WO2022217971A1

WO2022217971A1 - Lc filter

Info

Publication number: WO2022217971A1
Application number: PCT/CN2021/141614
Authority: WO
Inventors: 赖志国; 刘海瑞; 杨清华; 唐兆云
Original assignee: 苏州汉天下电子有限公司
Priority date: 2021-04-16
Filing date: 2021-12-27
Publication date: 2022-10-20
Also published as: CN113098423A

Abstract

An LC filter. The LC filter comprises: an input port, an output port, a series branch and at least two resonators, wherein two ends of the series branch are respectively connected to the input port and the output port; the at least two resonators are connected in parallel to the series branch, and each of the resonators comprise a first inductor and a first capacitor, which are connected in parallel; and the series branch is provided with a series unit at a position between two adjacent resonators, and the series unit is a second capacitor, or the series unit is a second inductor. The LC filter has the characteristics of being easily integrated on a chip and having great near stopband suppression performance.

Description

an LC filter

technical field

The present invention relates to the technical field of electronic communication devices, in particular to an LC filter.

Background technique

LC filters are one of the key components of modern communication equipment and are currently widely used in mobile communication applications such as 4G and 5G.

In the prior art, omnipolar LC filters and elliptical LC filters are the two most common types of LC filters at present, both of which are usually composed of series resonators and parallel resonators. It consists of inductors and capacitors. Among them, the omnipolar LC filter has no out-of-band zeros, so the near-stop-band suppression is weak. In addition, the omnipolar LC filter also has the problem that the inductance value in some resonators is too large (usually it can reach more than 10nH or even higher). Those skilled in the art know that the size of an inductor is proportional to its inductance value, that is, the larger the inductance value, the larger the size of the inductor. When the inductor value exceeds a certain value (usually 5nH), the size of the inductor is no longer easy to implement on-chip integration. That is, the existing omnipolar LC filter has a problem that it is not easy to integrate on-chip. Compared with the omnipolar LC filter, the elliptical LC filter can improve the near-stop-band suppression to a certain extent by introducing an out-of-band zero point, but the inductance value of some resonators is too large and it is not easy to integrate on-chip. Still can't get it resolved.

SUMMARY OF THE INVENTION

In order to overcome the above-mentioned defects in the prior art, the present invention provides an LC filter, which comprises:

an input port, an output port, a series branch, and at least two resonators;

Both ends of the series branch are respectively connected to the input port and the output port;

the at least two resonators are connected in parallel to the series branch, wherein each of the resonators includes a first inductor and a first capacitor connected in parallel;

The series branch is provided with a series unit at a position between two adjacent resonators, and the series unit is a second capacitor, or the series unit is a second inductor.

According to an aspect of the present invention, in the LC filter, the number of the resonators is N, and the number of the series units is N-1, where N is an integer and N≥2; the input port side To the output port side, the first inductance in the i-th resonator has the same inductance value as the first inductance in the N+1-i-th resonator, and the i-th resonator has the same inductance value. The first capacitor has the same capacitance value as the first capacitor in the N+1-ith resonator, wherein, if N is an even number, 1≤i≤N/2, and if N is an odd number, 1≤i ≤(N-1)/2; from the input port side to the output port side, the jth series unit and the N-jth series unit have the same capacitance or inductance value, wherein, if N is 1≤j≤N/2-1 for an even number, and 1≤j≤(N-1)/2 if N is an odd number.

According to another aspect of the present invention, in the LC filter, for the case where the series unit is the second capacitor, the first inductances in the at least two resonators have the same inductance value; For the case where the series unit is the second inductor, the first capacitors in the at least two resonators all have the same capacitance value.

According to another aspect of the present invention, in the LC filter, the inductance values of the first inductor and the second inductor are both less than or equal to 5nH.

According to still another aspect of the present invention, in the LC filter, for the case where the series unit is the second capacitor, there is a coupling between the first inductors in at least two of the resonators.

According to yet another aspect of the present invention, in the LC filter, when the number of the resonators is greater than or equal to 4, there is a coupling between the first inductances in the resonators of at least two non-adjacent orders. .

According to still another aspect of the present invention, in the LC filter, there exists a gap between the first inductance of the first resonator and the last one of the resonators from the input port side to the output port side. coupling.

According to still another aspect of the present invention, in the LC filter, one of the first resonator from the input port side to the output port side and the first inductance in the penultimate resonator There is coupling between the two resonators from the input port side to the output port side and the first inductance in the last one of the resonators; or the input port side to There is a coupling between the first of the resonators on the output port side and the first inductance in the penultimate one of the resonators, and between the second and the last of the resonators There is coupling between the first inductors.

According to still another aspect of the present invention, in the LC filter, there exists a gap between the first inductance of the first resonator and the last one of the resonators from the input port side to the output port side. coupling, and there is a coupling between the first inductance in the first of the resonators and the penultimate one of the resonators; or the first of the resonances from the input port side to the output port side there is a coupling between the resonator and the first inductance in the last of the resonators, and there is a coupling between the second of the resonators and the first inductance in the last of the resonators; or the There is coupling between the first inductance of the first said resonator and the last one of the resonators from the input port side to the output port side, the first said resonator and the second to last said There is a coupling between the first inductances in a resonator and a coupling between the first inductances in the second of the resonators and the last of the resonators.

According to yet another aspect of the present invention, the LC filter further includes a third capacitor, the third capacitor is disposed on the series branch, at the input port and the first side from the input port side to the output port side Between each of the resonators; and/or a fourth capacitor, the fourth capacitor is provided on the series branch, the last resonator and the output from the input port side to the output port side between ports.

The LC filter provided by the present invention includes an input port, an output port, a series branch, and at least two resonators; two ends of the series branch are respectively connected to the input port and the output port; the At least two resonators are connected in parallel to the series branch, wherein each of the resonators includes a first inductor and a first capacitor connected in parallel; the series branch is located between two adjacent resonators A series unit is arranged at the position of , and the series unit is the second capacitor or the series unit is the second inductor. In the case of the same operating frequency, compared with the existing LC filter, the LC filter provided by the present invention has a certain improvement in the near-stop-band suppression. At the same time, all the inductances of the LC filter provided by the present invention can be realized by a small inductance value. That is to say, compared with the existing LC filter, the LC filter provided by the present invention is easier to realize on-chip integration.

Description of drawings

Other features, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

1 is a circuit diagram of a typical omnipolar LC filter in the prior art;

2 is a circuit diagram of a typical elliptical LC filter in the prior art;

Fig. 3 is the amplitude-frequency response curve of the omnipolar LC filter shown in Fig. 1;

Fig. 4 is the amplitude-frequency response curve of the elliptic LC filter shown in Fig. 2;

5 is a circuit diagram of an LC filter according to a preferred embodiment of the present invention;

6 is a circuit diagram of an LC filter according to another preferred embodiment of the present invention;

Fig. 7 is the amplitude frequency response curve of the LC filter shown in Fig. 5;

Fig. 8 is the amplitude frequency response curve of the LC filter shown in Fig. 6;

Fig. 9 is the amplitude-frequency response curve after introducing coupling between the first resonator in the structure shown in Fig. 5 and the first inductance in the last resonator;

Fig. 10 shows the coupling introduced between the first resonator and the first inductance in the last resonator of the structure shown in Fig. 5, and the introduction between the first inductance in the first resonator and the penultimate resonator The coupled amplitude-frequency response curve;

FIG. 11 is a circuit diagram of an LC filter according to yet another preferred embodiment of the present invention.

The same or similar reference numbers in the drawings represent the same or similar parts.

Detailed ways

In order to better understand and explain the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

The present invention provides a kind of LC filter, this LC filter comprises:

an input port, an output port, a series branch, and at least two resonators;

Hereinafter, each component of the above-mentioned LC filter will be described in detail.

Specifically, the LC filter provided by the present invention includes an input port and an output port, the input port is used for inputting the signal to be filtered, and the output port is used for outputting the signal of a specific frequency obtained after filtering.

The LC filter provided by the present invention further includes a series branch and at least two resonators. The one series branch is arranged between the input port and the output port, that is, one end of the series branch is connected to the input port and the other end is connected to the output port. The at least two resonators are connected in parallel to the series branch, that is, one end of the resonator is connected to the series branch and the other end is grounded. In this embodiment, the resonator includes an inductance (referred to as a first inductance hereinafter) and a capacitance (referred to as a first capacitance hereinafter), wherein the first inductance and the second capacitor are connected in parallel. On the series branch, a series unit is arranged at a position between two adjacent resonators. Specifically, if the number of resonators is two, a series unit is provided on the series branch, two ends of the series unit are respectively connected to the input port and the output port, and a resonator is connected in parallel between the input port and the series unit On the node of , another resonator is connected in parallel to the node between the series unit and the output port. If the number of resonators is greater than two, at least two series units are provided on the series branch, wherein the specific number of series units should be one less than the number of resonators. In this case, a plurality of series units are connected in series, wherein the input terminal of the first series unit is connected to the input port, the output terminal of the last series unit is connected to the output port, and the resonators are connected in parallel to the input port and the first series unit respectively. On the node between two series units, on the node between two adjacent series units, and on the node between the last series unit and the output port. In this embodiment, all the series units on the series branch are capacitors (represented by the second capacitor below), or alternatively, all the series units on the series branch are inductors (represented by the second inductance below).

Based on the LC filter with the above structure, all the first inductors and all the second inductors can be implemented by using inductors with relatively small inductance values. Specifically, the inductance values of all the first inductors and all the second inductors do not exceed 5nH.

When the existing omnipolar LC filter and the LC filter provided by the present invention work at the same frequency, all the inductances of the LC filter provided by the present invention can be realized by a small inductance value, and can be completely realized by on-chip integrated to achieve. That is to say, compared with the existing omnipolar LC filter, the LC filter provided by the present invention is easier to realize on-chip integration. At the same time, the near-stopband suppression of the LC filter provided by the present invention is also enhanced.

Preferably, the LC filter provided by the present invention has symmetry in structure. Specifically, since a series unit is disposed between two adjacent resonators, the number of resonators is one more than the number of series units. It is assumed that the number of resonators is N and the number of series units is N-1, where N is an integer and 2 or more. The symmetry of the LC filter in this embodiment means: for the resonator, from the input port side to the output port side, the first inductance in the i-th resonator and the N+1-i-th resonator in the The first inductance has the same inductance value, and the first capacitor in the i-th resonator has the same capacitance value as the first capacitor in the N+1-i-th resonator, where, if N is an even number, 1≤i ≤N/2, if N is an odd number, 1≤i≤(N-1)/2. For the series unit, the jth series unit and the N-jth series unit have the same capacitance value or inductance value, wherein, if N is an even number, 1≤j≤N/2-1, if N is an odd number, then 1 ≤j≤(N-1)/2. For example, the number of resonators is 4 and the number of series units is 3 (ie, N=4). From the input port side to the output port side, in the first resonator and the fourth resonator, the inductance value of the first inductor is the same, the capacitance value of the first capacitor is the same, and the second resonator and the third resonator have the same inductance value. One inductor has the same inductance value, the first capacitor has the same capacitance value, and the first series unit and the third series unit have the same capacitance value or the same inductance value. For example, the number of resonators is 5 and the number of series units is 4 (ie, N=5). From the input port side to the output port side, the inductance value of the first inductor and the capacitance value of the first capacitor in the first resonator and the fifth resonator are the same, and the capacitance value of the first capacitor in the second resonator and the fourth resonator is the same. One inductor has the same inductance value, the first capacitor has the same capacitance value, the first series unit and the fourth series unit have the same capacitance value or the same inductance value, the second series unit and the third series unit have the same capacitance value or the same inductance value. The symmetry of the LC filter structure can effectively simplify the design of the LC filter and bring convenience to the design of the LC filter.

In the case where the LC filter structure has symmetry, more preferably, for the case where the series unit in the LC filter is the second capacitor, the first inductances in all the resonators are designed to have the same inductance value. For the case where the series unit in the LC filter is the second inductor, the first capacitors in all the resonators are designed to have the same capacitance value. In this way, the design of the LC filter can be further simplified. Of course, those skilled in the art can understand that in the case where the LC filter does not have structural symmetry, when the series unit is the second capacitor, the first inductances in all the resonators can also be designed to have the same inductance value; when the series unit is the second inductor, the first capacitors in all resonators can also be designed to have the same capacitance value. Although the structure of the LC filter is not asymmetric, but all the first inductors have the same inductance value, or all the first capacitors have the same capacitance value, the design of the LC filter can be simplified to a certain extent.

The LC filter provided by the present invention will be described below with specific embodiments in conjunction with FIGS. 1 to 8 .

Four LC filters are designed, represented by LC filter 1, LC filter 2, LC filter 3 and LC filter 4, respectively. Wherein, the LC filter 1 is a typical omnipolar LC filter in the prior art, the LC filter 2 is a typical elliptical filter in the prior art, and the LC filter 3 and the LC filter 4 are both of the present invention. The provided LC filter differs in that the series unit in the LC filter 3 is the second capacitor, and the series unit in the LC filter 4 is the second inductor. The four LC filters are suitable for 5G communications, and their operating frequency bands are all 4.4GHz to 5GHz.

As shown in FIG. 1, the LC filter 1 includes an input port, an output port, two series resonators connected in series between the input port and the output port, and two parallel resonators connected in parallel between the input port and the output port device. The two series resonators are respectively a series resonator S _A1 and a series resonator S _A2 , wherein the series resonator S _A1 is composed of a series inductance L _A2 and a capacitor C _A2 , and the series resonator S _A2 is composed of a series inductance L _A4 and capacitor C _A4 . The two parallel resonators are the parallel resonator P _A1 and the parallel resonator P _A2 respectively, the parallel resonator P _A1 is connected in parallel to the node between the input port and the resonator S _A1 , and the parallel resonator P _A2 is connected in parallel with the series resonator S on the node between _A1 and the series resonator S _A2 . The parallel resonator P _A1 is composed of the parallel inductance L _A1 and the capacitor C _A1 , and the parallel resonator P _A2 is composed of the parallel inductance L _A3 and the capacitor C _A3 . Among them, the inductance value of the inductor L _A2 in the series resonator S _A1 is 16.31nH, the capacitance value of the capacitor C _A2 is 73.4fF, the inductance value of the inductor L _A4 in the series resonator S _A2 is 10.57nH, and the capacitance value of the capacitor C _A4 is 10.57nH. is 113.3fF; the inductance value of the inductor _LA1 in the parallel resonator P _A1 is 283.2pH, the capacitance value of the capacitor C _A1 is 4.228pF, the inductance value of the inductor L _A3 in the parallel resonator P _A2 is 183.5pH, and the capacitance value of the capacitor C _A3 The value is 6.524pF.

As shown in FIG. 2, the LC filter 2 includes an input port, an output port, two series resonators connected in series between the input port and the output port, and three parallel resonators connected in parallel between the input port and the output port device. The two series resonators are respectively a series resonator S _B1 and a series resonator S _B2 , wherein the series resonator S _B1 is composed of a series inductance L _B2 and a capacitor C _B2 , and the series resonator S _B2 is composed of a series inductance L _B5 and capacitor C _B5 . The three parallel resonators are the parallel resonator P _B1 , the parallel resonator P _B2 , and the parallel resonator P _B3 , respectively. The parallel resonator PB1 is connected in parallel to the node between the input port and the resonator _SB1 , and the parallel resonator _PB2 and the parallel resonator _PB3 are connected in parallel to the _node between the series resonator _SB1 and the series resonator _SB2 . The parallel resonator P _B1 is composed of an inductance L _B1 and a capacitor C _B1 connected in parallel, the parallel resonator P _B2 is composed of an inductance L _B3 and a capacitor C _B3 connected in series, and the parallel resonator P _B3 is composed of an inductance L _B4 and a capacitor C _B4 connected in series . Among them, the inductance value of the inductor L _B2 in the series resonator S _B1 is 19.58nH, the capacitance value of the capacitor C _B2 is 58.56fF, the inductance value of the inductor L _B5 in the series resonator S _B2 is 7.253nH, and the capacitance value of the capacitor C _B5 is 7.253nH. is 158.1fF; the inductance value of inductor _LB1 in parallel resonator P _B1 is 339.4pH, the capacitance value of capacitor C _B1 is 3.379pF, the inductance value of inductor L _B3 in parallel resonator P _B2 is 3.075nH, and the capacitance value of capacitor C _B3 is 3.075nH The value is _528.3fF , the inductance value of the inductor LB4 in the parallel resonator P _B3 is 2.17nH, and the capacitance value of the capacitor C _B4 is 372.9F.

As shown in FIG. 5, the LC filter 3 includes an input port, an output port, three second capacitors connected in series between the input port and the output port, and four resonators connected in parallel between the input port and the output port . The three second capacitors are a second capacitor C ₅ , a second capacitor C ₆ and a second capacitor C ₇ in sequence from the input port side to the output port side. The three resonators are respectively the resonator P ₁ , the resonator P ₂ , the resonator P ₃ and the resonator P ₄ , wherein the resonator P ₁ is connected in parallel to the node between the input port and the second capacitor C ₅ , and the resonator P2 is connected in parallel to the node between the _second capacitor _C5 and the second capacitor _C6 , the resonator _P3 is connected in parallel to the node between the second capacitor _C6 and the second capacitor _C7 , and the resonator P4 is connected in parallel to the node between the second capacitor C6 and the second capacitor C7 _. _on the node between the second capacitor C7 and the output port. _The resonator P1 is composed of the first inductor L1 and the _first capacitor _C1 connected in parallel, the resonator P2 is composed of the _first inductor L2 and the first capacitor _C2 connected in parallel, and the resonator _P3 is composed _of the first inductor connected in parallel. L ₃ and a first capacitor C ₃ are formed, and the resonator P ₄ is formed by a first inductance L ₄ and a first capacitor C ₄ connected in parallel. The capacitance values of the second capacitor C ₅ , the second capacitor C ₆ and the second capacitor C ₇ are respectively 551.1fF, 443.6fF and 551.1fF; the first inductor L ₁ , the first inductor L ₂ , and the first inductor L ₃ and the inductance values of the first inductor L ₄ are the same as 277.1pH; the capacitance values of the first capacitor C ₁ , the first capacitor C ₂ , the first capacitor C ₃ and the first capacitor C ₄ are 3.677pF, 3.233pF, 3.233pF and 3.677pF.

The difference between the LC filter 4 shown in FIG. 6 and the LC filter 3 shown in FIG. 5 is only that the series unit is the second inductor, that is, the second inductor L ₅ , the second inductor L ₆ and the second inductor L ₇ are used respectively. The structure of the LC filter 4 shown in FIG. 6 can be obtained by replacing the second capacitor C ₅ , the second capacitor C ₆ and the second capacitor C ₇ in FIG. 5 . For the sake of brevity, the structure of the LC filter 4 will not be described in detail here. The inductance values of the second inductance L ₅ , the second inductance L ₆ and the second inductance L ₇ are 2.09nH, 2.596nH and 2.09nH respectively; the first inductance L ₁ , the first inductance L ₂ and the first inductance L ₃ And the inductance values of the first inductance L4 are _307.2nH , 348.4nH, 348.4nH and 307.2nH, respectively. The capacitance values of the first capacitor C ₁ , the first capacitor C ₂ , the first capacitor C ₃ and the first capacitor C ₄ are all 4.228pF.

Please refer to FIG. 3, FIG. 4, FIG. 7 and FIG. 8, wherein, FIG. 3 is the amplitude-frequency response curve of the omnipolar LC filter shown in FIG. 1, and FIG. 4 is the amplitude-frequency response curve of the elliptical LC filter shown in FIG. 2 Response curve, Figure 7 is the amplitude-frequency response curve of the LC filter shown in Figure 5, and Figure 8 is the amplitude-frequency response curve of the LC filter shown in Figure 6.

It can be seen from the comparison that there are inductances with large inductance values in the LC filter 1, such as the inductance values of the inductance L _A2 and the inductance L _A4 are much larger than 5nH, which makes the LC filter 1 difficult to integrate on-chip. In addition, it can be seen from FIG. 3 that the near stopband suppression of LC filter 1 is weak. LC filter 2 has improved near-stop-band rejection compared to LC filter 1 due to the introduction of zeros in both the left and right near-stop bands (as can be seen in Figure 4). However, there are still inductances with large inductance values in the LC filter 2, for example, the inductance values of the inductance L _B2 and the inductance L _B5 are both larger than 5nH (the inductance value of the inductance L _B2 is much larger than 5nH). All inductances (including the first inductance and the second inductance) in the LC filter 3 have inductance values lower than 1 nH. The inductance values of all the inductances (including the first inductance and the second inductance) in the LC filter 4 are lower than 3nH. That is, compared with the prior art, the LC filter provided by the present invention is easier to realize on-chip integration. In terms of performance, it can be seen from Figure 7 and Figure 8 that compared to LC filter 1, LC filter 3 has enhanced roll-off at the left edge and near stopband suppression on the left, and LC filter 4 is at the right edge. The roll-off and near stopband rejection on the right is enhanced.

Preferably, for the LC filter provided by the present invention in which the series unit is the second capacitor, there are at least two resonators, and coupling exists between the first inductors in the two resonators. By introducing coupling between the first inductances of the resonators, a zero can be introduced near the stop band to further enhance edge roll-off and near stop band rejection. Wherein, through a reasonable design of the position of the first inductance in the resonator (for example, setting the first inductances that need to be coupled in close proximity, etc.), the coupling can be formed between the first inductances. Those skilled in the art can understand that the above-mentioned method of introducing coupling by reasonably designing the position of the first inductance is only a preferred embodiment, and in other embodiments, the first inductance can also be realized by means of magnetic circuit coupling or circuit coupling coupling between. In addition, the coupling coefficient between the first inductances needs to be set according to actual design requirements, which is not limited herein. More preferably, when the number of resonators is greater than or equal to 4, the resonators with coupling are not adjacent, that is, there is coupling between the first inductances in the resonators of non-adjacent orders. More preferably, the number of resonators is an even number of 4 or more. In a preferred embodiment, there is a coupling between the first resonator from the input port side to the output port side and the first inductance in the last resonator, which introduces a zero near the stopband on the left, further making the left Edge roll-off and near stopband rejection on the left are enhanced. In another preferred embodiment, there is a coupling between the first resonator from the input port side to the output port side and the first inductance in the penultimate resonator, which introduces a zero on the right near the stop band, thereby The right edge roll-off and the right near stopband suppression are further enhanced. In yet another preferred embodiment, there is a coupling between the first resonator and the first inductance in the last resonator from the input port side to the output port side, and between the first resonator and the penultimate resonator There is coupling between the first inductances of Near stopband rejection is enhanced.

Still take the LC filter shown in Figure 5 as an example. On the basis of the LC filter shown in Figure 5, coupling is introduced between the first inductor L ₁ and the first inductor L ₄ (the coupling coefficient is equal to 1%), and the amplitude-frequency response curve of the LC filter after the coupling is introduced is shown in Figure 9 shown. It can be seen from Fig. 9 that, compared with the LC filter without coupling as shown in Fig. 5, the roll-off of the left edge and the suppression of the left near stop band of the LC filter with coupling are further enhanced. On the basis of the LC filter shown in FIG. ₅ , a coupling (coupling coefficient equal to ₁ %) is introduced between the first inductance L1 and the _first inductance L4, and between the first inductance L1 and the _first inductance L3 When coupling is introduced (coupling coefficient is equal to 3.7%), the amplitude-frequency response curve of the LC filter after the coupling is introduced is shown in Figure 10. It can be seen from Figure 10 that, compared with the LC filter without coupling as shown in Figure 5, the roll-off of the left edge and the near-stopband suppression on the left side of the LC filter with the introduction of coupling, as well as the roll-off of the right edge and the right near stopband rejection are further enhanced.

For the case where the LC filter has structural symmetry, except by passing between the first inductance in the first resonator and the last resonator, and in the first resonator and the penultimate resonator In addition to introducing the zero point by introducing coupling between the first inductances of , it is also possible to introduce coupling between the first inductances in the second resonator and the last resonator. By introducing coupling between the second resonator from the input port side to the output port side and the first inductor in the last resonator, a zero point can be introduced near the stop band on the right side, so that the roll-off of the right edge and the suppression of the near stop band on the right side are obtained. strengthen. In a specific embodiment, there is a coupling between the second resonator from the input port side to the output port side and the first inductance in the last resonator, so that the right edge roll-off and the right near stopband rejection are enhanced. In another specific embodiment, there is coupling between the first resonator and the first inductance in the penultimate resonator from the input port side to the output port side, and between the second resonator and the last resonator There is a coupling between the first inductances of , so that the right edge roll-off and the right near stopband rejection are enhanced. In yet another specific embodiment, there is coupling between the first resonator and the first inductance in the last resonator from the input port side to the output port side, and the second resonator and the first inductance in the last resonator There is a coupling between an inductor such that the left edge roll-off and left near-stopband rejection, and the right-edge roll-off and right near-stopband rejection are enhanced. In yet another specific embodiment, there is a coupling between the first resonator and the first inductance in the last resonator from the input port side to the output port side, the coupling between the first resonator and the penultimate resonator There is a coupling between the first inductance, and between the second resonator and the first inductance in the last resonator, such that the left edge roll-off and the left near-stop band rejection, and the right edge roll-off and the right near-stop Band inhibition is enhanced.

It should be noted that, introducing coupling between the first inductance in the first resonator and the last resonator, and between the first inductance in the first resonator and the penultimate resonator, can be The left and right near stopbands respectively introduce zeros. between the first inductance in the first resonator and the last resonator, between the first resonator and the first inductance in the penultimate resonator, and between the second resonator and the last resonator Coupling is introduced between the first inductors in , and zeros can also be introduced into the left and right near stopbands respectively. Wherein, by adjusting the coupling coefficient between the first inductances, the specific position of the zero point and the magnitude of the suppression outside the zero point can be adjusted. Although the above two methods can introduce zero points on the left and right near stopbands respectively, the former method is to introduce zero points through the coupling between two groups of first inductors, and the latter method is to introduce zero points through three groups of first inductors coupling between to introduce zeros. Compared with the former method, since the latter method introduces more coupling between a group of first inductors, on the one hand, it can make the adjustment of the zero point position and the suppression outside the zero point more flexible, on the other hand It is also more convenient to adjust the zero point to the desired position while keeping the outboard suppression of the zero point within the desired range.

Preferably, the LC filter provided by the present invention further includes a third capacitor and/or a fourth capacitor, wherein the third capacitor is arranged on the series branch and is located at the input port and the first resonance from the input port side to the output port side Between the resonators, a fourth capacitor is provided on the series branch between the last resonator from the input port side to the output port side and the output port. The third capacitor helps to adjust the impedance matching of the input port, and the fourth capacitor helps to adjust the impedance matching of the output port. Wherein, whether to set only the third capacitor or the fourth capacitor, or to set the third capacitor and the fourth capacitor at the same time, and the specific parameters of the third capacitor and the fourth capacitor need to be set according to actual design requirements, which is not limited herein. Describe with a specific embodiment. Please refer to FIG. 11 . FIG. 11 is based on the LC filter shown in FIG. 5 . A third capacitor C _p1 is set at the input port and a fourth capacitor C _p2 is set at the output port. The third capacitor C _p1 is set at the input port. And between the connection node of the resonator P ₁ and the series branch, a fourth capacitance C _p2 is provided between the output port and the connection node of the resonator P ₄ and the series branch. It can be understood by those skilled in the art that FIG. 11 is only a schematic example. For an LC filter with coupling between the first inductances of the resonators, the settings of the third capacitor and the fourth capacitor are also applicable. This is not an exhaustive list of all possible LC filter structures.

It will be apparent to those skilled in the art that the present invention is not limited to the details of the above-described exemplary embodiments, but that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments are to be regarded in all respects as illustrative and not restrictive, and the scope of the invention is to be defined by the appended claims rather than the foregoing description, which are therefore intended to fall within the scope of the claims. All changes within the meaning and range of the equivalents of , are included in the present invention. Any reference signs in the claims shall not be construed as limiting the involved claim. Furthermore, it is clear that the word "comprising" does not exclude other elements, units or steps and the singular does not exclude the plural. Several means, units or means recited in the system claims can also be implemented by one means, unit or means by means of software or hardware.

The above disclosures are only some preferred embodiments of the present invention, which of course cannot limit the scope of the rights of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

An LC filter comprising:

an input port, an output port, a series branch, and at least two resonators;

Both ends of the series branch are respectively connected to the input port and the output port;

the at least two resonators are connected in parallel to the series branch, wherein each of the resonators includes a first inductor and a first capacitor connected in parallel;

The series branch is provided with a series unit at a position between two adjacent resonators, and the series unit is a second capacitor, or the series unit is a second inductor.
The LC filter of claim 1, wherein:

The number of the resonators is N, and the number of the series units is N-1, where N is an integer and N≥2;

From the input port side to the output port side, the first inductance in the i-th resonator has the same inductance value as the first inductance in the N+1-i-th resonator, and the i-th inductance has the same inductance value. The first capacitor in the resonator has the same capacitance value as the first capacitor in the N+1-ith resonator, wherein, if N is an even number, 1≤i≤N/2, if N is an even number For odd numbers, 1≤i≤(N-1)/2;

From the input port side to the output port side, the jth series unit and the N-jth series unit have the same capacitance value or inductance value, wherein, if N is an even number, 1≤j≤N/2 -1, if N is odd, then 1≤j≤(N-1)/2.
LC filter according to claim 1 or 2, wherein:

For the case where the series unit is the second capacitor, the first inductances in the at least two resonators have the same inductance value;

For the case where the series unit is the second inductor, the first capacitors in the at least two resonators all have the same capacitance value.
LC filter according to claim 1 or 2, wherein:

The inductance values of the first inductance and the second inductance are both less than or equal to 5nH.
LC filter according to claim 1 or 2, wherein:

For the case where the series unit is the second capacitor, there is a coupling between the first inductances in at least two of the resonators.
The LC filter of claim 5, wherein:

When the number of the resonators is greater than or equal to 4, there is a coupling between the first inductances in at least two non-adjacent orders of the resonators.
The LC filter of claim 6, wherein:

There is a coupling between the first inductance in the first of the resonators and the last of the resonators from the input port side to the output port side.
The LC filter of claim 6, wherein:

there is a coupling between the first inductance in the first of the resonators and the penultimate one of the resonators from the input port side to the output port side; or

There is a coupling between the first inductance in the second of the resonators and the last of the resonators from the input port side to the output port side; or

There is a coupling between the first inductance of the first said resonator and the second to last said resonator from the input port side to the output port side, and the second said resonator and the last There is a coupling between the first inductances in one of the resonators.
The LC filter of claim 6, wherein:

There is a coupling between the first inductance of the first said resonator and the last one of the resonators from the input port side to the output port side, and the first said resonator and the penultimate There is coupling between the first inductances in the resonators; or

There is a coupling between the first inductance in the first of the resonators and the last of the resonators from the input port side to the output port side, and the second of the resonators and the last of the resonators. there is coupling between the first inductances in the resonator; or

There is a coupling between the first inductance of the first said resonator and the last one of the resonators from the input port side to the output port side, the first said resonator and the second to last said resonator. There is coupling between the first inductances in the resonators, and coupling between the first inductances in the second and last of the resonators.
The LC filter of claim 5, further comprising:

a third capacitor provided on the series branch between the input port and the first resonator from the input port side to the output port side; and/or

a fourth capacitor, which is provided on the series branch between the last resonator and the output port from the input port side to the output port side.