CN117713732A

CN117713732A - Filter and multiplexer

Info

Publication number: CN117713732A
Application number: CN202311812237.5A
Authority: CN
Inventors: 黄文涛; 何成功; 牛建; 左成杰; 何军
Original assignee: Anhui Annuqi Technology Co Ltd
Current assignee: Anhui Annuqi Technology Co Ltd
Priority date: 2023-12-25
Filing date: 2023-12-25
Publication date: 2024-03-15

Abstract

The invention discloses a filter and a multiplexer. The filter comprises a first port, a second port and at least one filtering unit; the filtering unit comprises a pi-type LC network and a resonator; the pi-type LC network comprises at least one first element and at least two second elements; the first element is connected in series between the first port and the second port, the first end of the at least one second element is connected between the first port and the first end of the first element, and the first end of the at least one second element is connected between the second port and the second end of the first element; the second ends of the at least two second elements are connected to the resonator after connection. Two transmission zero points can be formed in the range of the passband high-frequency side adjacent band of the filter, meanwhile, the frequency difference between the zero point and the pole of the filter can be reduced, the roll off slope of the passband high-frequency side adjacent band of the filter is greatly improved, the passband high-frequency side adjacent band inhibition of the filter is greatly improved, and the filtering performance of the filter is further improved.

Description

Filter and multiplexer

Technical Field

The embodiment of the invention relates to the technical field of signal processing, in particular to a filter and a multiplexer.

Background

In a communication system, signal interference can substantially reduce signal transmission efficiency. The filter can effectively inhibit out-of-band signal interference so as to improve signal transmission efficiency. In modern communications, there is an increasing demand for filters with low insertion loss and high roll-off characteristics.

Disclosure of Invention

The invention provides a filter and a multiplexer to improve roll-off characteristics of the filter.

In a first aspect, an embodiment of the present invention provides a filter, including a first port, a second port, and at least one filtering unit;

the filtering unit comprises a pi-type LC network and a resonator; the pi-type LC network comprises at least one first element and at least two second elements; the first element is connected in series between the first port and the second port, a first end of at least one of the second elements is connected between the first port and the first end of the first element, and a first end of at least one of the second elements is connected between the second port and the second end of the first element; and the second ends of at least two second elements are connected and then connected with the resonators.

Optionally, the pi-type LC network includes one of the first elements and two of the second elements;

the first element comprises a first inductive element connected in series between the first port and the second port; and/or the number of the groups of groups,

the two second elements comprise a first capacitive element and a second capacitive element, wherein a first end of the first capacitive element is connected between the first port and a first end of the first element, a first end of the second capacitive element is connected between the second port and a second end of the first element, and the second end of the first capacitive element is connected with the second end of the second capacitive element and then is connected with the resonator.

Optionally, the filter includes at least two filter units, and the at least two filter units are connected in series between the first port and the second port.

Optionally, the filter further comprises at least one third port, at least one of said third ports being arranged between adjacent said filter units.

Optionally, frequencies corresponding to transmission zeros of different filtering units are equal.

Optionally, the filter further comprises at least one electromagnetic filter network connected in series between the first port and the second port.

Optionally, the filter includes at least two filter units, and when at least two filter units are connected in series between the first port and the second port, at least one electromagnetic filter network is connected between adjacent filter units.

Optionally, the electromagnetic filter network comprises a second inductive element connected in series between the first port and the second port.

Optionally, the electromagnetic filter network further comprises a third capacitive element connected in series and/or in parallel with the second inductive element.

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

According to the technical scheme, the resonator in the filter unit is connected with the pi-type LC network in series, so that the Z parameter of the resonator is added with the Z parameter of the pi-type LC network, two transmission zeros can be formed in the passband high-frequency side adjacent band range of the filter, meanwhile, the frequency difference between the zeros and poles of the filter can be reduced, the roll off slope of the passband high-frequency side adjacent band of the filter is greatly improved, the passband high-frequency side adjacent band suppression of the filter is greatly improved, and the filtering performance of the filter is further improved.

Drawings

Fig. 1 is a schematic structural diagram of a filter according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of another filter according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of an LC filter according to the prior art;

FIG. 4 is a schematic diagram illustrating performance comparison of different filters according to an embodiment of the present invention;

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

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

fig. 7 is a schematic structural diagram of another filter according to an embodiment of the present invention;

fig. 8 is a schematic structural diagram of another filter according to an embodiment of the present invention;

fig. 9 is a schematic structural diagram of another filter according to an embodiment of the present invention;

fig. 10 is a schematic structural diagram of another filter 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 invention is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting thereof. It should be further noted that, for convenience of description, only some, but not all of the structures related to the present invention are shown in the drawings.

Fig. 1 is a schematic structural diagram of a filter according to an embodiment of the present invention. As shown in fig. 1, the filter comprises a first port a, a second port B and at least one filtering unit 10; the filter unit 10 comprises a pi-LC network 11 and a resonator 12; the pi-LC network 11 comprises at least one first element 111 and at least two second elements 112; the first element 111 is connected in series between the first port a and the second port B, the first end of the at least one second element 112 is connected between the first port a and the first end of the first element 111, and the first end of the at least one second element 112 is connected between the second port B and the second end of the first element 111; the second ends of the at least two second elements 112 are connected to the resonator 12.

Specifically, the pi-type LC network 11 includes a capacitive element and an inductive element, and is configured to form a pi-type LC filter network, so as to implement a filtering function of a signal. The pi-type LC network 11 may be a low-pass filter network. Illustratively, the first element 111 may comprise an inductive element and the second element may comprise a capacitive element. When the first element 111 is one and the second element 112 is two, the first element 111 and the second element 112 may constitute a third-order low-pass filter network. When the passband of the pi-type LC network 11 transitions to the stopband, the Z parameter of the pi-type LC network 11 has a maximum value point, while the Y parameter does not have a minimum value point, and at this time, the stopband of the filter does not have a transmission zero point. Wherein, the Z parameter is the impedance parameter of the pi-type LC network 11, and the Y parameter is the admittance parameter of the pi-type LC network 11.

The resonator 12 may be an acoustic wave resonator. By way of example, the resonator 12 may be at least one of a bulk acoustic wave (Bulk Acoustic Wave, BAW) resonator, a surface wave (Surface Acoustic Wave, SAW) resonator, and a film cavity acoustic resonator (Film bulk acoustic resonator, FBAR) filter. The resonator 12 has a bandpass characteristic, and the adjacent band on the high-frequency side of the passband has a transmission zero point, that is, in the transmission characteristic of the resonator 12, the Z parameter has a maximum point on the adjacent band on the high-frequency side of the passband, so that the resonator 12 has a strong suppressing effect at a frequency corresponding to the transmission zero point, and thus the resonator 12 has a large roll-off slope at a frequency corresponding to the transmission zero point. When the second ends of the at least two second elements 112 are connected, they are connected to the resonator 12, so that the resonator 12 is connected in series with the pi-LC network 11. The Z-parameter of the filter at this time is the sum of the Z-parameter of the resonator 12 and the Z-parameter of the pi-LC network 11. When the Z parameter of the pi-LC network 11 is added to the Z parameter of the resonator 12, the Z parameter of the filter is at the passband high-frequency adjacent-band side maximum point, and the Y parameter has the minimum point, so that the roll-off slope of the passband high-frequency adjacent-band can be increased, the passband high-frequency adjacent-band suppression of the filter is improved, and the filtering performance of the filter is further improved. Meanwhile, the resonator 12 has a bandpass characteristic, and has a minimum point of the Z parameter within the passband, i.e., a maximum point of the Y parameter within the passband. When the Z parameter of the resonator 12 is added to the Z parameter of the pi-LC network 11, the frequency difference between the zero and the pole of the filter can be further reduced on the basis of the original frequency difference between the zero and the pole of the resonator 12, so that the roll-off slope between the passband and the high-frequency side can be further increased, the adjacent band suppression of the passband of the filter on the high-frequency side is further improved, and the filtering performance of the filter is further improved. In addition, on the passband high frequency side of the resonator 12, the Z parameter of the pi-type LC network 11 and the Z parameter of the resonator 12 are different in value, so that the sum of the Z parameter of the pi-type LC network 11 and the Z parameter of the resonator 12 additionally generates a maximum point in the passband high frequency side adjacent band range, that is, in the filtering unit 10, a transmission zero point is additionally generated in the passband high frequency side adjacent band of the filtering unit 10, thereby further increasing the roll off slope of the passband high frequency side adjacent band, improving the passband high frequency side adjacent band suppression of the filter, and further improving the filtering performance of the filter. The adjacent band can be a frequency band above or below the passband, even the transition band between the adjacent band and the passband is only 0 MHz-tens of MHz, and the bandwidth of the adjacent band is a frequency band range of more than 10% of the center frequency of the passband.

It should be noted that, after one end of the resonator 12 is connected in series with the pi-type LC network 11, the other end of the resonator 12 serves as a port of the filter, and may be connected to an external circuit, so that the filter may be connected to different types of external circuits, thereby increasing the application range of the filter.

Fig. 2 is a schematic structural diagram of another filter according to an embodiment of the present invention. As shown in fig. 2, the pi-type LC network 11 includes one first element 111 and two second elements 112; the first element 111 includes a first inductive element L1, the first inductive element L1 being connected in series between the first port a and the second port B; and/or, the two second elements 112 include a first capacitive element C1 and a second capacitive element C2, the first end of the first capacitive element C1 is connected between the first port a and the first end of the first element 111, the first end of the second capacitive element C2 is connected between the second port B and the second end of the first element 111, and the second end of the first capacitive element C1 and the second end of the second capacitive element C2 are connected to the resonator 12.

Specifically, fig. 2 exemplarily shows that the first element 111 includes a first inductive element L1, and the two second elements 112 include a first capacitive element C1 and a second capacitive element C2, respectively, where the first inductive element L1 is connected in series between the first port a and the second port B, while a first end of the first capacitive element C1 is connected between the first port a and a first end of the first element 111, and a first end of the second capacitive element C2 is connected between the second port B and a second end of the first element 111, so that the first inductive element L1, the first capacitive element C1, and the second capacitive element C2 form a third-order low-pass filter network. Meanwhile, after the second end of the first capacitive element C1 and the second end of the second capacitive element C2 are connected, the second end of the first capacitive element C1 and the second end of the second capacitive element C2 are connected with the resonator 12, so that the resonator 12 and the pi-type LC network 11 are connected in series, Z parameters of the resonator 12 and Z parameters of the pi-type LC network 11 can be added, two transmission zero points can be formed in a passband high-frequency side adjacent band range of the filter, meanwhile, frequency difference between the zero point and a pole of the filter can be reduced, roll-off slope of the passband high-frequency side adjacent band of the filter is greatly improved, passband high-frequency side adjacent band suppression of the filter is greatly improved, and filtering performance of the filter is further improved.

Fig. 3 is a schematic structural diagram of an LC filter according to the prior art. The specific structure is the same as that of the pi-type LC network 11 in fig. 2. Fig. 4 is a schematic diagram illustrating performance comparison of different filters according to an embodiment of the present invention. Wherein the abscissa is frequency and the ordinate is insertion loss. Curve 1 is the frequency-insertion loss curve of the filter provided in fig. 2, and curve 2 is the frequency-insertion loss curve of the filter provided in fig. 3. As shown in fig. 4, the curve 1 forms two transmission zeroes M in the adjacent band range of the passband high frequency side, the suppression degree of one transmission zeroes reaches below-20 dB, the suppression degree of the other transmission zeroes reaches about-40 dB, and the roll off slope is steep. And the curve 2 has no transmission zero point in the adjacent band range of the passband high frequency side, the inhibition degree is relatively poor, and the roll off slope is relatively gentle. It can be seen that when a resonator 12 is connected in series on the basis of the LC filter provided in fig. 3, two transmission zeros can be formed in the adjacent band range of the high frequency side of the passband of the filter, so that the roll off slope of the adjacent band of the high frequency side of the passband can be greatly improved, the adjacent band suppression of the high frequency side of the passband of the filter is greatly improved, and the filtering performance of the filter is further improved.

It should be noted that, in other embodiments, the first element 111 may further include a plurality of inductive elements, and the plurality of inductive elements may be connected in series and/or in parallel. The second element 112 may also comprise at least a plurality of capacitive elements, and may further comprise inductive elements on the basis of the plurality of capacitive elements. At least a plurality of capacitive elements may be connected in series and/or in parallel. Alternatively, the first element 111 and/or the second element 112 may further comprise a resistive element in series or parallel with the inductive element and/or the capacitive element for adjusting the resonance frequency of the pi-type LC network 11. The capacitive element may be a capacitive element, or may be parasitic capacitance generated between different elements. The resistance of the capacitive element may be set as required, and is not limited herein.

Fig. 5 is a schematic structural diagram of another filter according to an embodiment of the present invention. As shown in fig. 5, the filter includes at least two filter units 10, and the at least two filter units 10 are connected in series between a first port a and a second port B.

Specifically, the filter illustrated by way of example in fig. 5 comprises two filter units 10, the two filter units 10 being connected in series between a first port a and a second port B. When at least two filter units 10 are connected in series between the first port a and the second port B, different filter units 10 can generate two transmission zeros in the adjacent band on the passband high frequency side of the filter, so that the roll off slope of the adjacent band on the passband high frequency side of the filter can be greatly improved by at least two filter units 10, and therefore the adjacent band suppression on the passband high frequency side of the filter can be further improved to a great extent, and the filtering performance of the filter is further improved.

Illustratively, the transmission zeros of the different filter units 10 correspond to equal frequencies.

Specifically, parameters of the pi-type LC network 11 and the resonator 12 in the different filter units 10 may be the same, so that frequencies corresponding to transmission zeros of the different filter units 10 are equal, at this time, passband frequencies of the different filter units 12 are the same, and transmission zeros are formed at the same frequency, so that a roll off slope of a neighboring band on a high frequency side of the passband may be further increased. Illustratively, in different filter units 10, the elements of the pi-type LC network 11 are identical, and the element parameters at the same location are identical. While the parameters of the resonators 12 in the different filter units 10 are identical, so that the resonance frequencies of the different filter units 10 can be made equal.

In other embodiments, frequencies corresponding to the transmission zeros of different filter units 10 may be set to be different, so that the filter has a plurality of transmission zeros in a neighboring band range on the high-frequency side of the passband, and the roll off slope of the neighboring band on the high-frequency side of the passband may be further increased when there are two transmission zeros in relation to one filter unit 10. Illustratively, the elements of the pi-type LC network 11 may be different in different filter cells 10, and/or the parameters of the elements at the same location may be different, and/or the parameters of the resonators 12 in different filter cells 10.

It should be noted that, in other embodiments, the filter may include a plurality of filter units 10, where the plurality of filter units 10 are connected in series between the first port a and the second port B, which is not limited herein.

Fig. 6 is a schematic structural diagram of another filter according to an embodiment of the present invention. As shown in fig. 6, the filter further comprises at least one third port E, which is arranged between adjacent filter units 10.

Specifically, the filter shown in fig. 6 includes two filter units 10, and a third port E is provided between the two filter units 10. The third port E may be used for connection with external circuits so that the filter may be connected with different types of external circuits, increasing the range of application of the filter. In addition, the third port E can be connected with an equivalent large-impedance element, so that the third port E is equivalent to open circuit, and different use scenes of the filter can be met.

It should be noted that, when the filter includes a plurality of filter units 10, the third port E may be disposed between two adjacent filter units 10, or may be disposed between the filter unit 10 and the first port a and/or the second port B, and the filter may include a plurality of third ports E. Or may be disposed between the spaced filtering units 10, where the filter may include at least one third port E, which is not limited herein.

Fig. 7 is a schematic structural diagram of another filter according to an embodiment of the present invention. As shown in fig. 7, the filter further comprises at least one electromagnetic filter network 20, the electromagnetic filter network 20 being connected in series between the first port a and the second port B.

In particular, electromagnetic filter network 20 may include inductive elements and/or capacitive elements. When the electromagnetic filter network 20 only includes an inductive element or a capacitive element, the electromagnetic filter network 20 can compensate the pi-type LC network 11, so that the insertion loss of the pi-type LC network 11 can be reduced, and the filtering performance of the filter can be further improved. When the electromagnetic filter network 20 includes both inductive and capacitive elements, the electromagnetic filter network 20 may adjust the passband of the filter so that the filter has a wider passband.

Fig. 8 is a schematic structural diagram of another filter according to an embodiment of the present invention. As shown in fig. 8, the electromagnetic filter network 20 includes a second inductive element L2, and the second inductive element L2 is connected in series between the first port a and the second port B.

Specifically, fig. 8 exemplarily illustrates that the electromagnetic filter network 20 includes a second inductive element L2, where the second inductive element L2 is connected in series between the second port B and the filter unit 10, and when the first element 111 includes an inductive element and the second element 112 includes a capacitive element, the second inductive element L2 can compensate for the insertion loss of the pi-type LC network 11, so that the filtering performance of the filter can be further improved.

It should be noted that, in other embodiments, the electromagnetic filter network 20 may also include only a capacitive element, and by providing the capacitive element, the frequency of the filter unit 10 may be adjusted, and may also be used as a high-pass filter network in the filter to adjust the passband of the filter.

In other embodiments, fig. 9 is a schematic structural diagram of another filter according to an embodiment of the present invention. As shown in fig. 9, the electromagnetic filter network 20 further includes a third capacitive element C3, and the third capacitive element C3 is connected in series and/or in parallel with the second inductive element L2.

In particular, fig. 9 exemplarily shows that the third capacitive element C3 is connected in series with the second inductive element L2, and the second inductive element L2 and the third capacitive element C3 may form a filter network for adjusting the passband of the filter so that the filter has a wider passband. When the filter comprises the electromagnetic filter network 20 and the filter unit 10, the filter can have a wider passband, and the roll-off slope of the adjacent band of the high-frequency side of the passband of the filter can be improved, so that the adjacent band inhibition of the high-frequency side of the passband of the filter is improved to a great extent, and the filtering performance of the filter is improved.

It should be noted that, in other embodiments, the second inductive element L2 and the third capacitive element C3 may be further configured to be connected in parallel, so as to adjust the performance of the filter according to the requirement of the filter. Alternatively, when at least one of the second inductive element L2 and the third capacitive element C3 includes a plurality, the second inductive element L2 and the third capacitive element C3 may be provided to be connected in series and/or in parallel as needed, which is not limited herein.

Fig. 10 is a schematic structural diagram of another filter according to an embodiment of the present invention. As shown in fig. 10, the filter includes at least two filter units 10, and when the at least two filter units 10 are connected in series between the first port a and the second port B, at least one electromagnetic filter network 20 is connected between adjacent filter units 10.

In particular, fig. 10 exemplarily shows that the filter includes two filter units 10, and the electromagnetic filter network 20 is connected between the two filter units 10, so that different filter units 10 may be disposed at intervals.

It should be noted that, in other embodiments, the electromagnetic filter network 20 may be disposed between the first port a and the filter unit 10, or between the second port B and the filter unit 10, which is not limited herein.

The embodiment of the invention 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 a filter 100 provided in any embodiment of the present invention.

With continued reference to FIG. 11, the multiplexer includes a first end IN and at least two second ends; each filter 100 is connected IN series between the first terminal IN and either of the second terminals of the multiplexer.

Specifically, fig. 11 exemplarily shows that the multiplexer includes a first terminal IN and n second terminals OUT1, OUT2 … … OUTn, respectively. Each filter 100 is connected IN series between a first terminal IN and a second terminal. For example, a first filter 100 is connected IN series between the first terminal IN and the first second terminal OUT1, a second filter 100 is connected IN series between the first terminal IN and the first second terminal OUT2 … …, and so on. The multiplexer has the filter 100 provided by any embodiment of the invention, so that the multiplexer has the same beneficial effect as the filter 100, namely the roll-off slope of the adjacent band at the low frequency side of the pass band of the multiplexer, so that the adjacent band suppression at the low frequency side of the pass band of the filter is greatly improved, and the filtering performance of the filter is further improved.

It should be noted that the multiplexer may further include other filters, which are connected IN series between the first end IN and any of the second ends, and the other filters may be a low-pass filter, a high-pass filter, or a band-pass filter, which is not limited by the embodiment of the present invention.

Note that the above is only a preferred embodiment of the present invention and the technical principle applied. 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 invention. Therefore, while the invention has been described in connection with the above embodiments, the invention is not limited to the embodiments, but may be embodied in many other equivalent forms without departing from the spirit or scope of the invention, which is set forth in the following claims.

Claims

1. A filter comprising a first port, a second port and at least one filtering unit;

2. The filter of claim 1, wherein the pi-type LC network comprises one of the first element and two of the second elements;

3. A filter according to claim 1 or 2, characterized in that the filter comprises at least two of the filter units, which are connected in series between the first port and the second port.

4. A filter according to claim 3, further comprising at least one third port, at least one of said third ports being disposed between adjacent said filter cells.

5. A filter according to claim 3, wherein the frequencies corresponding to the transmission zeros of different ones of the filter units are equal.

6. The filter of claim 1, further comprising at least one electromagnetic filter network connected in series between the first port and the second port.

7. The filter of claim 6, wherein the filter comprises at least two of the filter units, at least one of the electromagnetic filter networks being connected between adjacent ones of the filter units when the at least two filter units are connected in series between the first port and the second port.

8. The filter according to claim 6 or 7, wherein the electromagnetic filter network comprises a second inductive element connected in series between the first port and the second port.

9. The filter according to claim 8, characterized in that the electromagnetic filter network further comprises a third capacitive element connected in series and/or in parallel with the second inductive element.

10. A multiplexer comprising a filter as claimed in any one of claims 1 to 9.