CN116032243A - Band-pass filter circuit of high roll-off of big bandwidth - Google Patents
Band-pass filter circuit of high roll-off of big bandwidth Download PDFInfo
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- CN116032243A CN116032243A CN202310045691.6A CN202310045691A CN116032243A CN 116032243 A CN116032243 A CN 116032243A CN 202310045691 A CN202310045691 A CN 202310045691A CN 116032243 A CN116032243 A CN 116032243A
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- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
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Abstract
The invention discloses a band-pass filter circuit with large bandwidth and high roll-off; the band-pass filter circuit comprises an LC filter circuit and an acoustic wave resonance unit. The input end of the LC filter circuit is connected with an input trunk; the output end of the LC filter circuit is connected with an output trunk. And the input trunk and/or the output trunk are connected with a plurality of acoustic wave resonance units. The sound wave resonance unit comprises a plurality of resonance branches; the resonant branch includes an inductive element and a first acoustic wave resonator in series. Each resonant branch is connected in parallel between the input main circuit and the ground wire or between the output main circuit and the ground wire. The invention uses the acoustic wave resonator with high quality factor to form various structures and then is connected with the LC filter circuit. A plurality of transmission zero points are introduced into adjacent band areas at two sides of a pass band of the LC filter circuit, and on the basis of retaining the original large-broadband characteristic of the LC filter circuit, the adjacent band inhibition at two sides of the pass band of the LC filter circuit and the roll off slope of a transition area are improved.
Description
Technical Field
The invention belongs to the technical field of filter circuits, and particularly relates to a band-pass filter circuit with a large bandwidth and high roll-off.
Background
With the gradual development of mobile phone technology, the requirements of modern communication on filters are increasing. Hundreds of filters may be required in a future cell phone to maintain their requirements for each frequency band. While today's communications are increasingly demanding in terms of filtering circuits for large bandwidths.
Although the traditional LC filter can realize large bandwidth, the defects of wide adjacent band rejection, slow roll-off and the like are always difficult to avoid. If the order of the filter circuit is increased blindly to improve roll-off, the loss of the whole circuit is increased to cause the deterioration of in-band interpolation loss, the filtering effect is reduced, and the size of the whole filter caused by excessive order is too large to be suitable for the current requirement of miniaturization design of the mobile phone.
Disclosure of Invention
The invention aims to provide a band-pass filter circuit with large bandwidth and high roll-off.
The invention discloses a band-pass filter circuit with large bandwidth and high roll-off, which comprises an LC filter circuit and an acoustic wave resonance unit. The input end of the LC filter circuit is connected with an input trunk; the output end of the LC filter circuit is connected with an output trunk. And the input trunk and/or the output trunk are connected with a plurality of acoustic wave resonance units. The sound wave resonance unit comprises a plurality of resonance branches; the resonant branch includes an inductive element and a first acoustic wave resonator in series. Each resonant branch is connected in parallel between the input main circuit and the ground wire or between the output main circuit and the ground wire.
Preferably, according to practical implementation, the LC filter circuit adopts any one of an IPD filter, an MLCC filter, and an LTCC filter; the first acoustic resonator is any one of a CMR resonator, a SAW resonator, an SMR resonator, and an FBAR resonator.
Preferably, the series resonance points of all the first acoustic wave resonators are located on adjacent bands of the passband edge of the LC filter circuit. The series resonance points of all the first acoustic wave resonators are different.
Preferably, the series resonance points of all the first acoustic wave resonators located on the input trunk are located in the area on the left side of the passband of the LC filter circuit. The series resonance points of all the first acoustic wave resonators on the output trunk are in the area to the right of the passband of the LC filter circuit.
Preferably, a plurality of second acoustic resonators are connected in series to the input trunk and/or the output trunk. When a plurality of second acoustic resonators are connected in series to the input trunk, acoustic resonance units are interposed between any two adjacent second acoustic resonators on the input trunk. A plurality of second acoustic resonators are connected in series on the output trunk; and an acoustic wave resonance unit is arranged between any two adjacent second acoustic wave resonators on the output trunk.
Preferably, the parallel resonance points of the second acoustic resonator are all located on adjacent bands of the passband edge of the LC filter circuit.
Preferably, the parallel resonance points of all the second acoustic resonators are different.
Preferably, the parallel resonance points of all the second acoustic resonators located on the input trunk are located in the area on the left side of the passband of the LC filter circuit. The parallel resonance points of all the second acoustic resonators on the output trunk are in the area to the right of the passband of the LC filter circuit. The second acoustic resonator is any one of CMR resonator, SAW resonator, SMR resonator, and FBAR resonator.
Preferably, each acoustic wave resonator unit includes only one resonant branch. When a plurality of acoustic wave resonant units are connected to the input trunk, a second acoustic wave resonator is arranged between any two adjacent acoustic wave resonant units on the input trunk and the connection point of the input trunk. And under the condition that a plurality of sound wave resonance units are connected to the output trunk, a second sound wave resonator is arranged between any two adjacent sound wave resonance units on the output trunk and the connection point of the output trunk.
Preferably, in the working process, the inductance element in each resonance branch and the electrostatic capacitance in the corresponding first acoustic wave resonator resonate, and a transmission zero point is added on the transmission curve; the transmission zero point is changed along with the change of the inductance value of the inductance element and is arranged on the adjacent band of the passband edge of the LC filter circuit.
Preferably, in the working process, the inductance element in each resonance branch and the electrostatic capacitance in the corresponding first acoustic wave resonator resonate, and a transmission zero point is added on the transmission curve; the transmission zero point is set in a frequency range outside the passband of the LC filter circuit as the inductance value of the inductance element changes.
The invention has the beneficial effects that:
1. the invention uses the acoustic wave resonator with high quality factor to form various structures and then is connected with the LC filter circuit. A plurality of transmission zero points are introduced into adjacent band areas at two sides of a pass band of the LC filter circuit, and on the basis of retaining the original large-broadband characteristic of the LC filter circuit, the adjacent band inhibition at two sides of the pass band of the LC filter circuit and the roll off slope of a transition area are improved. Finally, the dual-characteristic hybrid filter circuit with large bandwidth and high roll off slope is obtained.
2. On the basis of reserving large bandwidth of an LC filter circuit, the width of a transition area of the original LC filter circuit between 0.5GHz and 1GHz and even more than 1GHz is reduced to be less than 200MHz and even to be within 100 MHz; the adjacent band suppression of the conventional LC filter circuit is limited to be below-30 dB, so that the filtering performance of the band-pass filter circuit is improved.
Drawings
Fig. 1 is a schematic diagram of a bandpass filter circuit according to embodiment 1 of the present invention;
fig. 2 is a schematic structural diagram of a bandpass filter circuit according to embodiment 2 of the present invention;
fig. 3 is an S-parameter simulation diagram of the band-pass filter circuit provided in embodiment 2 of the present invention;
fig. 4 is a schematic structural diagram of a bandpass filter circuit according to embodiment 3 of the present invention;
fig. 5 is an S-parameter simulation diagram of the band-pass filter circuit provided in embodiment 3 of the present invention;
fig. 6 is a schematic structural diagram of a bandpass filter circuit according to embodiment 4 of the present invention;
fig. 7 is a schematic diagram of a band-pass filter circuit according to embodiment 5 of the present invention.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
The present invention will be described in detail with reference to specific embodiments and drawings. For convenience of description, the structures shown in the drawings are only relevant to the invention, and not all the structures.
Example 1
As shown in fig. 1, a band-pass filter circuit with a large bandwidth and a high roll-off includes an input interface, an output interface, an LC filter circuit 20, and two acoustic wave resonator units 10. An input main circuit is formed between the input interface and the input end of the LC filter circuit 20; an output trunk is formed between the output interface and the output of LC filter circuit 20.
The LC filter circuit adopts any one of an IPD filter, an MLCC filter and an LTCC filter; the first acoustic resonator is any one of a CMR resonator, a SAW resonator, an SMR resonator, and an FBAR resonator.
The first acoustic wave resonator 101 has a high quality factor and thus has good frequency selectivity. By setting the series resonance point of the acoustic wave resonator 101 on the adjacent band at the passband edge of the LC filter circuit 20, a zero point with a very large roll-off slope can be provided, so that the adjacent band suppression effect of the LC filter circuit 20 with a slow transition and the roll-off slope at the passband edge are improved.
In this embodiment, by adjusting the relevant parameters, the series resonance point of the first acoustic resonator 101 in the acoustic wave resonator unit 10 at the input end of the LC filter circuit 20 is placed on the adjacent band on the left side of the passband of the LC filter circuit 20, and the series resonance point of the first acoustic wave resonator 101 in the acoustic wave resonator unit 10 at the output end of the LC filter circuit 20 is placed on the adjacent band on the right side of the passband of the LC filter circuit 20, so as to achieve the purpose of optimizing both ends of the passband. Since the LC filter circuit 20 itself is characterized by a large bandwidth and a slow roll-off, the band-pass filter circuit optimized by this configuration has the dual characteristics of a large bandwidth and a high roll-off.
On the basis of embodiment 1, the acoustic wave resonator unit 10 may include a plurality of inductance elements 100 and a plurality of first acoustic wave resonators 101 in one-to-one correspondence. Each inductance element 100 is connected in series with a corresponding first acoustic wave resonator 101 to form a resonant branch; each resonant branch is connected in parallel between the input main circuit and the ground wire or between the output main circuit and the ground wire.
Example 2
As shown in fig. 2, a band-pass filter circuit with a large bandwidth and a high roll-off differs from embodiment 1 only in that: two second acoustic resonators 102 are also included. One of the second acoustic resonators 102 is connected in series on the input trunk. Another second acoustic resonator 102 is connected in series on the input rail. One of the acoustic wave resonator units 10 is connected in parallel between the input main and ground. The other acoustic wave resonator unit 10 is connected in parallel between the output main line and the ground line. The second acoustic resonator 102 and the acoustic wave resonator unit 10, which are connected together, form an L-shaped resonant structure 30. The second acoustic resonator 102 is any one of a CMR resonator, a SAW resonator, an SMR resonator, and an FBAR resonator.
The series resonance frequency of the first acoustic wave resonator 101 is on the adjacent band of the passband edge, so that a transmission zero is formed on the adjacent band to improve the adjacent band inhibition effect and the roll off slope of the passband edge; the inductance element 100 connected in series with the first acoustic wave resonator 101 can resonate with the electrostatic capacitance in the first acoustic wave resonator 101, so that a zero point is additionally added on the transmission curve, and the zero point can be positioned on the adjacent band at the edge of the passband by adjusting the inductance value of the inductance element 100; thereby further enhancing the adjacent band rejection and roll off slope of the passband edge, or locating the one zero out of band and further from the passband.
The parallel resonance point of the second acoustic resonator 102 is on the adjacent band of the passband edge, so that a transmission zero point is formed on the adjacent band to improve the adjacent band inhibition effect and the roll off slope of the passband edge; that is, one acoustic wave resonator unit 10 may additionally provide 3 transmission zeros in this structure to promote the adjacent band rejection and roll off slope of the band pass filter circuit. Therefore, the two acoustic wave resonator units 10 respectively connected to the input and output terminals of the LC filter circuit 20 can additionally provide at least 6 transmission zeros, and the adjacent band rejection and the roll off slope are optimized for both the left and right sides of the passband of the band-pass filter.
Fig. 3 is an S-parameter simulation diagram of the band-pass filter circuit provided in this embodiment. Wherein the abscissa is frequency and the ordinate is insertion loss. Curve 1 is the frequency response curve of the band-pass filter circuit provided in this embodiment, and curve 2 is the frequency response curve of the LC filter circuit alone. In curve 1, reference numerals 3, 4, 5 and 6 all point to transmission zeroes on the transmission curve; the transmission zero point pointed by the reference numeral 3 is provided by the first acoustic resonator 101 and the second acoustic resonator 102 in the L-shaped resonant structure 30 at the input end of the LC filter circuit 20, so as to improve the adjacent band rejection and roll off slope at the left side of the passband of the bandpass filter circuit; the transmission zero point indicated by the reference numeral 4 is provided by the first acoustic resonator 101 and the second acoustic resonator 102 in the L-shaped resonant structure 30 at the output end of the LC filter circuit 20, so as to improve the adjacent band rejection and roll off slope on the right side of the passband of the bandpass filter circuit. The transmission zeros indicated by reference numerals 5 and 6 are provided by the inductive elements 100 in the L-shaped resonant structure 30 at the input and output of the LC filter circuit 20, respectively, to further improve the adjacent band rejection of the band pass filter circuit and enhance the filtering performance.
As can be seen from fig. 3, the passband of curve 1 is in the range of 3.4-4.2 GHz, and the passband reaches 800MHz; the series resonance point of the first acoustic resonator 101 in the L-shaped resonance structure 30 at the input end of the LC filter circuit 20 is located on the adjacent band on the left side of the passband, the parallel resonance point of the second acoustic resonator 102 is located on the adjacent band on the left side of the passband, and noise signals with frequencies within the range of the adjacent band are blocked, so that the adjacent band suppression effect on the left side of the passband is improved, the transition band area is very narrow (less than 200 MHz), and the added acoustic resonance unit 10 and the second acoustic resonator 102 in the embodiment improve the filtering performance of the bandpass filter;
meanwhile, the series resonance point of the first acoustic resonator 101 in the L-shaped resonance structure 30 at the output end of the LC filter circuit 20 is located on the adjacent band on the right side of the passband, the parallel resonance point of the second acoustic resonator 102 is located on the adjacent band on the right side of the passband, and noise signals with frequencies within the adjacent band range are blocked, so that the adjacent band suppression effect on the right side of the passband is improved, and the transition band region is narrower than the left side and is less than 150MHz.
This can be explained by: the band-pass filter circuit provided by the embodiment has the dual characteristics of large bandwidth and high roll-off, and the filter effect is improved.
Example 3
As shown in fig. 4, a band-pass filter circuit with a large bandwidth and a high roll-off differs from embodiment 2 only in that: a second acoustic resonator 102 is connected in series with the input trunk; two acoustic wave resonance units 10 are connected in parallel between the input main circuit and the ground wire. The second acoustic resonator 102 is located between the connection points of the two acoustic wave resonator units 10 and the input trunk; a second acoustic resonator 102 is connected in series with the output trunk; two acoustic wave resonance units 10 are connected in parallel between the output trunk and the ground. The second acoustic resonator 102 is located between the two acoustic wave resonator units 10 and the connection point of the output trunk; the second acoustic resonator 102 and its adjacent two acoustic wave resonator elements 10 form a pi-shaped resonant structure 40.
Fig. 5 is an S-parameter simulation diagram of the band-pass filter circuit provided in this embodiment. The abscissa is frequency and the ordinate is insertion loss. Curve 7 is the frequency response curve of the band-pass filter circuit provided in this embodiment, and curve 8 is the frequency response curve of the LC filter circuit 20.
As can be seen from fig. 5, the passband range of curve 7 is likewise 800MHz; as more first acoustic resonators 101 and inductance elements 100 are connected, transmission zero points in the adjacent band range are further increased, noise signals with frequencies in the adjacent band range are further blocked, adjacent band rejection and transition band roll off slope of the passband edge are further increased, and filtering performance is improved. Obviously, the adjacent band suppression range is far more than 200MHz, and the transition band areas on the left side and the right side of the passband are very narrow and even less than 100MHz. It can be seen that this structure still allows the adjacent band rejection and the transition roll off slope of the overall filter circuit to be greatly improved by sacrificing less in-band insertion loss in the case where the transition region facing the LC filter circuit 20 is at 1GHz or even greater than 1 GHz. The band-pass filter circuit also has the double characteristics of large bandwidth and high roll-off, and the filter effect is obviously improved.
Example 4
As shown in fig. 6, a band-pass filter circuit with a large bandwidth and a high roll-off differs from embodiment 2 only in that: a second acoustic resonator 102 is connected in series with the input trunk; two acoustic wave resonance units 10 are connected in parallel between the input main circuit and the ground wire. The second acoustic resonator 102 is located between the connection points of the two acoustic wave resonator units 10 and the input trunk; two second acoustic resonators 102 are connected in series on the output trunk; three acoustic wave resonance units 10 are connected in parallel between the output trunk and the ground wire. A second acoustic resonator 102 is disposed between any two adjacent acoustic wave resonator units 10. The second acoustic resonator 102 and its adjacent two acoustic wave resonator elements 10 form a pi-shaped resonant structure 40.
Fig. 6 is a schematic structural diagram of a bandpass filter circuit according to the present embodiment. As shown in fig. 6, one side of the LC filter circuit 20 may be sequentially connected in series with 2 or more acoustic wave resonator units 10, and a combination structure 30 is shared between every two adjacent acoustic wave resonator units 10, so as to form a continuous pi-type structure. In the case that the plurality of acoustic wave resonance units 10 are connected, more transmission zeros can be provided in the adjacent band range on one side of the passband to filter noise signals in the adjacent band range, so that the range and the suppression effect of the adjacent band suppression area and the roll off slope of the transition area are further improved, and the performance of the bandpass filter circuit is improved.
Example 5
As shown in fig. 7, a band-pass filter circuit with a large bandwidth and a high roll-off differs from embodiment 2 only in that: two second acoustic resonators 102 are connected in series on the input trunk; three acoustic wave resonant units 10 are connected in parallel between the input main circuit and the ground wire. A second acoustic resonator 102 is disposed between any two adjacent acoustic wave resonator units 10. Two second acoustic resonators 102 are connected in series on the output trunk; three acoustic wave resonance units 10 are connected in parallel between the output trunk and the ground wire. A second acoustic resonator 102 is disposed between any two adjacent acoustic wave resonator units 10. The second acoustic resonator 102 and its adjacent two acoustic wave resonator elements 10 form a pi-shaped resonant structure 40.
On the basis of embodiment 5, the number of the acoustic wave resonator units 10 and the second acoustic wave resonator 102 can be further increased on the input trunk and the output trunk, and all the acoustic wave resonator units 10 are connected in parallel between the input trunk and the ground line, or between the input trunk and the ground line.
Claims (10)
1. A large bandwidth high roll-off bandpass filter circuit comprising an LC filter circuit (20); the method is characterized in that: further comprises an acoustic resonance unit (10); an input main circuit is connected with the input end of the LC filter circuit (20); an output end of the LC filter circuit (20) is connected with an output trunk; the input trunk and/or the output trunk are connected with a plurality of acoustic wave resonance units (10); the sound wave resonance unit (10) comprises a plurality of resonance branches; the resonant branch comprises an inductive element (100) and a first acoustic wave resonator (101) connected in series; each resonant branch is connected in parallel between the input main circuit and the ground wire or between the output main circuit and the ground wire.
2. The high-bandwidth high-roll-off bandpass filter circuit of claim 1, wherein: the LC filter circuit (20) adopts any one of an IPD filter, an MLCC filter and an LTCC filter; the first acoustic resonator (101) is any one of a CMR resonator, a SAW resonator, an SMR resonator, and an FBAR resonator.
3. The high-bandwidth high-roll-off bandpass filter circuit of claim 1, wherein: all the series resonance points of the first acoustic wave resonators (101) are positioned on the adjacent bands of the passband edge of the LC filter circuit (20); the series resonance points of all the first acoustic wave resonators (101) are different.
4. The high-bandwidth high-roll-off bandpass filter circuit of claim 1, wherein: all the series resonance points of the first acoustic wave resonators (101) on the input trunk are in the field of the left side of the passband of the LC filter circuit (20); the series resonance points of all the first acoustic wave resonators (101) on the output trunk are located in the area on the right side of the passband of the LC filter circuit (20).
5. A large bandwidth high roll-off bandpass filter circuit according to any one of claims 1-4, wherein: a plurality of second acoustic resonators (102) are connected in series on the input trunk and/or the output trunk; when a plurality of second acoustic resonators (102) are connected in series to an input trunk, acoustic resonance units (10) are arranged between any two adjacent second acoustic resonators (102) on the input trunk; a plurality of second acoustic resonators (102) are connected in series to the output trunk; an acoustic wave resonance unit (10) is arranged between any two adjacent second acoustic wave resonators (102) on the output trunk.
6. The high-bandwidth high-roll-off bandpass filter circuit of claim 5, wherein: the parallel resonance points of the second acoustic resonator (102) are all located on the adjacent bands of the passband edge of the LC filter circuit (20).
7. The high-bandwidth high-roll-off bandpass filter circuit of claim 5, wherein: the series resonance points of all the second acoustic wave resonators (102) are different.
8. The high-bandwidth high-roll-off bandpass filter circuit of claim 5, wherein: all the parallel resonance points of the second acoustic resonators (102) on the input trunk are in the field of the left side of the passband of the LC filter circuit (20); the parallel resonance points of all the second acoustic resonators (102) on the output trunk are in the area to the right of the passband of the LC filter circuit (20).
9. The high-bandwidth high-roll-off bandpass filter circuit of claim 1, wherein: each acoustic wave resonance unit (10) comprises only one resonance branch; under the condition that a plurality of sound wave resonance units (10) are connected to the input trunk, a second sound wave resonator (102) is arranged between any two adjacent sound wave resonance units (10) on the input trunk and the connection point of the input trunk; when a plurality of acoustic wave resonant units (10) are connected to the output trunk, a second acoustic wave resonator (102) is arranged between any two adjacent acoustic wave resonant units (10) on the output trunk and the connection point of the output trunk.
10. The high-bandwidth high-roll-off bandpass filter circuit of claim 1, wherein: in the working process, an inductance element (100) in each resonance branch and the electrostatic capacity in the corresponding first acoustic wave resonator (101) resonate, and a transmission zero point is added on a transmission curve; the transmission zero point is changed along with the change of the inductance value of the inductance element (100), and is arranged on the adjacent band of the passband edge of the LC filter circuit (20).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310045691.6A CN116032243A (en) | 2023-01-30 | 2023-01-30 | Band-pass filter circuit of high roll-off of big bandwidth |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202310045691.6A CN116032243A (en) | 2023-01-30 | 2023-01-30 | Band-pass filter circuit of high roll-off of big bandwidth |
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| CN116032243A true CN116032243A (en) | 2023-04-28 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117097298A (en) * | 2023-10-19 | 2023-11-21 | 苏州声芯电子科技有限公司 | Filter circuit for improving out-of-band rejection |
-
2023
- 2023-01-30 CN CN202310045691.6A patent/CN116032243A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117097298A (en) * | 2023-10-19 | 2023-11-21 | 苏州声芯电子科技有限公司 | Filter circuit for improving out-of-band rejection |
| CN117097298B (en) * | 2023-10-19 | 2024-02-09 | 苏州声芯电子科技有限公司 | Filter circuit for improving out-of-band rejection |
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