ece107_set2_nbg

ece107_set2_nbg - ECE 107 Electromagnetism Set 2...

Info iconThis preview shows pages 1–13. Sign up to view the full content.

View Full Document Right Arrow Icon
1 ECE 107: Electromagnetism Set 2: Transmission lines Instructor: Prof. Vitaliy Lomakin Department of Electrical and Computer Engineering University of California, San Diego, CA 92093
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 Outline Transmission Lines for Communications General description Lumped element model Transmission line equations Wave propagation in transmission lines Lossless transmission lines Reflection from loads and standing waves Input impedance and concepts of matching
Background image of page 2
3 General description (1) Electromagnetic Transmission Lines (TLs) are structures or media that transfer energy/ information between two points by means of electromagnetic fields. TL is a two-port network, where each port consists of two terminals
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
4 General description (2) Examples of transmission lines
Background image of page 4
Why 50 Ohms? General description (3)
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
General description (4) l v(t) ~ c As the switch is closed a voltage (and current) pulse moves down the wire. Time to travel length of wire is l /c. If voltage is not varying at this time scale then the system equilibrates such that the wire is at a constant voltage and no current flowing. However if the voltage varies at a frequency comparable to this time then the system is not in equilibrium. Close switch at t = 0 Close the switch attaching the battery to two wires
Background image of page 6
General description (5) Propagating signal can be thought of in terms of fields E and H or voltage V and current I. = 2 1 2 , 1 l d E V C = Q/V + + + + + + + + + + + + - - - - - - - - - - - - electo- statics magneto- statics
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
8 General description (8) How is a TL different from an electric circuit? Consider the following structure: When , i.e. the voltage does not depend on the length of the connecting wires When is not too small , i.e. the voltage depends on the length of the wires! What is low and high frequency regime? Look at ! If low frequency (no delay). If high frequency (large delay). 0 BB AA VV ω ′′ →⇒ = 0 () c o s ( ) t l c V t l c = = 2~ lc l l ωπ λ = ~1 or 1 ll λλ ? 1 l = response delay
Background image of page 8
General description (7) 60 Hz l = 5000 km UCT) TE Data rate 1 GHz (30 cm) Rise times 100 psec l ~ 1 – 30 cm circuit TL circuit TL
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon