WO2022178925A1 - 可调谐低通滤波器及制备方法 - Google Patents

可调谐低通滤波器及制备方法 Download PDF

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WO2022178925A1
WO2022178925A1 PCT/CN2021/080711 CN2021080711W WO2022178925A1 WO 2022178925 A1 WO2022178925 A1 WO 2022178925A1 CN 2021080711 W CN2021080711 W CN 2021080711W WO 2022178925 A1 WO2022178925 A1 WO 2022178925A1
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pass filter
mems
cpw
mems switch
tunable low
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PCT/CN2021/080711
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English (en)
French (fr)
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邱文才
赵纶
田学红
林满院
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广东大普通信技术有限公司
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Publication of WO2022178925A1 publication Critical patent/WO2022178925A1/zh

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/64—Filters using surface acoustic waves
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
    • H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material

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  • the present application relates to the technical field of radio frequency millimeter wave low-pass filters, for example, to a tunable low-pass filter and a preparation method thereof.
  • Tunable filters are widely used in military applications, for example, in multi-standard transceivers. Tunable filters reduce the size of the analog front end, suppress large-signal interference and enable multi-frequency conversion. However, the tunable filter has the problems of large volume and high power consumption. Radio Frequency Micro Electro Mechanical System (RF MEMS) technology offers the possibility of low loss, near-zero power consumption, high volume, and high linearity filtering comparable to integrated circuits. Some researchers have begun to apply RF MEMS to the development of tunable filters, which include centralized design filters and distributed design filters. While these filters are suitable for tunable designs, their often large size, non-coplanar nature, and low-Q problems with traditional lumped elements make these filters difficult to integrate with integrated circuits. At the same time, the designed filter can also be divided into an analog tuned filter and a digital tuned filter. The analog tuned filter can provide continuous passband frequency variation, but the tuning range is limited.
  • RF MEMS Radio Frequency Micro Electro Mechanical System
  • the present application provides a tunable low-pass filter and a preparation method, so as to achieve two times of tuning and maintain the characteristics of the Chebyshev filter, and to achieve a large tuning range while having improved isolation of out-of-band characteristics, and the pass-band ripple is less than 2dB , and the maximum out-of-band rejection is higher than 20dB.
  • a tunable low-pass filter comprising: at least one slow-wave coplanar waveguide (Coplanar Waveguide, CPW) filtering unit;
  • the slow-wave CPW filter unit includes an inductance series circuit and a MEMS switch parallel circuit, and the slow-wave CPW filter unit is configured to realize low-pass by changing the inductance in the inductance series circuit and the capacitor in the MEMS switch parallel circuit Filter tuning.
  • a preparation method of a tunable low-pass filter comprising:
  • the seed layer of titanium/gold (Titanium/Aurum, Ti/Au) is added with a bottom slow-wave CPW circuit and a bias network, and the bottom slow-wave CPW circuit and the bias network are coated with a thickness of 2 microns.
  • the seed layer of Ti/Au is added with the support pier of the MEMS switch, and a metal protective layer with a thickness of 4 microns is coated on the support pier to form a MEMS bridge;
  • the deposition thickness is Plasma Enhanced Chemical Vapor Deposition (PECVD) silicon nitride to the dielectric layer of the CPW main transmission line and the dielectric layer of the MEMS bridge;
  • PECVD Plasma Enhanced Chemical Vapor Deposition
  • Polyimide was used as a sacrificial layer, the sacrificial layer was laid on the CPW main transmission line and the MEMS bridge, the sacrificial layer was patterned and thermally cured at a temperature of 200° C. to The CPW main transmission line and the MEMS bridge are patterned and thermally cured;
  • FIG. 1 is a simplified equivalent circuit model diagram of a low-pass filter unit provided in Embodiment 1 of the present application;
  • FIG. 2 is a schematic diagram of a low-pass filtering unit of a CPW structure provided in Embodiment 1 of the present application;
  • Fig. 3 is the manufacturing process flow chart of a kind of low-pass filter provided in the second embodiment of the present application.
  • 4a is a schematic diagram of a buttress formed by a CPW line and a MEMS switch according to the second embodiment of the present application;
  • FIG. 4b is a schematic diagram of patterning of a dielectric layer provided in Embodiment 2 of the present application.
  • 4c is a schematic diagram of a sacrificial layer spinning and aluminum bridge evaporation provided in the second embodiment of the present application;
  • FIG. 4d is a schematic diagram of sacrificial layer etching and MEMS bridge release according to the second embodiment of the present application.
  • Embodiment 1 is a simplified equivalent circuit model diagram of a low-pass filter unit provided in Embodiment 1 of the present application.
  • the tunable low-pass filter provided by this embodiment includes:
  • At least one slow wave CPW filter unit 10 At least one slow wave CPW filter unit 10 .
  • the slow-wave CPW filter unit 10 includes an inductor series circuit 11 and a MEMS switch parallel circuit 12.
  • the slow-wave CPW filter unit 10 is configured to realize low-pass filter tuning by changing the CPW pipeline.
  • the MEMS switch parallel circuit 12 and the inductor series circuit 11 are the main circuits in the equivalent circuit, and C1, C2 and C3 are metal-insulator-metal (MIM) controlled by MEMS capacitive switches. ) capacitor.
  • L1, L2, and L3 are the inductances that make up the main transmission line, respectively.
  • L3 is a gate inductance. The calculation formula of the linear or strip inductance can be written as:
  • L is the segment inductance in nanohenries
  • l, w, and t are the segment length, width, and thickness, in centimeters, respectively.
  • the upstream and downstream capacitances can be expressed as:
  • A is the plate area on top of the center conductor
  • d is the distance between the bridge and the CPW wire in the up state
  • t is the thickness of the dielectric material on top of the CPW wire
  • ⁇ r is the dielectric constant of the material used
  • ⁇ 0 is the dielectric constant in vacuum
  • C frng is the additional capacitance generated by fringe field effect
  • t rough is the effective thickness considering roughness.
  • the inductor series circuit 11 includes a main transmission line formed by a first given number of gate inductors connected in series.
  • the first given number may be an integer greater than one.
  • the slow-wave CPW filter unit 10 includes an inductor series circuit 11 , and the inductor series circuit 11 is composed of six gate inductors.
  • the inductance values of the first given number of gate inductances included in the inductance series circuit 11 represent the inductance values of the main transmission line.
  • the MEMS switch parallel circuit 12 includes a second given number of electrostatic drive bridges; the second given number of electrostatic drive bridges are fixed on the ground wire of the CPW transmission line, and are connected in parallel to form a low-pass second-order adjustable device filter.
  • An electrostatic drive bridge is included in the MEMS switch parallel circuit 12 . As shown in FIG. 1 , the MEMS switch parallel circuit 12 includes five electrostatic drive bridges connected in parallel.
  • the capacitors in the electrostatic drive bridge are metal-insulator-metal capacitors controlled by MEMS capacitive switches.
  • the second given number is 5; the electrostatic drive bridge forms a MEMS switch by being applied with a pull-down voltage, and when the MEMS switch is regulated on and off, the capacitance value of the capacitor in the electrostatic drive bridge changes accordingly, so as to control the filter Cut-off frequency.
  • the -3dB point is the cut-off frequency.
  • the cutoff frequency of the filter is determined by the values of C1, C2, C3, L1, L2 and L3.
  • FIG. 2 is a schematic diagram of a low-pass filter unit with a CPW structure provided in Embodiment 1 of the present application.
  • the low-pass filter includes five electrostatic drive bridges 121.
  • the graph of the filter as shown in picture 2.
  • a high frequency structure simulation (High Frequency Structure Simulator, HFSS) software is used to establish a filter device model, which can simulate parameters in multiple states.
  • Table 1 shows the parameters of the filter. As shown in Table 1, the frequency of the filter can be adjusted twice, and the range can be as large as 30% and 105%. When the insertion loss is less than 1.2dB, the maximum isolation can be greater than 27dB.
  • the characteristics of the tunable filter were measured using a vector network analyzer.
  • the -3dB cutoff frequency of the tunable low-pass filter when the MEMS switch is switched to the "on" or “off” state, the capacitance of the filter changes, and the -3dB cutoff frequency of these three states is 8.2 GHz, 10.5GHz and 16.8GHz.
  • the insertion loss is less than 2dB, and the out-of-band isolation of the three states is higher than 20dB. Due to MEMS parasitics and dielectric surface roughness layers, the measured -3dB cutoff frequency, insertion loss and out-of-band isolation of the three states are not completely consistent with the simulation results, and the driving voltage of the MEMS switch is about 40V.
  • This application shows the tunability of the filter based on the MEMS capacitive switch structure through the test results.
  • the -3dB cutoff frequencies of the filters can be tuned to 8.2GHz, 10.5GHz, and 16.8GHz, respectively.
  • the tunable low-pass filter can be tuned twice while maintaining Chebyshev filter characteristics, enabling a large tuning range with improved out-of-band characteristic isolation.
  • the filter can be used in radar tunable RF front-end systems, wireless and multi-frequency communication systems, etc.
  • the tunable low-pass filter provided in this embodiment solves the problems of difficult integration of the filter and limited tuning range, and can be tuned twice while maintaining the characteristics of the Chebyshev filter, achieving a large tuning range and improving the isolation of out-of-band characteristics. Effect.
  • Embodiment 3 is a flowchart of a manufacturing process of a low-pass filter provided in Embodiment 2 of the present application. This embodiment is applicable to the case of manufacturing a low-pass filter, and the steps include:
  • Step 210 providing a preparation substrate of a standard radio frequency microelectromechanical system MEMS process, and laying 520-micron-thick quartz on the preparation substrate.
  • Step 220 by evaporating Ti/Au
  • the seed layer is added with a bottom slow-wave coplanar waveguide CPW circuit and a bias network, and a metal protective layer with a thickness of 2 microns is coated to form a CPW circuit.
  • Step 230 by evaporating Ti/Au
  • the seed layer of the MEMS switch is added, and a metal protective layer with a thickness of 4 microns is coated to form a MEMS bridge.
  • Step 240 deposition Thick PECVD silicon nitride to dielectric layers for CPW lines and MEMS bridges.
  • Step 250 using polyimide as a sacrificial layer to pattern and thermally cure the CPW circuit and the MEMS bridge at a high temperature of 200°C.
  • Step 260 evaporating the MEMS bridge using 2 micron thick aluminum, removing the sacrificial layer using oxygen plasma, and releasing the MEMS switch.
  • Step 270 Obtain the tunable low-pass filter described in the above embodiment.
  • each MEMS switch has a length of 460 microns and a width of 160 microns.
  • Each MEMS switch is controlled by three independent DC sheet voltages.
  • the ground-signal-ground (GSG) excitation filter used in the prepared tunable low-pass filter is a single-ended probe with a spacing of 150 microns.
  • a substrate 21 using a standard radio frequency MEMS process is used, and 520um thick quartz is laid on the substrate 21 .
  • Ti/Au by Evaporation on Quartz The bottom slow wave CPW line and bias network are added to the seed layer, and then gold is plated on the bottom slow wave CPW line and bias network, and the thickness of gold plating is 2um.
  • the buttress 22 of the MEMS switch is fabricated by the same method as above, but the thickness of gold plating is 4um.
  • the next step, as shown in Figure 4b, is to deposit Thick PECVD silicon nitride to form the dielectric layer 23 and to avoid shorts between the MEMS bridge and the CPW lines.
  • polyimide is used as the sacrificial layer 24, and the sacrificial layer 24 is patterned to be arranged as hanging contact bars.
  • the sacrificial layer 24 is patterned and thermally cured at a high temperature of about 200°C.
  • the MEMS bridge is evaporated with 2-micron thick aluminum.
  • the sacrificial layer 24 is removed by an oxygen plasma process to release the MEMS switch.
  • the fabricated tunable low-pass filter consists of five MEMS switches and CPW pipelines. MEMS switches are 460um and 160um in length and width. Each MEMS switch is controlled by three independent DC bias lines, and the filters are excited using GSG single-ended probes spaced 150um apart. The chip size of the low-pass filter including the DC bias line is 2.5mm x 1.2mm.

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Abstract

本文公开了一种可调谐低通滤波器及制备方法。可调谐低通滤波器包括：至少一个慢波CPW滤波单元；慢波CPW滤波单元中包括电感串联电路以及MEMS开关并联电路，慢波CPW滤波单元设置为通过改变电感串联电路中的电感和MEMS开关并联电路中的电容器实现低通滤波调谐。

Description

可调谐低通滤波器及制备方法
本申请要求在2021年02月26日提交中国专利局、申请号为202110220575.4的中国专利申请的优先权，该申请的全部内容通过引用结合在本申请中。
技术领域
本申请涉及射频毫米波低通滤波器技术领域，例如涉及一种可调谐低通滤波器及制备方法。
背景技术
可调谐滤波器已广泛应用于军事领域，例如，多标准收发器。可调滤波器降低了模拟前端的尺寸，抑制了大信号干扰并可以完成多频转换。但是可调谐滤波器存在体积大，耗电量大的问题。射频微电子机械系统(Radio Frequency Micro Electro Mechanical System，RF MEMS)技术提供了低损耗，接近零功耗，高体积以及与集成电路相当的高线性度滤波的可能性。一些研究者开始将RF MEMS应用到可调谐滤波器的发展上，设计出的滤波器包括集中式设计滤波器和分布式设计滤波器。虽然这些滤波器适用于可调设计，但是它们通常具有大尺寸、非共面特性，以及传统集总元件的低Q值的问题，使得这些滤波器很难与集成电路集成。同时，还可以将设计出的滤波器分为模拟调谐滤波器和数字调谐滤波器，模拟调谐滤波器可以提供连续通带频率变化，但调谐范围有限。
发明内容
本申请提供一种可调谐低通滤波器及制备方法，以实现调谐两次并保持切比雪夫滤波器特性，并实现大调谐范围的同时具备改进的带外特性隔离，通带纹波小于2dB，且最大带外抑制高于20dB。
提供了一种可调谐低通滤波器，包括：至少一个慢波共面波导(Coplanar Waveguide，CPW)滤波单元；
所述慢波CPW滤波单元中包括电感串联电路以及MEMS开关并联电路，所述慢波CPW滤波单元设置为通过改变所述电感串联电路中的电感和所述MEMS开关并联电路中的电容器实现低通滤波调谐。
还提供了一种可调谐低通滤波器的制备方法，包括：
提供标准射频MEMS工艺的制备基板，在所述制备基板上铺设厚度为520微米的石英；
在所述石英上通过蒸发厚度为
Figure PCTCN2021080711-appb-000001
的钛/金(Titanium/Aurum，Ti/Au)的种子层增设底部慢波CPW线路和偏置网络，并在所述底部慢波CPW线路和所述偏置网络上涂镀厚度为2微米的金属保护层，形成CPW主传输线路；
在所述石英上通过蒸发厚度为
Figure PCTCN2021080711-appb-000002
的Ti/Au的种子层增设MEMS开关的支墩，并在所述支墩上涂镀厚度为4微米的金属保护层，形成MEMS桥；
沉积厚度为
Figure PCTCN2021080711-appb-000003
的等离子体增强化学的气相沉积法(Plasma Enhanced Chemical Vapor Deposition，PECVD)氮化硅到所述CPW主传输线路的电介质层和所述MEMS桥的电介质层；
采用聚酰亚胺作为牺牲层，所述牺牲层铺设在所述CPW主传输线路和所述MEMS桥上，对所述牺牲层进行图案化以及在200℃的温度下热固化，以对所述CPW主传输线路和所述MEMS桥进行图案化和热固化；
采用厚度为2微米的铝蒸发所述MEMS桥，采用氧等离子体去除所述牺牲层，以及释放所述MEMS开关；
获得上述的可调谐低通滤波器。
附图说明
图1是本申请实施例一提供的一种低通滤波单元的简化等效电路模型图；
图2是本申请实施例一提供的一种CPW结构的低通滤波单元示意图；
图3是本申请实施例二提供的一种低通滤波器的制造工艺流程图；
图4a是本申请实施例二提供的一种CPW线与MEMS开关成型的支墩示意图；
图4b是本申请实施例二提供的一种介质层图案化示意图；
图4c是本申请实施例二提供的一种牺牲层旋压与铝桥蒸发示意图；
图4d是本申请实施例二提供的一种牺牲层腐蚀与MEMS桥释放示意图。
具体实施方式
下面结合附图和实施例对本申请进行说明。
实施例一
图1为本申请实施例一提供的一种低通滤波单元的简化等效电路模型图，本实施例提供的可调谐低通滤波器，包括：
至少一个慢波CPW滤波单元10。
慢波CPW滤波单元10中包括电感串联电路11以及MEMS开关并联电路12，慢波CPW滤波单元10设置为通过改变CPW管线实现低通滤波调谐。
如图1所示，MEMS开关并联电路12和电感串联电路11是等效电路中的主要电路，C1、C2和C3是由MEMS电容开关控制的金属-绝缘体-金属(Metal-Insulator-Metal，MIM)电容器。L1，L2，L3分别是组成主传输线路的电感，L3是一个栅极电感，直线或条形电感计算公式可以写成：
Figure PCTCN2021080711-appb-000004
式中，L是段电感，单位为毫微亨利，l，w，t为节段长度、宽度和厚度，分别以厘米为单位。上行和下行电容可表示为：
Figure PCTCN2021080711-appb-000005
式中，A是中心导体顶部的板面积，d是向上状态下桥梁和CPW线之间的距离，t d是CPW线顶部的电介质材料的厚度，ε r是所用材料的介电常数，ε 0为真空中的介电常数。C frng是边缘场效应产生的附加电容，t rough是考虑粗糙度的有效厚度。
在本实施例中，电感串联电路11包括由第一给定数量的栅极电感串联连接形成的主传输线路。
第一给定数量可以是大于1的整数。如图1所示，慢波CPW滤波单元10中包括电感串联电路11，电感串联电路11由6个栅极电感组成。
电感串联电路11中包括的第一给定数量的栅极电感的电感值表示所述主传输线路的电感值。
在本实施例中，MEMS开关并联电路12包括第二给定数量的静电驱动桥；第二给定数量的静电驱动桥固定在CPW输电线路的地线上，并联构成二阶可调器件低通滤波器。
MEMS开关并联电路12中包括静电驱动桥。如图1所示，MEMS开关并联电路12中包括5个并联的静电驱动桥。
静电驱动桥内的电容器为由MEMS电容开关控制的金属-绝缘体-金属电容器。
第二给定数量为5；静电驱动桥通过被施加下拉式电压构成MEMS开关，且MEMS开关进行开、关状态调控时，静电驱动桥内电容器的电容值随之改变，以此控制滤波器的截止频率。
当保持滤波器的输入信号的幅度不变，改变输入信号的频率使滤波器的输出信号降至最大值的0.707倍时，用频响特性来表述，则-3dB点处即为截止频率。滤波器的截止频率是由C1、C2、C3、L1、L2和L3的值确定。一旦MEMS电桥被加上下拉电压，开关将被设置并且电容值将被更换，滤波器的截止频率将同时更换。
图2是本申请实施例一提供的一种CPW结构的低通滤波单元示意图，如图2所示，低通滤波器中包括5个静电驱动桥121，当有信号输入时，滤波器的图形如图2所示。
在本实施例中，采用高频结构仿真(High Frequency Structure Simulator，HFSS)软件建立了滤波装置模型，可以模拟出多个状态下的参数。表1为滤波器的参数，如表1所示，滤波器的频率可调两次，量程可大达30％和105％，插入损耗小于1.2dB时，最大隔离度可以大于27dB。
表1滤波器的参数
Parameter State a State b State c
-3dB截止频率 7.1 9.2 14.55
插入损耗(dB) <1.2 <0.79 <1.01
最大隔离度(dB) 27.1 27.9 63
在本实施例中，使用矢量网络分析仪测量了可调谐滤波器的特性。通过对可调谐低通滤波器的-3dB截止频率进行测量，当MEMS开关切换到“开”或“关”状态，滤波器的电容发生了变化，这三种状态的-3dB截止频率分别为8.2GHz、10.5GHz和16.8GHz。插入损耗小于2dB，三种状态的带外隔离均高于20dB。由于MEMS的寄生效应以及电介质表面粗糙度层，测量的-3dB截止频率，插入损耗和三种状态的带外隔离与仿真结果不完全一致，MEMS开关的驱动电压约为40V。
本申请通过测试结果表明了基于MEMS电容开关结构的滤波器的可调谐性。通过操作MEMS开关，滤波器的-3dB截止频率可以分别调至8.2GHz、10.5GHz和16.8GHz。可调低通滤波器可以调谐两次并保持切比雪夫滤波器特性，实现大调谐范围的同时具备改进的带外特性隔离。该滤波器可以应用在雷达的可调谐射频前端系统、无线和多频通信系统等。
本实施例提供的可调谐低通滤波器，解决滤波器难以集成和调谐范围有限 的问题，可以调谐两次并保持切比雪夫滤波器特性，实现大调谐范围的同时具备改进的带外特性隔离的效果。
实施例二
图3是本申请实施例二提供的一种低通滤波器的制造工艺流程图，本实施例可适用于对低通滤波器进行制造的情况，步骤包括：
步骤210、提供标准射频微电子机械系统MEMS工艺的制备基板，在制备基板上铺设520微米厚石英。
步骤220、通过蒸发Ti/Au
Figure PCTCN2021080711-appb-000006
的种子层增设底部慢波共面波导CPW线路和偏置网络，并涂镀厚度为2微米的金属保护层，形成CPW线路。
步骤230、通过蒸发Ti/Au
Figure PCTCN2021080711-appb-000007
的种子层增设MEMS开关的支墩，并涂镀厚度为4微米的金属保护层，形成MEMS桥。
步骤240、沉积
Figure PCTCN2021080711-appb-000008
厚PECVD氮化硅到CPW线路和MEMS桥的电介质层。
步骤250、采用聚酰亚胺作为牺牲层，以将CPW线路和MEMS桥在高温度200℃范围内进行图案化和热固化。
步骤260、采用2微米厚的铝蒸发MEMS桥，采用氧等离子体去除牺牲层，以及释放MEMS开关。
步骤270、获得上述实施例中所述的可调谐低通滤波器。
在本实施例中，每个MEMS开关的长度为460微米，宽度为160微米。
每个MEMS开关由三个独立的直流片压线控制。
所制备可调谐低通滤波器中使用的接地-信号-接地(Ground-Singal-Ground，GSG)激励滤波器为间距为150微米的单端探针。
如图4a所示，在带有MEMS开关的可调低通滤波器的制造过程中，采用标准射频MEMS工艺的基板21，在基板21上铺设520um厚的石英。在石英上通过蒸发Ti/Au
Figure PCTCN2021080711-appb-000009
的种子层增设底部慢波CPW线路和偏置网络，然后在底部慢波CPW线路和偏置网络上镀金，镀金的厚度均为2um。
如图4a所示，MEMS开关的支墩22是用与上述同样的方法制作的，但是镀金的厚度是4um。下一步，如图4b所示，沉积
Figure PCTCN2021080711-appb-000010
厚PECVD氮化硅，以形成介电层23，并避免MEMS桥和CPW线路之间短路。如图4c所示，聚酰亚胺用作牺牲层24，并且图案化牺牲层24以设置为悬挂接触棒。牺牲层24被图案化并且在约200℃的高温下热固化。接下来，MEMS桥是用2微米厚的铝蒸发。最后，如图4d所示，利用氧等离子体工艺去除牺牲层24，释放MEMS开 关。制作的可调谐低通的滤波器由五个MEMS开关和CPW管线组成。MEMS开关长宽460um和160um。每个MEMS开关由三条独立的直流偏压线控制，滤波器使用间距为150um的GSG单端探头激励。包括直流偏置线的低通滤波器的芯片尺寸为2.5mm×1.2mm。

Claims (10)

  1. 一种可调谐低通滤波器，包括：至少一个慢波共面波导CPW滤波单元；
    所述慢波CPW滤波单元中包括电感串联电路以及微电子机械系统MEMS开关并联电路，所述慢波CPW滤波单元设置为通过改变所述电感串联电路中的电感和所述MEMS开关并联电路中的电容器实现低通滤波调谐。
  2. 根据权利要求1所述的可调谐低通滤波器，其中，所述电感串联电路包括由第一给定数量的栅极电感串联连接形成的主传输线路。
  3. 根据权利要求2所述的可调谐低通滤波器，其中，所述电感串联电路中包括的所述第一给定数量的栅极电感的电感值表示所述主传输线路的电感值。
  4. 根据权利要求1所述的可调谐低通滤波器，其中，所述MEMS开关并联电路包括第二给定数量的静电驱动桥；
    所述第二给定数量的静电驱动桥固定在所述慢波CPW滤波单元的CPW输电线路的地线上，所述第二给定数量的静电驱动桥并联构成二阶可调器件低通滤波器。
  5. 根据权利要求4所述的可调谐低通滤波器，其中，所述静电驱动桥内的电容器为由MEMS电容开关控制的金属-绝缘体-金属电容器。
  6. 根据权利要求4所述的可调谐低通滤波器，其中，所述第二给定数量为5；
    所述静电驱动桥设置为通过被施加下拉式电压构成MEMS开关，所述MEMS开关设置为在所述MEMS开关的开关状态被调控的情况下，改变所述静电驱动桥内的电容器的电容值，以控制所述可调谐低通滤波器的截止频率。
  7. 一种可调谐低通滤波器的制备方法，包括：
    提供标准射频微电子机械系统MEMS工艺的制备基板，在所述制备基板上铺设厚度为520微米的石英；
    在所述石英上通过蒸发厚度为
    Figure PCTCN2021080711-appb-100001
    的钛/金Ti/Au的种子层增设底部慢波共面波导CPW线路和偏置网络，并在所述底部慢波CPW线路和所述偏置网络上涂镀厚度为2微米的金属保护层，形成CPW主传输线路；
    在所述石英上通过蒸发厚度为
    Figure PCTCN2021080711-appb-100002
    的Ti/Au的种子层增设MEMS开关的支墩，并在所述支墩上涂镀厚度为4微米的金属保护层，形成MEMS桥；
    沉积厚度为
    Figure PCTCN2021080711-appb-100003
    的等离子体增强化学的气相沉积法PECVD氮化硅到所述CPW主传输线路的电介质层和所述MEMS桥的电介质层；
    采用聚酰亚胺作为牺牲层，所述牺牲层铺设在所述CPW主传输线路和所述 MEMS桥上，对所述牺牲层进行图案化以及在200℃的温度下热固化，以对所述CPW主传输线路和所述MEMS桥进行图案化和热固化；
    采用厚度为2微米的铝蒸发所述MEMS桥，采用氧等离子体去除所述牺牲层，以及释放所述MEMS开关；
    获得权利要求1-7任一项所述的可调谐低通滤波器。
  8. 根据权利要求7所述的制备方法，其中，所述MEMS开关的长度为460微米，宽度为160微米。
  9. 根据权利要求7所述的制备方法，其中，所述MEMS开关由三个独立的直流片压线控制。
  10. 根据权利要求7所述的制备方法，其中，所述可调谐低通滤波器中使用的接地-信号-接地激励滤波器为间距为150微米的单端探针。
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