CN216981874U - Filter circuit and multiplexer - Google Patents

Abstract

The embodiment of the utility model discloses a filter circuit and a multiplexer, wherein the filter circuit comprises a first end, a second end and at least one branch circuit arranged between the first end and the second end; the branch comprises at least one LC parallel unit and at least one capacitive device; one end of the capacitive element is connected between the first end and the second end, the other end of the capacitive element is connected with one end of the LC parallel unit, and the other end of the LC parallel unit is connected with a first potential end; the other end of the LC parallel unit is connected with the first potential end through the inductive device. The filter circuit provided by the embodiment of the utility model can generate a plurality of transmission zeros in the frequency response, so that the problem that the existing filter circuit is small in the number of the transmission zeros is solved, and the performance of the filter is favorably improved.

Description

Filter circuit and multiplexer

Technical Field

The embodiment of the utility model relates to the technical field of filtering, in particular to a filtering circuit and a multiplexer.

Background

In the field of filtering, a filter circuit having a plurality of transmission zeros is one of the important research directions of designers. How to generate a plurality of transmission zeros on the topology structure of the filter circuit or in the layout design process is a core idea considered by designers.

With the increasing miniaturization of filter circuits and filters, how to generate as many transmission zeros as possible in a limited layout space has become a great challenge for designers. At present, the number of transmission zero points of the existing filter circuit is small, and the performance of the filter is difficult to effectively improve.

SUMMERY OF THE UTILITY MODEL

Embodiments of the present invention provide a filter circuit and a multiplexer, so as to generate a plurality of transmission zeros in a frequency response of the filter circuit, which is beneficial to improving performance of a filter.

In a first aspect, an embodiment of the present invention provides a filter circuit, including a first end, a second end, and at least one branch disposed between the first end and the second end;

the branch comprises at least one LC parallel unit and at least one capacitive device; one end of the capacitive element is connected between the first end and the second end, the other end of the capacitive element is connected with one end of the LC parallel unit, and the other end of the LC parallel unit is connected with a first potential end;

the branch circuit further comprises an inductive device, and the other end of the LC parallel unit is connected with the first potential end through the inductive device.

Optionally, the LC parallel unit includes a first capacitor and a first inductor, and the first capacitor and the first inductor are connected in parallel.

Optionally, the device further comprises a first metal plate, wherein the first metal plate is used for connecting a first potential provided by the first potential terminal; the capacitive device comprises a first polar plate, a first dielectric layer and a second polar plate which are arranged in a stacked mode, and the inductive device is formed between the capacitive device and the first metal plate.

Optionally, the first capacitor includes a third electrode plate, a second dielectric layer, and a fourth electrode plate, which are stacked, and the third electrode plate and the second electrode plate are disposed in the same layer.

Optionally, the first inductor is disposed in the same layer as the second plate.

Optionally, the capacitor further comprises a first terminal and a second terminal, the first terminal is disposed between the second metal plate and the third metal plate, and the first terminal is used for connecting one end of the first inductor and one end of the first capacitor; the second wiring terminal is arranged between the first metal plate and the second metal plate, and the second wiring terminal is used for connecting a fourth pole plate of the first capacitor and the first metal plate; the second terminal is used for forming part of the parasitic inductance.

Optionally, the resonant frequency of the capacitive device and the inductive device is the same or different from the resonant frequency of the LC parallel unit.

Optionally, a plurality of said branches are included between said first end and said second end; the resonant frequency of each of the branches may be the same or different.

Optionally, the apparatus further comprises a coupling unit connected in series between the first end and the second end.

In a second aspect, an embodiment of the present invention further provides a multiplexer, including the filter circuit according to the first aspect.

According to the technical scheme provided by the embodiment of the utility model, at least one branch circuit is arranged between the first end and the second end of the filter circuit; the filter circuit comprises at least one capacitive device, at least one LC parallel unit and an inductive device which are sequentially connected in series between a first end and a second end of the filter circuit and a first potential end, and one branch circuit can generate a plurality of transmission zeros because the capacitive device and the inductive device can generate one transmission zero and the LC parallel unit can generate one transmission zero. Therefore, the filter circuit provided by the embodiment of the utility model can generate a plurality of transmission zeros in the frequency response, so that the problem that the existing filter circuit is small in transmission zeros is solved, and the performance of the filter is improved.

Drawings

Fig. 1 is a circuit diagram of an LC parallel resonant filter circuit in the prior art;

FIG. 2 is a frequency-gain waveform diagram of the LC parallel resonant filter circuit of FIG. 1;

FIG. 3 is a circuit diagram of a prior art LC series resonant filter circuit;

FIG. 4 is a frequency-gain waveform diagram of the LC series resonant filter circuit of FIG. 3;

fig. 5 is a schematic structural diagram of a filter circuit according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of another filter circuit according to an embodiment of the present invention;

FIG. 7 is a frequency-gain waveform diagram of the filter circuit of FIG. 6;

FIG. 8 is a schematic diagram of a filter circuit according to another embodiment of the present invention;

FIG. 9 is a frequency-gain waveform diagram for the filter circuit of FIG. 8;

FIG. 10 is a schematic diagram of a multi-layer structure of a filter circuit according to an embodiment of the present invention;

fig. 11 is a schematic structural diagram of a multiplexer according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the utility model and are not to be construed as limiting the utility model. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

Just as the transmission zero point quantity of the existing filter circuit mentioned in the background art is too small, there is a technical problem that it is difficult to effectively improve the performance of the filter, and the utility model people have found through careful research that, taking the band pass filter as an example, the reason for this technical problem is that fig. 1 is a circuit diagram of an LC parallel resonance filter circuit in the prior art, fig. 2 is a frequency-gain waveform diagram of the LC parallel resonance filter circuit in fig. 1, and as seen in fig. 1 and fig. 2, it is known that the LC parallel mode on the normal branch cannot generate the transmission zero point; in addition, fig. 3 is a circuit diagram of an LC series resonant filter circuit in the prior art, fig. 4 is a frequency-gain waveform diagram of the LC series resonant filter circuit in fig. 3, and referring to fig. 3 and 4, it can be understood that the LC series mode on the normal branch can only generate one transmission zero. Therefore, the conventional filter circuit has the defect of small transmission zero number, so that the performance of the filter is difficult to effectively improve.

In order to solve the technical problems, the utility model provides the following solutions:

fig. 5 is a schematic structural diagram of a filter circuit according to an embodiment of the present invention, referring to fig. 5, the filter circuit includes a first terminal 110, a second terminal 120, and at least one branch 130 disposed between the first terminal 110 and the second terminal 120. The branch 130 comprises at least one LC parallel cell 132 and at least one capacitive device 131; one end of the capacitive element 131 is connected between the first terminal 110 and the second terminal 120, the other end of the capacitive element 131 is connected to one end of the LC parallel unit 132, and the other end of the LC parallel unit 132 is connected to the first potential terminal 134. The branch 130 further comprises an inductive device 133 and the other end of the LC parallel unit 132 is connected to a first potential terminal 134 via the inductive device 133.

Wherein the second terminal 120 is used for generating an output signal when the first terminal 110 is used for accessing an input signal, or the second terminal 120 is used for accessing an input signal when the first terminal 110 is used for generating an output signal. It is appreciated that the branch 130 disposed between the first end 110 and the second end 120 is configured to generate a plurality of transmission zeros in the frequency response of the filter circuit.

As can be seen, the LC parallel unit 132 refers to an inductor and a capacitor connected in parallel. In addition, the capacitive device 131 is a device that lags a voltage behind a current, and may be a capacitor, for example. The inductive device 133 is suitably a device that leads the voltage to the current, such as an inductor. It is understood that the first potential terminal 134 refers to a port having a specific potential value, and the potential value or the potential value of the first potential terminal 134 may be zero, in which case the first potential terminal 134 is a ground terminal.

It is noted that the capacitive device 131 is connected in series with the inductive device 133 between the first terminal 110 and the second terminal 120 via the LC parallel unit 132 and between the first potential terminal 134, whereby it can be seen that in one branch 130 the capacitive device 131, the LC parallel unit 132 and the inductive device 133 are connected in series in this order. Therefore, the capacitive device 131 and the inductive device 133 can generate one transmission zero, and the LC parallel unit 132 can generate one transmission zero, that is, one branch circuit 130 can generate a plurality of transmission zeros. It is understood that the specific number and parameters of the capacitive device 131, the LC parallel unit 132 and the inductive device 133 may be adaptively adjusted according to the number of transmission zeros to be generated by the filter circuit, which is not limited in the present invention.

In summary, in the embodiments of the present invention, at least one branch is disposed between the first end and the second end of the filter circuit, and at least one capacitive device, at least one LC parallel unit, and an inductive device are sequentially connected in series between the first end and the second end of the filter circuit and the first potential end. Therefore, the filter circuit provided by the embodiment of the utility model can generate a plurality of transmission zeros in the frequency response, so that the problem that the existing filter circuit is small in transmission zeros is solved, and the performance of the filter is improved.

It should be noted that fig. 5 exemplarily shows that the number of the branches 130 is 1, but the utility model is not limited thereto.

In addition to the above embodiments, specific configurations of the LC parallel cells, resonant frequency settings of the filter circuit, and other structural designs of the filter circuit are described below, but the present invention is not limited thereto.

Fig. 6 is a schematic structural diagram of another filter circuit provided in the embodiment of the present invention, referring to fig. 6, optionally, the LC parallel unit 132 includes a first capacitor C1 and a first inductor L1, and the first capacitor C1 is connected in parallel with the first inductor L1.

The first capacitor C1 may be an aluminum electrolytic capacitor, a chip tantalum capacitor, or the like, and the first inductor L1 may be a magnetic core, a serpentine wire, or the like, around which an enameled wire is wound. It is understood that the specific parameters of the first capacitor C1 and the first inductor L1 can be adaptively adjusted according to the frequency of the transmission zero to be generated by the LC parallel unit 132.

In addition, since specific parameters of the capacitive device 131, the inductive device 133, the first capacitor C1 and the first inductor L1 may be adaptively selected according to design requirements of the filter circuit, optionally, the resonant frequency of the capacitive device 131 and the inductive device 133 is the same as or different from the resonant frequency of the LC parallel unit 132.

It is known that the resonant frequency of the capacitive device 131 and the inductive device 133 refers to the frequency at which the capacitive device 131 and the inductive device 133 exhibit a state independent of the frequency, i.e., a pure resistance state, during the oscillation of the capacitive device 131 and the inductive device 133. Accordingly, the resonant frequency of the LC parallel unit 132 is a frequency at which the first capacitor C1 and the first inductor L1 exhibit a state independent of the frequency, that is, a pure resistance state, while the first capacitor C1 and the first inductor L1 oscillate.

Based on this, the calculation formula of the resonance frequency is shown in formula (1):

where f is the resonant frequency, L is the inductance, and C is the capacitance.

It is understood that for the capacitive device 131 and the inductive device 133, f of equation (1) represents the resonant frequency of the capacitive device 131 and the inductive device 133, L represents the inductance value of the inductive device 133, and C represents the capacitance value of the capacitive device 131; for the LC parallel unit 132, f of equation (1) represents the resonance frequency of the LC parallel unit 132, L represents the inductance value of the first inductor L1, and C represents the capacitance value of the first capacitor C1.

As can be seen from equation (1), when the product of the capacitance value of the capacitive device 131 and the inductance value of the inductive device 133 is equal to the product of the capacitance value of the first capacitor C1 and the inductance value of the first inductor L1, the resonant frequency of the capacitive device C1 and the inductive device L1 is the same as the resonant frequency of the LC parallel unit 132, and at this time, the filter circuit has only one transmission zero. Adaptively, when the product of the capacitance value of the capacitive device 131 and the inductance value of the inductive device 133 is not equal to the product of the capacitance value of the first capacitor C1 and the inductance value of the first inductor L1, the resonant frequency of the capacitive device 131 and the inductive device 133 is different from the resonant frequency of the LC parallel unit 132, and the filter circuit has two transmission zeros, that is, one transmission zero is generated at each of the low frequency end and the high frequency end of the pass band of the filter circuit. It can be understood that the absolute value of the gain of the filter circuit is larger and the filtering effect is superior when the resonance frequency of the capacitive device 131 and the inductive device 133 is the same as the resonance frequency of the LC parallel unit 132, compared to the case where the resonance frequency of the capacitive device 131 and the inductive device 133 is different from the resonance frequency of the LC parallel unit 132.

Optionally, the filter circuit further comprises a coupling unit 140, and the coupling unit 140 is connected in series between the first terminal 110 and the second terminal 120.

Wherein the coupling unit 140 is used to widen the bandwidth of the filter circuit, for example, the coupling unit 140 may be, but is not limited to, a capacitor.

With continued reference to fig. 6, according to the connection relationship between the filter circuit and the coupling units 140, it can be known that, assuming that the number of branches 130 in the filter circuit is n, the number of coupling units 140 is n + 1.

Based on the filter circuit shown in fig. 6, fig. 7 is a frequency-gain waveform diagram of the filter circuit shown in fig. 6, and referring to fig. 7, it can be known that, at this time, the filter circuit has two transmission zeros, that is, the product of the capacitance value of the capacitive device 131 and the inductance value of the inductive device 133 is unequal to the product of the capacitance value of the first capacitor C1 and the inductance value of the first inductor L1, that is, the resonant frequency of the capacitive device 131 and the inductive device 133 is different from the resonant frequency of the LC parallel unit 132.

In summary, in the embodiment of the present invention, the plurality of coupling units are disposed between the first end and the second end of the filter circuit, so that the bandwidth of the filter circuit is widened, and the filtering effect of the filter circuit is optimized. In addition, the embodiment of the utility model can also set the parameters of the capacitive device, the inductive device and the first capacitor and the first inductor in the LC parallel unit, so that the resonant frequency of the capacitive device and the inductive device is the same as or different from the resonant frequency of the LC parallel unit, and the filter circuit can generate one or more transmission zeros. Based on this, the filter circuit provided by the embodiment of the utility model can generate a plurality of transmission zeros in the frequency response, so that the problem that the existing filter circuit has a small number of transmission zeros is solved, and the performance of the filter is improved.

It should be noted that fig. 6 exemplarily shows that the number of the coupling units 140 is 2, but the utility model is not limited thereto.

In addition to the above embodiments, the number of branches of the filter circuit and the resonance characteristics will be described below, but the present invention is not limited thereto.

Fig. 8 is a schematic structural diagram of another filter circuit provided in an embodiment of the present invention, referring to fig. 8, optionally, a plurality of branches 130 are included between the first end 110 and the second end 120, and a resonant frequency of each branch 130 is the same or different.

The resonant frequency of each branch 130 is the same, which means that the product of the capacitance value of the capacitive device 131 and the inductance value of the inductive device 133 in each branch 130 and the product of the capacitance value of the first capacitor C1 and the inductance value of the first inductor L1 are all equal. Adaptively, the difference of the resonant frequency of each branch 130 means that the product of the capacitance value of the capacitive device 131 and the inductance value of the inductive device 133 in each branch 130 and/or the product of the capacitance value of the first capacitor C1 and the inductance value of the first inductor L1 are not equal.

It can be known that, assuming that the number of branches 130 is N, when the resonant frequency of each branch 130 is different, the filter circuit can generate 2N transmission zeros at most, that is, N transmission zeros are generated at the low frequency end and the high frequency end of the pass band.

It is to be understood that fig. 8 exemplarily shows the filter circuit structure when N is equal to 2, but does not limit the present invention. Based on the filter circuit shown in fig. 8, fig. 9 is a frequency-gain waveform diagram of the filter circuit in fig. 8. Referring to fig. 9, it can be seen that, at this time, the filter circuit has four transmission zeros. With continued reference to fig. 8, the reason why the filter circuit generates four transmission zeros is that, assuming that two branches in the filter circuit are a left branch and a right branch, respectively, when the product of the capacitance value of the capacitive device in the left branch and the inductance value of the inductive device is unequal to the product of the capacitance value of the first capacitor and the inductance value of the first inductor, and the product of the capacitance value of the capacitive device in the right branch and the inductance value of the inductive device is unequal to the product of the capacitance value of the first capacitor and the inductance value of the first inductor, the left branch will generate two transmission zeros, and the right branch will also generate two transmission zeros accordingly, so that the filter circuit has four transmission zeros. Adaptively, the filter circuit can also generate one, two or three transmission zeros by changing parameters of the corresponding capacitive device, inductive device, first capacitor and first inductor in the left and right branches.

Therefore, the filter circuit provided by the embodiment of the utility model can generate a plurality of transmission zeros in the frequency response, overcomes the problem that the existing filter circuit has a small number of transmission zeros, and is beneficial to improving the performance of the filter.

It should be noted that fig. 8 exemplarily shows that the number of the coupling units 140 is 3, but the utility model is not limited thereto.

Based on the above embodiment, in the practical application process, the filter circuit may adopt a multilayer board structure, and at this time, the capacitive device in the branch and the first potential end form a parasitic inductance, and the value of the parasitic inductance is smaller than that of the actual inductance. It can know, at the high band of radio frequency, filter circuit is lower to the demand of inductance, and parasitic inductance can satisfy filter circuit's inductance needs, therefore filter circuit need not additionally to set up inductive device. On the contrary, in the low frequency band of the radio frequency, the requirement of the filter circuit for the inductance is high, and the requirement of the filter circuit for the inductance is difficult to be met only by the aid of the capacitive device in the branch circuit and the parasitic inductance formed by the first potential end, so that an inductive device needs to be additionally arranged on the filter circuit. It can be understood that, if the inductive device is an actual inductor, the connection sequence of the capacitive device, the LC parallel unit and the inductive device in the embodiment of the present invention may be adaptively adjusted according to the actual working condition of the filter circuit, for example, one end of the inductive device is connected between the first end and the second end of the filter circuit, the other end of the inductive device is connected to one end of the LC parallel unit, the other end of the LC parallel unit is connected to the first potential end through the capacitive device, and the like. The following is an example of a filter circuit having a multi-layer structure with the number of branches being 1, and the actual structural design of the filter circuit will be described, but the present invention is not limited thereto.

Fig. 10 is a schematic diagram of a multi-layer structure of a filter circuit according to an embodiment of the present invention, referring to fig. 10, and optionally, further includes a first metal plate 210, where the first metal plate 210 is used for connecting to a first potential provided by a first potential terminal; the capacitive device includes a first plate 220, a first dielectric layer and a second plate 230, which are stacked to form an inductive device with the first metal plate 210.

The first metal plate 210 is used as a first potential terminal, and the first potential may be zero potential, and the material of the first metal plate 210 may be copper. It is known that the first plate 220 is an upper plate of a capacitive device, the second plate 230 is a lower plate of the capacitive device, the materials of the first plate 220 and the second plate 230 may be, but are not limited to, metals and oxides thereof, such as aluminum, and the material of the first dielectric layer (not shown in fig. 10) may be paraffin, mica, ceramic, and the like.

It can be understood that, forming the inductive device between the capacitive device and the first metal plate 210 means that a parasitic inductance between the capacitive device and the first metal plate 210 is used as the inductive device, and based on the foregoing analysis of this embodiment, at this time, the filter circuit operates in a high frequency band of a radio frequency, and the parasitic inductance can meet the inductance requirement of the filter circuit. In addition, the present embodiment can further change the inductance value of the inductive device by adjusting the height of the capacitive device relative to the first metal plate 210.

Optionally, the first capacitor includes a third plate 240, a second dielectric layer, and a fourth plate 250, which are stacked, and the third plate 240 and the second plate 230 are disposed in the same layer.

Wherein the third plate 240 is an upper plate of the first capacitor, the fourth plate 250 is a lower plate of the first capacitor, the materials of the third plate 240 and the fourth plate 250 may be, but are not limited to, metals and oxides thereof, such as aluminum, and the material of the second dielectric layer (not shown in fig. 10) may be paraffin, mica, ceramic, and the like. It can be understood that, by arranging the third polar plate 240 and the second polar plate 230 in the same layer, the third polar plate 240 can be manufactured while the second polar plate 230 is manufactured, so that the technical effects of simplifying the manufacturing process of the filter circuit and simplifying the manufacturing flow of the filter circuit are achieved.

Optionally, the first inductor L1 is disposed on the same layer as the second plate 230.

The first inductor L1, the second plate 230, and the third plate 240 are all disposed on the same layer, and by disposing the first inductor L1 and the second plate 230 on the same layer, the third plate 240 and the first inductor L1 can be fabricated while the second plate 230 is fabricated in this embodiment, so that the fabrication process of the filter circuit is simplified, and the fabrication flow of the filter circuit is simplified.

With continued reference to fig. 6, it can be seen that the first inductor L1 is connected in parallel with the first capacitor C1, and thus two ends of the first inductor L1 are respectively connected to the upper plate and the lower plate of the first capacitor C1, however, since the first inductor L1 and the second plate 230 are disposed on the same layer, the first inductor L1 cannot be directly connected to the fourth plate 250 on the same layer. Based on this, with continued reference to fig. 10, the present embodiment realizes the connection of the first inductor L1 and the fourth plate 250 by providing a via hole.

Optionally, a first terminal post 260 and a second terminal post 270 are further included, the first terminal post 260 is disposed between the second metal plate and the third metal plate, and the first terminal post 260 is used for connecting one end of the first inductor L1 and one end of the first capacitor; the second terminal 270 is disposed between the first metal plate 210 and the second metal plate, and the second terminal 270 is used for connecting the fourth plate 250 of the first capacitor and the first metal plate 210; the second post 270 serves to form part of a parasitic inductance.

The material of the first post 260 and the second post 270 may be metal, and may be copper, for example. As can be known, the first terminal 260 is the aforementioned via hole for connecting the first inductor L1 and the fourth plate 250, the second metal plate refers to a metal layer in a filter circuit where the fourth plate 250 of the first capacitor is located, and the third metal plate refers to a metal layer in another filter circuit where the third plate 240 of the first capacitor, the second plate 230 of the capacitive device, and the first inductor L1 coexist. It is understood that the second post 270 can also form part of parasitic inductance, and thus it can be seen that the inductive device can be composed of part of parasitic inductance formed by the second post 270 and the parasitic inductance formed by the capacitive device and the first metal plate 210.

In summary, in the embodiment of the present invention, the parasitic inductance formed by the second terminal and the parasitic inductance formed by the capacitive device and the first metal plate are used as the inductive device, so that the circuit structure of the filter circuit is simplified, the size of the filter circuit is reduced, and the manufacturing cost of the filter circuit is saved. In addition, the filter circuit provided by the embodiment of the utility model can generate a plurality of transmission zeros in frequency response, overcomes the problem that the existing filter circuit has a small number of transmission zeros, and is beneficial to improving the performance of the filter.

The embodiment of the utility model also provides a multiplexer. Fig. 11 is a schematic structural diagram of a multiplexer according to an embodiment of the present invention. As shown in fig. 11, the multiplexer includes the filter circuit according to any embodiment of the present invention.

With continued reference to fig. 11, the multiplexer includes a third terminal IN, at least two fourth terminals, and at least two filter circuits, each filter circuit being connected IN series between the third terminal IN and a fourth terminal of the multiplexer.

Specifically, fig. 11 exemplarily shows that the multiplexer includes a third terminal IN and n fourth terminals, OUT1, OUT2, … …, OUTn, respectively. Each filter circuit is connected IN series between the third terminal IN and a fourth terminal. For example, a first filter circuit is connected IN series between the third terminal IN and the first fourth terminal OUT1, a second filter circuit is connected IN series between the third terminal IN and the second fourth terminal OUT2, and so on. Since the multiplexer has the filter circuit provided in any of the embodiments of the present invention, the multiplexer has the beneficial effect of the filter circuit, and details are not described herein.

It should be noted that the multiplexer may further include another filter circuit, the other filter circuit is connected IN series between the third terminal IN and a fourth terminal, and the other filter circuit may be a low-pass filter circuit, a high-pass filter circuit, or a band-pass filter circuit, which is not limited IN the embodiment of the present invention.

It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the utility model. Therefore, although the present invention has been described in some detail by the above embodiments, the utility model is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the utility model, and the scope of the utility model is determined by the scope of the appended claims.

Claims (10)

1. A filter circuit comprising a first terminal, a second terminal, and at least one branch disposed between the first terminal and the second terminal;

the branch comprises at least one LC parallel unit and at least one capacitive device; one end of the capacitive element is connected between the first end and the second end, the other end of the capacitive element is connected with one end of the LC parallel unit, and the other end of the LC parallel unit is connected with a first potential end;

the branch circuit further comprises an inductive device, and the other end of the LC parallel unit is connected with the first potential end through the inductive device.

2. The filter circuit of claim 1, wherein the LC shunt unit comprises a first capacitor and a first inductor, and wherein the first capacitor and the first inductor are connected in parallel.

3. The filter circuit according to claim 2, further comprising a first metal plate for connecting to a first potential provided by the first potential terminal; the capacitive device comprises a first polar plate, a first dielectric layer and a second polar plate which are arranged in a stacked mode, and the inductive device is formed between the capacitive device and the first metal plate.

4. The filter circuit of claim 3, wherein the first capacitor comprises a third plate, a second dielectric layer and a fourth plate, which are stacked, and the third plate and the second plate are disposed on the same layer.

5. The filter circuit according to claim 3 or 4, wherein the first inductor is disposed in the same layer as the second plate.

6. The filter circuit according to claim 5, further comprising a first terminal and a second terminal, wherein the first terminal is disposed between the second metal plate and the third metal plate, and the first terminal is configured to connect one end of the first inductor and one end of the first capacitor; the second wiring terminal is arranged between the first metal plate and the second metal plate, and the second wiring terminal is used for connecting a fourth pole plate of the first capacitor and the first metal plate; the second binding post is used for forming part of parasitic inductance.

7. The filter circuit according to claim 5, wherein the resonant frequency of the capacitive device and the inductive device is the same or different from the resonant frequency of the LC parallel unit.

8. The filter circuit according to claim 1, comprising a plurality of said branches between said first terminal and said second terminal; the resonant frequency of each of the branches may be the same or different.

9. The filter circuit of claim 1, further comprising a coupling unit connected in series between the first terminal and the second terminal.

10. A multiplexer, comprising the filter circuit of any one of claims 1 to 9.

Images