WO2021147628A1 - Method for designing low group-delay fluctuation filter - Google Patents
Method for designing low group-delay fluctuation filter Download PDFInfo
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- WO2021147628A1 WO2021147628A1 PCT/CN2020/140942 CN2020140942W WO2021147628A1 WO 2021147628 A1 WO2021147628 A1 WO 2021147628A1 CN 2020140942 W CN2020140942 W CN 2020140942W WO 2021147628 A1 WO2021147628 A1 WO 2021147628A1
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- the present invention relates to the technical field of filters, in particular to a design method of low group delay fluctuation filters.
- radio frequency devices have been widely used in the communication field.
- mobile terminals such as mobile phones and notebook computers
- filters and duplexers on mobile terminals such as mobile phones and notebook computers
- the radio frequency signal improve the communication quality, and enhance the user experience.
- the acoustic wave filter based on the principle of mechanical acoustic wave can just meet its requirements.
- the resonators that constitute this type of acoustic wave filter mainly include: bulk acoustic wave resonator (Film Bulk Acoustic Resonator, FBAR) and surface acoustic wave resonator (Surface Acoustic Wave, SAW) Among them, the bulk acoustic wave resonator, compared with the surface acoustic wave resonator, has a higher Q value and a higher operating frequency, which has attracted the attention of the industry.
- the bulk acoustic wave resonator uses the piezoelectric effect of a piezoelectric crystal to generate resonance. Since resonance is generated by mechanical waves instead of electromagnetic waves as the source of resonance, the wavelength of mechanical waves is much shorter than that of electromagnetic waves.
- the volume of the bulk acoustic wave resonator and the filter composed of it is greatly reduced compared with the traditional electromagnetic filter.
- the loss of the resonator is extremely small, the quality factor is high, and it can cope with complex design requirements such as steep transition band and low insertion loss. Due to the small size, high roll-off, and low insertion loss of the bulk acoustic wave filter, the filter with this as the core has been widely used in communication systems.
- the improvement of the modulation mode also puts forward higher requirements on the performance of the communication channel.
- the channel quality is not high, which will directly affect the EVM characteristics, resulting in data transmission rate degradation and signal distortion.
- fluctuations in group delay will affect the data transmission rate and signal fidelity.
- the main purpose of the present invention is to provide a method for designing a low group delay fluctuation filter, which ensures that the filter performance remains unchanged or is not seriously deteriorated, so that it has a smaller group delay fluctuation.
- a method for designing a low group delay fluctuation filter which includes the following steps:
- Step 1 According to the filter index, design a Gaussian low-pass filter to obtain the inductance and capacitance values of the Gaussian low-pass filter;
- Step 2 Convert the low-pass filter into a band-pass filter, where the inductance in the low-pass filter is transformed into an LC series resonant circuit in the band-pass filter, and the capacitor in the low-pass filter is transformed into a band-pass filter
- Step 3 Connect a capacitor in parallel with each LC series resonance circuit to form a BVD circuit model; connect a capacitor in series with each LC parallel resonance circuit to convert the parallel branch into a BVD circuit model;
- Step 4 Take the capacitance value and inductance value in the BVD circuit model as the initial value of the objective optimization function, and through the iterative method, make the objective optimization function approach zero or reach the minimum value, and record the capacitance value and inductance value at this time;
- Step 5 Calculate each resonator parameter based on the capacitance value and inductance value obtained in step 4, and replace the BVD circuit model with a bulk acoustic wave resonator with this parameter, thereby constructing a low group delay fluctuation filter.
- the inductance value and the capacitance value of the Gaussian low-pass filter are obtained by the root of the transfer function, and the transfer function is:
- ⁇ c is the cutoff frequency
- the conversion formula for converting the low-pass filter into the band-pass filter is:
- ⁇ 0 is the center frequency
- ⁇ is the filter bandwidth
- the conversion formula for converting the parallel branch into the BVD circuit model is:
- C0i is the capacitor in parallel on the LC series resonant circuit or the capacitor in series on the LC parallel resonant circuit
- Ci is the capacitor in the LC series resonant circuit or the capacitor in the LC parallel resonant circuit
- Li is the inductance or in the LC series resonant circuit The inductance in the LC parallel resonant circuit
- Li1 is the inductance in the parallel branch after being transformed into the BVD circuit model
- Ci1 is the parallel capacitance in the parallel branch after being transformed into the BVD circuit model
- C0i1 is the parallel branch after being transformed into the BVD circuit model Series capacitors in.
- the objective optimization function is:
- H( ⁇ ) is the amplitude-frequency function of the filter
- D( ⁇ ) is the group delay function of the filter
- H d ( ⁇ ) is the amplitude-frequency objective function of the filter
- D d ( ⁇ ) is the filter’s Group delay objective function.
- the objective optimization function is approached to zero or reaches the minimum value.
- the resonator parameters include the effective electromechanical coupling coefficient Resonator area A, series resonance frequency f s .
- the design method in the technical scheme of the present invention is based on a Gaussian prototype filter, and a filter with low group delay fluctuation is obtained through optimization iteration; the group delay fluctuation of the filter is obvious when the performance of the filter remains unchanged or is not severely deteriorated. The reduction.
- FIG. 1 is a flowchart of a design method of a low group delay fluctuation filter provided by this embodiment
- Figure 2 is a comparison diagram of group delay fluctuations between an elliptic function filter and a Gaussian filter
- Figure 3a is a circuit diagram of the inductance in the low-pass filter transformed into the LC series resonant circuit in the band-pass filter;
- Fig. 3b is a circuit diagram of a capacitor in a low-pass filter transformed into an LC parallel resonant circuit in a band-pass filter;
- Figure 4 is a schematic diagram of the topology of a bandpass filter
- Figure 5 is a schematic diagram of the topological structure of the band-pass filter after correction
- Figure 6 is a BVD equivalent circuit diagram
- Figure 7 is a topological structure diagram of the band-pass filter after conversion
- Figure 8 is a topological structure diagram of a ladder filter composed of BVD
- Figure 9 shows the parameters of each resonator of the low group delay fluctuation filter designed by this method.
- FIG. 10 is a comparison diagram of group delay fluctuations between a traditional filter and the filter designed by the method of this embodiment
- 11 is a comparison diagram of the passband insertion loss of the traditional filter and the filter designed by the method of this embodiment
- Fig. 12 is a diagram of out-of-band suppression in the 0-3 GHz range of the filter designed by the method of this embodiment.
- Fig. 1 is a flow chart of a design method of a low group delay fluctuation filter provided by this embodiment. As shown in Fig. 1, the method includes the following steps:
- ⁇ c is the cut-off frequency
- the inductance and capacitance values of the Gaussian low-pass filter are obtained through the root of the transfer function
- the Gaussian function filter has a smaller group delay fluctuation
- Figure 2 is a comparison diagram of the group delay of the elliptic function filter and the Gaussian filter, as shown in Figure 2.
- the solid line is the fluctuation range of the Gaussian filter
- the dashed line is the fluctuation range of the elliptic function filter.
- the group delay fluctuation range of the elliptic function filter (about 14ns) is much larger than that of the Gaussian filter.
- the fluctuation range (about 4ns).
- Figures 3a and 3b are schematic diagrams of converting a low-pass filter into a band-pass filter.
- the inductance in the low-pass filter is transformed into an LC series resonant circuit in the band-pass filter.
- the low-pass filter in Figure 3b The capacitor in the band-pass filter is transformed into an LC parallel resonant circuit in the bandpass filter; the above-mentioned LC series-parallel resonant circuit is composed of a ladder structure as shown in Figure 4.
- C0i is the capacitor connected in parallel on the LC series resonant circuit or the capacitor connected in series on the LC parallel resonant circuit
- Ci is the capacitor in the LC series resonant circuit or the capacitor in the LC parallel resonant circuit
- L1 is the capacitor in the LC series resonant circuit in Figure 5
- Li1 is the inductance in the parallel branch in Figure 7
- Ci1 is the parallel capacitance in the parallel branch in Figure 7
- C0i1 is the series capacitance in the parallel branch in Figure 7.
- the converted band-pass filter structure is obtained, as shown in Figure 7; the resonant circuit of each stage of the series branch and the resonant circuit of the parallel branch have been converted into a BVD circuit model, so the corresponding bulk acoustic wave resonance can be further used Instead of the device, the circuit diagram shown in Figure 8 is constructed.
- H( ⁇ ) is the amplitude-frequency function of the filter
- D( ⁇ ) is the group delay function of the filter
- H d ( ⁇ ) is the amplitude-frequency objective function of the filter
- D d ( ⁇ ) is the filter’s Group delay objective function
- the capacitance value and inductance value in the BVD circuit model are used as the initial value of the objective optimization function, and the objective optimization function approaches zero through an iterative method, preferably, Newton iteration method, genetic algorithm, etc. , Or reach the minimum value, record the capacitance value and inductance value at this time;
- step S5 Calculate each resonator parameter based on the capacitance value and inductance value obtained in step S4, such as the effective electromechanical coupling coefficient Resonator area A, series resonance frequency f s, etc., using a bulk acoustic wave resonator with these parameters to replace the BVD circuit model, thereby constructing a low group delay wave filter.
- Figure 9 shows the parameters of each resonator of the low group delay wave filter designed by this method.
- the filter includes 5 series resonators S11, S12, S13, S14 and S15, and 4 parallel resonators P11, P12, P13 and P14, the resonator parameters include series resonance frequency f s , resonator area A and effective electromechanical coupling coefficient
- Figure 10 is a comparison diagram of fluctuations between a traditional filter and the filter designed by the method of this embodiment. As shown in Figure 10, the dashed line is the fluctuation range of the traditional filter, and the solid line is the fluctuation of the filter designed by the method of this embodiment. The fluctuation range of the broken line is about 20 ns, and the fluctuation range of the solid line is about 6 ns. It can be seen that the group delay fluctuation of the filter designed by the method of this embodiment is significantly improved compared with the prior art.
- FIG. 11 is a comparison diagram of the passband insertion loss of the traditional filter and the filter designed by the method of this embodiment. As shown in FIG. 11, the solid line is the insertion loss of the filter designed by the method of this embodiment, and the dashed line is the traditional The insertion loss of the filter, the insertion loss of some frequency bands in the passband of the filter designed by the method of this embodiment is slightly deteriorated.
- FIG. 12 is a diagram of out-of-band suppression of the filter designed by the method of this embodiment in the range of 0-3 GHz. As shown in FIG. 12, the out-of-band suppression of the filter is greater than 40 dB.
- the filter obtained by the method of this embodiment can significantly improve its group delay fluctuation under the condition that the performance is not severely deteriorated.
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Abstract
The present invention relates to the technical field of filters, and particularly relates to a method for designing a low group-delay fluctuation filter, comprising the following steps: according to a filter index, designing a Gaussian low-pass filter, and obtaining the inductance and capacitance values of the Gaussian low-pass filter; converting the low-pass filter to a band-pass filter; connecting a capacitor in parallel with each LC series resonant circuit to form a BVD circuit model; connecting a capacitor in series to each LC parallel resonant circuit so as to convert the parallel branch into a BVD circuit model; taking the capacitance value and inductance value in the BVD circuit model as the initial values of a target optimization function, by means of an iterative method, causing the objective optimization function to approach zero, or reach a minimum value, and recording the capacitance and inductance values at that time; calculating each resonator parameter according to the obtained capacitance value and inductance value. According to the filter obtained by the present design method, as long as performance is constant and there is no serious deterioration, the group-delay fluctuation is significantly reduced.
Description
本发明涉及滤波器技术领域,特别地涉及一种低群时延波动滤波器的设计方法。The present invention relates to the technical field of filters, in particular to a design method of low group delay fluctuation filters.
随着移动通信技术的快速发展,许多射频器件在通信领域得到广泛应用,例如,在移动终端如手机、笔记本电脑上对滤波器、双工器等产生了大量需求,主要用来滤除不需要的射频信号,改善通信质量,提升用户体验。由于移动通信终端固有的特性,如便携、轻薄,所以对滤波器、双工器除性能上有较高的要求外,还对体积尺寸提出较高的要求。基于机械声波原理的声波滤波器刚好可以满足其要求,构成此类声波滤波器的谐振器主要包括:体声波谐振器(Film Bulk Acoustic Resonator,FBAR)和表面声波谐振器(Surface Acoustic Wave,SAW),其中体声波谐振器,相比表面声波谐振器,具有更高的Q值,更高的工作频率,受到了业内的关注。体声波谐振器利用压电晶体的压电效应产生谐振。由于谐振由机械波产生,而非电磁波作为谐振来源,机械波的波长比电磁波波长短很多。因此,体声波谐振器及其组成的滤波器体积相对传统的电磁滤波器尺寸大幅度减小。另一方面,由于压电晶体的晶向生长目前能够良好控制,谐振器的损耗极小,品质因数高,能够应对陡峭过渡带和低插入损耗等复杂设计要求。由于体声波滤波器具有的尺寸小、高滚降、低插损等特性,以此为核心的滤波器在通信系统中得到了广泛的应用。With the rapid development of mobile communication technology, many radio frequency devices have been widely used in the communication field. For example, there is a large demand for filters and duplexers on mobile terminals such as mobile phones and notebook computers, which are mainly used to filter out unnecessary The radio frequency signal, improve the communication quality, and enhance the user experience. Due to the inherent characteristics of mobile communication terminals, such as portability, lightness and thinness, in addition to higher performance requirements for filters and duplexers, higher requirements are also imposed on the volume and size. The acoustic wave filter based on the principle of mechanical acoustic wave can just meet its requirements. The resonators that constitute this type of acoustic wave filter mainly include: bulk acoustic wave resonator (Film Bulk Acoustic Resonator, FBAR) and surface acoustic wave resonator (Surface Acoustic Wave, SAW) Among them, the bulk acoustic wave resonator, compared with the surface acoustic wave resonator, has a higher Q value and a higher operating frequency, which has attracted the attention of the industry. The bulk acoustic wave resonator uses the piezoelectric effect of a piezoelectric crystal to generate resonance. Since resonance is generated by mechanical waves instead of electromagnetic waves as the source of resonance, the wavelength of mechanical waves is much shorter than that of electromagnetic waves. Therefore, the volume of the bulk acoustic wave resonator and the filter composed of it is greatly reduced compared with the traditional electromagnetic filter. On the other hand, since the crystal orientation growth of the piezoelectric crystal can be well controlled at present, the loss of the resonator is extremely small, the quality factor is high, and it can cope with complex design requirements such as steep transition band and low insertion loss. Due to the small size, high roll-off, and low insertion loss of the bulk acoustic wave filter, the filter with this as the core has been widely used in communication systems.
通信终端发展的另一个重要趋势是更高的数据传输量,无论是基于WLAN协议的Wi-Fi通信,还是基于3GPP协议的LTE通信,数据传输量相比3G时代已经有了指数级的飞跃。提高数据传输量的途径主要有两种:一是通过载波聚合实现信道的扩展,但是这需要对终端硬件及软件设计做较大的升级 改动,且实现的带宽扩展最多为2-3倍。二是通过提高调制解调效率,从早期的BPSK,QPSK调试,到大数据传输量的16-QAM,64-QAM,甚至256-QAM,数据传输速率理论上最大可以得到上百倍的提升。但是,调制模式的提高,对通信信道的性能也提出了更高的要求,信道质量不高,将直接影响EVM特性,从而导致数据传输速率退化,信号失真。对于滤波器来说,群时延波动会影响数据的传输速率和信号保真度。Another important trend in the development of communication terminals is higher data transmission volume. Whether it is Wi-Fi communication based on WLAN protocol or LTE communication based on 3GPP protocol, the data transmission volume has taken an exponential leap compared with the 3G era. There are two main ways to increase data transmission: one is to achieve channel expansion through carrier aggregation, but this requires major upgrades and changes to the terminal hardware and software design, and the achieved bandwidth expansion is up to 2-3 times. Second, by improving the modulation and demodulation efficiency, from the early debugging of BPSK and QPSK, to 16-QAM, 64-QAM, and even 256-QAM with large data transmission volume, the data transmission rate can theoretically be increased by hundreds of times. However, the improvement of the modulation mode also puts forward higher requirements on the performance of the communication channel. The channel quality is not high, which will directly affect the EVM characteristics, resulting in data transmission rate degradation and signal distortion. For filters, fluctuations in group delay will affect the data transmission rate and signal fidelity.
发明内容Summary of the invention
有鉴于此,本发明的主要目的是提供一种低群时延波动滤波器的设计方法,在确保滤波器性能不变或者没有严重恶化的情况下,使其具有较小的群时延波动。In view of this, the main purpose of the present invention is to provide a method for designing a low group delay fluctuation filter, which ensures that the filter performance remains unchanged or is not seriously deteriorated, so that it has a smaller group delay fluctuation.
为实现上述目的,根据本发明的一个方面,提供了一种低群时延波动滤波器的设计方法,包括以下步骤:To achieve the above objective, according to one aspect of the present invention, a method for designing a low group delay fluctuation filter is provided, which includes the following steps:
步骤1:根据滤波器指标,设计高斯型低通滤波器,得到高斯型低通滤波器的电感值和电容值;Step 1: According to the filter index, design a Gaussian low-pass filter to obtain the inductance and capacitance values of the Gaussian low-pass filter;
步骤2:将低通滤波器转换成带通滤波器,其中,低通滤波器中的电感转变成带通滤波器中的LC串联谐振电路,低通滤波器中的电容转变成带通滤波器中的LC并联谐振电路;Step 2: Convert the low-pass filter into a band-pass filter, where the inductance in the low-pass filter is transformed into an LC series resonant circuit in the band-pass filter, and the capacitor in the low-pass filter is transformed into a band-pass filter The LC parallel resonant circuit in
步骤3:在每个LC串联谐振电路上并联一个电容从而构成BVD电路模型;在每个LC并联谐振电路上串联一个电容,从而将并联支路转化为BVD电路模型;Step 3: Connect a capacitor in parallel with each LC series resonance circuit to form a BVD circuit model; connect a capacitor in series with each LC parallel resonance circuit to convert the parallel branch into a BVD circuit model;
步骤4:以BVD电路模型中的电容值和电感值作为目标优化函数的初始值,通过迭代方法,使得目标优化函数趋近于零,或者达到最小值,记录此时的电容值和电感值;Step 4: Take the capacitance value and inductance value in the BVD circuit model as the initial value of the objective optimization function, and through the iterative method, make the objective optimization function approach zero or reach the minimum value, and record the capacitance value and inductance value at this time;
步骤5:根据步骤4中得到的电容值和电感值计算各谐振器参数,利用具有该参数的体声波谐振器替代BVD电路模型,从而构建成低群时延波动滤波器。Step 5: Calculate each resonator parameter based on the capacitance value and inductance value obtained in step 4, and replace the BVD circuit model with a bulk acoustic wave resonator with this parameter, thereby constructing a low group delay fluctuation filter.
可选地,所述步骤1中:通过传输函数的根得到高斯型低通滤波器的电感值和电容值,传输函数为:Optionally, in the step 1: the inductance value and the capacitance value of the Gaussian low-pass filter are obtained by the root of the transfer function, and the transfer function is:
其中,ω
c为截止频率。
Among them, ω c is the cutoff frequency.
可选地,所述步骤2中:将低通滤波器转换成带通滤波器的转换公式为:Optionally, in the step 2: the conversion formula for converting the low-pass filter into the band-pass filter is:
其中,ω
0为中心频率,Δω为滤波器带宽。
Among them, ω 0 is the center frequency, and Δω is the filter bandwidth.
可选地,所述步骤3中:将并联支路转化为BVD电路模型的转换公式为:Optionally, in the step 3: the conversion formula for converting the parallel branch into the BVD circuit model is:
Li1=Li(1+β
i)
2 i=6,…9
Li1=Li(1+β i ) 2 i=6,...9
Ci1=Ci/(1+β
i) i=6,…9
Ci1=Ci/(1+β i ) i=6,...9
C0i1=C0i/(1+β
i) i=6,…9
C0i1=C0i/(1+β i ) i=6,...9
其中,C0i为LC串联谐振电路上并联的电容或LC并联谐振电路上串联的电容;Ci为LC串联谐振电路中的电容或LC并联谐振电路中的电容;Li为LC串联谐振电路中的电感或LC并联谐振电路中的电感;Li1为转化为BVD电路模型后并联支路中的电感;Ci1为转化为BVD电路模型后并联支路中的并联电容;C0i1为转化为BVD电路模型后并联支路中的串联电容。Among them, C0i is the capacitor in parallel on the LC series resonant circuit or the capacitor in series on the LC parallel resonant circuit; Ci is the capacitor in the LC series resonant circuit or the capacitor in the LC parallel resonant circuit; Li is the inductance or in the LC series resonant circuit The inductance in the LC parallel resonant circuit; Li1 is the inductance in the parallel branch after being transformed into the BVD circuit model; Ci1 is the parallel capacitance in the parallel branch after being transformed into the BVD circuit model; C0i1 is the parallel branch after being transformed into the BVD circuit model Series capacitors in.
可选地,所述步骤4中:目标优化函数为:Optionally, in the step 4: the objective optimization function is:
S(ω)=A[H(ω)-H
d(ω)]
2+B[D(ω)-D
d(ω)]
2
S(ω)=A[H(ω)-H d (ω)] 2 +B[D(ω)-D d (ω)] 2
其中,H(ω)为滤波器的幅频函数,D(ω)为滤波器的群时延函数;H
d(ω)为滤波器的幅频目标函数,D
d(ω)为滤波器的群时延目标函数。
Among them, H(ω) is the amplitude-frequency function of the filter, D(ω) is the group delay function of the filter; H d (ω) is the amplitude-frequency objective function of the filter, and D d (ω) is the filter’s Group delay objective function.
可选地,所述步骤4中:通过牛顿迭代方法或遗传算法,使得目标优化函数趋近于零,或者达到最小值。Optionally, in the step 4: using a Newton iteration method or a genetic algorithm, the objective optimization function is approached to zero or reaches the minimum value.
可选地,所述步骤5中:谐振器参数包括有效机电耦合系数
谐振器面积A,串联谐振频点f
s。
Optionally, in the step 5: the resonator parameters include the effective electromechanical coupling coefficient Resonator area A, series resonance frequency f s .
本发明技术方案中的设计方法,基于高斯原型滤波器,通过优化 迭代得到具有低群时延波动滤波器;该滤波器在性能不变或者没有严重恶化的情况下,其群时延波动得到明显的降低。The design method in the technical scheme of the present invention is based on a Gaussian prototype filter, and a filter with low group delay fluctuation is obtained through optimization iteration; the group delay fluctuation of the filter is obvious when the performance of the filter remains unchanged or is not severely deteriorated. The reduction.
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:For purposes of illustration and not limitation, the present invention will now be described according to preferred embodiments of the present invention, particularly with reference to the accompanying drawings, in which:
图1是本实施例提供的低群时延波动滤波器的设计方法的流程框图;FIG. 1 is a flowchart of a design method of a low group delay fluctuation filter provided by this embodiment;
图2为椭圆函数型滤波器和高斯型滤波器的群时延波动对比图;Figure 2 is a comparison diagram of group delay fluctuations between an elliptic function filter and a Gaussian filter;
图3a是低通滤波器中的电感转变成带通滤波器中的LC串联谐振电路图;Figure 3a is a circuit diagram of the inductance in the low-pass filter transformed into the LC series resonant circuit in the band-pass filter;
图3b是低通滤波器中的电容转变成带通滤波器中的LC并联谐振电路图;Fig. 3b is a circuit diagram of a capacitor in a low-pass filter transformed into an LC parallel resonant circuit in a band-pass filter;
图4是带通滤波器的拓扑结构示意图;Figure 4 is a schematic diagram of the topology of a bandpass filter;
图5是修正后的带通滤波器拓扑结构示意图;Figure 5 is a schematic diagram of the topological structure of the band-pass filter after correction;
图6是BVD等效电路图;Figure 6 is a BVD equivalent circuit diagram;
图7是转换后的带通滤波器拓扑结构图;Figure 7 is a topological structure diagram of the band-pass filter after conversion;
图8是BVD组成的梯型滤波器拓扑结构图;Figure 8 is a topological structure diagram of a ladder filter composed of BVD;
图9为采用本方法设计的低群时延波动滤波器各谐振器的参数;Figure 9 shows the parameters of each resonator of the low group delay fluctuation filter designed by this method;
图10为传统滤波器与本实施例方法设计得到的滤波器的群时延波动对比图;FIG. 10 is a comparison diagram of group delay fluctuations between a traditional filter and the filter designed by the method of this embodiment;
图11为传统滤波器与本实施例方法设计得到的滤波器的通带插损情况对比图;11 is a comparison diagram of the passband insertion loss of the traditional filter and the filter designed by the method of this embodiment;
图12为本实施例方法设计得到的滤波器0-3GHz范围的带外抑制图。Fig. 12 is a diagram of out-of-band suppression in the 0-3 GHz range of the filter designed by the method of this embodiment.
图1是本实施例提供的低群时延波动滤波器的设计方法的流程框图,如图1所示,该方法包括以下步骤:Fig. 1 is a flow chart of a design method of a low group delay fluctuation filter provided by this embodiment. As shown in Fig. 1, the method includes the following steps:
S1:根据滤波器指标,设计高斯型低通滤波器,其传输函数为:S1: According to the filter index, design a Gaussian low-pass filter, and its transfer function is:
其中,ω
c为截止频率;通过传输函数的根得到高斯型低通滤波器的电感值和电容值;
Among them, ω c is the cut-off frequency; the inductance and capacitance values of the Gaussian low-pass filter are obtained through the root of the transfer function;
高斯函数型滤波器相比于现有的椭圆函数型滤波器,其群时延波动较小;图2为椭圆函数型滤波器和高斯型滤波器的群时延对比图,如图2所示,实线部分为高斯型滤波器的波动范围,虚线为椭圆函数型滤波器的波动范围,由图2可知,椭圆函数型滤波器的群时延波动范围(约14ns)远大于高斯型滤波器的波动范围(约4ns)。Compared with the existing elliptic function filter, the Gaussian function filter has a smaller group delay fluctuation; Figure 2 is a comparison diagram of the group delay of the elliptic function filter and the Gaussian filter, as shown in Figure 2. , The solid line is the fluctuation range of the Gaussian filter, and the dashed line is the fluctuation range of the elliptic function filter. As shown in Figure 2, the group delay fluctuation range of the elliptic function filter (about 14ns) is much larger than that of the Gaussian filter. The fluctuation range (about 4ns).
S2:将低通滤波器转换成带通滤波器,转换公式为:S2: Convert the low-pass filter into a band-pass filter, the conversion formula is:
其中,ω
0为中心频率,Δω为滤波器带宽。图3a和图3b为低通滤波器转换成带通滤波器的示意图,图3a中,低通滤波器中的电感转变成带通滤波器中的LC串联谐振电路,图3b中低通滤波器中的电容转变成带通滤波器中的LC并联谐振电路;上述LC串并联谐振电路按照梯形结构组成的滤波器如图4所示。
Among them, ω 0 is the center frequency, and Δω is the filter bandwidth. Figures 3a and 3b are schematic diagrams of converting a low-pass filter into a band-pass filter. In Figure 3a, the inductance in the low-pass filter is transformed into an LC series resonant circuit in the band-pass filter. The low-pass filter in Figure 3b The capacitor in the band-pass filter is transformed into an LC parallel resonant circuit in the bandpass filter; the above-mentioned LC series-parallel resonant circuit is composed of a ladder structure as shown in Figure 4.
S3:在每个LC串联谐振电路上并联一个电容,在每个LC并联谐振电路上串联一个电容,得到如图5所示的修正后的带通滤波器,图6为BVD等效电路,由图6可知,图5所示的电路中,串联支路的每一级已经是BVD电路模型,而并联支路并不是BVD电路模,需要进行转换,将并联支路转化为BVD电路模型的转换公式为:S3: Connect a capacitor in parallel with each LC series resonant circuit, and connect a capacitor in series with each LC parallel resonant circuit to obtain the corrected bandpass filter as shown in Figure 5. Figure 6 is the BVD equivalent circuit. Figure 6 shows that in the circuit shown in Figure 5, each level of the series branch is already a BVD circuit model, while the parallel branch is not a BVD circuit model, and conversion is required to convert the parallel branch into a BVD circuit model. The formula is:
Li1=Li(1+β
i)
2 i=6,…9
Li1=Li(1+β i ) 2 i=6,...9
Ci1=Ci/(1+β
i) i=6,…9
Ci1=Ci/(1+β i ) i=6,...9
C0i1=C0i/(1+β
i) i=6,…9
C0i1=C0i/(1+β i ) i=6,...9
其中,C0i为LC串联谐振电路上并联的电容或LC并联谐振电路上串联的电容;Ci为LC串联谐振电路中的电容或LC并联谐振电路中 的电容;L1为图5中LC串联谐振电路中的电感或LC并联谐振电路中的电感;Li1为图7中并联支路中的电感;Ci1为图7中并联支路中的并联电容;C0i1为图7中并联支路中的串联电容。Among them, C0i is the capacitor connected in parallel on the LC series resonant circuit or the capacitor connected in series on the LC parallel resonant circuit; Ci is the capacitor in the LC series resonant circuit or the capacitor in the LC parallel resonant circuit; L1 is the capacitor in the LC series resonant circuit in Figure 5 Li1 is the inductance in the parallel branch in Figure 7; Ci1 is the parallel capacitance in the parallel branch in Figure 7; C0i1 is the series capacitance in the parallel branch in Figure 7.
最终,得到转换后的带通滤波器结构,如图7所示;串联支路每一级谐振电路和并联支路的谐振电路都已转换为BVD电路模型,所以进一步可以用相应的体声波谐振器代替,构成如图8所示的电路图。Finally, the converted band-pass filter structure is obtained, as shown in Figure 7; the resonant circuit of each stage of the series branch and the resonant circuit of the parallel branch have been converted into a BVD circuit model, so the corresponding bulk acoustic wave resonance can be further used Instead of the device, the circuit diagram shown in Figure 8 is constructed.
S4:设计目标函数为:S4: The design objective function is:
S(ω)=A[H(ω)-H
d(ω)]
2+B[D(ω)-D
d(ω)]
2
S(ω)=A[H(ω)-H d (ω)] 2 +B[D(ω)-D d (ω)] 2
其中,H(ω)为滤波器的幅频函数,D(ω)为滤波器的群时延函数;H
d(ω)为滤波器的幅频目标函数,D
d(ω)为滤波器的群时延目标函数;以BVD电路模型中的电容值和电感值作为目标优化函数的初始值,通过迭代方法,优选地,通过牛顿迭代法、遗传算法等方法,使得目标优化函数趋近于零,或者达到最小值,记录此时的电容值和电感值;
Among them, H(ω) is the amplitude-frequency function of the filter, D(ω) is the group delay function of the filter; H d (ω) is the amplitude-frequency objective function of the filter, and D d (ω) is the filter’s Group delay objective function; the capacitance value and inductance value in the BVD circuit model are used as the initial value of the objective optimization function, and the objective optimization function approaches zero through an iterative method, preferably, Newton iteration method, genetic algorithm, etc. , Or reach the minimum value, record the capacitance value and inductance value at this time;
S5:根据步骤S4中得到的电容值和电感值计算各谐振器参数,如,有效机电耦合系数
谐振器面积A,串联谐振频点f
s等,利用具有该参数的体声波谐振器替代BVD电路模型,从而构建成低群时延波动滤波器。
S5: Calculate each resonator parameter based on the capacitance value and inductance value obtained in step S4, such as the effective electromechanical coupling coefficient Resonator area A, series resonance frequency f s, etc., using a bulk acoustic wave resonator with these parameters to replace the BVD circuit model, thereby constructing a low group delay wave filter.
图9为采用本方法设计的低群时延波动滤波器各谐振器的参数,该滤波器包括5个串联谐振器S11、S12、S13、S14和S15,及4个并联谐振器P11、P12、P13和P14,谐振器参数包括串联谐振频点f
s、谐振器面积A和有效机电耦合系数
图10为传统滤波器与本实施例方法设计得到的滤波器的波动对比图,如图10所示,虚线为传统滤波器的波动范围,实线为本实施例方法设计得到的滤波器的波动范围,其中,虚线的波动范围为20ns左右,而实线的波动范围为6ns左右,由此可知本实施例方法设计得到的滤波器的群时延波动相比于现有技术得到明显改善。
Figure 9 shows the parameters of each resonator of the low group delay wave filter designed by this method. The filter includes 5 series resonators S11, S12, S13, S14 and S15, and 4 parallel resonators P11, P12, P13 and P14, the resonator parameters include series resonance frequency f s , resonator area A and effective electromechanical coupling coefficient Figure 10 is a comparison diagram of fluctuations between a traditional filter and the filter designed by the method of this embodiment. As shown in Figure 10, the dashed line is the fluctuation range of the traditional filter, and the solid line is the fluctuation of the filter designed by the method of this embodiment. The fluctuation range of the broken line is about 20 ns, and the fluctuation range of the solid line is about 6 ns. It can be seen that the group delay fluctuation of the filter designed by the method of this embodiment is significantly improved compared with the prior art.
图11为传统滤波器与本实施例方法设计得到的滤波器的通带插损情况对比图,如图11所示,实线为本实施例方法设计得到的滤波器的插损,虚线为传统滤波器的插损,本实施例方法设计得到的滤波器通带内部分频段的插损略有恶化。图12为本实施例方法设计得到的滤波器0-3GHz范围的带外抑制图,如图12可知,该滤波器的带外抑制大于40dB。FIG. 11 is a comparison diagram of the passband insertion loss of the traditional filter and the filter designed by the method of this embodiment. As shown in FIG. 11, the solid line is the insertion loss of the filter designed by the method of this embodiment, and the dashed line is the traditional The insertion loss of the filter, the insertion loss of some frequency bands in the passband of the filter designed by the method of this embodiment is slightly deteriorated. FIG. 12 is a diagram of out-of-band suppression of the filter designed by the method of this embodiment in the range of 0-3 GHz. As shown in FIG. 12, the out-of-band suppression of the filter is greater than 40 dB.
由此可知,利用本实施例方法得到滤波器,在性能不被严重恶化的情况下,可明显改善其群时延波动。From this, it can be seen that the filter obtained by the method of this embodiment can significantly improve its group delay fluctuation under the condition that the performance is not severely deteriorated.
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。The foregoing specific implementations do not constitute a limitation on the protection scope of the present invention. Those skilled in the art should understand that, depending on design requirements and other factors, various modifications, combinations, sub-combinations, and substitutions can occur. Any modification, equivalent replacement and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (7)
- 一种低群时延波动滤波器的设计方法,其特征在于,包括以下步骤:A design method of low group delay fluctuation filter is characterized in that it comprises the following steps:步骤1:根据滤波器指标,设计高斯型低通滤波器,得到高斯型低通滤波器的电感值和电容值;Step 1: According to the filter index, design a Gaussian low-pass filter to obtain the inductance and capacitance values of the Gaussian low-pass filter;步骤2:将低通滤波器转换成带通滤波器,其中,低通滤波器中的电感转变成带通滤波器中的LC串联谐振电路,低通滤波器中的电容转变成带通滤波器中的LC并联谐振电路;Step 2: Convert the low-pass filter into a band-pass filter, where the inductance in the low-pass filter is transformed into an LC series resonant circuit in the band-pass filter, and the capacitor in the low-pass filter is transformed into a band-pass filter The LC parallel resonant circuit in步骤3:在每个LC串联谐振电路上并联一个电容从而构成BVD电路模型;在每个LC并联谐振电路上串联一个电容,从而将并联支路转化为BVD电路模型;Step 3: Connect a capacitor in parallel with each LC series resonance circuit to form a BVD circuit model; connect a capacitor in series with each LC parallel resonance circuit to convert the parallel branch into a BVD circuit model;步骤4:以BVD电路模型中的电容值和电感值作为目标优化函数的初始值,通过迭代方法,使得目标优化函数趋近于零,或者达到最小值,记录此时的电容值和电感值;Step 4: Take the capacitance value and inductance value in the BVD circuit model as the initial value of the objective optimization function, and through iterative methods, make the objective optimization function approach zero or reach the minimum value, and record the capacitance and inductance values at this time;步骤5:根据步骤4中得到的电容值和电感值计算各谐振器参数,利用具有该参数的体声波谐振器替代BVD电路模型,从而构建成低群时延波动滤波器。Step 5: Calculate each resonator parameter based on the capacitance value and inductance value obtained in step 4, and replace the BVD circuit model with a bulk acoustic wave resonator with this parameter, thereby constructing a low group delay fluctuation filter.
- 根据权利要求1所述的低群时延波动滤波器的设计方法,其特征在于,所述步骤1中:The design method of a low group delay fluctuation filter according to claim 1, wherein, in the step 1:通过传输函数的根得到高斯型低通滤波器的电感值和电容值,传输函数为:Obtain the inductance and capacitance values of the Gaussian low-pass filter through the roots of the transfer function. The transfer function is:其中,ω c为截止频率。 Among them, ω c is the cutoff frequency.
- 根据权利要求1所述的低群时延波动滤波器的设计方法,其特征在于,所述步骤2中:The design method of a low group delay fluctuation filter according to claim 1, wherein, in the step 2:将低通滤波器转换成带通滤波器的转换公式为:The conversion formula for converting a low-pass filter into a band-pass filter is:其中,ω 0为中心频率,Δω为滤波器带宽。 Among them, ω 0 is the center frequency, and Δω is the filter bandwidth.
- 根据权利要求1所述的低群时延波动滤波器的设计方法,其特征在于,所述步骤3中:The method for designing a low group delay fluctuation filter according to claim 1, wherein in the step 3:将并联支路转化为BVD电路模型的转换公式为:The conversion formula to convert the parallel branch into the BVD circuit model is:Li1=Li(1+β i) 2 i=6,…9 Li1=Li(1+β i ) 2 i=6,...9Ci1=Ci/(1+β i) i=6,…9 Ci1=Ci/(1+β i ) i=6,...9C0i1=C0i/(1+β i) i=6,…9 C0i1=C0i/(1+β i ) i=6,...9其中,C0i为LC串联谐振电路上并联的电容或LC并联谐振电路上串联的电容;Ci为LC串联谐振电路中的电容或LC并联谐振电路中的电容;Li为LC串联谐振电路中的电感或LC并联谐振电路中的电感;Li1为转化为BVD电路模型后并联支路中的电感;Ci1为转化为BVD电路模型后并联支路中的并联电容;C0i1为转化为BVD电路模型后并联支路中的串联电容。Among them, C0i is the capacitor in parallel on the LC series resonant circuit or the capacitor in series on the LC parallel resonant circuit; Ci is the capacitor in the LC series resonant circuit or the capacitor in the LC parallel resonant circuit; Li is the inductance or in the LC series resonant circuit The inductance in the LC parallel resonant circuit; Li1 is the inductance in the parallel branch after being transformed into the BVD circuit model; Ci1 is the parallel capacitance in the parallel branch after being transformed into the BVD circuit model; C0i1 is the parallel branch after being transformed into the BVD circuit model Series capacitors in.
- 根据权利要求1所述的低群时延波动滤波器的设计方法,其特征在于,所述步骤4中:The method for designing a low group delay fluctuation filter according to claim 1, wherein in the step 4:目标优化函数为:The objective optimization function is:S(ω)=A[H(ω)-H d(ω)] 2+B[D(ω)-D d(ω)] 2 S(ω)=A[H(ω)-H d (ω)] 2 +B[D(ω)-D d (ω)] 2其中,H(ω)为滤波器的幅频函数,D(ω)为滤波器的群时延函数;H d(ω)为滤波器的幅频目标函数,D d(ω)为滤波器的群时延目标函数。 Among them, H(ω) is the amplitude-frequency function of the filter, D(ω) is the group delay function of the filter; H d (ω) is the amplitude-frequency objective function of the filter, and D d (ω) is the filter’s Group delay objective function.
- 根据权利要求1所述的低群时延波动滤波器的设计方法,其特征在于,所述步骤4中:The method for designing a low group delay fluctuation filter according to claim 1, wherein in the step 4:通过牛顿迭代或遗传算法方法,使得目标优化函数趋近于零,或者达到最小值。Through Newton iteration or genetic algorithm methods, the objective optimization function is approached to zero or reaches the minimum value.
- 根据权利要求1所述的低群时延波动滤波器的设计方法,其特征在于,所述步骤5中:The design method of a low group delay fluctuation filter according to claim 1, wherein in the step 5:
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