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Lecture Notes

ENGINEERING TRIPOS PART IB

PAPER 5 - ELECTRICAL ENGINEERING (3)

Electromagnetic Fields and Waves

Leader: Prof A. C. Ferrari


Timing: Weeks 6-8 Lent term

Structure: 6 lectures, 2 lectures/week

Handouts:

Handout1;

Handout2;

Handout3;

AIMS

  • Starting from the first year background work of phasors, capacitance and inductance, the aim is to explain why one needs both E and H to describe electromagnetic waves and to show how these waves propagate in free space.

OBJECTIVES

As the frequency of electronic circuits rises, one can no longer assume that voltages and currents are instantly transmitted by a wire. The objectives of this course are that students should be able to:

  • Appreciate when a wave theory is needed.
  • Derive and solve simple transmission line problems
  • Understand the importance of matching to the characteristic impedance of a transmission cable.
  • Understand basic principles of EM waves propagation in free-space, across interfaces and the use of antennae

SYLLABUS

  1. Descriptive introduction of how information is sent along wires and through free space.
  2. A descriptive introduction of propagation along two wires. Capacitance per unit length. Inductance per unit length. Resistance per unit length.
  3. Equations for V and I in differential form. Normalisation to a characteristic impedance.
  4. Solutions - forward and reverse waves - phase velocity and significance of characteristic impedance. Effects of load resistances of the wrong characteristic impedance.
  5. One dimensional wave motion with Maxwell's equations seen as a transmission line analogy with E corresponding to V and H corresponding to I. Implications for transmission in free space and along optical fibres (descriptive only).

REFERENCES

Please see the Booklist for Part IB Courses for references for this module.