Filtering circuit and multiplexer

Abstract

The embodiment of the present application discloses a filter circuit and a multiplexer, the filter circuit comprising a first end, a second end and at least one branch arranged between the first end and the second end; the branch comprising at least one LC parallel unit and at least one capacitive device; one end of the capacitive device is connected between the first end and the second end, the other end of the capacitive device is connected with one end of the LC parallel unit, the other end of the LC parallel unit is connected with the first potential end; the branch further comprises an inductive device, 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 present application can generate multiple transmission zeros in the frequency response, thereby overcoming the problem that the number of transmission zeros of the existing filter circuit is small, and being beneficial to improving the performance of the filter.

Description

TECHNICAL FIELD

[0001] The embodiment of the present application relates to the technical field of filtering, in particular to a filtering circuit and a multiplexer. BACKGROUND

[0002] In the field of filtering, the filtering circuit with multiple transmission zeros is one of the key research directions of designers. How to generate multiple transmission zeros in the topology structure of the filtering circuit or in the layout design process is the core essence of the designers' thinking.

[0003] With the miniaturization of the filtering circuit and the filter, how to generate as many transmission zeros as possible in the limited layout space has become a great challenge for designers. At present, the number of transmission zeros of the existing filtering circuit is small, and it is difficult to effectively improve the performance of the filter. SUMMARY

[0004] The embodiment of the present application provides a filtering circuit and a multiplexer to generate multiple transmission zeros in the frequency response of the filtering circuit, which is beneficial to improve the performance of the filter.

[0005] In a first aspect, the embodiment of the present application provides a filtering circuit, comprising a first end, a second end and at least one branch provided between the first end and the second end.

[0006] The branch comprises at least one LC parallel unit and at least one capacitive device; one end of the capacitive device is connected between the first end and the second end, the other end of the capacitive device 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.

[0007] The branch 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.

[0008] Optionally, the LC parallel unit comprises a first capacitor and a first inductor, and the first capacitor and the first inductor are connected in parallel.

[0009] Optionally, it further comprises a first metal plate, the first metal plate is used for accessing a first potential provided by the first potential end; the capacitive device comprises a first electrode plate, a first dielectric layer and a second electrode plate which are stacked, and the inductive device is formed between the capacitive device and the first metal plate.

[0010] Optionally, the first capacitor comprises a third electrode plate, a second dielectric layer and a fourth electrode plate which are stacked, and the third electrode plate is provided in the same layer as the second electrode plate.

[0011] Optionally, the first inductor is provided in the same layer as the second electrode plate.

[0012] Optionally, the filter circuit further comprises a first lug and a second lug, the first lug is arranged between the second metal plate and the third metal plate, and the first lug is used for connecting one end of the first inductor and one end of the first capacitor; the second lug is arranged between the first metal plate and the second metal plate, and the second lug is used for connecting the fourth plate of the first capacitor and the first metal plate; and the second lug is used for forming part of the parasitic inductor.

[0013] Optionally, 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.

[0014] Optionally, a plurality of branches are arranged between the first end and the second end; and the resonant frequency of each branch is the same as or different from.

[0015] Optionally, the filter circuit further comprises a coupling unit, the coupling unit is arranged in series between the first end and the second end.

[0016] In the second aspect, the embodiments of the present application further provide a multiplexer, comprising the filter circuit of the first aspect.

[0017] The technical scheme provided by the embodiments of the present application is that at least one branch is arranged 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 arranged in series between the first end and the second end of the filter circuit and between the first end and the second end and the first potential end, and the capacitive device and the inductive device can generate a transmission zero point, and the LC parallel unit can generate a transmission zero point, so that one branch can generate multiple transmission zero points. Therefore, the filter circuit provided by the embodiments of the present application can generate multiple transmission zero points in the frequency response, thereby overcoming the problem of insufficient number of transmission zero points of the existing filter circuit, and being beneficial to improving the performance of the filter. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a circuit diagram of an LC parallel resonant filter circuit in the prior art;

[0019] Figure 2 is Figure 1 is a frequency-gain waveform diagram of the LC parallel resonant filter circuit in the prior art;

[0020] Figure 3 is a circuit diagram of an LC series resonant filter circuit in the prior art;

[0021] Figure 4 is Figure 3 is a frequency-gain waveform diagram of the LC series resonant filter circuit in the prior art;

[0022] Figure 5 is a structural schematic diagram of a filter circuit provided by an embodiment of the present application;

[0023] Figure 6 is a structural schematic diagram of another filter circuit provided by an embodiment of the present application;

[0024] Figure 7 is a frequency-gain waveform diagram of the filter circuit in Figure 6

[0025] Figure 8 is a structural schematic diagram of still another filter circuit provided by an embodiment of the present application;

[0026] Figure 9 is a frequency-gain waveform diagram of the filter circuit in Figure 8

[0027] Figure 10 is a multi-layer structural schematic diagram of a filter circuit provided by an embodiment of the present application;

[0028] Figure 11 is a structural schematic diagram of a multiplexer provided by an embodiment of the present application. DETAILED DESCRIPTION

[0029] The present application will be further described below in conjunction with the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application. In addition, it should be noted that, for the convenience of description, only the parts related to the present application are shown in the drawings, but not all the structures.

[0030] As mentioned in the background art, the prior art filter circuit has a small number of transmission zeros, and there is a technical problem that it is difficult to effectively improve the performance of the filter. The inventors have found, through careful research, that the cause of this technical problem is that, for example, in a band-pass filter, Figure 1 is a circuit diagram of an LC parallel resonant filter circuit in the prior art, Figure 2 is a frequency-gain waveform diagram of the LC parallel resonant filter circuit in Figure 1 Figure 1 and Figure 2 It can be seen that the LC parallel mode on the normal branch cannot produce transmission zeros. In addition, Figure 3 is a circuit diagram of an LC series resonant filter circuit in the prior art, Figure 4 is a frequency-gain waveform diagram of the LC series resonant filter circuit in Figure 3 Figure 3 and Figure 4 ​​​​It can be understood that the LC series mode on the normal branch can only generate one transmission zero point.

[0031] In view of the above technical problems, the present application provides the following solutions:

[0032] Figure 5 is a structural schematic diagram of a filter circuit provided by an embodiment of the present application, referring to Figure 5 The filter circuit comprises a first end 110, a second end 120, and at least one branch 130 arranged between the first end 110 and the second end 120. The branch 130 comprises at least one LC parallel unit 132 and at least one capacitive device 131; one end of the capacitive device 131 is connected between the first end 110 and the second end 120, the other end of the capacitive device 131 is connected with one end of the LC parallel unit 132, and the other end of the LC parallel unit 132 is connected with a first potential end 134. The branch 130 further comprises an inductive device 133, and the other end of the LC parallel unit 132 is connected with the first potential end 134 through the inductive device 133.

[0033] Wherein, when the first end 110 is used for accessing an input signal, the second end 120 is used for generating an output signal, or when the first end 110 is used for generating an output signal, the second end 120 is used for accessing an input signal. It can be known that the branch 130 arranged between the first end 110 and the second end 120 is used for generating multiple transmission zero points in the frequency response of the filter circuit.

[0034] It can be known that the LC parallel unit 132 refers to an inductor and a capacitor connected in parallel. In addition, the capacitive device 131 refers to a device that will make the voltage lag behind the current, which can be a capacitor, for example. Adaptively, the inductive device 133 refers to a device that will make the voltage lead the current, which can be an inductor, for example. It can be understood that the first potential end 134 refers to a port with a certain specific potential value or potential value, for example, the potential value or potential value of the first potential end 134 can be zero, at this time, the first potential end 134 is a ground end.

[0035] It can be known that the capacitive device 131 is connected in series with the inductive device 133 through the LC parallel unit 132 between the first end 110 and the second end 120 and between the first potential end 134, and thus 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 sequence. Therefore, the capacitive device 131 and the inductive device 133 can generate one transmission zero point, and the LC parallel unit 132 can generate one transmission zero point, that is, one branch 130 can generate multiple transmission zero points. It can be understood that the specific number and parameters of the capacitive device 131, the LC parallel unit 132 and the inductive device 133 can be adaptively adjusted according to the number of transmission zero points to be generated by the filter circuit, and the present application does not limit this.

[0036] In summary, the embodiment of the present application is provided with at least one branch between the first end and the second end of the filter circuit, between the first end and the second end of the filter circuit and between the first potential end, including at least one capacitive device, at least one LC parallel unit and an inductive device connected in series in sequence. Since the capacitive device and the inductive device can generate one transmission zero point, and the LC parallel unit can generate one transmission zero point, one branch can generate multiple transmission zero points. Therefore, the filter circuit provided by the embodiment of the present application can generate multiple transmission zero points in the frequency response, thereby overcoming the problem of insufficient number of transmission zero points of the existing filter circuit, and being beneficial to improving the performance of the filter.

[0037] It should be noted that, Figure 5 It is exemplarily shown that the number of branches 130 is 1, but it is not as a limitation of the present application.

[0038] On the basis of the above-mentioned embodiment, the specific structure of the LC parallel unit, the resonance frequency setting of the filter circuit and the other structure design of the filter circuit are described below, but not as a limitation of the present application.

[0039] Figure 6 is another structure diagram of the filter circuit provided by the embodiment of the present application, referring to Figure 6 Optionally, the LC parallel unit 132 includes a first capacitor C1 and a first inductor L1, and the first capacitor C1 and the first inductor L1 are connected in parallel.

[0040] Among them, the first capacitor C1 can be an aluminum electrolytic capacitor, a patch tantalum capacitor, etc., and the first inductor L1 can adopt a magnetic core surrounded by an enameled wire, a snakelike wire, etc. It can be known 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 point to be generated by the LC parallel unit 132.

[0041] In addition, since the specific parameters of the capacitive device 131, the inductive device 133, the first capacitor C1 and the first inductor L1 can be adaptively selected according to the 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.

[0042] It is known that the resonant frequency of the capacitive device 131 and the inductive device 133 refers to the frequency when the capacitive device 131 and the inductive device 133 are in a state independent of 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 refers to the frequency when the first capacitor C1 and the first inductor L1 are in a state independent of frequency, i.e. a pure resistance state, during the oscillation of the first capacitor C1 and the first inductor L1.

[0043] Based on this, the calculation formula of the resonant frequency is shown in formula (1):

[0044]

[0045] In the formula, f is the resonant frequency, L is the inductance value, and C is the capacitance value.

[0046] It can be understood that for the capacitive device 131 and the inductive device 133, f in formula (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 in formula (1) represents the resonant 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.

[0047] According to equation (1), when the product of the capacitance of the capacitive device 131 and the inductance of the inductive device 133 is equal to the product of the capacitance of the first capacitor C1 and the inductance 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. In this case, the filter circuit has only one transmission zero. Adaptively, when the product of the capacitance of the capacitive device 131 and the inductance of the inductive device 133 is not equal to the product of the capacitance of the first capacitor C1 and the inductance 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. In this case, the filter circuit has two transmission zeros, namely, one transmission zero each at the low-frequency end and the high-frequency end of the filter circuit's passband. It can be understood that, compared with the case where 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, when the resonant frequency of the capacitive device 131 and the inductive device 133 is the same as the resonant frequency of the LC parallel unit 132, the absolute value of the gain of the filtering circuit is larger and the filtering effect is better.

[0048] Optionally, the filter circuit further includes a coupling unit 140 , which is connected in series between the first end 110 and the second end 120 .

[0049] The coupling unit 140 is used to broaden the bandwidth of the filter circuit. Exemplarily, the coupling unit 140 may be, but is not limited to, a capacitor.

[0050] Continue to see Figure 6 According to the connection relationship between the filter circuit and the coupling unit 140 , it can be seen that, assuming that the number of branches 130 in the filter circuit is n, the number of coupling units 140 is n+1.

[0051] based on Figure 6 The filter circuit shown, Figure 7 yes Figure 6 The frequency-gain waveform of the filter circuit is shown in Figure 2. Figure 7 It can be seen that at this time, the filtering 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 not equal 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.

[0052] In conclusion, the embodiment of the present application sets multiple coupling units between the first end and the second end of the filter circuit, widens the bandwidth of the filter circuit, and is beneficial to optimizing the filtering effect of the filter circuit. In addition, the embodiment of the present application can 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 frequencies of the capacitive device and the inductive device are 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 present application can generate multiple transmission zeros in the frequency response, overcoming the problem of too few transmission zeros of the existing filter circuit, and is beneficial to improving the performance of the filter.

[0053] It should be noted that, Figure 6 Exemplarily, the number of the coupling units 140 is 2, but this does not limit the present application.

[0054] On the basis of the above-mentioned embodiment, the number of branches and the resonant characteristics of the filter circuit are described below, but this does not limit the present application.

[0055] Figure 8 is another structure diagram of the filter circuit provided by the embodiment of the present application, referring to Figure 8 Optionally, the first end 110 and the second end 120 include multiple branches 130, and the resonant frequencies of each branch 130 are the same or different.

[0056] Wherein, the resonant frequencies of each branch 130 are 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 resonant frequencies of each branch 130 are different, 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 / or the product of the capacitance value of the first capacitor C1 and the inductance value of the first inductor L1 are not equal.

[0057] It can be known that, assuming that the number of the branches 130 is N, when the resonant frequencies of each branch 130 are all different, the filter circuit can generate at most 2N transmission zeros, that is, N transmission zeros at the low frequency end and the high frequency end of the passband.

[0058] It can be understood that, Figure 8 Exemplarily, the structure of the filter circuit when N is equal to 2 is shown, but this does not limit the present application. Based on Figure 8 the filter circuit shown in the figure, Figure 9 is Figure 8 the frequency-gain waveform diagram of the filter circuit in Figure 9 It can be known that, at this time, the filter circuit has four transmission zeros. Referring to Figure 8The reason that 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 a capacitive device and the inductance value of an inductive device in the left branch is not equal 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 a capacitive device and the inductance value of an inductive device in the right branch is not equal to the product of the capacitance value of the first capacitor and the inductance value of the first inductor, the left branch generates two transmission zeros, and the right branch also generates 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 the parameters of the corresponding capacitive device, inductive device, first capacitor and first inductor in the left and right branches.

[0059] Therefore, the filter circuit provided by the embodiment of the present application can generate multiple transmission zeros in the frequency response, and overcomes the problem of insufficient number of transmission zeros of the existing filter circuit, which is beneficial to improving the performance of the filter.

[0060] It should be noted that, Figure 8 It is exemplarily shown that the number of coupling units 140 is 3, but this does not limit the present application.

[0061] Based on the above embodiment, in actual application, the filter circuit can adopt a multi-layer board structure, at this time, the capacitive device in the branch forms a parasitic inductance with the first potential end, and compared with the actual inductance, the value of the parasitic inductance is smaller. It can be known that in the high frequency band of radio frequency, the demand of the filter circuit for inductance is lower, and the parasitic inductance can meet the inductance demand of the filter circuit, so that the filter circuit does not need to additionally set the inductive device. On the contrary, in the low frequency band of radio frequency, the demand of the filter circuit for inductance is higher, and it is difficult for the parasitic inductance formed by the capacitive device in the branch and the first potential end to meet the inductance demand of the filter circuit, so that the filter circuit needs to additionally set the inductive device. It can be understood that if the inductive device is an actual inductance, the connection order of the capacitive device, the LC parallel unit and the inductive device in the embodiment of the present application can 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 with one end of the LC parallel unit, the other end of the LC parallel unit is connected with the first potential end through the capacitive device, etc. Hereinafter, the filter circuit with the number of branches being 1 and having a multi-layer board structure is taken as an example to illustrate the actual structure design of the filter circuit, but this does not limit the present application.

[0062] Figure 10 is a multi-layer structure schematic diagram of a filter circuit provided by the embodiment of the present application, referring to Figure 10Optionally, the first metal plate 210 is further included for accessing a first potential provided by the first potential terminal; the capacitive device includes a first electrode plate 220, a first dielectric layer and a second electrode plate 230 which are stacked, and the inductive device is formed between the capacitive device and the first metal plate 210.

[0063] The first metal plate 210 is used as the first potential terminal, and the first potential is exemplarily zero potential, and the material of the first metal plate 210 can be copper. It can be understood that the first electrode plate 220 is the upper electrode plate of the capacitive device, the second electrode plate 230 is the lower electrode plate of the capacitive device, and the materials of the first electrode plate 220 and the second electrode plate 230 can be but are not limited to metal and its oxides, for example, can be aluminum, and the material of the first dielectric layer (not shown in the figure) can be paraffin, mica, ceramic and the like. Figure 10

[0064] It can be understood that the inductive device formed between the capacitive device and the first metal plate 210 refers to that the parasitic inductance between the capacitive device and the first metal plate 210 is used as the inductive device. Based on the foregoing analysis of the embodiment, it can be known that at this time, the filter circuit works at a high frequency band of radio frequency, and the parasitic inductance can meet the inductance requirement of the filter circuit. In this way, the circuit structure of the filter circuit can be simplified, the volume of the filter circuit can be reduced, and the manufacturing cost of the filter circuit can be saved. In addition, the height of the capacitive device relative to the first metal plate 210 can be adjusted, and the inductance value of the inductive device can be changed.

[0065] Optionally, the first capacitor includes a third electrode plate 240, a second dielectric layer and a fourth electrode plate 250 which are stacked, and the third electrode plate 240 is arranged in the same layer as the second electrode plate 230.

[0066] The third electrode plate 240 is the upper electrode plate of the first capacitor, the fourth electrode plate 250 is the lower electrode plate of the first capacitor, and the materials of the third electrode plate 240 and the fourth electrode plate 250 can be but are not limited to metal and its oxides, for example, can be aluminum, and the material of the second dielectric layer (not shown in the figure) can be paraffin, mica, ceramic and the like. Figure 10 It can be understood that by arranging the third electrode plate 240 in the same layer as the second electrode plate 230, the third electrode plate 240 can be manufactured at the same time as the second electrode plate 230, so that the manufacturing process of the filter circuit is simplified, and the manufacturing process of the filter circuit is simplified.

[0067] Optionally, the first inductor L1 is arranged in the same layer as the second electrode plate 230.

[0068] ​The first inductor L1, the second plate 230 and the third plate 240 are arranged in the same layer, the first inductor L1 is arranged in the same layer with the second plate 230, the third plate 240 and the first inductor L1 can be manufactured at the same time when the second plate 230 is manufactured, and thus the manufacturing process of the filter circuit is simplified, and the manufacturing process of the filter circuit is simplified.

[0069] Continuing to refer to Figure 6 It can be known that the first inductor L1 is connected in parallel with the first capacitor C1, and thus the two ends of the first inductor L1 are connected with the upper plate and the lower plate of the first capacitor C1 respectively. However, since the first inductor L1 is arranged in the same layer with the second plate 230, the first inductor L1 cannot be directly connected in the same layer with the fourth plate 250. Based on this, continuing to refer to Figure 10 The first inductor L1 and the fourth plate 250 are connected through the via hole.

[0070] Optionally, the first terminal post 260 and the second terminal post 270 are further included, the first terminal post 260 is arranged 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 post 270 is arranged between the first metal plate 210 and the second metal plate, and the second terminal post 270 is used for connecting the fourth plate 250 of the first capacitor and the first metal plate 210; the second terminal post 270 is used for forming part of the parasitic inductor.

[0071] The material of the first terminal post 260 and the second terminal post 270 can be metal, for example, copper. It can be known that the first terminal post 260 is the via hole used for connecting the first inductor L1 and the fourth plate 250, the second metal plate refers to a metal layer in a filter circuit in which the fourth plate 250 of the first capacitor is located, and the third metal plate refers to a metal layer in another filter circuit in which the third plate 240 of the first capacitor, the second plate 230 of the capacitive device and the first inductor L1 coexist. It can be understood that the second terminal post 270 can also form part of the parasitic inductor, and thus it can be seen that the inductive device can be composed of part of the parasitic inductor formed by the second terminal post 270 and the parasitic inductor formed by the capacitive device and the first metal plate 210.

[0072] In summary, the embodiment of the present application simplifies the circuit structure of the filter circuit by taking the partial parasitic inductance formed by the second terminal post and the parasitic inductance formed by the capacitive device and the first metal plate as inductive devices, reduces the volume of the filter circuit, is conducive to saving the manufacturing cost of the filter circuit, and meanwhile, by arranging the first inductor, the second plate and the third plate in the same layer, the embodiment of the present application can manufacture the third plate and the first inductor at the same time as the second plate, and further simplifies the manufacturing process of the filter circuit and the manufacturing process of the filter circuit. In addition, the filter circuit provided by the embodiment of the present application can generate multiple transmission zeros in the frequency response, overcomes the problem of insufficient number of transmission zeros of the existing filter circuit, and is conducive to improving the performance of the filter.

[0073] The embodiment of the present application also provides a multiplexer. Figure 11 is a structural schematic diagram of a multiplexer provided by the embodiment of the present application. As shown in the figure, Figure 11 the multiplexer includes the filter circuit provided by any embodiment of the present application.

[0074] Continuing to refer to Figure 11 , the multiplexer includes a third end IN, at least two fourth ends, and at least two filter circuits, each filter circuit being connected in series between the third end IN of the multiplexer and a fourth end.

[0075] Specifically, Figure 11 the multiplexer is exemplarily shown in the figure to include a third end IN and n fourth ends, respectively OUT1, OUT2, …, OUTn. Each filter circuit is connected in series between the third end IN and a fourth end. For example, the first filter circuit is connected in series between the third end IN and the first fourth end OUT1, the second filter circuit is connected in series between the third end IN and the second fourth end OUT2, and so on. Since the multiplexer has the filter circuit provided by any embodiment of the present application, the multiplexer has the beneficial effects of the filter circuit, which will not be described herein again.

[0076] It should be noted that the multiplexer can also include other filter circuits connected in series between the third end IN and a fourth end, and the other filter circuits can be low-pass filter circuits, high-pass filter circuits or band-pass filter circuits, which are not limited by the embodiment of the present application.

[0077] Note that the above merely describes preferred embodiments of the present application and the principles of the technology applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and that various obvious changes, modifications and substitutions can be made without departing from the scope of the present application. Therefore, although the present application has been described in detail through the above embodiments, the present application is not limited to the above embodiments, and can include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the claims.

Claims

1. A filter circuit, characterized in that: comprising a first end, a second end, and at least one branch disposed between the first end and the second end; The branch includes at least one LC parallel unit and at least one capacitive device; one end of the capacitive device is connected between the first end and the second end, the other end of the capacitive device is connected to one end of the LC parallel unit, and the other end of the LC parallel unit is connected to the first potential end; The branch further includes an inductive device, and the other end of the LC parallel unit is connected to the first potential end through the inductive device; Also included is a first metal plate, the first metal plate being used to access the first potential provided by the first potential terminal; The capacitive device includes a first electrode plate, a first dielectric layer, and a second electrode plate that are stacked, and the inductive device is formed between the capacitive device and the first metal plate; The first metal plate further includes a second terminal, which is disposed between the first metal plate and the second metal plate and is used to connect the fourth plate of the first capacitor and the first metal plate; the second terminal is used to form a portion of the parasitic inductance; the second metal plate is a metal layer in a filter circuit where the lower plate of the capacitor in the LC parallel unit is located; According to the frequency band of the working radio frequency of the filter circuit, the inductance of the inductive component in the branch is adjusted by adjusting the distance between the capacitive component and the first metal plate and / or by setting the parameters of the second terminal.

2. The filter circuit according to claim 1, wherein: The LC parallel unit includes a first capacitor and a first inductor, and the first capacitor and the first inductor are connected in parallel.

3. The filter circuit according to claim 1, wherein: The first capacitor includes a third plate, a second dielectric layer, and a fourth plate that are stacked together. The third plate and the second plate are arranged in the same layer.

4. The filter circuit according to claim 1 or 3, characterized in that: The first inductor and the second electrode plate are arranged in the same layer.

5. The filter circuit according to claim 4, characterized in that: It also includes a first terminal, which is arranged between the second metal plate and the third metal plate, and is used to connect one end of the first inductor and one end of the first capacitor.

6. The filter circuit according to claim 4, characterized in that: The resonant frequencies of the capacitive component and the inductive component are the same as or different from the resonant frequency of the LC parallel unit.

7. The filter circuit according to claim 1, wherein: A plurality of branches are included between the first end and the second end; and the resonant frequency of each branch is the same or different.

8. The filter circuit according to claim 1, wherein: The device further includes a coupling unit connected in series between the first end and the second end.

9. A multiplexer, characterized in that: The filter circuit comprises the filter circuit according to any one of claims 1 to 8.

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