CN117375573A - Reflection-free acoustic wave filter unit, reflection-free acoustic wave filter and manufacturing method - Google Patents
Reflection-free acoustic wave filter unit, reflection-free acoustic wave filter and manufacturing method Download PDFInfo
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/08—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of resonators or networks using surface acoustic waves
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02228—Guided bulk acoustic wave devices or Lamb wave devices having interdigital transducers situated in parallel planes on either side of a piezoelectric layer
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
- H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/25—Constructional features of resonators using surface acoustic waves
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/64—Filters using surface acoustic waves
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- Acoustics & Sound (AREA)
- Engineering & Computer Science (AREA)
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- Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
- Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
Abstract
The invention discloses a reflection-free acoustic wave filter unit, a reflection-free acoustic wave filter and a manufacturing method. The reflection-free acoustic wave filter unit comprises an acoustic wave resonator and a resistor, wherein the acoustic wave resonator and the resistor are connected in parallel to form a series branch, the acoustic wave resonator and the resistor are connected in series to form a parallel branch, and the reflection-free branch is arranged at a port of the filter, so that the reflection-free effect of the port can be realized. The reflection-free branch provided by the invention can absorb out-of-band reflection signals and improve out-of-band inhibition. The non-reflection filter realized by the structure is superior to the non-reflection filter with the traditional structure in physical size, electrical performance and process realization.
Description
Technical Field
The invention relates to the field of radio frequency micro-electromechanical devices, in particular to a non-reflection acoustic wave filter unit, a non-reflection acoustic wave filter and a manufacturing method.
Background
With the development of mobile communication, the radio frequency front end has a great demand for an acoustic wave filter, and the technology can accurately filter communication signals. The acoustic wave filter can eliminate interference of nearby signals, reduce radio frequency distortion, improve the reliability of a radio frequency link, reduce the power consumption of a system, enhance the sensitivity of a circuit and optimize the performance of radio frequency equipment, so that the acoustic wave filter plays an irreplaceable role in a radio frequency front end.
In the electronic industry, acoustic wave filters are widely used in mobile communication devices such as mobile phones and tablet computers. With the development of the 5G age, the opening and use of higher communication frequency bands have led to an increasing market demand for bulk acoustic wave filtering technology. The acoustic wave filter is widely applied to frequency bands (sub-6G) below 6G because of the advantages of high quality factor (Q), high frequency, micro volume, suitability for mass production and the like.
As market demand increases, full band non-reflective or low reflective filters are required under certain conditions to reduce the impact of the filters on the pre-circuits. The traditional reflection-free filter has a complex structure and a huge size, and is not beneficial to popularization in practical application.
Disclosure of Invention
To overcome the drawbacks and disadvantages of the prior art, a first object of the present invention is to provide a reflectionless acoustic wave filter unit, in particular a monolithically integrated reflectionless acoustic wave filter unit;
a second object of the present invention is to provide a monolithically integrated reflectionless acoustic wave filter;
a third object of the present invention is to provide a method for manufacturing a monolithically integrated reflection-free acoustic wave filter unit.
Based on the basic principle of no reflection, the invention provides an improved method of the no-reflection acoustic wave filter with a new structure based on the traditional trapezoidal acoustic wave filter, and realizes single-port no reflection and double-port no reflection of the reflection filter.
The first object of the invention adopts the following technical scheme:
a reflection-free acoustic wave filter unit comprises an acoustic wave resonator and a resistor which are connected in series or in parallel;
the acoustic wave resonator is connected with the resistor in series to form a parallel branch, and the admittance value of the series resonance point of the acoustic wave resonator is reduced along with the increase of the resistance value of the series resistor;
the acoustic wave resonator is connected in parallel with the resistor to form a series branch, and the admittance value of the parallel resonance point of the acoustic wave resonator increases with the increase of the resistance value of the parallel resistor.
Further, the acoustic wave resonator includes a first metal layer, a piezoelectric layer, and a second metal layer, and a resistive layer is provided on the same plane as the second metal layer.
Further, the acoustic wave resonator is connected in series with the resistor, and the resistor layer is directly connected with the second metal layer; the acoustic wave resonator is connected in parallel with the resistor, the resistor layer is connected with the first metal layer through the piezoelectric layer through hole, and the resistor layer is directly connected with the second metal layer.
Further, the acoustic wave resonator is a bulk acoustic wave resonator, a surface acoustic wave resonator or a lamb wave resonator, and the metal of the resistance layer is chromium or platinum.
Further, the resistance of the series branch is between 50 and 200 ohms.
Further, the parallel branch has a resistance between 100 and 300 ohms.
The second object of the invention is achieved by the following technical scheme:
the non-reflection acoustic wave filter comprises an acoustic wave resonator network and a non-reflection branch, wherein the non-reflection branch is arranged at a port of the acoustic wave resonator network, which needs to absorb reflection, and is formed by non-reflection acoustic wave filter units, and the non-reflection branch comprises a parallel branch and a serial branch.
Further, the acoustic wave resonator network implements a single-port or dual-port reflectionless filter using reflectionless branches.
Further, the serial branch in the non-reflection branch is connected with a single port or a double port of the acoustic wave resonator network, so that the single port or the double port non-reflection filter is realized.
The third object of the invention is achieved by the following technical scheme:
a method of fabricating a monolithically integrated reflectionless acoustic wave filter cell comprising:
preparing a first metal layer on a silicon wafer, and carrying out graphical etching on the first metal layer;
preparing a piezoelectric layer and a second metal layer, and specifically growing the piezoelectric layer and the second metal layer by adopting an MOCVD or MBE method;
patterning and etching the second metal layer;
patterning and etching the piezoelectric layer, and manufacturing a bonding pad through hole to form a piezoelectric layer through hole;
preparing a resistor layer and patterning;
preparing a metal pad layer;
the back of the acoustic wave resonator is released.
The invention has the beneficial effects that:
1) The reflection-free structure provided by the invention has universality, can be applied to most acoustic wave filter structures, can convert a circuit with reflection into a reflection-free circuit by adjusting a port circuit structure, and has simple principle and easy realization of circuit improvement.
2) The invention breaks through several fixed structures of the traditional reflectionless filter, creatively proposes the reflectionless branch composed of the acoustic wave filter units, and can realize reflectionless of a certain port by only changing a circuit at the port of the acoustic wave filter to connect the reflectionless branch.
3) The reflectionless filter provided by the invention only needs to add one-step process flow in the manufacturing process of the acoustic wave filter, has little area variation on the acoustic wave filter, and has the advantages of simple manufacture, small use area and great practical significance compared with the traditional method for constructing the reflectionless filter by a PCB.
4) The reflectionless filter provided by the invention is superior to the reflectionless filter with the traditional structure in the performances of physical size, insertion loss, out-of-band suppression, rectangularity and the like.
5) The out-of-band absorption and reflection part of the traditional reflection-free structure does not participate in filtering, and has single function, and the reflection-free port structure provided by the invention not only absorbs out-of-band signal reflection, but also improves out-of-band inhibition, thereby improving the selectivity of the filter.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following description is made with reference to the accompanying drawings of the embodiments of the present invention or the related technical solutions in the prior art, and it should be understood that the drawings in the following description are only for convenience and clarity of describing some embodiments in the technical solutions of the present invention, and other drawings may be obtained according to these drawings without the need of inventive labor for those skilled in the art.
FIG. 1 is a schematic diagram of a conventional acoustic wave resonator of the prior art;
FIG. 2 is a schematic diagram of a series arrangement of an acoustic wave resonator and a resistor according to the present invention;
FIG. 3 is a side cross-sectional view of the acoustic wave resonator and resistor series configuration of the present invention;
FIG. 4 is a schematic diagram of Y parameter variation of the acoustic wave resonator and resistor series structure of the present invention;
FIG. 5 is a schematic diagram of a parallel structure of an acoustic wave resonator and a resistor according to the present invention;
FIG. 6 is a side cross-sectional view of an acoustic wave resonator and resistor parallel structure of the present invention;
FIG. 7 is a schematic diagram of Y parameter variation of the parallel structure of the acoustic wave resonator and the resistor of the present invention;
FIG. 8 is a schematic diagram of the structure of the non-reflective arm of the present invention;
FIG. 9 is a schematic diagram of a single port reflectionless filter circuit configuration of the present invention;
FIG. 10 is a schematic diagram of a dual port reflectionless filter circuit of the present invention;
FIG. 11 is a circuit diagram showing the specific structure of the original filter according to embodiment 2 of the present invention;
FIG. 12 is a specific circuit diagram of a single-port reflectionless filter obtained by modification of the original filter of embodiment 2 of the present invention;
FIG. 13 is a specific circuit diagram of a dual port reflectionless filter obtained by modification of the original filter of example 2 of the present invention;
FIG. 14 is a graph comparing the scattering curves of the single port reflectionless filter of example 2 of the present invention with the original filter;
FIG. 15 is a graph comparing the scattering curves of the dual port reflectionless filter of example 2 of the present invention with the original filter;
FIGS. 16 (a) -16 (j) are schematic views of the preparation process of example 3 of the present invention.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative only and are not to be construed as limiting the invention. The step numbers in the following embodiments are set for convenience of illustration only, and the order between the steps is not limited in any way, and the execution order of the steps in the embodiments may be adaptively adjusted according to the understanding of those skilled in the art.
In the description of the present invention, it should be understood that references to orientation descriptions such as upper, lower, front, rear, left, right, etc. are based on the orientation or positional relationship shown in the drawings, are merely for convenience of description of the present invention and to simplify the description, and do not indicate or imply that the apparatus or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present invention.
In the description of the present invention, a number means one or more, a number means two or more, and greater than, less than, exceeding, etc. are understood to not include the present number, and above, below, within, etc. are understood to include the present number. The description of the first and second is for the purpose of distinguishing between technical features only and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.
Furthermore, in the description of the present invention, unless otherwise indicated, "a plurality" means two or more. "and/or", describes an association relationship of an association object, and indicates that there may be three relationships, for example, a and/or B, and may indicate: a exists alone, A and B exist together, and B exists alone. The character "/" generally indicates that the context-dependent object is an "or" relationship.
In the description of the present invention, unless explicitly defined otherwise, terms such as arrangement, installation, connection, etc. should be construed broadly and the specific meaning of the terms in the present invention can be reasonably determined by a person skilled in the art in combination with the specific contents of the technical scheme.
Example 1
A reflection-free acoustic wave filter unit, in particular to a monolithic integrated reflection-free acoustic wave filter unit, which mainly comprises an acoustic wave resonator and a resistor. The general acoustic wave resonator is shown in fig. 1, and comprises a first metal layer, a piezoelectric layer and a second metal layer, based on the basic structure of the prior art in fig. 1, a resistance layer is added on the acoustic wave resonator, the position of the resistance layer is in the same plane with that of the second metal layer, and the parallel connection or series connection of the acoustic wave resonator and the resistance is realized by adjusting the connection mode of the resistance layer and the first metal layer and the second metal layer.
If the acoustic wave resonator does not have the first metal layer, the resistor layer is connected with the second metal layer to realize a series and parallel structure.
As shown in fig. 2 and fig. 3, the acoustic wave resonator is connected in series with a resistor, specifically, the resistor layer is directly connected with the second metal layer to form a parallel branch. As shown in fig. 4, the admittance value of the series resonance point of the acoustic wave resonator decreases as the resistance value of the parallel branch increases, while the parallel resonance point is not affected by the resistance change.
As shown in fig. 5 and 6, the acoustic wave resonator is connected in parallel with the resistor, specifically, the resistor layer is connected with the first metal layer through the through hole of the piezoelectric layer, and the resistor layer is directly connected with the second metal layer to form a series branch. As shown in fig. 7, as the resistance value of the series branch becomes larger, the admittance value of the parallel resonance point of the acoustic wave resonator becomes smaller, and the series resonance point is not affected by the resistance change.
R in FIG. 4 p And R in FIG. 7 s Representing the resistance value.
It should be noted that:
further, the acoustic wave resonator is a bulk acoustic wave resonator, a surface acoustic wave resonator, or a lamb wave resonator.
Further, the metal of the resistive layer is inactive, stable at normal temperature, and chromium or platinum is preferable in this embodiment.
As shown in fig. 8, the reflection-free branch is composed of a parallel branch and a serial branch, the serial branch is composed of an acoustic wave resonator and a resistor in parallel, and the parallel branch is composed of the acoustic wave resonator and the resistor in series.
Further, the resistance value of the series branch is 50-200 ohms.
Further, the resistance value of the parallel branch is between 100 and 300 ohms.
The area occupied by the on-chip resistors in the non-reflective branches is substantially negligible in the planar dimensions of the filter compared to the area of the acoustic wave resonator.
When a signal passes through the non-reflection branch, the impedance of the parallel resonance point of the serial branch and the impedance of the serial resonance point of the parallel branch are increased by the resistor, so that the signal of the band-stop part of the filter is absorbed, and the change of the resistor is hardly generated on the serial resonance point of the serial branch and the parallel resonance point of the parallel branch, so that the signal in the passband is not influenced basically, and the effect of full-band low reflection of the signal is realized. The non-reflective branch is connected to a port within the reflective bandpass filter network that needs to be changed to non-reflective, changing the original reflective circuit to a non-reflective circuit.
Example 2
A monolithically integrated reflectionless acoustic wave filter comprises an acoustic wave resonator network with a filtering function and a reflectionless branch, wherein the acoustic wave resonator network is an original reflectionless filter, and the reflectionless branch is arranged at a port of the acoustic wave resonator network, which needs to absorb reflection. The series resonators in the non-reflective leg refer to the series resonator design of the acoustic wave resonator network and the parallel resonators in the non-reflective leg refer to the parallel resonator design of the acoustic wave resonator network.
As shown in fig. 9, when the original filter is used as the acoustic wave resonator network and a circuit structure without reflection signals at a single port needs to be changed, the reflection-free branch is arranged at the single port of the acoustic wave resonator network where the signal needs to be absorbed.
The method specifically comprises the following steps: the series branch of the reflection-free branch is connected with the acoustic wave resonator network.
As shown in fig. 10, when the original filter is used as the acoustic wave resonator network and the circuit structure of the dual-port no-reflection signal is required to be changed, no-reflection branches are arranged at two ends of the acoustic wave resonator network.
The method specifically comprises the following steps: the two ports of the acoustic wave resonator network are respectively connected with the serial branches of the non-reflection branch.
As shown in fig. 11, the acoustic wave resonator network, i.e., the original filter in this embodiment 2, adopts a second-order pi-type filter operating in the n41 frequency band, and the structure thereof includes three acoustic wave resonators.
As shown in fig. 12, one end of the second-order pi-filter is provided with a schematic structure of a non-reflection branch, and a parallel branch in the non-reflection branch is connected with one end of the acoustic wave resonator network.
As shown in fig. 13, two ends of the second-order pi-type filter are provided with a structure schematic diagram of a non-reflection branch, and two ends of the second-order pi-type filter are respectively provided with a non-reflection branch.
As shown in fig. 14, the filter single-ended non-reflection structure is compared with the scattering curve of the original filter, which is a second-order pi-type filter;
as shown in fig. 15, a comparison of the filter double-ended non-reflective structure with the original filter scattering curve.
As can be seen from fig. 14 and 15, adding the filter port without the reflection branch can make the reflection signal realize the suppression of 5dB of the full frequency band, and at the same time, the addition of the reflection branch improves the out-of-band suppression of the filter. The increase in impedance in the circuit affects the signal in the passband, so the effect that a dual port reflectless circuit has on the passband is greater than that of a single port reflectless circuit.
In a conventional method for implementing a reflectionless filter in the prior art, the reflectionless filter, such as a complementary duplexer structure, is formed by a main channel and an auxiliary channel filtering unit of a complementary transfer function. The auxiliary channel absorbing signal reflection enlarges the complexity of the circuit and simultaneously brings in-band inhibition to degrade the insertion loss.
The method provided by the invention combines the auxiliary channel into the main channel, absorbs the reflected signal and has a certain influence on the band interpolation loss, but improves the selectivity of the out-of-band signal.
Example 3
A method for manufacturing a monolithically integrated reflection-free acoustic wave filter unit, as shown in fig. 16 (a) -16 (j), taking a back-etched bulk acoustic wave resonator as an example, includes the steps of:
a: and (5) cleaning the silicon wafer.
And selecting a high-resistance double-sided polished silicon wafer, and cleaning the silicon wafer by adopting a standard semiconductor cleaning process.
B: preparing a first metal layer
The first metal layer is grown using MOCVD (metal organic chemical vapor deposition) or MBE (molecular beam epitaxy).
C: patterning the first metal layer
And transferring the pattern on the mask plate onto a wafer through photoetching, and realizing patterning through plasma gas etching.
D: preparation of piezoelectric layer and second Metal layer
The piezoelectric layer and the second metal layer are grown by the same method as B
E: preparing a second metal layer thickening layer
And depositing a second metal thickening layer which is the same as the second metal layer on the second metal layer by adopting a magnetron sputtering method, and realizing patterning by a stripping process.
F: patterning the second metal layer
And (3) patterning the second metal layer by adopting the same method as C.
G: manufacturing a piezoelectric layer through hole
And C, patterning the piezoelectric layer by adopting the same method as C, and manufacturing a through hole of the bonding pad lead.
H: manufacturing metal electrode
Using electron beam evaporation method, depositing metal with good conductivity, such as gold (Au) as device connecting wire and metal pad, and stripping metal to realize patterning.
I: manufacturing a resistor layer
And (3) depositing a metal material with stable properties such as resistivity and the like around the device by using a magnetron sputtering method, and realizing patterning by metal stripping.
J: back release
Reversing the wafer, patterning the back of the wafer, and using sulfur hexafluoride (SF 6 ) With octafluorocyclobutane (C) 4 F 8 ) And (3) performing ICP deep silicon etching to form an inverted trapezoid on the cross section of the back opening. The resonator is released from the substrate by removing the silicon-based substrate from the bottom of the acoustic wave resonator. Before the back is released, the whole wafer can be thinned, and the etching uniformity of different opening sizes is ensured.
The manufacturing method of the invention only deposits the resistance layer on the same surface of the second metal layer, realizes the serial connection or parallel connection with the second metal layer, further forms a reflection-free branch and realizes the reflection-free filter.
The invention has simple processing and is easy to realize in the existing acoustic wave resonator network, only the resistive layer is additionally manufactured in one step when the acoustic wave resonator is manufactured, and other manufacturing steps do not need any change, thus the invention has wide applicability.
Furthermore, unless indicated to the contrary, one or more of the functions and/or features described may be integrated in a single physical device or one or more functions and/or features may be implemented in separate physical devices or software modules. It should be understood that a detailed discussion of the actual implementation of each module is not necessary to an understanding of the present invention. Rather, the actual implementation of the various functional modules in the apparatus disclosed herein will be apparent to those skilled in the art from consideration of their attributes, functions and internal relationships. Accordingly, one of ordinary skill in the art can implement the invention as set forth in the claims without undue experimentation. It is also to be understood that the specific concepts disclosed are merely illustrative and are not intended to be limiting upon the scope of the invention, which is to be defined in the appended claims and their full scope of equivalents.
In the foregoing description of the present specification, reference has been made to the terms "one embodiment/example", "another embodiment/example", "certain embodiments/examples", and the like, means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: many changes, modifications, substitutions and variations may be made to the embodiments without departing from the spirit and principles of the invention, the scope of which is defined by the claims and their equivalents.
The embodiments described above are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the embodiments described above, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principles of the present invention should be made in the equivalent manner, and are included in the scope of the present invention.
Claims (8)
1. A reflection-free acoustic wave filter unit, characterized by comprising an acoustic wave resonator and a resistor connected in series or parallel;
the acoustic wave resonator is connected with the resistor in series to form a parallel branch;
the acoustic wave resonator is connected with the resistor in parallel to form a series branch;
the acoustic wave resonator comprises a first metal layer, a piezoelectric layer and a second metal layer, and a resistance layer is arranged on the same plane with the second metal layer;
the acoustic wave resonator is connected with the resistor in series, and the resistor layer is directly connected with the second metal layer; the acoustic wave resonator is connected in parallel with the resistor, the resistor layer is connected with the first metal layer through the piezoelectric layer through hole, and the resistor layer is directly connected with the second metal layer.
2. The reflectionless acoustic wave filter unit of claim 1, wherein the acoustic wave resonator is a bulk acoustic wave resonator, a surface acoustic wave resonator, or a lamb wave resonator, and the metal of the resistive layer is chromium or platinum.
3. The reflectionless acoustic wave filter unit of claim 1, wherein the series branch has a resistance value between 50-200 ohms.
4. The reflectionless acoustic wave filter unit of claim 1, wherein the parallel branch has a resistance between 100-300 ohms.
5. A non-reflective acoustic wave filter, comprising an acoustic wave resonator network and a non-reflective branch, wherein the non-reflective branch is arranged at a port of the acoustic wave resonator network where absorption and reflection are required, the non-reflective branch is formed by the non-reflective acoustic wave filter unit according to any one of claims 1-4, and the non-reflective branch comprises a parallel branch and a serial branch.
6. The reflectionless acoustic wave filter of claim 5, in which the acoustic wave resonator network implements a single port or dual port reflectionless filter using a reflectionless leg.
7. The reflectionless acoustic wave filter of claim 5, wherein the series of the reflectionless branches is connected to a single port or a dual port of an acoustic wave resonator network to implement a single port or a dual port reflectionless filter.
8. A method of manufacturing a reflectionless acoustic wave filter unit in accordance with any one of claims 1-4, comprising:
preparing a first metal layer on a silicon wafer, and carrying out graphical etching on the first metal layer;
preparing a piezoelectric layer and a second metal layer, and growing the piezoelectric layer and the second metal layer by adopting an MOCVD or MBE method;
patterning and etching the second metal layer;
patterning and etching the piezoelectric layer, and manufacturing a bonding pad through hole to form a piezoelectric layer through hole;
preparing a resistor layer and patterning;
preparing a metal pad layer;
the back of the acoustic wave resonator is released.
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