CN213402952U - Filter structure - Google Patents
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- CN213402952U CN213402952U CN202022679389.0U CN202022679389U CN213402952U CN 213402952 U CN213402952 U CN 213402952U CN 202022679389 U CN202022679389 U CN 202022679389U CN 213402952 U CN213402952 U CN 213402952U
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Abstract
The invention provides a filter structure, which comprises a first port, a first filter, a second filter and a second port which are connected in sequence, wherein the second filter comprises at least one series unit and at least one parallel branch, the at least one series unit is connected between the first filter and the second port in series, and the at least one parallel branch is connected between the first filter and the second port in parallel; the first filter is an LC band-pass filter or an LC high-pass filter, each parallel branch in the second filter comprises an acoustic resonator, and each series unit is realized by adopting a non-acoustic passive device; or, the first filter is an LC band-pass filter or an LC low-pass filter, each series unit in the second filter includes an acoustic resonator, and each parallel branch is implemented by a non-acoustic passive device. The filter structure provided by the invention has the characteristics of both broadband and sharp stop band.
Description
Technical Field
The invention relates to the technical field of communication, in particular to a filter structure.
Background
LC filters and acoustic filters are two types of filters that are currently commercially available.
LC filters are non-acoustic filters that include passive components and are currently widely used in harmonic management schemes. The LC filter typically has a wide band and relatively good wide stopband characteristics, but there is no particularly sharp stopband at frequencies near the passband, that is, the roll-off loss of the LC filter is high at passband edge frequencies, which is undesirable in the co-existing band.
An acoustic filter is a filter implemented using acoustic devices. Typical acoustic devices include, among others, acoustic resonator implementations, such as Surface Acoustic Wave (SAW) resonators, Bulk Acoustic Wave (BAW) resonators, and the like. Acoustic filters are commonly used in prior art radio frequency electronic systems, such as the radio frequency front end of mobile phones, etc. Since the acoustic filter has a higher quality factor than the LC filter, the acoustic filter can provide higher rejection at frequencies close to the passband relative to the LC filter to avoid too high edge roll-off loss, but the acoustic filter is more difficult to implement for broadband functionality.
That is, neither the LC filter nor the acoustic filter has the characteristics of both a wide band and a sharp stop band. Therefore, in some applications requiring the filter to have both of the above characteristics, neither LC filter nor acoustic filter can be used to meet the application requirements well.
SUMMERY OF THE UTILITY MODEL
In order to overcome the above-mentioned drawbacks of the prior art, the present invention provides a filter structure, comprising:
the filter comprises a first port, a first filter connected with the first port, a second filter cascaded with the first filter, and a second port connected with the second filter, wherein the second filter comprises at least one series unit and at least one parallel branch, the at least one series unit is connected between the first filter and the second port in series, and the at least one parallel branch is connected between the first filter and the second port in parallel;
the first filter is an LC band-pass filter or an LC high-pass filter, each parallel branch in the second filter comprises an acoustic resonator, and each series unit is realized by adopting a non-acoustic passive device; or, the first filter is an LC band-pass filter or an LC low-pass filter, each of the series units in the second filter includes an acoustic resonator, and each of the parallel branches is implemented by a non-acoustic passive device.
According to one aspect of the invention, each of the parallel branches in the second filter comprises an acoustic resonator, and each of the series units is implemented by using a non-acoustic passive device, and comprises: each of the parallel branches includes an acoustic resonator and a first inductor connected in series, and each of the series units is a second inductor.
According to another aspect of the present invention, each of the parallel branches in the second filter includes an acoustic resonator, and each of the series units is implemented using a non-acoustic passive device, including: each of the parallel branches is an acoustic resonator, and each of the series units includes a third inductor and a first capacitor connected in parallel.
According to yet another aspect of the invention, each of the series units in the second filter comprises an acoustic resonator, and each of the parallel branches is implemented using a non-acoustic passive device, comprising: each of the series units is an acoustic resonator, and each of the parallel branches includes a second capacitor and a fourth inductor connected in series.
According to yet another aspect of the invention, each of the series units in the second filter comprises an acoustic resonator, and each of the parallel branches is implemented using a non-acoustic passive device, comprising: each of the series units includes an acoustic resonator and a fifth inductor connected in parallel, and each of the parallel branches is a sixth inductor.
According to still another aspect of the present invention, in the filter structure, the second filter includes N series units and N parallel branches, and one parallel branch is respectively connected in parallel between the first filter and the series unit connected in series therewith, and between two adjacent series units, or one parallel branch is respectively connected in parallel between two adjacent series units, and between the second port and the series unit connected in series therewith; or the second filter comprises N series units and N +1 parallel branches, and one parallel branch is respectively connected in parallel between the first filter and the series unit connected in series with the first filter, between two adjacent series units, and between the second port and the series unit connected in series with the second filter; or the second filter comprises N +1 series units and N parallel branches, and one parallel branch is connected between every two adjacent series units in parallel; wherein N is an integer of 1 or more.
According to still another aspect of the present invention, in the filter structure, the number of the parallel branches is 2 or more.
According to still another aspect of the present invention, in the filter structure, for a case that the first filter is an LC band-pass filter or an LC high-pass filter, each of the parallel branches of the second filter includes an acoustic resonator, and each of the series units is implemented by a non-acoustic passive device, the first transmission zero of the first filter is located on the left side of the pass band of the filter structure, and the second transmission zero of the second filter is located on the right side of the pass band of the filter structure.
According to still another aspect of the present invention, in the filter structure, for a case that the first filter is an LC band-pass filter or an LC low-pass filter, each of the series units in the second filter includes an acoustic resonator, and each of the parallel branches is implemented by a non-acoustic passive device, the first transmission zero of the first filter is located on the right side of the pass band of the filter structure, and the second transmission zero of the second filter is located on the left side of the pass band of the filter structure.
According to yet another aspect of the invention, the filter structure further comprises one or more of a first port matching network, a second port matching network, and an interstage matching network, wherein the first port matching network is disposed between the first port and the first filter, the second port matching network is disposed between the second port and the second filter, and the interstage matching network is disposed between the first filter and the second filter.
The filter structure provided by the invention comprises a first port, a first filter connected with the first port, a second filter cascaded with the first filter, and a second port connected with the second filter, wherein the second filter comprises at least one series unit and at least one parallel branch, the at least one series unit is connected between the first filter and the second port in series, and the at least one parallel branch is connected between the first filter and the second port in parallel; the first filter is an LC band-pass filter or an LC high-pass filter, each parallel branch in the second filter comprises an acoustic resonator, and each series unit is realized by adopting a non-acoustic passive device; or, the first filter is an LC band-pass filter or an LC low-pass filter, each series unit in the second filter includes an acoustic resonator, and each parallel branch is implemented by a non-acoustic passive device. The first filter is an LC filter, which has a wide band and relatively good wide stop band characteristics, and the acoustic resonators in the second filter can provide higher rejection at frequencies close to the pass band without too high edge roll-off loss, so that the filter structure provided by the present invention has both wide band and sharp stop band characteristics accordingly.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments made with reference to the following drawings:
FIG. 1 is a schematic diagram of a filter structure according to an embodiment of the present invention;
fig. 2 is a circuit diagram of a filter structure according to a preferred embodiment of the present invention;
fig. 3 is a circuit diagram of a filter structure according to another preferred embodiment of the present invention;
fig. 4 is a circuit diagram of a filter structure according to yet another preferred embodiment of the present invention;
fig. 5 is a circuit diagram of a filter structure according to yet another preferred embodiment of the present invention;
FIG. 6 is a plot of the amplitude-frequency response of the filter structure of FIG. 2;
FIG. 7 is a plot of the amplitude-frequency response of the filter structure of FIG. 6 over the left-hand side of the passband;
FIG. 8 is a plot of the amplitude-frequency response of the filter structure of FIG. 6 within the pass band;
fig. 9 is a schematic diagram of a filter structure according to another embodiment of the present invention.
The same or similar reference numbers in the drawings identify the same or similar elements.
Detailed Description
For a better understanding and explanation of the present invention, reference will now be made in detail to the present invention as illustrated in the accompanying drawings.
The invention provides a filter structure comprising:
the filter comprises a first port, a first filter connected with the first port, a second filter cascaded with the first filter, and a second port connected with the second filter, wherein the second filter comprises at least one series unit and at least one parallel branch, the at least one series unit is connected between the first filter and the second port in series, and the at least one parallel branch is connected between the first filter and the second port in parallel;
the first filter is an LC band-pass filter or an LC high-pass filter, each parallel branch in the second filter comprises an acoustic resonator, and each series unit is realized by adopting a non-acoustic passive device; or, the first filter is an LC band-pass filter or an LC low-pass filter, each of the series units in the second filter includes an acoustic resonator, and each of the parallel branches is implemented by a non-acoustic passive device.
The respective constituent parts of the above-described filter structure will be described in detail below.
Specifically, as shown in fig. 1, the filter structure includes a first port 30a, a first filter 10, a second filter 20, and a second port 30b, wherein the first port 30a, the first filter 10, the second filter 20, and the second port 30b are connected in sequence.
The filter structure provided by the invention is suitable for multi-purpose scenes. In a specific embodiment, the filter structure is used in a radio frequency communication system, and the filter structure is disposed between an antenna and an amplifier, wherein, according to the practical application requirement, the first port 30a of the filter structure is connected to the antenna, the second port 30b is connected to the amplifier, or the first port 30a of the filter structure is connected to the amplifier, and the second port 30b is connected to the antenna. It should be noted that, the specific signal flow directions of the first port 30a and the second port 30b of the filter structure are not limited in any way. In some embodiments, the first port 30a of the filter structure is used for signal input, and the second port 30b is used for signal output, that is, a signal is input from the first port 30a, passes through the first filter 10 and the second filter 20, and then reaches the second port 30b for output. In other embodiments, the second port 30b of the filter structure is used for signal input, and the first port 30a is used for signal output, that is, a signal is input from the second port 30b, passes through the second filter 20 and the first filter 10, and then reaches the first port 30a for output.
The first filter 10 is an LC filter. The second filter 20 is a hybrid passive acoustic filter, i.e. a filter consisting of acoustic resonators and non-acoustic passive devices. The acoustic resonator may be a surface acoustic wave resonator, a bulk acoustic wave resonator, or the like. The non-acoustically passive devices may be inductors, capacitors, and the like. In the present embodiment, the second filter 20 comprises at least one series unit and at least one parallel branch. Wherein the at least one series unit is connected in series between the first filter 10 and the second port 30b to form a series branch. The at least one parallel branch is connected in parallel between the first filter 10 and the second port 30b, i.e. for each parallel branch, one end is connected to a node between the first filter 10 and the second port 30b, and the other end is grounded.
There are two possibilities for the structure formed by the first filter 10 and the second filter 20 cascaded. The first possibility is: the first filter 10 is an LC band-pass filter or an LC high-pass filter. Accordingly, the acoustic resonator comprised by the second filter 20 is arranged in its parallel branch. Specifically, each parallel branch in the second filter 20 is provided with an acoustic resonator, and each series unit is implemented by a non-acoustic passive device. The second possibility is: the first filter 10 is an LC band-pass filter or an LC low-pass filter. Accordingly, the acoustic resonator comprised by the second filter 20 is arranged in its series branch. Specifically, each series unit of the second filter 20 is provided with an acoustic resonator, and each parallel branch is implemented by a non-acoustic passive device.
The LC filter can provide broadband and relatively good wide stop-band characteristics, and the acoustic resonators in the hybrid passive acoustic filter can provide higher suppression at a near stop band without too high edge roll-off loss, so that the filter structure formed by cascading the LC filter and the hybrid passive acoustic filter has the broadband and sharp stop-band characteristics. The acoustic resonators are arranged in the parallel branches and can achieve passband left side near-stop band suppression, and the acoustic resonators are arranged in the series branches and can achieve passband right side near-stop band suppression.
Two specific embodiments will be described below with respect to the case where the acoustic resonators are arranged on the parallel arms in the second filter.
In a specific embodiment, each parallel branch of the second filter includes an acoustic resonator (hereinafter, referred to as a first acoustic resonator) and an inductor (hereinafter, referred to as a first inductor) connected in series, where the connection order of the first acoustic resonator and the first inductor is not limited in this document, and may be that one end of the first acoustic resonator is connected to the series branch of the second filter, and the other end is connected to one end of the first inductor, and the other end of the first inductor is grounded, or that one end of the first inductor is connected to the series branch of the second filter, and the other end is connected to one end of the first acoustic resonator, and the other end of the first acoustic resonator is grounded. Each series unit of the second filter is an inductor (hereinafter referred to as second inductor), i.e. one or more second inductors are connected in series between the first filter and the second port. In a preferred embodiment, as shown in fig. 2, the filter structure comprises a first port 30a, a first filter 10 connected to the first port 30a, a second filter 20 connected to the first filter 10, and a second port 30b connected to the second filter. The first filter 10 includes three third capacitors connected in series between the first port 30a and the second filter 20, which are a third capacitor 101a, a third capacitor 101b, and a third capacitor 101c in this order from the first port 30a to the second filter 20. The first filter 10 further includes two parallel branches, each of which includes a seventh inductor and a fourth capacitor connected in series, where one of the parallel branches is connected to a node between the third capacitor 101a and the third capacitor 101b, one end of the seventh inductor 102a in the parallel branch is connected to the node, the other end of the seventh inductor is connected to one end of the fourth capacitor 103a, and the other end of the fourth capacitor 103a is grounded; the other parallel branch is connected to a node between the third capacitor 101b and the third capacitor 101c, one end of a seventh inductor 102b in the parallel branch is connected to the node, the other end is connected to one end of a fourth capacitor 103b, and the other end of the fourth capacitor 103b is grounded. The second filter 20 comprises four series units and three parallel branches. Each series unit is composed of a second inductor, that is, a second inductor 201a, a second inductor 201b, a second inductor 201c, and a second inductor 201d are connected in series between the first filter 10 and the second port 30b in sequence; each parallel branch includes a first acoustic resonator and a first inductor connected in series, wherein one parallel branch is connected to a node between the second inductor 201a and the second inductor 201b, one end of the first acoustic resonator 202a in the parallel branch is connected to the node, the other end is connected to one end of the first inductor 203a, and the other end of the first inductor 203a is grounded; the other parallel branch is connected to a node between the second inductor 201b and the second inductor 201c, one end of the first acoustic resonator 202b in the parallel branch is connected to the node, the other end is connected to one end of the first inductor 203b, and the other end of the first inductor 203b is grounded; a further parallel branch is connected to a node between the second inductor 201c and the second inductor 201d, one end of the first acoustic resonator 202c in the parallel branch is connected to the node, the other end is connected to one end of the first inductor 203c, and the other end of the first inductor 203c is grounded.
In another specific embodiment, each parallel branch of the second filter is an acoustic resonator (hereinafter referred to as a second acoustic resonator), i.e. one end of the second acoustic resonator is connected to the series branch of the second filter, and the other end is grounded; each series cell of the second filter comprises an inductor (hereinafter denoted as third inductor) and a capacitor (hereinafter denoted as first capacitor) connected in parallel. In a preferred embodiment, as shown in fig. 3, the filter structure comprises a first port 30a, a first filter 10 connected to the first port 30a, a second filter 20 connected to the first filter 10, and a second port 30b connected to the second filter. The first filter 10 has the same structure as the first filter 10 in the filter structure shown in fig. 2, and for the sake of brevity, the structure of the first filter 10 will not be described again. The second filter 20 comprises four series units and three parallel branches. Wherein each series unit is composed of a third inductor and a first capacitor connected in parallel, that is, a series unit 1 connected in parallel with a third inductor 210a and a first capacitor 211a, a series unit 2 connected in parallel with a third inductor 210b and a first capacitor 211b, a series unit 3 connected in parallel with a third inductor 210c and a first capacitor 211c, and a series unit 4 connected in parallel with a third inductor 210d and a first capacitor 211d are connected in series between the first filter 10 and the second port 30b in this order; each parallel branch is composed of a second acoustic resonator, wherein one parallel branch is connected to a node between the series unit 1 and the series unit 2, one end of the second acoustic resonator 212a in the parallel branch is connected to the node, and the other end is grounded; the other parallel arm is connected to a node between the series unit 2 and the series unit 3, and one end of the second acoustic resonator 212b in the parallel arm is connected to the node and the other end is grounded; a further parallel arm is connected to a node between the series unit 3 and the series unit 4, and the second acoustic resonator 212c in the parallel arm has one end connected to the node and the other end grounded.
The following description is also given of two specific embodiments for the case where the acoustic resonators are arranged in the series arms in the second filter.
In a specific embodiment, each series unit of the second filter is an acoustic resonator (hereinafter referred to as a third acoustic resonator), i.e. one or more third acoustic resonators are connected in series between the first filter and the second port. Each parallel branch of the second filter includes a capacitor (hereinafter, referred to as a second capacitor) and an inductor (hereinafter, referred to as a fourth inductor) connected in series, where the connection order of the second capacitor and the fourth inductor is not limited in this document, and one end of the second capacitor may be connected to the series branch of the second filter, and the other end of the second capacitor may be connected to one end of the fourth inductor, and the other end of the fourth inductor may be grounded, and one end of the fourth inductor may be connected to the series branch of the second filter, and the other end of the fourth inductor may be connected to one end of the second capacitor, and the other end of the second capacitor may be grounded. In a preferred embodiment, as shown in fig. 4, the filter structure comprises a first port 30a, a first filter 10 connected to the first port 30a, a second filter 20 connected to the first filter 10, and a second port 30b connected to the second filter. The first filter 10 includes three eighth inductors connected in series between the first port 30a and the second filter 20, which are an eighth inductor 110a, an eighth inductor 110b, and an eighth inductor 110c in this order from the first port 30a to the second filter 20. The first filter 10 further includes two parallel branches, each of which includes a fifth capacitor and a ninth inductor connected in series, wherein one of the parallel branches is connected to a node between the eighth inductor 110a and the eighth inductor 110b, one end of the fifth capacitor 111a in the parallel branch is connected to the node, the other end of the fifth capacitor is connected to one end of the ninth inductor 112a, and the other end of the ninth inductor 112a is grounded; the other parallel branch is connected to a node between the eighth inductor 110b and the eighth inductor 110c, one end of a fifth capacitor 111b in the parallel branch is connected to the node, the other end is connected to one end of a ninth inductor 112b, and the other end of the ninth inductor 112b is grounded. The second filter 20 comprises four series units and three parallel branches. Each series unit is composed of a third acoustic resonator, that is, the third acoustic resonator 220a, the third acoustic resonator 220b, the third acoustic resonator 220c and the third acoustic resonator 220d are sequentially connected in series between the first filter 10 and the second port 30 b; each parallel arm includes a second capacitor and a fourth inductor connected in series, where one parallel arm is connected to a node between the third acoustic resonator 220a and the third acoustic resonator 220b, one end of the second capacitor 221a in the parallel arm is connected to the node, the other end is connected to one end of the fourth inductor 222a, and the other end of the fourth inductor 222a is grounded; another parallel branch is connected to a node between the third acoustic resonator 220b and the third acoustic resonator 220c, one end of the second capacitor 221b in the parallel branch is connected to the node, the other end is connected to one end of the fourth inductor 222b, and the other end of the fourth inductor 222b is grounded; a further parallel branch is connected to a node between the third acoustic resonator 220c and the third acoustic resonator 220d, one end of the second capacitor 221c in the parallel branch is connected to the node, the other end is connected to one end of the fourth inductor 222c, and the other end of the fourth inductor 222c is grounded.
In another specific embodiment, each series unit of the second filter includes an acoustic resonator (hereinafter, fourth acoustic resonator) and an inductor (hereinafter, fifth inductor) connected in parallel. Each parallel branch of the second filter is an inductor (hereinafter referred to as a sixth inductor), i.e. one end of the sixth inductor is connected to the series branch of the second filter, and the other end is grounded. In a preferred embodiment, as shown in fig. 5, the filter structure comprises a first port 30a, a first filter 10 connected to the first port 30a, a second filter 20 connected to the first filter 10, and a second port 30b connected to the second filter. The first filter 10 has the same structure as the first filter 10 in the filter structure shown in fig. 4, and for the sake of brevity, the structure of the first filter 10 will not be described again. The second filter 20 comprises four series units and three parallel branches. Wherein each series unit is composed of a fourth acoustic resonator and a fifth inductor connected in parallel, that is, a series unit 1 connected in parallel by a fourth acoustic resonator 230a and a fifth inductor 231a, a series unit 2 connected in parallel by a fourth acoustic resonator 230b and a fifth inductor 231b, a series unit 3 connected in parallel by a fourth acoustic resonator 230c and a fifth inductor 231c, and a series unit 4 connected in parallel by a fourth acoustic resonator 230d and a fifth inductor 231d are sequentially connected in series between the first filter 10 and the second port 30 b; each parallel branch is composed of a sixth inductor, wherein one parallel branch is connected to a node between the series unit 1 and the series unit 2, one end of the sixth inductor 232a in the parallel branch is connected to the node, and the other end is grounded; the other parallel branch is connected to a node between the series unit 2 and the series unit 3, one end of a sixth inductor 232b in the parallel branch is connected to the node, and the other end is grounded; a further parallel branch is connected to a node between the series units 3 and 4, and a sixth inductor 232c in the parallel branch has one end connected to the node and the other end connected to ground.
It should be noted that fig. 2 to fig. 5 are only schematic examples, and do not limit the filter structure provided by the present invention. The specific structure of the first filter 10 and the second filter 20 can be designed accordingly according to the actual requirements of the filter structure.
The specific number of the series units and the parallel branches in the second filter is not limited, and the second filter can be designed correspondingly according to actual requirements. Preferably, however, the second filter includes N series units and N parallel branches (N is an integer greater than or equal to 1), that is, the order of the series branches is the same as that of the parallel branches, in which case, one parallel branch is respectively connected in parallel between the first filter and the series unit connected in series therewith, and between two adjacent series units, or one parallel branch is respectively connected in parallel between two adjacent series units, and between the second port and the series unit connected in series therewith. Further alternatively, the second filter includes N series units and N +1 parallel branches (N is an integer equal to or greater than 1), that is, the number of the series branches is less than 1, and in this case, one parallel branch is connected in parallel between the first filter and the series unit connected in series thereto, between two adjacent series units, and between the second port and the series unit connected in series thereto, respectively. Still alternatively, the second filter includes N +1 series units and N parallel branches (i.e., N is an integer greater than or equal to 1), that is, the order of the series branch is greater than that of the parallel branch by 1, in this case, one parallel branch is connected in parallel between two adjacent series units, as shown in the second filter in fig. 2 to 5.
Preferably, the number of the parallel branches of the second filter in the filter structure provided by the present invention is greater than or equal to 2, so as to meet the performance requirement of the filter structure on a wide frequency near stop band.
For the case where the first filter is an LC band-pass filter or an LC high-pass filter, and the acoustic resonators in the second filter are disposed in parallel branches, it is preferable to make the transmission zero (hereinafter, referred to as a first transmission zero) of the first filter on the left side of the pass band of the filter structure and the transmission zero (hereinafter, referred to as a second transmission zero) of the second filter on the right side of the pass band of the filter structure by proper design, so that the filter structure can be effectively ensured to have excellent insertion loss and return loss characteristics while achieving broadband and pass-band-left-side near-stop band rejection. Similarly, in the case where the first filter is an LC band-pass filter or an LC low-pass filter, and the acoustic resonator in the second filter is disposed in the series branch, it is preferable to properly design the first transmission zero of the first filter to be located on the right side of the passband of the filter structure, and the second transmission zero of the second filter to be located on the left side of the passband of the filter structure, so that the filter structure can be effectively ensured to have excellent insertion loss and return loss characteristics while achieving a broadband and passband-right-side near-stop band rejection.
The following description will be given by taking an example of constructing a 5GHz Wlan filter having a relative bandwidth of 12.7%. On the one hand, it is difficult to achieve with a purely acoustic resonator solution, since the relative bandwidth of 12.7% is wide. On the other hand, since the 5GHz Wlan band (the band is 5150MHz-5850MHz) and the N79 band (the band is 4400MHz-5000MHz) coexist, and the frequency interval between the two bands is only 150MHz, it is difficult to realize such a sharp stop band by using a pure LC filter. Based on this, the filter structure provided by the present invention is used for implementation, specifically, the structure shown in fig. 2 is used for implementation, where parameters of each element are as follows: the first filter 10 is 2 nd order elliptic high pass filtering in which the capacitance values of the third capacitor 101a, the third capacitor 101b and the third capacitor 101c are 0.59pf, 0.42pf and 0.89pf, respectively, the inductance values of the seventh inductor 102a and the seventh inductor 102b are 1.77nH and 2.18nH, respectively, and the capacitance values of the fourth capacitor 103a and the fourth capacitor 103b are 1.55pf and 0.68pf, respectively. In the second filter 20, the inductance values of the first inductor 201a, the first inductor 201b, the first inductor 201c, and the first inductor 201d are 0.01nH, 0.99nH, 1.29nH, and 0.01nH, respectively; the effective area areas of the first acoustic resonator 202a, the first acoustic resonator 202b, and the first acoustic resonator 202c are 2.519e-9m, respectively2、3.413e-9m2And 1.818e-9m2(ii) a The inductance values of the second inductor 203a, the second inductor 203b, and the second inductor 203c are 0.12nH, 0.01nH, and 0.01nH, respectively.
Simulated performance of the filter structure of fig. 2 is shown in fig. 6-8, where fig. 6 is the amplitude-frequency response curve of the filter structure of fig. 2, fig. 7 is the amplitude-frequency response curve of the filter structure of fig. 6 in the left range of the pass band, and fig. 8 is the amplitude-frequency response curve of the filter structure of fig. 6 in the pass band. As can be seen from fig. 6 to 8, on the one hand, the filter structure provided by the present invention realizes a wider relative bandwidth, i.e. realizes a wider bandwidth; on the other hand, the filter structure provided by the invention realizes the restraint of a near stop band on the left side of the passband, namely a sharp stop band is realized on the coexisting frequency band of the 5GHz Wlan frequency band and the N79 frequency band.
Preferably, the filter structure provided by the present invention further comprises a matching network, which may be one or more of a first port matching network, a second port matching network, and an interstage matching network. Wherein the first port matching network is disposed between the first port and the first filter, the second port matching network is disposed between the second port and the second filter, and the interstage matching network is disposed between the first filter and the second filter. A specific embodiment is described. As shown in fig. 9, the filter structure provided by the present invention further includes matching networks that are a first port matching network 40a disposed between the first port 30a and the first filter 10, a second port matching network 40b disposed between the second port 30b and the second filter 20, and an inter-stage matching network 50 disposed between the first filter 10 and the second filter 20. The arrangement of the first port matching network, the second port matching network and the interstage matching network can effectively improve the return loss characteristic of the filter structure. It should be noted that, specific structures of the first port matching network, the second port matching network, and the inter-stage matching network are not limited in any way, and may be designed accordingly according to actual requirements of the filter structure.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned. Furthermore, it will be obvious that the term "comprising" does not exclude other elements, units or steps, and the singular does not exclude the plural. A plurality of components, units or means recited in the system claims may also be implemented by one component, unit or means in software or hardware.
The filter structure provided by the invention comprises a first port, a first filter connected with the first port, a second filter cascaded with the first filter, and a second port connected with the second filter, wherein the second filter comprises at least one series unit and at least one parallel branch, the at least one series unit is connected between the first filter and the second port in series, and the at least one parallel branch is connected between the first filter and the second port in parallel; the first filter is an LC band-pass filter or an LC high-pass filter, each parallel branch in the second filter comprises an acoustic resonator, and each series unit is realized by adopting a non-acoustic passive device; or, the first filter is an LC band-pass filter or an LC low-pass filter, each series unit in the second filter includes an acoustic resonator, and each parallel branch is implemented by a non-acoustic passive device. The first filter is an LC filter, which has a wide band and relatively good wide stop band characteristics, and the acoustic resonators in the second filter can provide higher rejection at frequencies close to the pass band without too high edge roll-off loss, so that the filter structure provided by the present invention has both wide band and sharp stop band characteristics accordingly.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.
Claims (10)
1. A filter structure, characterized in that it comprises:
the filter comprises a first port, a first filter connected with the first port, a second filter cascaded with the first filter, and a second port connected with the second filter, wherein the second filter comprises at least one series unit and at least one parallel branch, the at least one series unit is connected between the first filter and the second port in series, and the at least one parallel branch is connected between the first filter and the second port in parallel;
the first filter is an LC band-pass filter or an LC high-pass filter, each parallel branch in the second filter comprises an acoustic resonator, and each series unit is realized by adopting a non-acoustic passive device; or, the first filter is an LC band-pass filter or an LC low-pass filter, each of the series units in the second filter includes an acoustic resonator, and each of the parallel branches is implemented by a non-acoustic passive device.
2. The filter structure of claim 1, wherein each of the parallel branches of the second filter comprises an acoustic resonator, and each of the series units is implemented using non-acoustic passive devices, comprising:
each of the parallel branches includes an acoustic resonator and a first inductor connected in series, and each of the series units is a second inductor.
3. The filter structure of claim 1, wherein each of the parallel branches of the second filter comprises an acoustic resonator, and each of the series units is implemented using non-acoustic passive devices, comprising:
each of the parallel branches is an acoustic resonator, and each of the series units includes a third inductor and a first capacitor connected in parallel.
4. The filter structure of claim 1, wherein each of the series cells in the second filter comprises an acoustic resonator, and each of the parallel branches is implemented using non-acoustic passive devices, comprising:
each of the series units is an acoustic resonator, and each of the parallel branches includes a second capacitor and a fourth inductor connected in series.
5. The filter structure of claim 1, wherein each of the series cells in the second filter comprises an acoustic resonator, and each of the parallel branches is implemented using non-acoustic passive devices, comprising:
each of the series units includes an acoustic resonator and a fifth inductor connected in parallel, and each of the parallel branches is a sixth inductor.
6. The filter structure according to any one of claims 1 to 5, characterized in that:
the second filter comprises N series units and N parallel branches, and one parallel branch is respectively connected in parallel between the first filter and the series unit connected in series with the first filter and between two adjacent series units, or one parallel branch is respectively connected in parallel between two adjacent series units and between the second port and the series unit connected in series with the second port; or
The second filter comprises N series units and N +1 parallel branches, and one parallel branch is respectively connected in parallel between the first filter and the series unit connected with the first filter in series, between two adjacent series units, and between the second port and the series unit connected with the second filter in series; or
The second filter comprises N +1 series units and N parallel branches, and one parallel branch is connected between every two adjacent series units in parallel;
wherein N is an integer of 1 or more.
7. The filter structure according to claim 6, characterized in that the number of parallel branches is greater than or equal to 2.
8. A filter structure according to any one of claims 1 to 3, characterized in that:
for the case that the first filter is an LC band-pass filter or an LC high-pass filter, each of the parallel branches of the second filter includes an acoustic resonator, and each of the series units is implemented by a non-acoustic passive device, a first transmission zero of the first filter is located on the left side of the passband of the filter structure, and a second transmission zero of the second filter is located on the right side of the passband of the filter structure.
9. The filter structure according to claim 1, 4 or 5, characterized in that:
for the case that the first filter is an LC band-pass filter or an LC low-pass filter, each of the series units in the second filter includes an acoustic resonator, and each of the parallel branches is implemented by a non-acoustic passive device, the first transmission zero of the first filter is located on the right side of the passband of the filter structure, and the second transmission zero of the second filter is located on the left side of the passband of the filter structure.
10. The filter structure according to any one of claims 1 to 5, characterized in that:
the filter structure further includes one or more of a first port matching network disposed between the first port and the first filter, a second port matching network disposed between the second port and the second filter, and an interstage matching network disposed between the first filter and the second filter.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116865714A (en) * | 2023-09-05 | 2023-10-10 | 深圳新声半导体有限公司 | Filter for N79 frequency band |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116865714A (en) * | 2023-09-05 | 2023-10-10 | 深圳新声半导体有限公司 | Filter for N79 frequency band |
| CN116865714B (en) * | 2023-09-05 | 2023-12-19 | 深圳新声半导体有限公司 | Filter for N79 frequency band |
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