WO2021185258A1 - 调整谐振频率的方法和滤波器、多工器、通信设备 - Google Patents

调整谐振频率的方法和滤波器、多工器、通信设备 Download PDF

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Publication number
WO2021185258A1
WO2021185258A1 PCT/CN2021/081139 CN2021081139W WO2021185258A1 WO 2021185258 A1 WO2021185258 A1 WO 2021185258A1 CN 2021081139 W CN2021081139 W CN 2021081139W WO 2021185258 A1 WO2021185258 A1 WO 2021185258A1
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resonator
resonators
series
filter
frequency
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PCT/CN2021/081139
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English (en)
French (fr)
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蔡华林
庞慰
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诺思(天津)微系统有限责任公司
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Publication of WO2021185258A1 publication Critical patent/WO2021185258A1/zh

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
    • H03B5/02—Details
    • H03B5/04—Modifications of generator to compensate for variations in physical values, e.g. power supply, load, temperature
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
    • H03B5/30—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element being electromechanical resonator
    • H03B5/32—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element being electromechanical resonator being a piezoelectric resonator

Definitions

  • the present invention relates to the technical field of filters, in particular to a method for adjusting resonance frequency, a filter, a multiplexer, and a communication device.
  • Acoustic wave filters generally use series resonance and parallel resonators to form a pass band.
  • the parallel resonant frequency of the parallel resonator needs to be close to the series resonant frequency of the series resonator.
  • its resonant frequency is basically the same; add a mass load with a certain amount of load to the parallel resonator to adjust the resonant frequency of the parallel resonator to make It is close to the series resonance frequency of the series resonator.
  • the existing filter can only ensure good matching in a narrow frequency band, and it is difficult to make the entire passband better match.
  • the present invention proposes to adapt the passband matching of the filter with a new resonator frequency distribution architecture, and provides a method for adjusting the resonant frequency of the filter and the filter, multiplexer, and communication equipment, which help the entire filter The passband and out-of-band have a better match.
  • a method for adjusting the resonance frequency to improve the performance of the filter is provided.
  • the method for adjusting the resonant frequency of the present invention is used to adjust the resonant frequency of a resonator in a filter.
  • the filter is an acoustic wave filter and includes at least three series resonators.
  • the method includes: A filter with an odd number of series resonators: for the odd number of series resonators other than the first and second series resonators, for the third resonator or choose to include the third resonator
  • the frequency of the two or more resonators is different from that of the first series resonator and the second series resonator; and/or, for a filter with an even number of series resonators between the input and output:
  • One or more of the even number of series resonators other than the first and second series resonators have a frequency different from that of the first series resonator and the second series resonator
  • the frequency of the resonator where: the first and second series resonators are the resonators closest
  • the filter further includes at least two parallel resonators.
  • the method further includes: in the parallel resonator, Two or more resonators, including the fifth parallel resonator and the fifth parallel resonator, make their frequencies different from those of other parallel resonators; among them: the fourth and fifth parallel resonators are the resonances closest to the input and output of the filter, respectively Device.
  • the number of the two or more resonators is smaller than the number of the parallel resonator.
  • the step of selecting the third resonator or selecting two or more resonators including the third resonator so that the frequency is different from the frequencies of the first series resonator and the second series resonator includes the following adjustments : Add mass load to the third resonator or two or more resonators including the third resonator or increase the thickness of one or more layers.
  • the frequency of one or more resonators among the even number of series resonators other than the first and second series resonators is different from that of the first and second series resonators.
  • the frequency steps of a series resonator and a second series resonator include the following adjustment: adding a mass load to the one or more resonators or increasing the thickness of one or more layers.
  • the frequencies of the adjusted resonators are made inconsistent.
  • the maximum frequency offset caused by the adjustment is less than 50% of the passband bandwidth.
  • the maximum frequency offset is less than 25% of the passband bandwidth.
  • the step of increasing the mass load includes: adding a mass load layer to the resonator, wherein: the shape of the mass load layer is a plurality of discontinuous blocks, or the shape of the mass load layer is One or several blocks hollowed out.
  • a filter which is an acoustic wave filter, wherein the resonator is a resonator whose resonance frequency is adjusted by the method of the present invention.
  • a multiplexer which includes the filter according to the present invention.
  • a communication device which includes the filter according to the present invention.
  • the whole passband of the filter can be better matched, and the filter There is a suitable impedance value outside the band.
  • Figure 1 is an impedance curve diagram of a series resonator and a parallel resonator in an existing filter
  • FIG. 2a is a schematic diagram of a structure for adjusting the resonant frequency of a resonator in a filter according to an embodiment of the present invention
  • FIG. 2b is a schematic diagram of another structure of a filter according to an embodiment of the present invention.
  • Fig. 3 is a graph of impedance and transmission characteristics of a filter according to an embodiment of the present invention.
  • Figure 4a is the comparison curve of the insertion loss of the filter
  • Figure 4b is the comparison curve of filter echo
  • Figure 5a is a comparison curve of filter insertion loss
  • Figure 5b is the roll-off comparison curve on the right side of the filter
  • Figure 5c is the roll-off comparison curve on the right side of the filter
  • Fig. 6a is a schematic diagram of the relationship between the real impedance part and the frequency of a series resonator
  • Figure 6b is a schematic diagram of the influence of the load on the passband
  • Figure 7a is a comparison curve of the filter passband
  • Figure 7b is the roll-off comparison curve on the left side of the filter
  • Figure 8a is a comparison curve of filter insertion loss
  • Figure 8b is a comparison curve of filter echo
  • Figure 8c is the roll-off comparison curve on the left side of the filter
  • Figure 9 is the comparison curve of the filter out-of-band impedance
  • Figure 10 is the comparison curve of the filter out-of-band suppression
  • Fig. 11 is a front view of the top of a resonator according to an embodiment of the present invention.
  • Fig. 12 is a front view of the top of another resonator according to an embodiment of the present invention.
  • the passband matching of the filter is applied with a new resonator frequency distribution architecture, which will be described in detail below.
  • Figure 1 is the impedance curve of the series resonator and the parallel resonator in the existing filter.
  • the solid line is the impedance curve of the series resonator
  • the dashed line is the impedance curve of the parallel resonator
  • the horizontal axis is the frequency
  • the vertical axis is the impedance value.
  • the frequency corresponding to the lowest impedance point of the series resonator is the series resonance point Fs
  • the highest impedance point of the series resonator is the impedance at the parallel resonance point Fp, and the frequency corresponding to the highest impedance point of the parallel resonator is the parallel resonance point Fp'. It can be seen from Figure 1 that in the existing filter, Fp' and Fs are close to each other to form a match at the center frequency in the passband, and the entire passband of the filter is between Fs' and Fp. Therefore, the frequency and The impedance distribution does not guarantee a good match in the entire passband.
  • a part of the resonator of the filter is selected, and the frequency of the part of the resonator is adjusted to differentiate its frequency from that of other resonators, or the frequency of the unselected resonator is adjusted to finally make the selection
  • the frequency parameters of the resonator and the unselected resonator are different, thereby changing the series resonant frequency/parallel resonant frequency and impedance distribution of each resonator in the filter, thereby significantly improving the impedance matching in the passband.
  • the way of frequency adjustment can be to increase or decrease (in the case of an existing mass loading layer) the mass load in the resonator, or to change the thickness of a certain layer or multiple layers of the resonator.
  • Fig. 2a is a schematic diagram of a structure of a filter according to an embodiment of the present invention.
  • an odd number (specifically 5, or 3, 7 or more) series resonators are connected in series between the input and output terminals (the black dots in the figure), which are series resonators 0, a, and b, c, and 0.
  • the principle to be followed when adjusting the frequency of the series resonator is: the frequency of the two series resonators on both sides (that is, close to the input end and the output end) is not performed.
  • the frequency of the series resonator b located in the middle needs to be adjusted, and each of the series resonators a and c may or does not need to adjust the frequency.
  • the frequency-adjusted series resonator is as follows: b, ab, bc, abc. It can be seen that, in addition to the first case, in the other three cases, an effect to be achieved by frequency adjustment is that the frequencies of all series resonators whose frequencies are adjusted cannot be the same. It will be seen in the following description that using this method to adjust the frequency of the resonator in the filter can improve the performance of the filter on the right side of the roll-off and the insertion loss echo.
  • the fourth case is adopted, that is, when the frequency of the series resonators abc is adjusted, the frequency shift caused by the largest mass load in the series resonators a, b, and c can be less than 50% of the passband bandwidth (preferably Less than 25%), which helps to avoid deterioration of the insertion loss on the left side of the resonator.
  • Fig. 2b is a schematic diagram of another structure of a filter according to an embodiment of the present invention.
  • Figure 2b includes an even number (at least 4, but more) series resonators, which are series resonators 0, a, b, and 0, respectively.
  • the principle to be followed when adjusting the frequency of the series resonator is: the frequency of the two series resonators on both sides (that is, close to the input end and the output end) is not performed.
  • the frequency-adjusted series resonator is as follows: a, b, ab.
  • the mass loads of the series resonators a and b are different, and the frequencies of the two are different. After the above frequency adjustment, it helps to improve the performance of the filter on the right side of the roll-off and the insertion loss echo.
  • the frequency shift caused by the maximum mass load in the series resonators a and b can be less than 50% (preferably less than 25%) of the passband bandwidth, which helps to avoid deterioration of the insertion loss on the left side of the resonator.
  • the filters in the figure all include four parallel resonators, namely parallel resonators d, e, f, and g.
  • the principle followed when adjusting the frequency of the parallel resonator is: the frequencies of the two series resonators d and g located on both sides are adjusted, and each of the parallel resonators e and f located in the middle may or does not need to adjust the frequency.
  • the parallel resonator whose frequency is adjusted is as follows: dge, dgf, dg, dgef.
  • the frequencies of the multiple parallel resonators whose frequencies are adjusted are not all the same. The above frequency adjustment helps to improve the performance of the left side roll-off and insertion loss echo of the resonator.
  • the first three methods are preferred.
  • Fig. 3 is a graph of impedance and transmission characteristics of the filter, which is the filter shown in Fig. 2b including 4 series resonators and 4 parallel resonators.
  • the thin solid line is the impedance curve of the series resonator
  • the thin dashed line is the impedance curve of the parallel resonator, corresponding to the left ordinate
  • the thick solid line is the transmission characteristic curve of the filter, corresponding to the right ordinate.
  • the series resonator and the parallel resonator have increased frequency types and matched at multiple positions in the pass band; in addition, the roll-off positions on the left and right sides of the filter (left The side roll-off position is about 1.685GHz ⁇ 1.7GHz, and the right side is 1.79GHz ⁇ 1.805GHz).
  • Fig. 4a is the comparison curve of the insertion loss of the filter
  • Fig. 4b is the comparison curve of the filter echo.
  • the solid line is the curve when the series resonant frequency Fs1 of the two series resonators 0
  • the dashed line is the curve when the mass load is added to the two series resonators 0 so that the series resonant frequency of the two series resonators is greater than Fs1.
  • Figure 5a is a comparison curve of the filter insertion loss
  • Figure 5b is a comparison curve of the roll-off on the right side of the filter.
  • the solid line corresponds to the mass load on the series resonator in the middle
  • the dashed line corresponds to the mass load on the series resonator in the middle.
  • the passband performance is almost unchanged, but the roll-off on the right side is improved after the mass load is added to the series resonator located in the middle.
  • Figure 5c is the roll-off comparison curve on the right side of the filter; among them, the mass loads in the series resonator a and the series resonator b are not equal, so that there is a 1MHz frequency difference between the two.
  • the roll-off of the filter is further improved. It can be seen that the series resonator in the middle increases the mass load, and when the mass load is not equal, the roll-off improvement is more obvious.
  • Figure 6a is a schematic diagram of the relationship between the real impedance part and frequency of a series resonator
  • Figure 6b is a schematic diagram of the influence of the load on the passband.
  • the solid line corresponds to the case where the mass load shifts the frequency of the series resonator by 10 MHz
  • the dashed line corresponds to the case where the mass load shifts the frequency of the series resonator by 20 MHz.
  • the area below the series resonance point Fs of the series resonator falls on the left side of the filter passband, and as shown in Fig. 6a, there is a period of loss increase below the series resonance point Fs.
  • the frequency shift caused by the largest mass load in the series resonator a and the series resonator b in the middle is preferably less than 50% of the passband bandwidth, and more preferably less than 25%, so as to avoid the series resonator. Insertion loss on the left side deteriorates.
  • Figure 7a is the comparison curve of the filter passband
  • Figure 7b is the comparison curve of the roll-off on the left side of the filter
  • the solid line is the filter curve when the frequency of the parallel resonator d, g, f is adjusted
  • the dashed line is the parallel resonator
  • the roll-off is better than the roll-off of the filter that adjusts the parallel resonator d, g, e, f.
  • Fig. 8a is a comparison curve of filter insertion loss
  • Fig. 8b is a comparison curve of filter echo
  • Fig. 8c is a comparison curve of roll-off on the left side of the filter.
  • the solid line is the filter performance curve with three different mass loads in the parallel resonator
  • the dashed line is the filter performance curve with two different mass loads in the parallel resonator; among them, three parallel resonators with different mass loads Among them, the frequency difference between the two parallel resonators with a relatively low frequency and the parallel resonator with the highest frequency is 3 MHz and 10 MHz, respectively.
  • Figure 9 shows the comparison curve of the out-of-band impedance of the filter.
  • the solid line is the out-of-band impedance curve of the filter according to the embodiment of the invention
  • the dashed line is the out-of-band impedance curve of the filter in the prior art.
  • the principle of filter matching is that the passband should be as close as possible to 50 ohms to ensure good passband matching, while the out-of-band part needs to be as far away as possible from 50 ohms to ensure out-of-band mismatch, so as to obtain better out-of-band suppression characteristics.
  • the passband range of the filter in the embodiment of the present invention is 1.71GHz to 1.785GHz. From the comparison of the curves in Figure 9, it can be seen that the out-of-band impedance of the solid line is higher than that of the dashed line, and the solid line part can obtain more Good out-of-band suppression.
  • Figure 10 is the comparison curve of the filter out-of-band suppression.
  • the solid line is the out-of-band suppression curve of the filter implemented in the present invention
  • the dashed line is the out-of-band suppression curve of the filter in the prior art. The curve has a significant improvement.
  • the mass loading when adjusting the mass loading, can be adjusted by controlling the area ratio of the mass loading layer, which is different from the existing thickness of adjusting the mass loading layer.
  • Fig. 11 is a front view of a top of a resonator according to an embodiment of the present invention
  • Fig. 12 is a front view of a top of another resonator according to an embodiment of the present invention.
  • the mass load layer in FIG. 11 is a circle set at the center, and the mass load layer in FIG. 12 is composed of multiple split structures.
  • the mass load layer can be split or monolithic.
  • the shape of the whole block or each split body can be arbitrarily selected, wherein the shape of the whole block can be convex or concave, and can also be hollowed out, and the arrangement of the split bodies can be in an irregular manner similar to that shown in FIG. 12.
  • the mass load layer can be arranged on the electrode layer or other layers, and accurate and diversified frequencies can be realized by controlling the area ratio.
  • the area ratio here can be 100%, that is, it fills the entire layer area.

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Abstract

一种调整滤波器谐振频率方法和滤波器、多工器、通信设备，有助于滤波器整个通带和带外均有较好的匹配。在该方法中，通过在部分串联谐振器和部分并联谐振器上增加质量负载，进而调整该部分谐振器的频率，这样可以使滤波器整个通带均有较好的匹配，同时滤波器带外有合适的阻抗值。

Description

调整谐振频率的方法和滤波器、多工器、通信设备 技术领域
本发明涉及滤波器技术领域，特别地涉及一种调整谐振频率方法和滤波器、多工器、通信设备。
背景技术
声波滤波器一般使用串联谐振和并联谐振器共同组成通带，其中，为了保证通带内匹配良好，需要使并联谐振器的并联谐振频率和串联谐振器的串联谐振频率相接近。常见的滤波器中，各串联谐振器由于各层材料相同，参数相同，因此其谐振频率也基本相同；在并联谐振器上加具有一定负载量的质量负载，调节并联谐振器的谐振频率，使其与串联谐振器的串联谐振频率接近。
但是，现有的滤波器只能保证一个较窄的频段内匹配良好，难以使整个通带有较好的匹配。同时，为了尽量保证通带内的阻抗匹配，带外的阻抗难以获得需要的值，从而使带外抑制也会恶化。
发明内容
有鉴于此，本发明提出以新的谐振器频率分布架构适用滤波器的通带匹配，提供了一种调整滤波器谐振频率方法和滤波器、多工器、通信设备，有助于滤波器整个通带和带外均有较好的匹配。
为实现上述目的，根据本发明的一个方面，提供了一种调整谐振频率来改善滤波器性能的方法。
本发明的调整谐振频率的方法，用于调整滤波器中谐振器的谐振频率，所述滤波器为声波滤波器，包括至少三个串联谐振器，该方法包括，对于输入端和输出端之间有奇数个串联谐振器的滤波器：对于所述奇数个串联谐振器中的 除第一和第二串联谐振器之外的其他谐振器，对于第三谐振器或者选择包含第三谐振器在内的2个以上谐振器，使其频率不同于第一串联谐振器和第二串联谐振器的频率；并且/或者，对于输入端和输出端之间有偶数个串联谐振器的滤波器：对于所述偶数个串联谐振器中的除所述第一和第二串联谐振器之外的其他谐振器中的1个或2个以上谐振器，使其频率不同于第一串联谐振器和第二串联谐振器的频率；其中：第一和第二串联谐振器分别是最接近滤波器的输入端和输出端的谐振器，第三谐振器是所述奇数个串联谐振器中的居中的谐振器。
可选地，所述滤波器还包括至少两个并联谐振器，对于输入端和输出端之间的并联谐振器的滤波器，该方法还包括：在所述并联谐振器中，对于包含第四和第五并联谐振器在内的2个以上谐振器，使其频率不同于其他并联谐振器的频率；其中：第四和第五并联谐振器分别是最接近滤波器的输入端和输出端的谐振器。
可选地，在所述并联谐振器中，所述2个以上谐振器的数目小于所述并联谐振器的数目。
可选地，所述对于第三谐振器或者选择包含第三谐振器在内的2个以上谐振器，使其频率不同于第一串联谐振器和第二串联谐振器的频率的步骤包括如下调整：对第三谐振器或者包含第三谐振器在内的2个以上谐振器增加质量负载或者增加一层或多层的厚度。
可选地，所述对于所述偶数个串联谐振器中的除所述第一和第二串联谐振器之外的其他谐振器中的1个或2个以上谐振器，使其频率不同于第一串联谐振器和第二串联谐振器的频率步骤包括如下调整：对所述1个或2个以上谐振器增加质量负载或者增加一层或多层的厚度。
可选地，在所述调整中，使被调整的谐振器的频率不一致。
可选地，在所述调整中，调整导致的最大频率偏移小于通带带宽的50％。
可选地，所述最大频率偏移小于通带带宽的25％。
可选地，所述增加质量负载的步骤包括：向谐振器增加质量负载层，其中：所述质量负载层的形状为多个互不连续的块状，或者所述质量负载层的形状为具有镂空的一个或几个块状。
根据本发明的另一方面，提供了一种滤波器，该滤波器为声波滤波器，其中的谐振器是经本发明所述的方法调整谐振频率的谐振器。
根据本发明的又一方面，提供了一种多工器，其包含本发明所述的滤波器。
根据本发明的又一方面，提供了一种通信设备，其包含本发明所述的滤波器。
根据本发明的技术方案，通过在部分串联谐振器和部分并联谐振器上增加质量负载，进而调整该部分谐振器的频率，这样可以使滤波器整个通带均有较好的匹配，同时滤波器带外有合适的阻抗值。
附图说明
为了说明而非限制的目的，现在将根据本发明的优选实施例、特别是参考附图来描述本发明，其中：
图1为现有的滤波器中串联谐振器和并联谐振器的阻抗曲线图；
图2a为本发明实施方式调整滤波器中谐振器的谐振频率的一种结构的示意图；
图2b为本发明实施方式涉及的滤波器的另一种结构的示意图；
图3为本发明实施方式涉及的滤波器的阻抗及传输特性曲线图；
图4a为滤波器的插损 对比曲线；
图4b为滤波器回波对比曲线；
图5a为滤波器插损对比曲线；
图5b为滤波器右侧滚降对比曲线；
图5c为滤波器右侧滚降对比曲线；
图6a为一个串联谐振器的阻抗实部和频率的关系示意图；
图6b为负载量大小对通带的影响示意图；
图7a为滤波器通带对比曲线；
图7b为滤波器左侧滚降对比曲线；
图8a为滤波器插损对比曲线；
图8b为滤波器回波对比曲线；
图8c为滤波器左侧滚降对比曲线；
图9为滤波器带外阻抗对比曲线；
图10为滤波器带外抑制的对比曲线；
图11为根据本发明实施方式的一种谐振器顶部的主视图；
图12为根据本发明实施方式的另一种谐振器顶部的主视图。
具体实施方式
本发明实施方式中，以新的谐振器频率分布架构适用滤波器的通带匹配，以下具体加以说明。
图1为现有的滤波器中串联谐振器和并联谐振器的阻抗曲线图，实线是串联谐振器的阻抗曲线，虚线是并联谐振器的阻抗曲线，横轴是频率，纵轴是阻抗值。如图1所示，串联谐振器的阻抗最低点对应的频率是串联谐振点Fs，并联谐振器的阻抗最低点对应的频率是串联谐振点Fs’，并联谐振器上因为有质量负载，所以频率降低M，即Fs’＝Fs-M。串联谐振器的阻抗最高点是并联谐振点Fp处的阻抗，并联谐振器的阻抗最高点对应的频率是并联谐振点Fp’。由图1可以看出现有的滤波器中，Fp’和Fs接近，从而组成通带内中心频率处的匹配，而滤波器的整个通带介于Fs’和Fp之间，因此，该频率和阻抗分布并不能保证整个通带内有良好 的匹配。
本发明实施方式中，选择出滤波器的部分谐振器，对该部分谐振器进行频率调整，使其频率区别于其他谐振器的频率，或者对未选择的谐振器进行频率调整，最终使得选择出的谐振器与未选择的谐振器，在频率参数上形成差异，从而改变滤波器中的各谐振器的串联谐振频率/并联谐振频率和阻抗分布，进而使得通带内阻抗匹配得到明显改善，以达到改善滤波器的回波、插损、带内杂波和滚降等性能的目的。频率调整的方式可以是增加或减少(在已有质量负载层的情况下)谐振器中的质量负载，或者改变谐振器某层或多层的厚度。以下对本发明的实施方式作详细说明。
图2a为本发明实施方式涉及的滤波器的一种结构的示意图。图2a中，输入输出端子(图中黑点)之间串联有奇数个(具体为5个，也可以是3个、7个或更多)串联谐振器，分别为串联谐振器0、a、b、c、和0。对于滤波器中包含奇数个串联谐振器的情况，在调节串联谐振器频率时所遵循的原则为：位于两侧的(即分别靠近输入端和输出端的)两个串联谐振器0的频率不进行调节，位于中间的串联谐振器b的频率需要进行调节，串联谐振器a和c中的每个可以或者无需调节频率。基于上述原则，被调节频率的串联谐振器为如下情况：b、ab、bc、abc。由此可知，除第1种情况之外，其他3种情况中，频率调节要达到的一个效果是，所有被调节频率的串联谐振器的频率不能都相同。在后文的说明中将会看出，采用此方法调整滤波器中的谐振器的频率，可以改善滤波器右侧滚降以及插损回波等性能。其中，采用第四种情况，即对串联谐振器abc都进行频率调整时，串联谐振器a、b、c中设置最大的质量负载导致的频率偏移可小于通带带宽的50％(优选地小于25％)，有助于避免谐振器左侧插损恶化。
图2b为本发明实施方式涉及的滤波器的另一种结构的示意图。图2b中包括偶数个(至少为4个，可以更多)串联谐振器，分别为串联谐振器0、a、b、0。对于滤 波器中包含偶数个串联谐振器的情况，在调节串联谐振器频率时所遵循的原则为：位于两侧的(即分别靠近输入端和输出端的)两个串联谐振器0的频率不进行调节，位于中间的串联谐振器即a和b，二者的频率至少调节一个。基于上述原则，被调节频率的串联谐振器为如下情况：a、b、ab。采用第三种情况时，串联谐振器a和b的质量负载不同，进而使两者的频率不同。经上述频率调整后，有助于改善滤波器右侧滚降以及插损回波等性能。串联谐振器a和b中最大质量负载导致的频率偏移可小于通带带宽的50％(优选地小于25％)，有助于避免谐振器左侧插损恶化。
如图2a和2b所示，图中滤波器均包括4个并联谐振器，分别为并联谐振器d、e、f、g。在调节并联谐振器频率时所遵循的原则为：位于两侧的两个串联谐振器d和g的频率均进行调节，位于中间的并联谐振器e和f中的每个可以或无需调节频率。基于上述原则，被调节频率的并联谐振器为如下情况：dge、dgf、dg、dgef。并且，被调节频率的多个并联谐振器的频率不都相同。上述频率调整有助于改善谐振器左侧滚降以及插损回波等性能，其中，上述四种情况中，优选前三种方式。
图3为滤波器的阻抗及传输特性曲线图，该滤波器是图2b所示的包括4个串联谐振器和4个并联谐振器的滤波器。图中细实线为串联谐振器的阻抗曲线，细虚线为并联谐振器的阻抗曲线，对应左侧纵坐标；粗实线为滤波器的传输特性曲线，对应右侧纵坐标。如图3所示，整个通带内，串联谐振器和并联谐振器均增加了频率种类，在通带内多个位置进行了匹配；另外在滤波器左侧和右侧的滚降位置(左侧滚降位置是1.685GHz～1.7GHz左右，右侧是1.79GHz～1.805GHz)，也有多个频率的谐振器进行频率和阻抗调节，以获得更好的匹配效果。对于图2a所示的滤波器，也有类似的更好的匹配效果。
另外从上文的描述可以看出，选择谐振器时需有一些原则，下面通过性能参数对比，证明遵 循这些原则的有益之处。
图4a为滤波器的插损对比曲线；图4b为滤波器回波对比曲线。图中，实线为两个串联谐振器0的串联谐振频率Fs1时的曲线，虚线为两个串联谐振器0上添加质量负载从而使二者串联谐振频率大于Fs1时的曲线。当向位于两侧的两个串联谐振器0上添加质量负载(频率偏移结构)时，会引起串联谐振频率偏移，图中所示为串联谐振频率偏移4MHz时的情形。从图4a和图4b可以看出，在向两个串联谐振器0上添加质量负载时，滤波器的插损和回波损耗性能均会变差。由此可知，串联谐振器频率调节时，位于两侧的谐振器不论是否已有质量负载层，其频率均不进行调节，以避免性能受到影响。
图5a为滤波器插损对比曲线，图5b为滤波器右侧滚降对比曲线。图中，实线对应于中间的串联谐振器上有质量负载，虚线对应于中间的串联谐振器上没有质量负载。其中，当存在质量负载时，串联谐振器a和串联谐振器b中的质量负载量相等。可以看出，串联谐振器上存在质量负载和不存在质量负载时，其通带性能几乎没有变化，但是，在位于中间的串联谐振器上加入质量负载后右侧的滚降得到改善。
图5c为滤波器右侧滚降对比曲线；其中，串联谐振器a和串联谐振器b中的质量负载量不相等，使两者存在1MHz的频率差。如图5c所示，当位于中间的串联谐振器存在质量负载，且质量负载量不等时，滤波器的滚降进一步得到改善。由此可知，位于中间的串联谐振器增加质量负载，且质量负载量不等时，滚降改善更加明显。
图6a为一个串联谐振器的阻抗实部和频率的关系示意图，图6b为负载量大小对通带的影响示意图。图中，实线对应于质量负载使串联谐振器频率偏移了10MHz的情形，虚线对应于质量负载使串联谐振器频率偏移了20MHz的情形。参考图3，串联谐振器的串联谐振点Fs以下的区域落在滤波器通带的左侧，再参见图6a所示，串联谐振点Fs以下有一段损耗的增加，由 此可知，当此区域落在通带内时，滤波器左侧插损会出现明显的恶化，因此在滤波器设计时需要尽量避免此区域落在通带内。假设串联谐振器上未加质量负载时的频率是Fs2，当加入质量负载时，为了保证通带匹配较好，加入质量负载的串联谐振器频率相比原来的频率会向低处移动，即频率为Fs2-F1，其中F1为正，未加质量负载的串联谐振器频率相比Fs向高处移动，即频率为Fs2+F2，其中F2为正。其中F1和F2分别表示移动的频率。如图6b所示，当未加质量负载的串联谐振器相比Fs向高处移动时，串联谐振器更多损耗增加的区域落在通带内，因此滤波器通带插损会有恶化。由此可知，位于中间的串联谐振器a和串联谐振器b中最大的质量负载导致的频率偏移最好是小于通带带宽的50％，更优地可小于25％，从而避免串联谐振器左侧插损恶化。
图7a为滤波器通带对比曲线，图7b为滤波器左侧滚降对比曲线；其中，实线为并联谐振器d、g、f的频率被调节时的滤波器曲线，虚线是并联谐振器d、g、e、f的频率被调节时的滤波器曲线，如图7a和7b可知，当实线和虚线的通带插损基本相同时，调节并联谐振器d、g、f的滤波器滚降优于调节并联谐振器d、g、e、f的滤波器滚降。
图8a为滤波器插损对比曲线，图8b为滤波器回波对比曲线，图8c为滤波器左侧滚降对比曲线。图中，实线为并联谐振器中有三个不同质量负载的滤波器性能曲线，虚线为并联谐振器中有两个不同质量负载的滤波器性能曲线；其中，三个不同质量负载的并联谐振器中，两个频率相对较低的并联谐振器和频率相对最高的并联谐振器的频率差值分别为3MHz和10MHz。由图8a、8b和8c可知，并联谐振器中频率越多，对通带的阻抗匹配效果越好，并且在通带和阻带交汇处的滚降位置也能按照需求获得合理的阻抗值(即通带阻抗尽量和50欧姆匹配，阻带尽量和50欧姆不匹配)，从而获得更好的插损、回波、滚降等性能。因此得出结论，在并联谐振器中，至少两个并联谐振器上设置不同的质量负载，从而存在两个不同频率的并联谐振器。
图9为滤波器带外阻抗 对比曲线。其中，实线为采用发明实施方式涉及的滤波器的带外阻抗曲线，虚线为现有技术中滤波器的带外阻抗曲线。滤波器匹配的原则为通带内尽量和50欧姆接近，保证通带匹配良好，而带外部分，需要尽量远离50欧姆，保证带外不匹配，从而获得较好的带外抑制特性。如图9所示，本发明实施方式中的滤波器通带范围是1.71GHz～1.785GHz，由图9中的曲线对比可知，实线的带外阻抗要高于虚线，实线部分可以获得更好的带外抑制。
图10为滤波器带外抑制的对比曲线。图中，实线是采用本发明实施的滤波器的带外抑制曲线，虚线是现有技术中滤波器的带外抑制曲线，由图10可知，采用本发明实施例的滤波器的带外抑制曲线具有明显的改善。
本发明实施方式中，在调节质量负载量时，可通过控制质量负载层的面积占比来调节质量负载量，与现有的调节质量负载层的厚度不同。图11为根据本发明实施方式的一种谐振器顶部的主视图；图12为根据本发明实施方式的另一种谐振器顶部的主视图。图11中质量负载层为设置在中心处的圆形，图12中质量负载层由多个分体结构组成。质量负载层可以是分体的或者整块。整块或者每块分体的形状可任意选择，其中整块形状可以是凸形或凹形，也可以带有镂空，分体的排布可以为类似于图12的无规则方式。该质量负载层可以设置在电极层或者其他层，通过控制面积占比可以实现精确的，多样化的频率。这里的面积占比可以为100％，即充斥其所在层的整层面积。
上述具体实施方式，并不构成对本发明保护范围的限制。本领域技术人员应该明白的是，取决于设计要求和其他因素，可以发生各种各样的修改、组合、子组合和替代。任何在本发明的精神和原则之内所作的修改、等同替换和改进等，均应包含在本发明保护范围之内。

Claims (12)

  1. 一种调整谐振频率的方法，用于调整滤波器中谐振器的谐振频率，所述滤波器为声波滤波器，包括至少三个串联谐振器，其特征在于，该方法包括，
    对于输入端和输出端之间有奇数个串联谐振器的滤波器：
    对于所述奇数个串联谐振器中的除第一和第二串联谐振器之外的其他谐振器，对于第三谐振器或者选择包含第三谐振器在内的2个以上谐振器，使其频率不同于第一串联谐振器和第二串联谐振器的频率；
    并且/或者，
    对于输入端和输出端之间有偶数个串联谐振器的滤波器：
    对于所述偶数个串联谐振器中的除所述第一和第二串联谐振器之外的其他谐振器中的1个或2个以上谐振器，使其频率不同于第一串联谐振器和第二串联谐振器的频率；
    其中：
    第一和第二串联谐振器分别是最接近滤波器的输入端和输出端的谐振器，第三谐振器是所述奇数个串联谐振器中的居中的谐振器。
  2. 根据权利要求1所述的方法，其特征在于，所述滤波器还包括至少两个并联谐振器，对于输入端和输出端之间的并联谐振器的滤波器，该方法还包括：
    在所述并联谐振器中，对于包含第四和第五并联谐振器在内的2个以上谐振器，使其频率不同于其他并联谐振器的频率；其中：
    第四和第五并联谐振器分别是最接近滤波器的输入端和输出端的谐振器。
  3. 根据权利要求2所述的方法，其特征在于，在所述并联谐振器中，所述2个以上谐振器的数目小于所述并联谐振器的数目。
  4. 根据权利要求1所述的方法，其特征在于，
    所述对于第三谐振器或者选择包含第三谐振器在内的2个以上谐 振器，使其频率不同于第一串联谐振器和第二串联谐振器的频率的步骤包括如下调整：对第三谐振器或者包含第三谐振器在内的2个以上谐振器增加质量负载或者增加一层或多层的厚度。
  5. 根据权利要求1所述的方法，其特征在于，
    所述对于所述偶数个串联谐振器中的除所述第一和第二串联谐振器之外的其他谐振器中的1个或2个以上谐振器，使其频率不同于第一串联谐振器和第二串联谐振器的频率步骤包括如下调整：对所述1个或2个以上谐振器增加质量负载或者增加一层或多层的厚度。
  6. 根据权利要求4或5所述的方法，其特征在于，在所述调整中，使被调整的谐振器的频率不一致。
  7. 根据权利要求4或5所述的方法，其特征在于，在所述调整中，调整导致的最大频率偏移小于通带带宽的50％。
  8. 根据权利要求7所述的方法，其特征在于，所述最大频率偏移小于通带带宽的25％。
  9. 根据权利要求4或5所述的方法，其特征在于，所述增加质量负载的步骤包括：向谐振器增加质量负载层，其中：
    所述质量负载层的形状为多个互不连续的块状，或者所述质量负载层的形状为具有镂空的一个或几个块状。
  10. 一种滤波器，该滤波器为声波滤波器，其特征在于，所述滤波器中的谐振器是经权利要求1至9中任一项所述的方法调整谐振频率的谐振器。
  11. 一种多工器，其特征在于，包含权利要求10所述的滤波器。
  12. 一种通信设备，其特征在于，包含权利要求10所述的滤波器。
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