• For high frequency Kirchhoff’s laws do not apply
anymore !!
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• 行波电压的时空分布特性
• Voltage has a time and space behavior • Space is neglected for low frequency applications
6.倒置微带线 (Inverted Microstrip TL)
第三章 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 的射频特性。
本章主要介绍射频电路元器件及特性, 传输线特性分析等方面的基础知识
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整体概概述二
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3.1 射频电路元器件及特性
电容元件的等效电路模型
Abs (Z) of a MIM/SMT Capacitor as a function of freque1n1cy
Electromagnetic Analysis
• Maxwell’s Equation
HJ D t
E B t
Dv
B0
• 金属导线的趋肤效应
Skin depth l
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2. 同轴线 (Co-axial cable TL)
Features: • Electric field is completely contained within both conductors • Perfect shielding of magnetic field • TEM modes up to a certain cut-off frequency 21
GaAs/InP PHEMT, ft =150GHz, GaN
封装型有源固态器件
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• 无源器件
封装型无源器件
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集成电路芯片中的无源器件
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二、 无源器件的射频特性
•No ideal lumped elements in RF anymore !
•无源器件有什么样的射频特性/特点？分布特性！ • Conventional Lumped Circuit Analysis – Ideal R is frequency independent
( L/10)
• For RF there can be a large spatial variation
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工作波长与电路尺寸相当时,必须采用电磁场 分析方法
• 传播的电磁波
ExEx0cos(tkz)
• 电磁波相速
vp1C rr f/2/k
• 电磁波群速
d vg dk
k 电磁波相位常数
• 行波电压
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电感线圈的频率特性
SMT电阻元件(0201/0402 /0603….)/CrN MMIC 电阻 电阻元件的等效电路模型
Abs (Z) of a thin-film resistor as a function of frequenc1y0
SMT电容元件(0201/ 0402/0603….)/MIM电容
resistance and inductance! density (r=a=1mm, Cu13)
2 GHz 功放的第一级放大器简化电路图
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2 GHz 功放电路版图(HMIC) 15
20-40GHz PHEMT
MMIC LNA
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3.2传输线分析
•电压测量实验
L=1.5cm: (1) f=300MHz (1m), (2) f=30 GHz (1cm) • For low frequency Kirchhoff’s laws apply
3. 微带线 (Microstrip TL) 4. 三层线 (Triple-layer transmission line)
Conductor is completely shielded between two ground pla2n2es
5. 共面波导(Co-planar Waveguide TL)
1
f c
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• Skin depth
Jdc I /a2,Rdc l /a2c
Jac pIJ0(pr)/2aJ1(pa), p2 jc
R/ Rdc a/2l,L/ Rdc a/2l
l 1/ f c
• A section of wire has
Frequency behavior of normalized RF current
v (t,z) E o xsin (t k z)/k
(v(t,z)Eoxdz)
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• 传输线种类 1. 双并行线( Two-wire Parallel TL)
Features:
• Alternating electric field between conductors • Alternating magnetic field surrounding conductors • Dielectric tends to confine field inside material
– Ideal inductor: – Ideal capacitor:
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Current and voltage vary spatially over the component size。
E (or V) and H (or I) fields
例1：电感元件特性
分布特性！
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电感线圈
电感线圈的 等效电路模型
一、 射频电路元器件种类
有源器件: (Vacuum/Solid-State) Diode,Transistor
无源器件: Resistor, Capacitor, Inductor, Transimision Line ，Crystal Resonator
• 有源固态器件
Two-terminal Diodes: Si/GaAs/GaN Gun/IMPATT Three-terminal Transistors: Material: Si/CMOS/GaAs/InGaAs/InP/SiGe//SiC/GaN Structures: BJT/HBT /MESFET/HEMT/PHEMT Catalog: Si BJT, ft=50GHz, SiGe HBT, ft=100GHz 3