Multiplexer and method of improving performance thereof, communication device
By employing a mixed doping design in the trapezoidal filter, with a highly doped resonator near the antenna end and undoped or low-doped resonators at other locations, the problem of insertion loss degradation caused by the small out-of-band reflection coefficient is solved, thus improving cost-effectiveness.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ROFS MICROSYST TIANJIN CO LTD
- Filing Date
- 2021-07-29
- Publication Date
- 2026-07-21
AI Technical Summary
While existing trapezoidal filter structures extend bandwidth, they also decrease out-of-band reflection coefficients, leading to deterioration of inter-filter insertion loss in duplexers and higher manufacturing costs.
By using a highly doped resonator in the filter near the antenna end, combined with undoped or low-doped resonators in other locations, a hybrid doped multiplexer structure is formed, which increases the out-of-band reflection coefficient at the antenna end and reduces the filter size.
This effectively reduces the insertion loss between filters and lowers manufacturing costs.
Smart Images
Figure CN115694416B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of filter technology, and particularly to a multiplexer and a method for improving its performance, as well as a communication device. Background Technology
[0002] The topology of a typical existing trapezoidal filter is as follows: Figure 1 As shown in the diagram, in this filter 100, there is a series branch consisting of inductors 121 and 122 and multiple resonators (usually called series resonators) 101 to 104 between the input terminal 131 and the output terminal 132. Multiple branches (usually called parallel branches) between the connection points of each series resonator and the ground terminal are respectively equipped with resonators 111 to 113 (usually called parallel resonators) and inductors 123 to 125. A mass load layer is added to each parallel resonator, causing a difference in frequency between the parallel resonators and the series resonators, thus forming the passband of the filter.
[0003] In recent years, to meet the increasing bandwidth requirements of RF front-end filters, wide-bandwidth filters have been implemented using methods such as parallel branch resonators with series large-value inductors in trapezoidal filter structures, grounding a large-value inductor at one end of the series path, or paralleling a large-value inductor across the series resonators. While such wide-bandwidth filter architectures extend bandwidth, they also reduce out-of-band reflection coefficients. The characteristics of the two filters within a duplexer are interdependent; for example, if the antenna reflection coefficient of one filter is relatively low in the passband of another filter, it can lead to a deterioration in the insertion loss of the other filter. Therefore, when designing multiplexers (including duplexers) containing wide-bandwidth filter architectures, it is crucial to consider not only the bandwidth but also the antenna reflection coefficient to avoid significantly impacting the insertion loss of other filters.
[0004] Therefore, there is an urgent need for multiplexers that reduce the impact on insertion loss of other filters and have lower manufacturing costs. Summary of the Invention
[0005] In view of this, the present invention proposes a hybrid doped multiplexer and communication device that can overcome the defects of the prior art.
[0006] The first aspect of the present invention provides a multiplexer, comprising a first filter and a second filter, both of which are trapezoidal structures. The first filter includes a bandwidth extension unit, wherein the inductance of the inductor in the bandwidth extension unit is greater than a preset value. At least one resonator near the antenna end of the first filter and all resonators in the second filter are highly doped resonators. The other resonators in the first filter are undoped or low-doped resonators.
[0007] Optionally, the doping concentration of the low-doped resonator is less than 5%, and the doping concentration of the high-doped resonator is greater than 8%.
[0008] Optionally, the electromechanical coupling coefficient of at least one stage resonator near the antenna end of the first filter is greater than the electromechanical coupling coefficient of other resonators in the first filter.
[0009] Optionally, the operating bandwidth of the filter composed of at least one resonator near the antenna end of the first filter is greater than the operating bandwidth of the filter composed of other resonators in the first filter.
[0010] Optionally, the highly doped resonator is disposed in the first die, and the undoped or low-doped resonator is disposed in the second die.
[0011] Optionally, at least one resonator near the antenna end of the first filter has the same doping concentration as all resonators in the entire second filter.
[0012] Optionally, the preset value is 0.8nH.
[0013] Optionally, the bandwidth extension unit includes an inductor, one end of which is connected to the resonator of a parallel branch of the first filter, and the other end is grounded.
[0014] Optionally, the bandwidth extension unit includes an inductor, one end of which is connected to a node in the series path of the first filter, and the other end is grounded.
[0015] Optionally, the bandwidth extension unit includes an inductor that is connected in parallel across a resonator in the series path of the first filter.
[0016] Optionally, the material of the piezoelectric thin film layer in the resonator is: single-crystal aluminum nitride, polycrystalline aluminum nitride, zinc oxide, or PZT, or the above materials doped with rare earth elements.
[0017] A second aspect of the present invention provides a communication device comprising any of the multiplexers disclosed herein.
[0018] A third aspect of the present invention proposes a method for improving the performance of a multiplexer, the multiplexer comprising a first filter and a second filter, both of which are trapezoidal structures. The first filter includes a bandwidth extension unit, wherein the inductance of the inductor in the bandwidth extension unit is greater than a preset value. The method comprises: setting at least one resonator of the first filter near the antenna end and all resonators in the entire second filter as highly doped resonators; and setting other resonators in the first filter as undoped or low-doped resonators to reduce the insertion loss impact of the first filter on other filters.
[0019] Optionally, the doping concentration of the low-doped resonator is less than 5%, and the doping concentration of the high-doped resonator is greater than 8%.
[0020] Optionally, the highly doped resonator is disposed in the first die, and the undoped or low-doped resonator is disposed in the second die.
[0021] Optionally, at least one resonator near the antenna end of the first filter has the same doping concentration as all resonators in the entire second filter.
[0022] Optionally, the preset value is 0.8nH.
[0023] According to the technical solution of the present invention, at least the following advantages are available:
[0024] 1. At least one stage of the first filter near the antenna end uses a highly doped resonator, which has a larger operating bandwidth than the operating bandwidth of the subsequent circuit. This can effectively increase the out-of-band reflection coefficient of the first filter at the antenna end, thereby reducing its impact on the insertion loss of other frequency band filters.
[0025] 2. Since at least one stage of the first filter near the antenna end and the entire second filter use highly doped resonators, the size of the filter can be effectively reduced and the manufacturing cost can be reduced due to the small 50-ohm area of the highly doped resonator. Attached Figure Description
[0026] For illustrative and not limiting purposes, the invention will now be described with reference to preferred embodiments thereof, particularly the accompanying drawings, in which:
[0027] Figure 1 The diagram shows the topology of a filter with a trapezoidal structure based on existing technology.
[0028] Figure 2 This is a cross-sectional schematic diagram of a thin-film bulk acoustic resonator structure.
[0029] Figure 3A This is the electrical symbol for an acoustic resonator. Figure 3B A schematic diagram of the equivalent electrical model of an acoustic resonator;
[0030] Figure 4 This is a schematic diagram of the impedance-frequency characteristics of an acoustic resonator.
[0031] Figure 5 This is a graph showing the relationship between the normalized electromechanical coupling coefficient of the resonator and the stack thickness ratio.
[0032] Figure 6 The graph shows the relationship between the doping concentration of the piezoelectric thin film layer of the resonator and its electromechanical coupling coefficient and Qp.
[0033] Figure 7 The graph shows the relationship between the resonator doping concentration and the piezoelectric thin film thickness and the area of the 50-ohm resonator.
[0034] Figure 8 A simplified schematic diagram of a trapezoidal filter architecture;
[0035] Figure 9 for Figure 8 The circuit diagram shown is an equivalent circuit diagram.
[0036] Figure 10 This is a schematic diagram of the comparative duplexer circuit topology of the present invention;
[0037] Figure 11 This is a schematic diagram of the duplexer circuit topology according to the first embodiment of the present invention;
[0038] Figure 12 This is a diagram showing the echo characteristics of C1 and C2 at the antenna end in the first filter of this embodiment of the invention;
[0039] Figure 13 This is a diagram showing the insertion loss frequency characteristics of C1 and C2 in the first filter of the first embodiment of the present invention;
[0040] Figure 14 The echo characteristics of the first filter at the antenna end are shown in the embodiments and comparative examples of the present invention.
[0041] Figure 15 The insertion loss frequency response diagrams of the second filter in the first embodiment and comparative example of the present invention are shown.
[0042] Figure 16 This is a topology diagram of a duplexer circuit according to a second embodiment of the present invention;
[0043] Figure 17 This is a topology diagram of a duplexer circuit according to the third embodiment of the present invention. Detailed Implementation
[0044] In the multiplexer of this invention, firstly, for the duplexer containing a wideband architecture filter, a reasonable design is used to reduce the degradation of insertion loss of other filters caused by the small reflection coefficient at the antenna end outside the passband of the wideband architecture filter; secondly, using highly doped resonators for some of the resonators in the duplexer can effectively reduce the size of the filter and help reduce manufacturing costs. This will be explained in detail below.
[0045] Figure 2 The diagram shows a cross-sectional view of an existing thin-film bulk acoustic resonator structure. The area highlighted by the dashed line represents the overlapping region of the air cavity 35, top electrode 34, bottom electrode 33, and piezoelectric thin film layer 32 in the thickness direction; this region is the effective resonant region of the resonator.
[0046] 31: Substrate, with optional materials including single-crystal silicon, gallium arsenide, sapphire, quartz, etc.
[0047] 35: Acoustic mirror, illustrated as a cavity. Acoustic mirrors can also be made using Bragg reflectors and other equivalent forms.
[0048] 33: Bottom electrode, the material can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite of the above metals or their alloys, etc.
[0049] 32: Piezoelectric thin film layer, which can be selected from materials such as single-crystal aluminum nitride, polycrystalline aluminum nitride, zinc oxide, PZT, etc., and contains rare earth element doping materials with a certain atomic ratio of the above materials. The thickness of the piezoelectric thin film layer is generally less than 10 micrometers. For example, it can be scandium-doped aluminum nitride, with the corresponding molecular formula Al. 1-x Sc x N, where x is the scandium doping concentration. When x is less than a certain specified value, the resonator is a low-doped resonator.
[0050] 34: Top electrode, the material can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite of the above metals or their alloys, the top electrode includes a mass loading layer.
[0051] Figure 3A This is the electrical symbol for an acoustic resonator. Figure 3B This is a schematic diagram of the equivalent electrical model of an acoustic resonator. Figure 4 This is a schematic diagram of the impedance-frequency characteristics of an acoustic resonator. Ignoring losses, the electrical model simplifies to a resonant circuit composed of Lm, Cm, and C0. According to the resonance condition, this resonant circuit has two resonant frequencies: one is fs, where the impedance of the resonant circuit reaches its minimum value; fs is defined as the series resonant frequency of this resonator, and the Q value of the resonator at fs is defined as Qs. The other is fp, where the impedance of the resonant circuit reaches its maximum value; fp is defined as the parallel resonant frequency of this resonator, and the Q value of the resonator at fp is defined as Qp.
[0052] Figure 5The figure shows the relationship between the normalized electromechanical coupling coefficient of the resonator and the stack thickness ratio. The vertical axis represents the effective electromechanical coupling coefficient normalized according to the intrinsic electromechanical coupling coefficient of the piezoelectric thin film material, and the horizontal axis, the stack thickness ratio, represents the ratio of the top electrode / bottom electrode thickness to the piezoelectric thin film thickness when the top electrode thickness is equal to the bottom electrode thickness. As can be seen from the figure, the effective electromechanical coupling coefficient of the resonator is related not only to the intrinsic electromechanical coupling coefficient of the piezoelectric material but also to the stack thickness ratio. Furthermore, as the stack thickness ratio increases, the effective electromechanical coupling coefficient of the resonator first increases and then decreases. When the piezoelectric material is constant, the maximum electromechanical coupling coefficient corresponding to the change in the stack thickness ratio is called the limiting effective electromechanical coupling coefficient of the resonator.
[0053] like Figure 6 The diagram shows the relationship between the doping concentration of the piezoelectric material in the resonator and its electromechanical coupling coefficient and Qp. Doping piezoelectric materials (such as aluminum nitride) with rare earth elements (such as scandium) can effectively improve the intrinsic electromechanical coupling coefficient of the piezoelectric material, thereby improving the effective electromechanical coupling coefficient of the resonator. The molecular expression for scandium-doped aluminum nitride is Al... 1-x Sc x N, where x is the scandium doping concentration. For example... Figure 6 As shown, the limiting effective electromechanical coupling coefficient of the resonator increases with increasing doping concentration, and the limiting effective electromechanical coupling coefficient of the resonator nearly doubles when the doping concentration increases to 20%.
[0054] Figure 7 The graph shows the relationship between the resonator doping concentration, the piezoelectric thin film thickness, and the area (A_50) of a 50-ohm resonator. The formula for calculating the area of the 50-ohm resonator is as follows:
[0055]
[0056] Where T is the thickness of the piezoelectric thin film layer, in meters; fs is the series resonant frequency of the resonator, in Hertz; ε0 is the vacuum permittivity, in Farads per meter; ε r ε is the relative permittivity of the piezoelectric material, expressed in farads per meter (Fd / m). The area of a 50-ohm resonator is determined by the thickness of the piezoelectric thin film and the relative permittivity of the piezoelectric material. As the doping concentration increases, the relative permittivity of the piezoelectric material increases. Taking scandium-doped aluminum nitride (Al1-xScxN) as an example, when x equals 0, ε... r =9.75, ε when x equals 0.08 r =10.3, ε when x equals 0.2 r=11.5; Under the condition that the effective electromechanical coupling coefficient of the resonator remains unchanged, the thickness of the piezoelectric thin film layer decreases with the increase of doping concentration; In summary, when the effective electromechanical coupling coefficient of the resonator remains unchanged, the area of the 50-ohm resonator decreases with the increase of doping concentration. Figure 8 As shown, when the resonator series resonant frequency is 1.8 GHz and the effective electromechanical coupling coefficient of the resonator is 6.2%, the thickness of the piezoelectric thin film layer of the resonator decreases and the area of the 50-ohm resonator decreases with the increase of doping concentration.
[0057] Figure 8 The diagram shows a simplified trapezoidal filter architecture from the prior art. This trapezoidal filter consists of series resonators S1 to S3 and parallel resonators P1 to P3. T1 and T2 are the signal input and signal output terminals, respectively. To achieve better matching, LC matching circuits may be included at the signal input and / or signal output terminals.
[0058] Figure 9 The circuit shown is Figure 8 The equivalent circuit diagram of the circuit shown is obtained by splitting the parallel resonator P1 into P1-1 and P1-2, the series resonator S2 into S2-1 and S2-2, the parallel resonator P2 into P2-1 and P2-2, and the series resonator S3 into S3-1 and S3-2. Therefore, Figure 8 The filter shown is called a 5-stage trapezoidal filter. ① is the first stage closest to the signal input terminal T1, ..., ⑤ is the fifth stage closest to the signal input terminal T1. Figure 8 The first stage of the filter, near the signal input, includes a series resonator S1 and a parallel resonator P1. Figure 8 The first two stages of the filter, near the signal input, include series resonators S1 and S2 and a parallel resonator P1.
[0059] Figure 10 The diagram shows the comparative duplexer circuit topology of this invention. The first filter (die D1) is a trapezoidal filter composed of series resonators S11-S14 and parallel resonators P11-P14, and the second filter (die D2) is a trapezoidal filter composed of series resonators S21-S24 and parallel resonators P21-P24. The first filter includes a bandwidth extension unit, meaning that this filter is a bandwidth extension architecture filter. Figure 10 The explanations of the various symbols in the text are as follows:
[0060] T1: Input port of the first filter signal.
[0061] T2: Second filter signal output port.
[0062] ANT: Antenna port.
[0063] L1 and L2: Output and input inductors of the first filter.
[0064] L6 and L7: Input and output inductors of the second filter.
[0065] LM: Parallel matching inductor at the antenna end.
[0066] L3, L4, and L5: These are grounding inductors in the parallel branches of the first filter. At least one of L3, L4, and L5 is an inductor with a large inductance value (greater than 0.8nH). This inductor with a large inductance value acts as a bandwidth extension unit in the first filter.
[0067] L8 and L9: These are the grounding inductors for the parallel branches of the second filter.
[0068] like Figure 10 In the comparative duplexer of the present invention shown, the first filter is a conventional extended bandwidth architecture filter. While achieving extended bandwidth, its special architecture leads to a relatively small reflection coefficient at the antenna end of the first filter, which in turn causes the insertion loss of the second filter to deteriorate.
[0069] Figure 11 The diagram shows the duplexer circuit topology of the first embodiment of the present invention. The first filter is a trapezoidal filter composed of series resonators S11-S14 and parallel resonators P11-P14, and the second filter is a trapezoidal filter composed of series resonators S21-S24 and parallel resonators P21-P24. The first two stages of the first filter near the antenna end and the entire second filter are located on the same die D1 (this is only an example of the first two stages of the first filter near the antenna end; it is not a limitation and could be one or more stages of the first filter near the antenna end). The resonators in die D1 are highly doped, and the remaining resonators in the first filter are located on die D2, where the resonators are undoped or lightly doped. The electromechanical coupling coefficient of at least one stage of the first filter near the antenna end is greater than that of the other resonators in the first filter. The operating bandwidth of the filter composed of at least one stage of the first filter near the antenna end is greater than that of the filter composed of the other resonators in the first filter. Figure 11 The explanations of the various symbols in the text are as follows:
[0070] T1: Input port of the first filter signal.
[0071] T2: Second filter signal output port.
[0072] ANT: Antenna port.
[0073] L1 and L2: Output and input inductors of the first filter.
[0074] L6 and L7: Input and output inductors of the second filter.
[0075] LM: Parallel matching inductor at the antenna end.
[0076] L3, L4, and L5: These are grounding inductors in the parallel branches of the first filter. The first filter is a wideband architecture filter, where at least one of L4 and L5 is an inductor with a large inductance value (greater than 0.8nH), and the parallel branch containing the inductor with the large inductance value is defined as the wideband unit.
[0077] L8 and L9: These are the grounding inductors for the parallel branches of the second filter.
[0078] Figure 11 In the duplexer of the first embodiment of the present invention shown, the first two stages of the first filter near the antenna end (circuit C1) use highly doped resonators, making its operating bandwidth greater than that of circuit C2. This can effectively increase the out-of-band reflection coefficient of the first filter at the antenna end, thereby reducing its impact on the insertion loss of other frequency band filters. Moreover, since the first two stages of the first filter near the antenna end and the entire second filter use highly doped resonators, the size of the filter can be effectively reduced, significantly reducing manufacturing costs.
[0079] Figure 12 The figure shows the echo characteristics of circuits C1 and C2 at the antenna end in the first filter of the duplexer according to the first embodiment of the present invention. The solid line represents the echo of circuit C1 at the antenna end, and the dashed line represents the echo of circuit C2 at the antenna end. As can be seen from the figure, outside the passband of the first filter, the reflection coefficient of circuit C1 is greater than that of circuit C2.
[0080] Figure 13 The figure shows the insertion loss frequency characteristics of circuits C1 and C2 in the first filter of the first embodiment of the duplexer of the present invention. The solid line represents the insertion loss frequency characteristic of circuit C1 in the first filter, and the dashed line represents the insertion loss frequency characteristic of circuit C2 in the first filter. As can be seen from the figure, the operating bandwidth of circuit C1 is greater than that of circuit C2.
[0081] Figure 14 The diagram shows a comparison of the echo characteristics of the first filter at the antenna end in the duplexer of the first embodiment of the present invention and the comparative duplexer. The solid line represents the echo characteristics of the first filter at the antenna end in the duplexer of the first embodiment of the present invention, and the dashed line represents the echo characteristics of the first filter at the antenna end in the comparative duplexer of the present invention. Figure 14 The frequency range indicated by the Second-band is the frequency range of the second filter passband. The echo at the antenna end of the first embodiment and the echo at the antenna end of the comparative embodiment differ by 0.7dB at the second filter passband.
[0082] like Figure 15The diagram shows a comparison of the insertion loss frequency characteristics of the second filter in the duplexer of the first embodiment of the present invention and the comparative duplexer. The solid line represents the insertion loss frequency characteristic curve of the second filter in the duplexer of the first embodiment, and the dashed line represents the insertion loss frequency characteristic curve of the second filter in the comparative duplexer. In the passband of the second filter, because the first filter in the duplexer of the first embodiment has a larger reflection coefficient at the antenna end compared to the first filter in the comparative duplexer, the first filter in the first embodiment has a smaller impact on the insertion loss of the second filter, resulting in an insertion loss improvement of approximately 0.35 dB compared to the comparative example.
[0083] Figure 16 The diagram shows the duplexer circuit topology of the second embodiment of the present invention. The difference between the second embodiment and the first embodiment lies in the difference in the bandwidth expansion unit (circuit C2 part) in the first filter. An inductor LS is added to ground at a certain node in the series path (the inductance of the inductor LS is greater than 0.8nH), and the parallel branch composed of the inductor LS is defined as the bandwidth expansion unit.
[0084] Figure 17 The diagram shows the duplexer circuit topology of the third embodiment of the present invention. The difference between the third embodiment and the first embodiment lies in the difference in the bandwidth extension unit (circuit C2 part) in the first filter. An inductor LS (the inductance of inductor LS is greater than 0.8nH) is added in parallel across a certain resonator in the series path. The parallel body composed of the above-mentioned series resonator and the inductor LS connected in parallel is defined as the bandwidth extension unit.
[0085] It should be noted that, although Figure 11 , Figure 16 and Figure 17 The three examples listed are all duplexers, but this is only for the convenience of illustration and not a limitation. The inventive idea can also be applied to multiplexers.
[0086] The communication device of the present invention may include a multiplexer of any of the embodiments disclosed herein.
[0087] The present invention discloses a method for improving the performance of a multiplexer, wherein the multiplexer includes a first filter and a second filter, both of which are trapezoidal structures. The first filter includes a bandwidth extension unit, wherein the inductance of the inductor in the bandwidth extension unit is greater than a preset value. The method includes: setting at least one resonator of the first filter near the antenna end and all resonators in the entire second filter as highly doped resonators; and setting other resonators in the first filter as undoped or low-doped resonators to reduce the insertion loss impact of the first filter on other filters.
[0088] The doping concentration of the low-doped resonator can be less than 5%, while the doping concentration of the high-doped resonator can be greater than 8%. The preset value can be 0.8nH.
[0089] The doping concentrations of at least one resonator near the antenna end of the first filter and all resonators in the second filter can be the same or different, and they can be placed on the same die or not. Preferably, the doping concentrations of at least one resonator near the antenna end of the first filter and all resonators in the second filter are the same, and the highly doped resonators are placed on the first die, while the undoped or low-doped resonators are placed on the second die. Placing resonators with the same doping level in the same die helps to ensure the uniformity of the resonators within the die, improves product performance, and reduces packaging complexity and increases production yield.
[0090] The technical solution according to the embodiments of the present invention has at least the following advantages:
[0091] 1. At least one stage of the first filter near the antenna end uses a highly doped resonator, which has a larger operating bandwidth than the operating bandwidth of the subsequent circuit. This can effectively increase the out-of-band reflection coefficient of the first filter at the antenna end, thereby reducing its impact on the insertion loss of other frequency band filters.
[0092] 2. Since at least one stage of the first filter near the antenna end and the entire second filter use highly doped resonators, the size of the filter can be effectively reduced and the manufacturing cost can be reduced due to the small 50-ohm area of the highly doped resonator.
[0093] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can occur depending on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.
Claims
1. A multiplexer, comprising a first filter and a second filter, both of which are trapezoidal structures, wherein the first filter includes a bandwidth extension unit, and the inductance of the inductor in the bandwidth extension unit is greater than a preset value, characterized in that, At least one resonator near the antenna end of the first filter and all resonators in the second filter are highly doped resonators; the other resonators in the first filter are undoped or low-doped resonators. The electromechanical coupling coefficient of at least one resonator near the antenna end of the first filter is greater than the electromechanical coupling coefficient of other resonators in the first filter; The operating bandwidth of the filter composed of at least one resonator near the antenna end of the first filter is greater than the operating bandwidth of the filter composed of other resonators in the first filter. The first filter has at least one resonator near the antenna end and all resonators in the entire second filter have the same doping concentration. The preset value is 0.8nH.
2. The multiplexer according to claim 1, characterized in that, The doping concentration of the low-doped resonator is less than 5%, and the doping concentration of the high-doped resonator is greater than 8%.
3. The multiplexer according to claim 1, characterized in that, The highly doped resonator is disposed in the first die, and the undoped or low-doped resonator is disposed in the second die.
4. The multiplexer according to any one of claims 1 to 3, characterized in that, The bandwidth extension unit includes an inductor, one end of which is connected to the resonator of a parallel branch of the first filter, and the other end is grounded.
5. The multiplexer according to any one of claims 1 to 3, characterized in that, The bandwidth extension unit includes an inductor, one end of which is connected to a node in the series path of the first filter, and the other end is grounded.
6. The multiplexer according to any one of claims 1 to 3, characterized in that, The bandwidth extension unit includes an inductor that is connected in parallel across a resonator in the series path of the first filter.
7. The multiplexer according to any one of claims 1 to 3, characterized in that, The material of the piezoelectric thin film layer in the resonator is: single-crystal aluminum nitride, polycrystalline aluminum nitride, zinc oxide, or PZT, or the above materials doped with rare earth elements.
8. A communication device, characterized in that, The multiplexer includes any one of claims 1 to 7.
9. A method for improving the performance of a multiplexer, the multiplexer comprising a first filter and a second filter, both of which are trapezoidal structures, characterized in that, The first filter includes a bandwidth extension unit, wherein the inductance of the inductor in the bandwidth extension unit is greater than a preset value. The method includes: At least one resonator of the first filter near the antenna end and all resonators in the entire second filter are set as highly doped resonators; and other resonators in the first filter are set as undoped or low-doped resonators to reduce the insertion loss effect of the first filter on other filters. Wherein, the electromechanical coupling coefficient of at least one stage resonator near the antenna end of the first filter is greater than the electromechanical coupling coefficient of other resonators in the first filter; The operating bandwidth of the filter composed of at least one resonator near the antenna end of the first filter is greater than the operating bandwidth of the filter composed of other resonators in the first filter. The first filter has at least one resonator near the antenna end and all resonators in the entire second filter have the same doping concentration. The preset value is 0.8nH.
10. The method according to claim 9, characterized in that, The doping concentration of the low-doped resonator is less than 5%, and the doping concentration of the high-doped resonator is greater than 8%.
11. The method according to claim 9, characterized in that, The highly doped resonator is disposed in the first die, and the undoped or low-doped resonator is disposed in the second die.