LC band-pass filter
By introducing full pass and attenuation network modules into the LC bandpass filter, the problems of high accuracy requirements and circuit complexity of high frequency LC filter components are solved, and high out-of-band rejection and wide relative bandwidth filters are realized, reducing the number of filters with high frequency LC filters. Cost and debugging difficulty.
Patent Information
- Application Number
- CN202420268814.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-02-04
- Publication Date
- 2025-02-11
- Estimated Expiration
- 2034-02-04
AI Technical Summary
In the prior art, the capacitance and inductance element values of high-frequency LC filters are small and have high accuracy requirements, which leads to increased process production difficulty and cost, and requires increased circuit order to achieve a high rectangular ratio, resulting in increased filter volume. Yamato costs have increased further.
An LC bandpass filter is designed. By introducing a full-pass network module, a bandpass filter network module and an attenuation network module into the circuit, the connection is the input terminal of the bandpass filter and the full-pass network module. The output end is connected, and the output end is connected to the input end of the attenuation network module to achieve high out-of-band rejection and wide relative bandwidth.
It effectively improves the return loss, signal delay and phase changes of the filter, reduces the dependence on component accuracy, simplifies circuit debugging, reduces costs, and has good application prospects.
Smart Images
Figure CN222464578U_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 filter's rectangular ratio, transmission rate, etc. 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 operating reliability, and low operating costs.
[0004] In the prior art, the capacitor and inductor components used in LC filters at high frequencies are small in value and require higher precision, which increases the difficulty and cost of process manufacturing. The high rectangular ratio requires an increase in the circuit order, which will increase the size of the filter, further increasing the difficulty and cost of process manufacturing. How to simplify the circuit model while realizing a high-frequency, broadband, high rectangular ratio LC bandpass filter, reduce dependence on component precision, and reduce the difficulty and cost of process manufacturing is an urgent problem to be solved. Utility Model Content
[0005] The utility model overcomes the shortcomings of the prior art that the volume of the filter is increased, the difficulty of process manufacturing and the cost are further increased, and provides an LC bandpass filter. To achieve the above purpose, the technical solution adopted by the utility model is: an LC bandpass filter, including: a body and a circuit arranged on the body;
[0006] The circuit includes an all-pass network module, a bandpass filter network module and an attenuation network module. The input end of the bandpass filter network module is connected to the output end of the all-pass network module, and the output end of the bandpass filter network module is connected to the input end of the attenuation network module.
[0007] In a preferred embodiment of the utility model, the bandpass filter network module includes an inductor L3, a capacitor C5, a capacitor C8, a capacitor C10, a capacitor C12, a capacitor C15 and an inductor L8 which are sequentially connected in series, the input end of the inductor L3 is the input end of the bandpass filter network module, and the output end of the inductor L8 is the output end of the bandpass filter network module; the output ends of the capacitors C5, C8, C10 and C12 are connected to the ground with capacitors; the output end of the capacitor C5 is sequentially connected in series with capacitors C7 and inductor L4 to the ground, and the output end of the capacitor C12 is sequentially connected in series with capacitors C14 and inductor L7 to the ground; the capacitor C8 is connected in parallel with the inductor L5, and the inductor L6 is connected in parallel with the capacitor C12.
[0008] In a preferred embodiment of the present invention, the number of the inductors is an even number.
[0009] In a preferred embodiment of the present invention, an even number of the inductors are symmetrically arranged in the bandpass filter network module.
[0010] In a preferred embodiment of the present invention, the circuit includes a plurality of capacitors, a plurality of resistors and a plurality of inductors, and the resistors are variable resistance resistors.
[0011] In a preferred embodiment of the utility model, the all-pass network module includes capacitors C2, C3, C4 and adjustable inductors L1 and L2, the input end of capacitor C2 is the input end of the all-pass network module, the output end of capacitor C4 serves as the output end of the all-pass network module, the input end of the all-pass network module is connected in series with inductor L2 and capacitor C3 to the ground, and the input end of capacitor C2 and the output end of capacitor C4 are connected with inductor L1.
[0012] 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.
[0013] In a preferred embodiment of the present invention, a capacitor C1 is disposed at the input end of the circuit, and a capacitor C16 is disposed at the output end of the circuit.
[0014] The utility model solves the defects existing in the background technology, and has the following beneficial effects:
[0015] The utility model provides an LC bandpass filter whose input end is connected to an all-pass network module and an attenuation network, and whose output end is connected to an attenuation network module, which can effectively improve the return loss of the filter, compensate for signal delay, and control phase change. The LC bandpass filter includes a 6th-order bandpass filter network module, which has high out-of-band suppression and can effectively resist signal interference. The LC bandpass filter has a relatively wide bandwidth, so the delay is small and flat, which is conducive to receiving pulse signals. The input and output ends of the LC bandpass filter are connected to the all-pass and attenuation network modules, which can effectively improve the return loss, in-band fluctuation, group delay fluctuation, and phase linearity of the filter, reduce dependence on the accuracy of components, and the circuit debugging is simple and low-cost, with good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, drawings of other embodiments can be obtained based on these drawings without paying creative work.
[0017] Figure 1 It is a schematic diagram of an LC bandpass filter described in an embodiment of the utility model;
[0018] Figure 2 This is a circuit diagram of an LC bandpass filter described in an embodiment of the utility model;
[0019] Figure 3 This is an original simulation waveform diagram of a 6th-order bandpass filter network module of an LC bandpass filter at a center frequency of 3000 MHz described in one embodiment of the utility model;
[0020] Figure 4 A group delay simulation diagram of an LC bandpass filter described in an embodiment of the utility model;
[0021] Figure 5 This is an original waveform diagram of the phase linearity of an LC bandpass filter described in one embodiment of the utility model;
[0022] Figure 6 A simulation waveform diagram of an LC bandpass filter introduced into an all-pass network module in an embodiment of the utility model;
[0023] Figure 7 A group delay waveform diagram of an LC bandpass filter introduced into an all-pass network module in one embodiment of the utility model;
[0024] Figure 8 A phase linearity waveform diagram of an LC bandpass filter introduced into an all-pass network module in one embodiment of the utility model;
[0025] Fig. 9 This is a simulation waveform diagram of an LC bandpass filter introduced with an attenuation network module in one embodiment of the utility model;
[0026] Fig.10 A group delay diagram of an LC bandpass filter introduced with an attenuation network module in one embodiment of the utility model;
[0027] Fig.11 This is a phase linearity diagram of an LC bandpass filter introduced with an attenuation network module as described in one embodiment of the present invention.
[0028] The reference numerals are as follows:
[0029] 10-device body; 20-circuit. DETAILED DESCRIPTION
[0030] In order to more clearly understand the above-mentioned purposes, features and advantages of the utility model, the utility model 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 utility model in a schematic manner. Therefore, they only show the structures related to the utility model. It should be noted that the embodiments in this application and the features in the embodiments can be combined with each other without conflict.
[0031] 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", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying 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 technical features indicated. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the invention of the present utility model, unless otherwise specified, "multiple" means two or more.
[0032] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood by specific circumstances.
[0033] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively with reference to the relevant drawings. The drawings provide 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. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly and comprehensively understood.
[0034] The utility model discloses an LC bandpass filter, wherein: Figure 1 As shown, it comprises: a filter body 10 and a circuit 20 arranged on the filter body.
[0035] Specifically, refer to Figure 2As shown, the circuit 20 includes an all-pass network module, a band-pass filter network module and an attenuation network module. The input end of the band-pass filter is connected to the all-pass network module, and the output end of the band-pass filter is connected to the attenuation network module.
[0036] The all-pass network module includes capacitors C2, C3, C4 and adjustable inductors L1 and L2. The input end of capacitor C2 is the input end of the all-pass network module, and the output end of capacitor C4 is the output end of the all-pass network module. The input end of the all-pass network module is connected in series with inductor L2 and capacitor C3 to the ground, and the input end of capacitor C2 and the output end of capacitor C4 are connected with inductor L1.
[0037] Specifically, the input end of the all-pass network module is connected to the output end of capacitor C1, the output end of capacitor C1 is connected to the input end of resistor R1 and the input end of resistor R2, the output end of resistor R1 is grounded, the output end of resistor R2 is connected to the input end of capacitor C2, the input end of resistor R3 is connected to the output end of resistor R2, and the other end of resistor R3 is grounded. The output end of capacitor C2 is connected to the input end of capacitor C4. Inductor L1 is connected in parallel with capacitor C2 and capacitor C4, the input end of capacitor C3 is connected to the input end of capacitor C2, the output end of capacitor C3 is connected to the input end of inductor L2, and the output end of inductor L2 is grounded.
[0038] When the filter order is finalized, the adjustable amount of the signal's group delay fluctuation and phase linearity is small. When the requirements for the two indicators are high, the introduction of the all-pass network module can greatly improve the signal's group delay fluctuation requirements and phase linearity stability, and increase the circuit's requirements for signal stability. Therefore, the component values of the inductors L1 and L2 are adjusted to effectively improve the stability of the group delay and phase and enhance the stability of the signal.
[0039] The bandpass filter network module includes an inductor L3, a capacitor C5, a capacitor C8, a capacitor C10, a capacitor C12, a capacitor C15 and an inductor L8 which are connected in series in sequence. The input end of the inductor L3 is the input end of the bandpass filter network module, and the output end of the inductor L8 is the output end of the bandpass filter network module; the output ends of the capacitors C5, C8, C10 and C12 are connected to the ground with capacitors; the output end of the capacitor C5 is connected to the ground in sequence with capacitor C7 and inductor L4 in series, and the output end of the capacitor C12 is connected to the ground in sequence with capacitor C14 and inductor L7 in series; the capacitor C8 is connected in parallel with the inductor L5, and the inductor L6 is connected in parallel with the capacitor C12.
[0040] Continue to refer to Figure 2Specifically, the input end of the bandpass filter network module is connected to the output end of the all-pass network module. Specifically, the input end of the inductor L3 is connected to the output end of the all-pass network module, the output end of the inductor L3 is connected to the input end of the capacitor C5, the output end of the capacitor C5 is connected to the input end of the capacitor C6, the output end of the capacitor C6 is grounded, the output end of the capacitor C5 is connected to the input end of the capacitor C7, the capacitor C7 is connected in series with the inductor L4, and the inductor L4 is grounded.
[0041] The input end of capacitor C6 is connected to the output end of capacitor C5, and the output end of capacitor C6 is grounded. The input end of inductor L5 is connected to the output end of capacitor C5. Capacitor C8 is connected in parallel with inductor L5, and the output end of inductor L8 is connected to the input end of capacitor C9, and the output end of capacitor C9 is grounded. The input end of capacitor C10 is connected to the output end of inductor L5, and the output end of capacitor C10 is connected to the input end of capacitor C11, and the output end of capacitor C11 is grounded. The input end of inductor L6 is connected to the output end of capacitor C10, and the output end of inductor L6 is connected to the input end of capacitor C15. Inductor L6 is connected in parallel with capacitor C12. The input end of capacitor C13 is connected to the output end of inductor L6, and the output end of capacitor C13 is grounded. The input end of capacitor C14 is connected to the output end of inductor L6, and the output end of capacitor C14 is connected to the input end of inductor L7, and the output end of inductor L7 is grounded. The output end of the capacitor C15 is connected to the input end of the inductor L8 , and the output end of the inductor L8 is the output end of the bandpass filter network module.
[0042] In other words, the bandpass filter network module is 6th order. In the 6th order bandpass filter network module, the capacitors can accurately adjust the capacitance parameters to achieve high precision and miniaturization. After the inductance and capacitance are fixed, the filter indicators are poor due to the influence of distributed parameters and shrinkage rate, such as large passband standing wave and large passband fluctuation. Therefore, the input end of the inductor L3 is used as the input end of the 6th order bandpass filter network module, connected to the all-pass network module. The all-pass network module plays a role in optimizing the passband amplitude by introducing full pass in the specified frequency range, and can effectively improve the group delay fluctuation and phase linearity; the output end of the inductor L8 is connected to the attenuation network module as the input and output end of the 6th order bandpass filter network module. The attenuation network module plays a role in input amplitude modulation by introducing attenuation in the specified frequency range, and can effectively improve the output return loss and out-of-band suppression.
[0043] The 6th-order bandpass filter network module first eliminates the suspended nodes through Norden transformation on the basis of the Chebyshev prototype, and adds grounding capacitors C6, C9, C11, and C13 to the suspended nodes to absorb the stray capacitance at the suspended nodes, and optimizes the component parameters through inversion transformation and balances the stopband suppression of the low and high ends. Finally, capacitors C7 and C14 are added through network transformation, wherein capacitor C7 forms a series resonant circuit with inductor L4, and capacitor C14 forms a series resonant circuit with inductor L7, which can form a transmission zero at the low-frequency end outside the passband, and the impedance is infinitesimal at the resonant frequency point, forming an attenuation pole, which greatly improves the stopband suppression at low frequencies. The circuit in which capacitor C8 and inductor L5 are connected in parallel, and capacitor C12 and inductor L6 are connected in parallel forms a cross-coupling, forming a transmission zero at the high-frequency end outside the passband, thereby generating another attenuation pole, which greatly improves the stopband suppression at high frequencies. In some embodiments, in order to improve the reliability of the process and improve the requirements for stopband suppression, the input and output ends of inductors L3 and L8 can increase the ground connection capacitance.
[0044] The attenuation network module includes a capacitor C16 and resistors R4, R5, and R6 whose resistance values can be adjusted; the output end of the capacitor C16 serves as the output end of the attenuation network module and is also the output end of the bandpass filter, and the input end is connected to the output end of the resistor R5 and the input end of the resistor R6; the input end of the resistor R5 serves as the input end of the attenuation network module and is connected to the input end of the resistor R4 and the output end of the bandpass filter network module; the output ends of the resistors R4 and R6 are both grounded.
[0045] Continue to refer to Figure 2 As shown, specifically, the input end of the attenuation network module is connected to the output end of the bandpass filter network module, the input end of the resistor R5 is the input end of the attenuation network module, the output end of the resistor R5 is connected to the input end of the resistor R6, and the output end of the resistor R6 is grounded. The input end of the resistor R4 is connected to the input end of the resistor R5, and the output end of the resistor R4 is grounded. The input end of the capacitor C16 is connected to the output end of the resistor R5, and the input end of the capacitor C16 is the output end of the attenuation network module, and the output end of the capacitor C16 is also the output end of the LC bandpass filter.
[0046] The resistor R1 , the resistor R2 , the resistor R3 , the resistor R4 , the resistor R5 and the resistor R6 are all resistors with variable resistance.
[0047] Since the capacitor and inductor components used in the filter are small in value, 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. Therefore, the value of the resistor element can be adjusted to effectively absorb the return, reduce standing waves and passband fluctuations, increase the effective bandwidth, and achieve impedance matching while changing the attenuation.
[0048] A LC bandpass filter in the utility model is simulated, referring to Figure 3-Figure 11 Through comparative analysis of the 6th-order bandpass filter network module after the introduction of the all-pass network module and the attenuation network module, the return loss of the filter is optimized from 10.17dB to 19.64dB, which reduces the difficulty of debugging the filter production process; the group delay fluctuation is optimized from 0.397ns to 0.289ns, and the stability of the filter is improved. The phase linearity is optimized from 11.59° to 8.58°. It can be determined that the utility model can provide a theoretical basis in actual operation.
[0049] It should be noted that the full-pass network module and the attenuation network module in the above-mentioned embodiment can be applied to bandpass filter network modules of different orders in different mathematical models (Butterworth, Chebychev, elliptic, etc.), and are not limited to the 6th-order bandpass filter network module in this embodiment. It can also play a good role in improving the filter's return loss, in-band fluctuation, group delay fluctuation, phase linearity, etc.
[0050] The utility model provides an LC bandpass filter whose input end is connected to an all-pass network module and an attenuation network, and whose output end is connected to an attenuation network module, which can effectively improve the return loss of the filter, compensate for signal delay, and control phase change. The LC bandpass filter includes a 6th-order bandpass filter network module, which has high out-of-band suppression and can effectively resist signal interference. The LC bandpass filter has a relatively wide bandwidth, so the delay is small and flat, which is conducive to receiving pulse signals. The input and output ends of the LC bandpass filter are connected to the all-pass and attenuation network modules, which can effectively improve the return loss, in-band fluctuation, group delay fluctuation, and phase linearity of the filter, reduce dependence on the accuracy of components, and the circuit debugging is simple and low-cost, with good application prospects.
[0051] The above embodiments only express several implementation methods of the utility model, and the descriptions are relatively specific and detailed, but they cannot be understood as limiting the scope of the utility model patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the utility model, which all belong to the protection scope of the utility model. Therefore, the protection scope of the utility model patent shall be based on the attached claims.
Claims
1. An LC bandpass filter, characterized in that: include: A device body and a circuit arranged on the device body; The circuit includes an all-pass network module, a band-pass filter network module and an attenuation network module. The input end of the band-pass filter is connected to the output end of the all-pass network module, and the output end of the band-pass filter is connected to the input end of the attenuation network module.
2. The LC bandpass filter according to claim 1, characterized in that: The bandpass filter network module includes an inductor L3, a capacitor C5, a capacitor C8, a capacitor C10, a capacitor C12, a capacitor C15 and an inductor L8 which are connected in series in sequence. The input end of the inductor L3 is the input end of the bandpass filter network module, and the output end of the inductor L8 is the output end of the bandpass filter network module; the output ends of the capacitors C5, C8, C10 and C12 are connected to the ground with capacitors; the output end of the capacitor C5 is connected to the ground in series with capacitors C7 and inductor L4 in sequence, and the output end of the capacitor C12 is connected to the ground in series with capacitors C14 and inductor L7 in sequence; the capacitor C8 is connected in parallel with the inductor L5, and the inductor L6 is connected in parallel with the capacitor C12.
3. The LC bandpass filter according to claim 2, characterized in that: The number of the inductors is an even number.
4. The LC bandpass filter according to claim 2, characterized in that: An even number of the inductors are symmetrically arranged in the bandpass filter network module.
5. The LC bandpass filter according to claim 1, characterized in that: The circuit includes a plurality of capacitors, a plurality of resistors and a plurality of inductors, and the resistors are variable resistance resistors.
6. The LC bandpass filter according to claim 1, characterized in that: The all-pass network module includes capacitors C2, C3, C4 and adjustable inductors L1 and L2. The input end of capacitor C2 is the input end of the all-pass network module, and the output end of capacitor C4 serves as the output end of the all-pass network module. The input end of the all-pass network module is connected in series with inductor L2 and capacitor C3 to the ground, and the input end of capacitor C2 and the output end of capacitor C4 are connected with inductor L1.
7. The LC bandpass filter according to claim 1, characterized in that: 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.
8. The LC bandpass filter according to claim 1, characterized in that: The input end of the circuit is provided with a capacitor C1 , and the output end of the circuit is provided with a capacitor C16 .