💯
University Notes
  • Introduction
  • High Level Math
    • Function, limitation, and continuity
      • What is function?
      • Two kinds of infinity
      • The limitation of a function
      • A model for getting limitation
    • Derivative and differential
      • Formulas of derivative
      • Use derivative formula
      • Goes deeper
      • Use derivative
        • Function analyzing in theory
          • First derivative
          • Second derivative
          • Domain and Extreme Value
          • Overall change
        • Derivative use in reality
    • Integration
      • Indefinite integral
        • Basic formulas
        • Use formula
        • Goes deeper
        • Integration by parts
      • Definite integral
        • Properties of definite integral
        • Second fundamental theorem of calculus
        • Multi-method for solving definite integral
    • Multivariable calculus
      • Limitation
      • Partial derivatives
      • Differential
      • Multiple integral
    • Series
    • Linear algebra
    • GaoKao
      • 1
      • The road for starting
      • Polar Coordinates
      • Tangent Line
  • Electrical Engineering
    • The Terminologys
    • DC
      • The circuit rule
      • KCL and KVL
      • Superposition
    • AC
      • Intuition
      • Resistor
      • Inductor
      • Capacitor
      • AC circuit
      • 三相电
        • 星形联结
        • 三角形联结
        • 实际电路
    • Voltage and Current Rule in Circuit
    • Response
      • Foundations
      • 零输入响应
      • 零状态响应
      • 一阶电路的全响应
  • Analog Electronics
    • Technical terms 1
    • DC stable source circuit 的分析与应用
      • 二极管的特性与应用
        • 半导体
        • PN junction
        • Diode
        • 测试二极管
      • 整流滤波电路的分析与应用
        • Rectifier circuit
      • 直流稳压电路的分析
        • Zener diode
        • Shunt voltage regulators
    • Thyristor
    • Technical terms 2
    • Amplifying circuit
      • Bipolar Junction Transistor
      • Common Emitter Configuration
      • Biasing
      • Analysis
      • Mess
      • Negative-feedback amplifier
      • Integrated Operational Amplifier
    • Algorithms
      • What's the ouput of a voltage rectifier circuit
      • PNP or NPN
      • Judging the state of a BJT
      • What's common in BJT
      • Does a amplifying circuit normal
      • What's the feedback type
      • What kind of distortion you are encounter
  • Digital Electronic Technology
    • Logic Gate
    • Logic expressions
    • Karnaugh map
    • Number system
    • Multiplexer
    • Flip-flop
  • Principles of Communications
    • Overviews
    • PCM
    • HDB3
    • Modulations
    • Cyclic code
  • Data Communications and Networking
    • Something about IPv4
  • Micro Control System 51 Series
    • The Delay function
    • The Interrupt function
  • Maintenance of Railway Optical Cable Lines
    • Questions
    • Pictures
  • Mobile Communications
    • Concepts
    • Coding and Modulation
    • Key Technologies
    • Mobile communication network structure
    • Radio wave Propagation and Interference
    • GSM
    • CDMA
    • GPRS
    • 3G
    • 4G
    • Base Station Maintenance
  • Multimedia Communication
    • Concept of Multimedia
    • Compression
    • Lossless Compression
    • Audio
    • Lossy Audio Coding
    • Graph Compression
    • All for the exam
  • Power system for Communication Devices
    • Overview
    • AC power Distribution Panel
    • UPS
    • HF Switched-mode Power Supply
    • Battery
    • Earthing or Use Lightning Arrester
    • Power Supply Monitoring System
    • All for the exam
  • Optical fiber Communication system
    • What is Optical fiber Communication system
      • Prepare
      • Something About Optical fiber
      • Passive Optical Devices
      • Active Optical Devices
      • Optical transmitter Test
      • Optical receiver Test
      • Compose an Optical Communication System
    • SDH (Synchronous Digital Hierarchy)
      • Frame Structure of SDH
      • SDH Equipments
      • Clock System
      • ZXONM E300 Practice
      • SDH protection
    • WDM (Wavelength-Division Multiplexing)
    • OTN (Optical Transport Network)
      • OverHead of OTN
      • OTN Alarms & Errors
      • Do it again, what's happened?
  • Communication Tech English
    • Fundamentals of Electricity
    • Digital Communications
    • Optical Communications
  • High-speed railway Communication Technology
    • Overview
    • Base Knowledge
    • FH98
    • MDS3400
    • Everything is for the exam
  • GSM for Railway
    • Overview
    • Wired Parts
    • Digital dispatch Communication System
    • Basic Knowledge of GSM-R
    • Key technologies for GSM-R
    • Structure of GSM-R
    • GSM-R Network Mode
    • Wireless Channels for GSM-R
    • Mobility Management
    • Connection Management
    • Security Management
    • GPRS
    • GSM-R/GPRS Wireless Access Platform
    • GSM-R Features
    • GSM-R Numbering Plan
    • ASCI
  • Network Configuration Training
    • Words I have learned
  • Broadband Access Technology
    • Using Copper Line
    • Using Optical Fiber
    • Wireless
    • All for the test
  • CIR
    • Basci Knowledge
    • Testing Equipment
    • The Structure of CIR
    • All for the exam
  • LTE
  • Script for ChaoXing
  • Transmission and access network
Powered by GitBook
On this page
  • 无线电波的波段是如何划分的? 简要说明各波段的作用。
  • 什么是反射波、绕射波和散射波?
  • 电波传播时会产生哪些效应?
  • 信号的衰落是怎样产生的? 快衰落与慢衰落有何不同?
  • 信道有哪些类型? 各有什么特点?
  • 狭义上
  • 广义上
  • 移动通信的噪声有哪些?
  • 移动通信中的干扰有哪些?
  • 如何减小或避免邻道干扰?
  • 如何减小互调干扰?

Was this helpful?

  1. Mobile Communications

Radio wave Propagation and Interference

无线电波的波段是如何划分的? 简要说明各波段的作用。

  1. ELF极低频 3~30Hz

  2. SLF超低频 30~300Hz

  3. ULF特低频 300~3000Hz

  4. VLF甚低频 3~30kHz

  5. LF低频 30~300kHz

  6. MF中频 300~3000kHz

  7. HF高频 3~30MHz

  8. VHF甚高频 30~300MHz

  9. UHF特高频 300~3000MHz | 短距离通信、移动通信、电视通信

  10. SHF超高频 3~30GHz

  11. EHF极高频 30~300GHz

什么是反射波、绕射波和散射波?

反射波: 当电磁波传播中遇到两种不同介质的光滑界面时,如果界面尺寸比电磁波波长大得多,就会产生镜面反射。反射发生于地球表面、建筑物和墙壁表面等。

绕射波: 当接收机与发射机之间的无线路径被尖利的边缘阻挡时发生绕射。绕射使得无线电信号绕地球曲线表面传播,使其能传播到阻挡物后面。

散射波: 当电波穿行的介质中存在小于波长的物体,并且单位体积内阻挡体个数非常多时,产生散射波。散射波产生于粗糙表面、小物体和其他不规则物体。

电波传播时会产生哪些效应?

  • 阴影效应: 由地形结构引起的传播损耗,属于慢衰落

  • 多徑效应: 由于散射引起同一信号沿多条路径传播,使得接收到的信号相互叠加、起伏变化大,属于快衰落

  • 多普勒效应: 由于物体高速移动,使得信号频率产生偏移,属于快衰落

信号的衰落是怎样产生的? 快衰落与慢衰落有何不同?

产生: 移动通信中,由于散射次数很多,接收点所收到的信号的强度(电平值)随机起伏

快衰落: 信号瞬时起伏变化

慢衰落: 信号慢速起伏变化

信道有哪些类型? 各有什么特点?

狭义上

  1. 有线信道: 电缆、光缆 ; 稳定、可靠

  2. 无线信道: 空气 ; 方便、灵活

广义上

  1. 调制信道

  2. 编码信道

移动通信的噪声有哪些?

  • 无线电噪声: 其他无线电

  • 工业噪声: 其他电气设备

  • 天电噪声: 来自大自然、宇宙

  • 内部噪声: 来自设备本身的电气元件

移动通信中的干扰有哪些?

  • 同信道(同频)干扰: 一山不容二虎,同一频率在同一区域会互相干扰

  • 相邻信道干扰: 由于频率切分不完全,所以多出来的一部分(偏移频率信号)会互相干扰

  • 互调干扰: 由传输系统中的非线性电路引起,内部元器件会互相干扰

如何减小或避免邻道干扰?

  • 信道间留一定的间隔

  • 提高接收机的频率稳定度和准确度

如何减小互调干扰?

  • 加大发射机与天线的距离

  • 采用单向隔离器件

  • 选用高级器件

  • 采用自动功率控制系统

  • 选用无三阶互调信道组

PreviousMobile communication network structureNextGSM

Last updated 6 years ago

Was this helpful?