduced.
[0041] The above embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the concept of the present invention, and these variations and improvements fall within the scope of protection of the present invention. Therefore, the scope of protection of the present utility model patent shall be determined by the appended claims.
Claims
1. An LC bandpass filter, characterized in that: include: A circuit board and a housing arranged on the circuit board, wherein the circuit board is provided with a circuit; The circuit includes a series resonance to ground, a cross-coupling zero point and a coupling capacitor. The input end of the circuit is connected to the coupling capacitor, and the output end of the bandpass filter is connected to the output end of the cross-coupling zero point.
2. The LC bandpass filter according to claim 1, wherein: The circuit includes multiple capacitors and multiple inductors.
3. The LC bandpass filter according to claim 1, wherein: The suspended node in the circuit is connected to a capacitor, one end of the capacitor is connected to the suspended node, and the other end of the capacitor is grounded.
4. The LC bandpass filter according to claim 1, wherein: The input end of the circuit is provided with a capacitor C2, and the output end of the circuit is provided with a capacitor C13.
5. The LC bandpass filter according to claim 1, wherein: One end of the capacitor C1 is connected to the input end of the circuit, and the other end is grounded; the band-pass filter group includes a capacitor C2, a capacitor C4, an inductor L2, a capacitor C9, an inductor L3, and a capacitor C13 connected in series in sequence, the input end of the capacitor C2 is the input end of a single channel of the band-pass filter group, and the output end of the capacitor C13 is the output end of a single channel of the band-pass filter group; the input end of the capacitor C2 is connected to the ground with a capacitor, and the output ends of the capacitor C2, the capacitor C4, the inductor L2, the capacitor C9, the inductor L3, and the capacitor C13 are connected to the ground with a capacitor; one end of the capacitor C3 is connected to the output end of the capacitor C2, and the other end is grounded.
6. The LC bandpass filter according to claim 2, wherein: The output end of the capacitor C4 is connected in series with a capacitor C5, an inductor L1 and a capacitor C6 to the ground, and the inductor L1 and the capacitor C6 are connected in parallel to the ground.
7. The LC bandpass filter according to claim 2, wherein: An input end of the capacitor C10 is connected to an input end of the capacitor C9 , and an output end of the capacitor C10 is connected to an output end of the capacitor C13 .
8. The LC bandpass filter according to claim 2, wherein: One end of capacitor C7 is connected to the input end of inductor L2, and the other end is grounded; one end of capacitor C8 is connected to the output end of inductor L2, and the other end is grounded; one end of capacitor C11 is connected to the input end of inductor L3, and the other end is grounded; one end of capacitor C12 is connected to the output end of inductor L3, and the other end is grounded; One end of the capacitor C14 is connected to the output end of the capacitor C13 , and the other end is grounded.
9. The LC bandpass filter according to claim 1, wherein: The low-frequency zero point of the band-pass filter group is a series zero point to ground formed by capacitor C5, adjustable inductor L1 and capacitor C6; the high-frequency zero point is a cross-coupling zero point controlled by capacitor C10.