Filters, multiplexers and electronic devices

Abstract

This invention discloses a filter, a multiplexer, and a communication device. The filter consists of a trapezoidal structure composed of multiple series resonators and multiple parallel resonators. The multiple parallel resonators include at least one large-frequency-difference parallel resonator and at least one ordinary parallel resonator. The series and parallel resonant frequencies of the large-frequency-difference parallel resonator are both located outside the filter's passband. The series resonant frequency of the ordinary parallel resonator is located at a low-frequency end outside the passband, and the parallel resonant frequency is located inside the passband. The resonators used to form the filter's passband employ a first stacking structure, and the large-frequency-difference resonator employs a second stacking structure. The asymmetry parameter of the first stacking structure is smaller than that of the second stacking structure.

Description

Technical Field

[0001] This invention relates to the field of filter technology, and particularly to a filter, multiplexer, and electronic device. Background Technology

[0002] In the field of filter technology, a large-frequency-difference resonator is typically defined as a resonator in a trapezoidal filter where both the series and parallel resonant frequencies are set outside the filter's passband. In a trapezoidal filter containing a large-frequency-difference resonator, the resonator can be positioned at either the low-frequency or high-frequency end outside the passband. This frequency difference can be achieved by differentiating the stack structure of the resonator forming the filter's passband and the stack of the large-frequency-difference resonator. When the asymmetry parameter of the resonator forming the filter's passband is large, a pseudo-passband is formed outside the filter's higher-order resonances, severely affecting the filter's out-of-band rejection characteristics.

[0003] Therefore, there is an urgent need to propose a filter that incorporates a large frequency difference resonator to improve the out-of-band suppression characteristics of the filter. Summary of the Invention

[0004] In view of this, the present invention proposes filters, multiplexers and electronic devices with good out-of-band suppression characteristics.

[0005] The first aspect of the present invention provides a filter, the filter comprising a trapezoidal structure of multiple series resonators and multiple parallel resonators, wherein the multiple parallel resonators include at least one large-frequency-difference parallel resonator and at least one ordinary parallel resonator, the series resonant frequency and the parallel resonant frequency of the large-frequency-difference parallel resonator are both set outside the passband of the filter, the resonators used to form the passband of the filter adopt a first stacking structure, the large-frequency-difference resonator adopts a second stacking structure, and the asymmetry parameter of the first stacking structure is smaller than the asymmetry parameter of the second stacking structure.

[0006] Optionally, the asymmetry parameter of the first stacked structure is less than a preset threshold.

[0007] Optionally, the preset threshold is 0.25 or 0.4.

[0008] Optionally, the equivalent capacitance of the large-frequency-difference parallel resonator should be less than or equal to Where F0 is the passband center frequency of the filter, and Fx is the series resonant frequency of the equivalent capacitance and equivalent inductance of the resonator in the large-frequency-difference parallel branch containing the large-frequency-difference parallel resonator.

[0009] Optionally, the large frequency difference parallel resonator is connected in series with an inductor to form a large frequency difference resonant branch, one end of which is connected to a node of the series branch of the filter and the other end is grounded; or, the two ends of the large frequency difference parallel resonator are respectively connected to the two ends of an ordinary parallel resonator.

[0010] Optionally, the parallel branch containing the large-frequency-difference parallel resonator is coupled to another parallel branch containing the ordinary parallel resonator.

[0011] Optionally, the parallel branch containing the large-frequency-difference parallel resonator is coupled to the signal input / output matching circuit.

[0012] Optionally, the coupling is inductive coupling or capacitive coupling.

[0013] Optionally, the structure below the top electrode of the first stacked structure is the same as that of the second stacked structure. By adjusting the thickness of the top electrode of the first stacked structure and the second stacked structure, the asymmetry parameter of the first stacked structure is made smaller than that of the second stacked structure.

[0014] Optionally, the large frequency difference resonator can be replaced by a large frequency difference resonator group consisting of multiple resonators with the same or different resonant frequencies connected in series and / or in parallel.

[0015] A second aspect of the present invention provides a multiplexer comprising any of the filters disclosed herein.

[0016] A third aspect of the present invention provides an electronic device, including any of the filters or multiplexers disclosed in the present invention.

[0017] By controlling the asymmetry parameter of the stack of the resonator used to form the filter passband to be smaller than the asymmetry parameter of the stack of the large-frequency-difference resonator, and limiting the asymmetry parameter of the stack of the resonator forming the filter passband to be smaller than a certain specified value, the formation of a pseudo-passband outside the filter band can be avoided. Furthermore, by setting the capacitance of the large-frequency-difference resonator to be less than or equal to... This can reduce the degradation of filter insertion loss caused by adding the WF branch. Attached Figure Description

[0018] For illustrative and not limiting purposes, the invention will now be described with reference to preferred embodiments thereof, particularly the accompanying drawings, in which:

[0019] Figure 1 This is a schematic diagram of a thin-film bulk acoustic resonator;

[0020] Figure 2This is a diagram showing the real part frequency response of the impedance of a thin-film bulk acoustic resonator with different stacks.

[0021] Figure 3 This is a schematic diagram of a ladder-structure filter circuit architecture;

[0022] Figure 4 It is a graph showing the insertion loss frequency response of filters with different stacks;

[0023] Figure 5 This is a schematic diagram of the filter topology of the first embodiment of the present invention;

[0024] Figure 6 This is a schematic diagram of the WF branch in the first embodiment of the present invention;

[0025] Figure 7 These are insertion loss frequency response curves for different WF circuits;

[0026] Figure 8 This is a comparison chart of the filter insertion loss frequency response curves with and without the WF branch;

[0027] Figure 9 This is a diagram showing the insertion loss frequency characteristics of different WF branches in the first embodiment of the present invention;

[0028] Figure 10 This is a schematic diagram of the signal input echo corresponding to different WF branches in the first embodiment of the present invention;

[0029] Figure 11 This is a schematic diagram of the signal output echo corresponding to different WF branches in the first embodiment of the present invention;

[0030] Figure 12 This is a schematic diagram of the resonator stack setting when the resonant frequency of the resonator in the WF branch is at the low-frequency end outside the passband;

[0031] Figure 13 This is a schematic diagram of the resonator stack setting when the resonant frequency of the resonator in the WF branch is at the high-frequency end outside the passband;

[0032] Figure 14 This is a schematic diagram of the filter topology according to the second embodiment of the present invention;

[0033] Figure 15 This is a schematic diagram of the filter topology according to the third embodiment of the present invention;

[0034] Figure 16 This is a schematic diagram comparing the insertion loss characteristics of the filters in the first and third embodiments of the present invention. Detailed Implementation

[0035] In this embodiment of the invention, a technical solution is proposed based on a trapezoidal architecture filter containing a large frequency difference resonator: "the asymmetry coefficient of the stacked structure of the passband resonator is smaller than the asymmetry coefficient of the stacked structure of the large frequency difference resonator". This avoids the formation of a pseudo passband outside the filter band and improves the out-of-band suppression characteristics of the filter. The following is a detailed explanation.

[0036] Figure 1 The diagram shown is a schematic of a thin-film bulk acoustic resonator.

[0037] 31: Substrate, with optional materials including single-crystal silicon, gallium arsenide, sapphire, quartz, etc.

[0038] 32: Piezoelectric thin film layer, which may be made of materials such as monocrystalline aluminum nitride, polycrystalline aluminum nitride, zinc oxide, PZT, etc., and contain rare earth element doping materials in a certain atomic ratio of the above materials.

[0039] 33: Bottom electrode, materials can be selected from metals such as molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, and chromium.

[0040] 34: Top electrode (including mass loading layer), materials can be selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium and other metals, the top electrode includes mass loading layer.

[0041] 35: Acoustic mirror, shown in this diagram as a cavity. It can also be a Bragg reflector layer.

[0042] 36: Passivation layer, which may be made of materials such as monocrystalline aluminum nitride, polycrystalline aluminum nitride, zinc oxide, PZT, etc., and contain rare earth element doping materials in a certain atomic ratio of the above materials.

[0043] The area between the two dashed lines in the figure is the effective resonant region, which is the area where the top electrode, bottom electrode, piezoelectric layer and acoustic mirror overlap. When the thin film bulk acoustic resonator has an additional boundary structure (such as a protruding structure, a recessed structure, a cantilever structure, etc., not shown in the figure), the effective region can be further defined by the inner edge of the additional boundary structure. The stacked structure described later in this patent is the stack within this effective region.

[0044] Figure 2 This is the impedance-frequency response curve of a thin-film bulk acoustic wave (BAS) resonator. The BAS resonator exhibits two main resonance frequencies: one is the series resonance frequency fs when the main resonant impedance reaches its minimum value; the other is the parallel resonance frequency fp when the main resonant impedance reaches its maximum value. Furthermore, due to the structural characteristics of the BAS resonator, higher-order resonances are generated at higher frequencies simultaneously with the main resonance. The frequency position and strength of these higher-order resonances are related to the symmetry of the resonator stack. The resonator stack asymmetry parameter s is defined as follows:

[0045]

[0046] Where D36 is the density of the passivation layer, D34 is the density of the top electrode (including the mass load layer), D33 is the density of the bottom electrode, T36 is the thickness of the passivation layer, T34 is the thickness of the top electrode, and T33 is the thickness of the bottom electrode. The smaller the resonator stack asymmetry parameter s, the better its symmetry and the weaker its higher-order resonances.

[0047] Figure 2 The thin solid line represents the real part impedance frequency response curve of the resonator Res-1 with stack 1, and the thick solid line represents the real part impedance frequency response curve of the resonator Res-2 with stack 2. The asymmetry parameter s_stack1 of stack 1 is less than the asymmetry parameter s_stack2 of stack 2 (s_stack1...). <s_stack2)。

[0048] The resonator stack with an asymmetry parameter less than a certain specified value is collectively referred to as stack1, and the resonator stack with an asymmetry parameter greater than a certain specified value is collectively referred to as stack2.

[0049] Figure 3 The diagram shows a trapezoidal filter architecture. The trapezoidal filter consists of series resonators S1-S4 and parallel resonators P1-P4. L3 and L4 are parallel branch grounding inductors. T1 and T2 are the signal input and signal output terminals, respectively. L1 and L2 are the inductors connecting 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.

[0050] Figure 4 The figure shows the insertion loss frequency response curves of filters with different stacks. The solid line represents... Figure 3 The filter shown has an insertion loss frequency response curve when the resonator stack adopts a stack2 structure. Due to the large asymmetry parameter s_stack2 of the resonator stack2 (greater than 0.25), the frequency positions corresponding to the higher-order resonances of the resonator are generated. Figure 4 The pseudo-passband shown severely affects the out-of-band rejection characteristics of the filter; the dashed line represents... Figure 3 The insertion loss frequency response curve of the filter is shown when the resonator stack in the filter adopts the stack1 structure. Since the asymmetry parameter s_stack1 of stack1 is small (less than 0.15), the higher-order resonance of the resonator is relatively weak, and the above-mentioned pseudo-passband will not be generated at the high-frequency end of the filter.

[0051] like Figure 5The diagram shows the filter topology of the first embodiment of the present invention. The trapezoidal filter consists of series resonators S1-S4, a large-frequency-difference parallel resonator P0, and ordinary parallel resonators P1-P4. The series and parallel resonant frequencies of the large-frequency-difference parallel resonator P0 are both set at the low-frequency end or the high-frequency end outside the passband; the series resonant frequency of the ordinary parallel resonators is set at the low-frequency end outside the passband, and the parallel resonant frequency is set within the passband. The series resonators S1-S4 and the ordinary parallel resonators P1-P4 all adopt a stack1 structure, while the large-frequency-difference parallel resonator P0 adopts a stack2 structure. L3, L4, and L5 are parallel branch grounding inductors. T1 and T2 are the signal input and signal output terminals, respectively. L1 and L2 are the signal input and signal output connection inductors, respectively. To achieve better matching, LC matching circuits may be included at the signal input and / or signal output terminals. The WF branch can be connected to any node in the series branch, and the resonator P0 in the WF branch can be composed of multiple resonators with the same or different resonant frequencies connected in series and / or in parallel.

[0052] like Figure 6 As shown Figure 5 The filter circuit includes a parallel branch (WF branch) of a large frequency difference resonator P0. The stack of resonator P0 differs from other parallel resonators; through specific design, its main resonant frequency is set at either a high-frequency end or a low-frequency end outside the passband.

[0053] like Figure 7 The following are the insertion loss frequency response curves for different WF circuits. Frequency band 51 represents the filter passband, 52 represents the main resonance of resonator P0, 53 represents the higher-order resonance of resonator P0, and Frej is the series resonant frequency of the capacitor (capacitance value C) and inductor L5 (inductance value L) of resonator P0. The relationship between Frej (in Hz) and C (in F) and L (in nH) is as follows: In the rectangular-marked curve WF1, the capacitance of resonator P0 is 0.5C0 (pF), and the inductance of inductor L5 is 2L0 (nH). In the circular-marked curve WF2, the capacitance of resonator P0 is C0, and the inductance of inductor L5 is L0. In the triangular-marked curve WF3, the capacitance of resonator P0 is 2C0, and the inductance of inductor L5 is 0.5L0. This means that changing the capacitance and inductance of the WF circuit while keeping Frej (frej equals 2F0, where F0 is the center frequency of the filter passband) constant is necessary. From Z = jwL + 1 / jwC, it can be seen that as the capacitance value increases, the suppression in the Frej band increases, and the insertion loss at 51 in the passband increases. Therefore, the WF circuit must make a trade-off between the suppression at Frej and the deterioration of the filter insertion loss.

[0054] like Figure 8To compare the insertion loss frequency response curves of the filter in the comparative example with those in the first embodiment, the circuit topology of the first embodiment excluding the WF branch is the comparative circuit topology. The thin solid line represents the insertion loss frequency response curve of the comparative filter, the thick solid line represents the insertion loss frequency response curve of the first embodiment of the present invention, and the dashed line represents... Figure 6 The impedance-frequency characteristic curve of the WF branch in the first embodiment of the present invention is shown. A suppression point is generated near the series resonant frequency (including higher-order resonances) of the resonator P0 outside the filter passband. Simultaneously, a suppression point is generated at the series resonant frequency of the parallel plate capacitor and inductor L5 of resonator P0, thereby improving the out-of-band suppression characteristics of the filter. Since the resonators forming the filter passband in the comparative example and the first embodiment (series resonators S1-S4 and parallel resonators P1-P4) all adopt a stack1 structure, the higher-order resonances of the resonators are relatively weak, and no pseudo-passband is formed in the high-frequency range of the passband. To form a larger frequency difference with the aforementioned resonators, resonator P0 has a stack2 structure, but its main resonance and higher-order resonances do not significantly deteriorate the out-of-band suppression of the filter. In summary, the asymmetry parameter of the stack of the resonators used to form the filter passband in the trapezoidal structure filter with the WF branch should be less than a certain specified value, while the asymmetry parameter of the stack of the large-frequency-difference resonator in the WF branch can be a larger value.

[0055] like Figure 9 The diagram shows the filter insertion loss frequency characteristics for different WF branches according to the first embodiment of the present invention. In the rectangular-marked curve WF1, the capacitance of resonator P0 is 0.5C0, and the inductance of inductor L5 is 2L0 (the current filter peak insertion loss is 1.2dB); in the circular-marked curve WF2, the capacitance of resonator P0 is C0, and the inductance of inductor L5 is L0; in the triangular-marked curve WF3, the capacitance of resonator P0 is 2C0, and the inductance of inductor L5 is 0.5L0. In the above three cases, the echo at the filter signal input and signal output are equivalent (e.g., ...). Figure 10 and Figure 11 Under the conditions shown, with filter center frequency F0 = 3GHz and Frej = 6GHz, the insertion loss of WF2 deteriorates by 0.1dB compared to WF1, and the insertion loss of WF3 deteriorates by 0.4dB compared to WF1. That is, when Frej remains constant, the larger the capacitance value, the greater the deterioration of the filter insertion loss. The influence of the WF branch on the filter passband insertion loss is not only related to the capacitance and inductance values, but also to the frequency difference between Frej and the filter center frequency F0. The smaller the frequency difference, the greater the influence of the WF branch on the filter insertion loss.

[0056] Since bulk acoustic wave filters generally have good stopband suppression, the frequency band that needs to be boosted is usually at the second harmonic or a frequency band further away from the passband. Therefore, Frej >= 2 * F0, according to the formula... The capacitance of the resonator P0 can be calculated to be 1.68pF when the filter center frequency F0 = 3GHz, Frej = 6GHz, and the insertion loss deteriorates by 0.4dB. For a filter with a center frequency Fx, in order to ensure that the insertion loss deterioration is less than 30% after adding a large frequency difference resonator, the capacitance Cx of the large frequency difference resonator should be less than or equal to...

[0057] Figure 10 This is a schematic diagram of the signal input echo corresponding to different WF branches in the first embodiment of the present invention; Figure 11 This is a schematic diagram of the signal output echo corresponding to different WF branches in the first embodiment of the present invention. Figure 10 and Figure 11 As shown, for the three different WF branches mentioned above, the signal input echo can be achieved by adjusting the matching network at the filter input and output ends. Figure 10 ) and signal output echo ( Figure 11 They are comparable to each other.

[0058] like Figure 12 The diagram shows the resonator stack configuration in the WF branch when the resonant frequency is at the low-frequency end of the passband. The resonator stack used to form the filter passband uses a stack1 structure, while the stack for the large-frequency-difference resonator at the low-frequency end of the passband uses a stack2 structure. The asymmetry parameter of stack1 is smaller than that of stack2. The stack structure only needs to satisfy the above asymmetry parameter relationship. To simplify the manufacturing process, the film structure below the top electrode is identical for both stack1 and stack2.

[0059] like Figure 13 The diagram shows the resonator stack configuration in the WF branch when the resonant frequency is at the high-frequency end of the passband. The resonator stack used to form the filter passband uses a stack1 structure, while the stack for the large-frequency-difference resonator at the high-frequency end of the passband uses a stack2 structure. The asymmetry parameter of stack1 is smaller than that of stack2. The stack structure only needs to satisfy the above asymmetry parameter relationship. Here, to simplify the process, the film structure below the top electrode is exactly the same for stack1 and stack2.

[0060] comprehensive Figure 12 and Figure 13 It is known that, in order to simplify the process steps, the structure below the top electrode of the first stacked structure and the second stacked structure are the same. By adjusting the thickness of the top electrode of the first stacked structure and the second stacked structure, the asymmetry parameter of the first stacked structure is made smaller than that of the second stacked structure.

[0061] like Figure 14The diagram shows the filter topology of the second embodiment of the present invention. The trapezoidal filter consists of series resonators S1-S4 and parallel resonators P0-P4. Both series resonators S1-S4 and parallel resonators P1-P4 adopt a stack 1 structure. The resonant frequency of parallel resonator P0 is set at the low-frequency end or high-frequency end outside the passband. Parallel resonator P0 adopts a stack 2 structure. L3, L4, and L5 are grounding inductors for the parallel branch. T1 and T2 are the signal input terminal and signal output terminal, respectively. L1 and L2 are the inductors connecting the signal input terminal and the signal output terminal, respectively. To achieve better matching, an LC matching circuit may be included at the signal input terminal and / or the signal output terminal. The difference between the second embodiment of the present invention and the first embodiment is that resonator P0 is connected in parallel with one of the resonators in the parallel branch.

[0062] like Figure 15 The diagram shows the filter topology of the third embodiment of the present invention. The difference between the third embodiment and the first embodiment is that the WF branch is coupled to another parallel branch, or the WF branch is coupled to the signal input / output matching circuit. The coupling can be inductive or capacitive.

[0063] Figure 16 This is a schematic diagram comparing the insertion loss characteristics of the filters in the first and third embodiments of the present invention. Figure 16 It can be seen that setting coupling between the inductor in the large frequency difference parallel branch and the low inductance in the ordinary parallel branch can improve the out-of-band rejection characteristics of the filter in the characteristic frequency band, further increasing the design flexibility.

[0064] According to other embodiments of the filter of the present invention, a single large-frequency-difference resonator can be replaced with a group of large-frequency-difference resonators composed of multiple resonators with the same or different resonant frequencies connected in series and / or in parallel. Each resonator within the large-frequency-difference resonator group adopts a stack2 structure.

[0065] 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 filter, characterized in that, The filter consists of a trapezoidal structure composed of multiple series resonators and multiple parallel resonators, wherein... The plurality of parallel resonators includes at least one large-frequency-difference parallel resonator and at least one ordinary parallel resonator. The series resonant frequency and parallel resonant frequency of the large-frequency-difference parallel resonator are both set outside the passband of the filter. The resonators used to form the passband of the filter employ a first stacking structure, while the large-frequency-difference parallel resonators employ a second stacking structure. The asymmetry parameter of the first stacked structure is smaller than that of the second stacked structure; The formula for calculating the asymmetry parameter is as follows: Wherein, D36 is the density of the passivation layer, D34 is the density of the top electrode including the mass load layer, D33 is the density of the bottom electrode, T36 is the thickness of the passivation layer, T34 is the thickness of the top electrode, and T33 is the thickness of the bottom electrode.

2. The filter according to claim 1, characterized in that, The asymmetry parameter of the first stacked structure is less than a preset threshold.

3. The filter according to claim 2, characterized in that, The preset threshold is 0.25 or 0.

4.

4. The filter according to claim 1, characterized in that, The equivalent capacitance of the large-frequency-difference parallel resonator should be less than or equal to... Where F0 is the passband center frequency of the filter, and Fx is the series resonant frequency of the equivalent capacitance and equivalent inductance of the resonator in the large-frequency-difference parallel branch containing the large-frequency-difference parallel resonator.

5. The filter according to claim 1, characterized in that, The large-frequency-difference parallel resonator and the inductor are connected in series to form a large-frequency-difference resonant branch. One end of the large-frequency-difference resonant branch is connected to a node of the series branch of the filter, and the other end is grounded; or, The two ends of the large frequency difference parallel resonator are respectively connected to the two ends of an ordinary parallel resonator.

6. The filter according to claim 1, characterized in that, The parallel branch containing the large-frequency-difference parallel resonator is coupled to another parallel branch containing the ordinary parallel resonator.

7. The filter according to claim 1, characterized in that, The parallel branch containing the large frequency difference parallel resonator is coupled to the signal input / output matching circuit.

8. The filter according to claim 6 or 7, characterized in that, The coupling is either inductive coupling or capacitive coupling.

9. The filter according to claim 6 or 7, characterized in that, The structure below the top electrode of the first stacked structure is the same as that of the second stacked structure. By adjusting the thickness of the top electrode of the first stacked structure and the second stacked structure, the asymmetry parameter of the first stacked structure is made smaller than that of the second stacked structure.

10. The filter according to claim 1, characterized in that, The large frequency difference parallel resonator is replaced by a large frequency difference resonator group consisting of multiple resonators with the same or different resonant frequencies connected in series and / or in parallel.

11. A multiplexer, characterized in that, The filter includes any one of claims 1 to 10.

12. An electronic device, characterized in that, Includes the filter according to any one of claims 1 to 10 or the multiplexer according to claim 11.

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