Lecture 24 Lecture Notes

Lecture 24 Lecture Notes - 7.5.6.1 Complex Dipole Moment...

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Electric field Outside source area: 7.5.4 Far field (Radiation Zone) Recap: Electric Dipole Radiation Magnetic field 7.5.3 Near field Amplitude of smaller than that of dominates Observations: 1) 2) is basically static dipole field in this approximation (compare Griffith Eqn. 3.104) Scaling: Two independent length scales Source dimension d 1) Multipole expansion requires Second length scale from field distribution 2) Lec 24 - 9. Mar March 08 09 10:54 PM Lecture Notes Page 1

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Observations: 1) and transverse (orthogonal to ) 2) Comparable amplitudes for and . 7.5.5 Definition of radiated power (Griffith 11.1.1) Signature of radiation! sphere of radius r around source radiated power: time average can fall off not more rapidly than to have 7.5.6 Power radiation of oscillating dipole

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Unformatted text preview: 7.5.6.1 Complex Dipole Moment Consider dipole with single frequency for example dipole More generally Total dipole moment: But real In this case vector in complex dipole moment vector in 7.5.6.2 Complex notation for fields Lecture Notes Page 2 Similarly The same replacement strategy holds also for near and far field approximation Note: (for large r) radiation characteristics, for example real => no radiation along dipole axis and 7.5.6.3 Radiated power (far field approximation) Lecture Notes Page 3 7.6.5.4 Radiation characteristics Angular distribution of radiated power: Polar diagram for power distribution: for any direction, length of vector gives radiated power into that direction Lecture Notes Page 4...
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Lecture 24 Lecture Notes - 7.5.6.1 Complex Dipole Moment...

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