LC band-pass filter with high suppression based on elliptical model

Abstract

The utility model relates to a kind of LC band-pass filter based on ellipse model to realize high rejection system, belong to the microwave radio frequency technical field in the communication technology field;Including impedance matching unit is composed of inductance L1, capacitor C1 and capacitor C2, first resonant unit is composed of inductance L2, capacitor C3, second resonant unit is composed of inductance L3, capacitor C4, third resonant unit is composed of inductance L4, capacitor C6, fourth resonant unit is composed of inductance L5, capacitor C7, fifth resonant unit is composed of inductance L6, capacitor C8, sixth resonant unit is composed of inductance L7, capacitor C10, seventh resonant unit is composed of inductance L8, capacitor C11, first shunt capacitor C5 and second shunt capacitor C9;The utility model is designed by ellipse model topology, replace a large amount of large inductance in traditional scheme with small inductance, filter overall volume is reduced by 30%, adapt to the development trend of communication equipment miniaturization, integration.

Description

Technical Field

[0001] This utility model relates to an LC bandpass filter with high suppression based on an elliptic model, belonging to the microwave radio frequency technology field within the communication technology field. Background Technology

[0002] Filters are core components of modern communication, and their performance directly determines the stability, transmission efficiency, and signal quality of the communication system. Out-of-band rejection (OBS), as a key technical indicator of filters, is crucial for reducing inter-band signal interference and improving the anti-interference capability of communication links. In the traditional design of LC bandpass filters, two main technical approaches are used to achieve high OBS performance: one is to increase the circuit order by increasing the number of inductors and capacitors to build a multi-stage filtering network. For example, the "High Suppression LC Bandpass Filter" disclosed in Chinese Utility Model Patent No. CN209844655U uses an eight-stage LC filter topology to achieve 60dB OBS rejection, using eight inductors. The other approach is to increase the inductance value of the inductors in the circuit, using the resonant characteristics of high-inductance inductors to enhance the OBS rejection effect. For example, the LC filtering scheme proposed in Chinese Invention Patent Application No. CN110277968A uses an 80nH large inductor to achieve high rejection, with the inductor volume increased by more than 70% compared to conventional small inductors.

[0003] Both of the above solutions have significant technical drawbacks: increasing the circuit order directly increases the amount of materials used for inductors and capacitors, leading to a 30% to 50% increase in the manufacturing cost of the filter. At the same time, multi-level topologies increase the wiring complexity of the circuit and reduce the mass production yield of the product. Increasing the inductance value will significantly increase the physical size of the inductor. Taking the commonly used surface mount inductor as an example, the package size of an 80nH large inductor is 1206 type, while a 10nH small inductor only requires a 0402 type package, with a size difference of more than 4 times. This cannot meet the miniaturization and integration design requirements of RF devices in communication equipment such as consumer electronics and base station modules. In application scenarios with strict size constraints, such as portable communication terminals and micro base stations, traditional large inductor, multi-order LC filtering solutions cannot even be adapted to the product's structural layout, directly limiting their application scope in miniaturized communication equipment. Summary of the Invention

[0004] In view of the technical problems existing in the prior art, this utility model provides an LC bandpass filter with high suppression based on an elliptic model, which not only ensures the performance indicators of the product, but also appropriately reduces the inductance value, thereby reducing the design and debugging difficulty to a certain extent.

[0005] To achieve the above objectives, the present invention employs the following technical solution: an LC bandpass filter with high suppression based on an elliptic model. The LC bandpass filter circuit structure is as follows: one end of inductor L1 is connected to a test port of a 50-ohm characteristic impedance; the other end of inductor L1 is connected to one end of capacitors C1 and C2 respectively; the other end of capacitor C2 is connected to one end of inductor L2, capacitor C3, and a parallel inductor L3 and capacitor C4 respectively; the other ends of the parallel inductor L3 and capacitor C4 are connected to one end of capacitor C5, and a parallel inductor L4 and capacitor C6 respectively. The other ends of inductor L4 and capacitor C6 are connected to one end of inductor L5, capacitor C7, and parallel inductor L6 and capacitor C8, respectively. The other ends of parallel inductor L6 and capacitor C8 are connected to one end of capacitor C9, parallel inductor L7 and capacitor C10, and parallel inductor L7 and capacitor C10 are connected to one end of inductor L8, capacitor C11, and the 50-ohm characteristic impedance test port. The other ends of capacitor C1, inductor L2, capacitor C3, capacitor C5, inductor L5, capacitor C7, capacitor C9, inductor L8, and capacitor C11 are connected to GND.

[0006] The technical effects of this utility model are: 1. Miniaturization advantage: By using elliptical model topology design, a large number of large inductors in the traditional scheme are replaced with small inductors, and the overall volume of the filter is reduced by 30%, which is in line with the development trend of miniaturization and integration of communication equipment.

[0007] 2. High suppression performance: Relying on the optimized distribution of zeros and poles of the elliptic function, the out-of-band suppression index achieved by the combination of small inductors reaches 43dB, which is almost on par with the suppression effect of traditional multi-inductor filtering schemes.

[0008] 3. Cost and power consumption optimization: Reducing the number of inductors and using smaller inductor components lowers the material cost and power consumption of the filter, while simplifying the production and assembly process and improving the feasibility of mass production. Attached Figure Description

[0009] Figure 1 This is the circuit schematic diagram of the LC bandpass filter of this utility model; Figure 2 The simulation results of the LC bandpass filter of this utility model are shown in the figure. Figure 3 The circuit schematic of an existing LC filter; Figure 4 The figure shows the simulation results of existing LC filters. Detailed Implementation

[0010] like Figure 1As shown, an LC bandpass filter with high suppression based on an elliptic model includes an impedance matching unit, a first resonant unit, a second resonant unit, a third resonant unit, a fourth resonant unit, a fifth resonant unit, a sixth resonant unit, a seventh resonant unit, a first shunt capacitor, and a second shunt capacitor. The impedance matching unit consists of an inductor L1, a capacitor C1, and a capacitor C2. One end of inductor L1 is connected to the test port of a 50-ohm characteristic impedance, and the other end of inductor L1 is connected to one end of capacitors C1 and C2. The first resonant unit consists of an inductor L2 and a capacitor C3. One end is connected to the other end of the impedance matching unit capacitor C2; the second resonant unit consists of inductor L3 and capacitor C4, with inductor L3 and capacitor C4 connected in parallel, and one end of the parallel connection of inductor L3 and capacitor C4 connected to one end of the first resonant unit inductor L2 and capacitor C3; the first shunt capacitor consists of capacitor C5 alone, with one end of capacitor C5 connected to the other end of the parallel connection of inductor L3 and capacitor C4 in the second resonant unit; the third resonant unit consists of inductor L4 and capacitor C6, with inductor L4 and capacitor C6 connected in parallel, and one end of the parallel connection of inductor L4 and capacitor C6 connected to one end of capacitor C5; the fourth resonant unit consists of inductor L4 and capacitor C6. The fifth resonant unit consists of inductor L5 and capacitor C7, with one end of inductor L5 and capacitor C7 connected in parallel to the other end of inductor L4 and capacitor C6 in the third resonant unit; the fifth resonant unit consists of inductor L6 and capacitor C8, with inductor L6 and capacitor C8 connected in parallel, and one end of inductor L6 and capacitor C8 connected in parallel to the other end of inductor L5 and capacitor C7 in the fourth resonant unit; the second shunt capacitor consists of capacitor C9 alone, with one end of capacitor C9 connected in parallel to the other end of inductor L6 and capacitor C8 in the fifth resonant unit; the sixth resonant unit consists of inductor L7 and capacitor C10, with inductor L7 and capacitor C10 connected in parallel, and inductor L7... One end of capacitor C10 is connected in parallel with one end of the second shunt capacitor, which is connected to one end of capacitor C9. The seventh resonant unit consists of inductor L8 and capacitor C11. One end of inductor L8 and capacitor C11 is connected to the other end of the parallel connection between inductor L7 and capacitor C10 of the sixth resonant unit and the test port of 50 ohms characteristic impedance. The other ends of capacitor C1 of the impedance matching unit, inductor L2 and capacitor C3 of the first resonant unit, capacitor C5 of the first shunt capacitor, inductor L5 and capacitor C7 of the fourth resonant unit, capacitor C9 of the second shunt capacitor, and inductor L8 and capacitor C11 of the seventh resonant unit are respectively connected to GND.

[0011] The inductance of inductor L1 is 59.4nH, the inductance of inductor L2 is 84.37nH, the inductance of inductor L3 is 38.5nH, the inductance of inductor L4 is 9.2nH, the inductance of inductor L5 is 4.60nH, the inductance of inductor L6 is 15.10nH, the inductance of inductor L7 is 6.80nH, and the inductance of inductor L8 is 3.5nH.

[0012] After the external radio frequency signal is input from the test port with a 50-ohm characteristic impedance, it first enters the elliptic model filter network. This network relies on the zero and pole distribution characteristics of the elliptic function and the resonant coordination of inductors L1~L8 and capacitors C1~C11: 1. In the target passband frequency band, the resonant circuit formed by the inductors and capacitors exhibits low impedance characteristics, allowing the effective signal to pass through and be transmitted to the output of the 50-ohm characteristic impedance test port without attenuation; 2. In the out-of-band interference frequency band, the topology of the elliptic model causes the inductors to produce a strong resonance suppression effect. Combined with the capacitive reactance adjustment of the capacitors, the out-of-band interference signal is discharged to ground through the grounded inductors L2, L5, L8 and capacitors C1, C3, C5, C7, C9 circuit, achieving the out-of-band suppression effect.

[0013] Below is a comparison of simulation examples of the prior art circuit structure and the elliptical structure of this utility model under the same specifications: The prior art LC filter circuit includes a first resonant unit, a second resonant unit, a third resonant unit, a fourth resonant unit, a fifth resonant unit, a sixth resonant unit, a seventh resonant unit, and an eighth resonant unit; wherein, the inductance value of inductor L9 is 2.90nH, the inductance value of inductor L10 is 68.4nH, the inductance value of inductor L11 is 52.1nH, the inductance value of inductor L12 is 37.2nH, the inductance value of inductor L13 is 75.6nH, the inductance value of inductor L14 is 30.9nH, the inductance value of inductor L15 is 19.8nH, and the inductance value of inductor L16 is 45.9nH.

[0014] Figure 3 This is a schematic diagram of a traditional structure in existing technology. Figure 4 The simulation results of the existing technology are shown in the figure. It can be seen from the figure that the inductance values ​​of inductors L10, L11, L13 and L16 are relatively large, and there are many inductors with large inductance values. In the actual production process, large inductance values ​​also mean large space size. When the design size is limited, product design and production will be restricted to a certain extent.

[0015] Figure 1 This is the circuit schematic diagram of the LC bandpass filter of this utility model. Figure 2 The figure shows the simulation results of the LC bandpass filter of this invention. As can be seen from the figure, under the same order, the inductance value of the inductors involved in this invention is reduced significantly, except for inductor L2. Moreover, the proportion of large inductance values ​​is also much smaller, which is equivalent to saving a lot of space resources in inductor design and greatly optimizing the design and operation difficulty of the product.

Claims

1. An LC bandpass filter with high suppression based on an elliptic model, characterized in that, The LC bandpass filter circuit structure is as follows: one end of inductor L1 is connected to the test port of a 50-ohm characteristic impedance; the other end of inductor L1 is connected to one end of capacitors C1 and C2 respectively; the other end of capacitor C2 is connected to one end of inductor L2, capacitor C3, and inductor L3 and capacitor C4 connected in parallel respectively; the other ends of inductor L3 and capacitor C4 connected in parallel are connected to one end of capacitor C5, inductor L4 and capacitor C6 connected in parallel respectively; and the other ends of inductor L4 and capacitor C6 connected in parallel are connected to inductor L5, inductor C5, inductor C6 ... Connect one end of capacitor C7, parallel inductor L6, and capacitor C8. Connect the other end of parallel inductor L6 and capacitor C8 to one end of capacitor C9, parallel inductor L7, and capacitor C10. Connect the other end of parallel inductor L7 and capacitor C10 to one end of inductor L8, capacitor C11, and the 50-ohm characteristic impedance test port. Connect the other ends of capacitor C1, inductor L2, capacitor C3, capacitor C5, inductor L5, capacitor C7, capacitor C9, inductor L8, and capacitor C11 to GND respectively.

2. The LC bandpass filter with high suppression based on an elliptic model according to claim 1, characterized in that, The inductance values ​​of inductors L1, L2, L3, L4, L5, L6, L7, and L8 are 59.4 nH, 84.37 nH, 38.5 nH, 9.2 nH, 4.60 nH, 15.10 nH, 6.80 nH, and 3.5 nH, respectively.

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