1. 7e Applied EM by Ulaby and Ravaioli
2. Transmission Lines
7e Applied EM by Ulaby and Ravaioli

2. Types of Transmission Lines

3. Transmission Lines = Roads for Wave
A transmission line connects a generator to a load
Transmission lines include:
Two parallel wires
Coaxial cable
Microstrip line
Optical fiber
Waveguide
etc.

4. Dispersion (분산 = 주파수에 따른 불균일 특성) 분산이 크면 신호왜곡 증가 Distortion (신호왜곡)

5. Modes in Transmission Line Mode: 전기장의 분포형태
- TEM (transverse electromagnetic) mode: Ez = 0, Hz = 0, # of conductors > 1
fc = 0 (차단 주파수)
- Quasi-TEM: TEM with mixed dielectric, fc (cutoff frequency) = 0
- TE (transverse electric) mode: Ez = 0, fc > 0
- TM (transverse magnetic) mode: Hz = 0, fc > 0
- Hybrid mode: TE+TM, fc > 0

6. Electric and Magnetic Fields in A Transmission Line
- 전송선에는 전기장 파동, 자기장 파동이 진행
- 회로이론 적용을 위해 전송선의 전압, 전류 개념 사용
Voltage and Current: obtained from E and H

7. Transmission Line Circuit Model

8. Transmission Line Parameters: R, L, G, C
R', G', C' from electrostabics; L' from magnetostatics
Expressions will be derived in later chapters

9. Transmission-Line Equations
ac signals: use phasors
Telegrapher’s equations

11. Phase constant
complex propagation constant
attenuation constant
(전파상수)
(감쇠정수)
(위상정수)

12. (특성임피던스)

13. Example 2-1: Air Line

14. Lossless Transmission Line
Lossless Line:
Lossless TEM Line:

15. Low-Loss Transmission Lines

16. Distortionless Transmission Line

17. |H(w)| = K and (w) = -w = -2fτ
These are plotted in the following figure.
|H(w)|
(w) K w w
-wτ
Amplitude response
Phase response
A physical transmission system may have amplitude and
phase responses such as those shown below:
(w)
|H(w)| w w

18. Distortionless Transmission Line: Heaviside Condition

19. Reflected Wave In general:
wave along +z because coefficients of t and z have opposite signs
wave along –z because coefficients of t and z have the same sign

20. Microstrip Line - A Quasi-TEM line
Quasi-TEM : Ez & Hz very small
Phase velocity in dielectric:
Phase velocity for microstrip:

21. Microstrip (cont.)
s = w/h

22. Coaxial Transmissioni Line (TEM Line)

23. Skin Depth (AC Resistance)
Table: Copper (Cu) skin depth