射频电路预备基础知识课件.ppt

第三章 射频电路预备基础知识射频电路预备基础知识 在现代电子通信系统射频电路中，其与低频电路的最大区别就在于器件及传输线器件及传输线的的射射频特性频特性本章主要介绍本章主要介绍射射频电路元器件及特性频电路元器件及特性, 传输线特性分析传输线特性分析等方面的基础知识等方面的基础知识3.1 射频电路元器件及特性射频电路元器件及特性一、一、 射频电路元器件种类射频电路元器件种类有源器件有源器件有源器件有源器件: (Vacuum/Solid-State) : (Vacuum/Solid-State) : (Vacuum/Solid-State) : (Vacuum/Solid-State) Diode,TransistorDiode,TransistorDiode,TransistorDiode,Transistor无源器件无源器件无源器件无源器件: Resistor, Capacitor, Inductor,: Resistor, Capacitor, Inductor,: Resistor, Capacitor, Inductor,: Resistor, Capacitor, Inductor, TransimisionTransimisionTransimisionTransimision Line Line Line Line ，，，，Crystal ResonatorCrystal ResonatorThree-terminal Transistors: Three-terminal Transistors: Three-terminal Transistors: Three-terminal Transistors: Material: Material: Material: Material: Si/CMOS/GaAs/InGaAs/InP/SiGe//SiC/GaNSi/CMOS/GaAs/InGaAs/InP/SiGe//SiC/GaNSi/CMOS/GaAs/InGaAs/InP/SiGe//SiC/GaNSi/CMOS/GaAs/InGaAs/InP/SiGe//SiC/GaNStructures: BJT/HBT /MESFET/HEMT/PHEMTStructures: BJT/HBT /MESFET/HEMT/PHEMTStructures: BJT/HBT /MESFET/HEMT/PHEMTStructures: BJT/HBT /MESFET/HEMT/PHEMTCatalog: Catalog: Catalog: Catalog: SiSiSiSi BJT, BJT, BJT, BJT, ft=50GHzft=50GHzft=50GHzft=50GHz, , , , SiGeSiGeSiGeSiGe HBT, HBT, HBT, HBT, ft=100GHzft=100GHzft=100GHzft=100GHz GaAs/InPGaAs/InPGaAs/InPGaAs/InP PHEMT, PHEMT, PHEMT, PHEMT, ftftftft = = = =150GHz150GHz150GHz150GHz, GaN, GaN, GaN, GaN HEMT:HEMT:HEMT:HEMT:ftftftft=280GHz=280GHz=280GHz=280GHz• • 有源固态器件有源固态器件有源固态器件有源固态器件Two-terminal Diodes: Two-terminal Diodes: Si/GaAs/GaNSi/GaAs/GaN Gun/IMPATT Gun/IMPATT 封装型有源固态器件封装型有源固态器件• 无源器件无源器件封装型无源器件封装型无源器件集成电路芯片中的无源器件集成电路芯片中的无源器件二、二、 无源器件的射频特性无源器件的射频特性•No ideal No ideal lumped elements in RF anymore !•无源器件有什么样的无源器件有什么样的无源器件有什么样的无源器件有什么样的射频射频射频射频特性特性特性特性/ / / /特点？分布特性！特点？分布特性！特点？分布特性！特点？分布特性！– – – – Ideal Ideal R R R R is frequency is frequency is frequency is frequency independentindependentindependentindependent– Ideal inductor:– Ideal inductor:– Ideal inductor:– Ideal inductor:– Ideal capacitor:– Ideal capacitor:– Ideal capacitor:– Ideal capacitor:• Conventional Lumped Circuit Analysis Conventional Lumped Circuit Analysis Conventional Lumped Circuit Analysis Conventional Lumped Circuit Analysis例例例例1 1 1 1：电感元件特性：电感元件特性：电感元件特性：电感元件特性Current and voltage Current and voltage Current and voltage Current and voltage vary spatially over vary spatially over vary spatially over vary spatially over the component sizethe component sizethe component sizethe component size。

分布特性！分布特性！分布特性！分布特性！E (or V) and H (or I) fields电感线圈电感线圈电感线圈电感线圈电感线圈的电感线圈的电感线圈的电感线圈的等效电路模型等效电路模型等效电路模型等效电路模型电感线圈的频率特性电感线圈的频率特性电感线圈的频率特性电感线圈的频率特性电阻元件的等效电路模型电阻元件的等效电路模型电阻元件的等效电路模型电阻元件的等效电路模型SMTSMTSMTSMT电阻元件电阻元件电阻元件电阻元件(0201/0402(0201/0402(0201/0402(0201/0402/0603….)//0603….)//0603….)//0603….)/CrNCrNCrNCrN MMIC MMIC MMIC MMIC 电阻电阻电阻电阻Abs (Z) of a thin-film resistor as a function of frequencyAbs (Z) of a thin-film resistor as a function of frequencySMTSMTSMTSMT电容元件电容元件电容元件电容元件(0201/(0201/(0201/(0201/0402/0603….)/MIM0402/0603….)/MIM0402/0603….)/MIM0402/0603….)/MIM电容电容电容电容电容元件的等效电路模型电容元件的等效电路模型电容元件的等效电路模型电容元件的等效电路模型Abs (Z) of a MIM/SMT Capacitor as a function of frequencyAbs (Z) of a MIM/SMT Capacitor as a function of frequencyElectromagnetic Analysis•Maxwell’s EquationSkin depth• 金属导线的趋肤效应金属导线的趋肤效应Frequency behavior of Frequency behavior of normalizednormalized RF RF current current densitydensity ( (r=a=1mm, Cu)r=a=1mm, Cu)• A section of wire has A section of wire has resistance and inductance!resistance and inductance!• Skin depth2 GHz 功放的第一级放大器简化电路图功放的第一级放大器简化电路图2 GHz 2 GHz 功放电路版图功放电路版图功放电路版图功放电路版图(HMIC)(HMIC)20-40GHz PHEMT MMIC LNA20-40GHz PHEMT MMIC LNA20-40GHz PHEMT MMIC LNA20-40GHz PHEMT MMIC LNA 3.2传输线分析传输线分析•电压测量实验电压测量实验• For low frequency For low frequency Kirchhoff’sKirchhoff’s laws apply laws apply• For high frequency For high frequency Kirchhoff’sKirchhoff’s laws do not apply laws do not apply anymore !!anymore !!L=1.5cm: (1) f=300MHz (1m), (2) f=30 GHz (1cm)L=1.5cm: (1) f=300MHz (1m), (2) f=30 GHz (1cm)• 行波电压的时空分布特性行波电压的时空分布特性•Voltage has a time and space behavior Voltage has a time and space behavior • • Space is neglected for low frequency applications Space is neglected for low frequency applications ( ) ( )• • For RF there can be a large spatial variationFor RF there can be a large spatial variation• 传播的电磁波传播的电磁波传播的电磁波传播的电磁波• 电磁波相速电磁波相速电磁波相速电磁波相速• 电磁波群速电磁波群速电磁波群速电磁波群速电磁波相位常数电磁波相位常数电磁波相位常数电磁波相位常数• 行波电压行波电压行波电压行波电压 工作波长与电路尺寸相当时工作波长与电路尺寸相当时,必须采用电磁场必须采用电磁场分析方法分析方法• 传输线种类传输线种类1. 1. 双并行线双并行线( Two-wire Parallel TL)( Two-wire Parallel TL)Features:• Alternating electric field between conductors Alternating electric field between conductors• Alternating magnetic field surrounding conductors Alternating magnetic field surrounding conductors• Dielectric tends to confine field inside material Dielectric tends to confine field inside material2 2 2 2. . 同轴线同轴线 (Co-axial cable TL)(Co-axial cable TL)Features:Features:• Electric field is completely contained Electric field is completely contained within within both both conductorsconductors• Perfect shielding of magnetic field Perfect shielding of magnetic field• TEM modes up to a certain cut-off frequency TEM modes up to a certain cut-off frequency3. 3. 微带线微带线 (Microstrip TL)(Microstrip TL)4. 4. 三层线三层线 (Triple-layer transmission line)Conductor is completely shielded between two ground planesConductor is completely shielded between two ground planes5. 5. 共面波导共面波导( (Co-planar Waveguide TL) )6.6.倒置微带线倒置微带线 ( (Inverted Microstrip TL) )8.8.波导波导( (Waveguide TL) )7.7.悬悬置置微带线微带线( (Suspended Microstrip TL) )9. 9. 镜像线镜像线( (Mirrored Microstrip TL) ) E面定位• 传输线分析理论传输线分析理论• QuestionsQuestionsKirchhoff’sKirchhoff’s laws at RF do not apply laws at RF do not apply anymore, How to analyze RF anymore, How to analyze RF circuit?circuit?•ApproachesApproaches1.1.1.1.EM TheoryEM TheoryEM TheoryEM Theory2.2.2.2.Equivalent Circuit TheoryEquivalent Circuit TheoryEquivalent Circuit TheoryEquivalent Circuit Theory•等效电路法特点等效电路法特点等效电路法特点等效电路法特点1.1.1.1.直观的物理图象直观的物理图象直观的物理图象直观的物理图象2.2.2.2.可用可用可用可用KirchhoffKirchhoffKirchhoffKirchhoff定理分析定理分析定理分析定理分析3.3.3.3.微观到宏观形式扩展的过程微观到宏观形式扩展的过程微观到宏观形式扩展的过程微观到宏观形式扩展的过程4.4.4.4.近为一维分析近为一维分析近为一维分析近为一维分析5.5.5.5.未考虑电路材料的非线性特征未考虑电路材料的非线性特征未考虑电路材料的非线性特征未考虑电路材料的非线性特征• 传输线方程传输线方程• • 微观微观微观微观 KirchhoffKirchhoffKirchhoffKirchhoff 电压电压电压电压/ / / /电流定律电流定律电流定律电流定律• • 传输线方程传输线方程传输线方程传输线方程 ( (电报方程电报方程电报方程电报方程) )K.V.L K.C.L Dividing by △z then △z->0 i(z, t)+v(z, t)_Zi(z, t)+v(z, t)_RLGC• 传输线方程传输线方程传输线方程传输线方程 ( (电报方程电报方程电报方程电报方程) Const.) Const. 典型的波动方程典型的波动方程典型的波动方程典型的波动方程! !• 波动方程的解波动方程的解波动方程的解波动方程的解K: K: K: K: 复传播常数复传播常数复传播常数复传播常数, , , , 传播常数传播常数传播常数传播常数 , , , , 衰减常数衰减常数衰减常数衰减常数• 传输线特性阻抗传输线特性阻抗传输线特性阻抗依赖于传输线上单位长度的传输线特性阻抗依赖于传输线上单位长度的传输线特性阻抗依赖于传输线上单位长度的传输线特性阻抗依赖于传输线上单位长度的R, L, R, L, G, C!G, C!• 传输线上单位长度的传输线上单位长度的R, L, G, CR, L, G, CCharacteristic line impedance as a function of Characteristic line impedance as a function of w/hw/h. .• 传输线特性阻抗与结构传输线特性阻抗与结构, 材料特性的关系材料特性的关系• Effect of conductor thickness on the characteristic impedance of a microstrip line• Characteristic impedance (Zo) ranges for the various structuresStructure Zo(Ω)Microstrip 20-125Inverted microstrip 20-130Trapped inverted microstrip (TIM) 30-140Suspended stripline 40-150Coplanar waveguide (CPW) 40-150Slotline 60-200Finline 10-400Imageline ≈26• 无损传输线特性无损传输线特性电压波电压波电压波电压波/ / / /电流波沿无损传输线传播无衰减电流波沿无损传输线传播无衰减电流波沿无损传输线传播无衰减电流波沿无损传输线传播无衰减! ! ! !无损传输线特性阻抗无损传输线特性阻抗无损传输线特性阻抗无损传输线特性阻抗无损传输线传播常数无损传输线传播常数无损传输线传播常数无损传输线传播常数无损传输线上电压波无损传输线上电压波无损传输线上电压波无损传输线上电压波/ /电流波特电流波特电流波特电流波特性性性性• 端接负载传输线的输入阻抗端接负载传输线的输入阻抗• 电压反射系数电压反射系数• 电压电压/电流波空间分布特性电流波空间分布特性无耗传输线情况下无耗传输线情况下另一坐标系统下另一坐标系统下• 端接负载传输线的输入阻抗端接负载传输线的输入阻抗• 驻波及驻波比驻波及驻波比(SWR/VSWR)(SWR/VSWR)• 驻波特性驻波特性驻波特性驻波特性Standing wave pattern for various instances of timeStanding wave pattern for various instances of time• 驻波比驻波比驻波比驻波比(SWR/VSWR)(SWR/VSWR)(SWR/VSWR)(SWR/VSWR)SWR is a measure of mismatch of theSWR is a measure of mismatch of the load to the lineload to the lineSWR=1 (matched) SWR=1 (matched) SWR= very large (mismatch----total mismatch)SWR= very large (mismatch----total mismatch)• 特殊情况分析与讨论特殊情况分析与讨论1. 1. 1. 1. 一一一一端端端端口短路传输线的输入阻抗口短路传输线的输入阻抗口短路传输线的输入阻抗口短路传输线的输入阻抗 Short LoadShort Load一端口短路传输线的输入阻抗与传输线长度关系一端口短路传输线的输入阻抗与传输线长度关系一端口短路传输线的输入阻抗与传输线长度关系一端口短路传输线的输入阻抗与传输线长度关系Voltage, current, and impedance as a function of line Voltage, current, and impedance as a function of line length for a short circuit termination.length for a short circuit termination.一端口短路给定长度传输线的输入阻抗与传输频一端口短路给定长度传输线的输入阻抗与传输频一端口短路给定长度传输线的输入阻抗与传输频一端口短路给定长度传输线的输入阻抗与传输频率率率率( (波长波长波长波长) )关系关系关系关系Magnitude of the input impedance for a 10 cm long, short-Magnitude of the input impedance for a 10 cm long, short-circuit transmission line as a function of frequencycircuit transmission line as a function of frequency2.2.2.2.一一一一端端端端口开路传输线的输入阻抗口开路传输线的输入阻抗口开路传输线的输入阻抗口开路传输线的输入阻抗( ( ( (Open LoadOpen LoadOpen LoadOpen Load) ) ) )3.3.3.3.一一一一端端端端口接负载口接负载口接负载口接负载Z Z Z ZL L L L传输线的输入阻抗传输线的输入阻抗传输线的输入阻抗传输线的输入阻抗• 阻抗匹配阻抗匹配阻抗匹配阻抗匹配( ( ( (转换转换转换转换) ) ) )阻抗匹配目的阻抗匹配目的阻抗匹配目的阻抗匹配目的(1)RF(1)RF(1)RF(1)RF无反射传输无反射传输无反射传输无反射传输, , , ,消除驻波消除驻波消除驻波消除驻波(2)(2)(2)(2)最小最小最小最小NFNFNFNF传输传输传输传输(3)(3)(3)(3)最大功率最大功率最大功率最大功率传输传输传输传输传输线阻抗匹配特点传输线阻抗匹配特点传输线阻抗匹配特点传输线阻抗匹配特点: (2n+1)fo, n=0,1,2…….: (2n+1)fo, n=0,1,2……. ZinZin for frequency range of 0 to 2 GHz and fixed length d. for frequency range of 0 to 2 GHz and fixed length d.• 端接源和负载传输线的特性端接源和负载传输线的特性• 无损传输线情况无损传输线情况无损传输线情况无损传输线情况• 功率传输特性功率传输特性两种情况两种情况:1. Load and source matched line1. Load and source matched line2. Mismatch at source, but match at load2. Mismatch at source, but match at load• 信号功率单位信号功率单位1. 瓦瓦/VA2. dBm3. dBW• 回波损耗和插损回波损耗和插损。