The document discusses various types of antennas, including infinitesimal, small, finite length, and half-wavelength dipoles, explaining their characteristics and applications. It covers topics such as current distribution, radiation resistance, directivity, and the effects of surrounding conductors on radiation patterns. Key distinctions are made between the theoretical and practical uses of these antennas in different configurations.

1. Linear Antenna

2. INFINITESIMAL DIPOLE
• (l >>λ)
• symmetrical at the origin
• Oriented along the z - axis

3. INFINITESIMAL DIPOLE
• not practical
• used to represent capacitor
plate antennas
• used as building block for
complex geometries

4. INFINITESIMAL DIPOLE
• (l << λ); (a <<λ)
• I0 is constant.

5. INFINITESIMAL DIPOLE
• Radiatd Fields

6. INFINITESIMAL DIPOLE
• Far-field Region

7. INFINITESIMAL DIPOLE
• Time - Average Radiated Power
and Radiation Resistance
• Directivity and Effective
Aperture

8. SMALL DIPOLE
• λ/50 < l ≤ λ/10
• symmetrical at the origin
• oriented along the z - axis

9. SMALL DIPOLE
• current distribution
- triangular

10. SMALL DIPOLE
• Radiation Resistance

11. SMALL DIPOLE
• Approximatio of Fields

12. FINITE LENGTH DIPOLE
• Length > λ/10
• current
-assuming a very thin wire
-I0 - constant
- ceter fed; current vanishes at end
points

13. FINITE LENGTH DIPOLE
• electric field of a finite lenght
dipole

14. FINITE LENGTH DIPOLE
• Radiatd Fields

15. FINITE LENGTH DIPOLE
• Radiation Resistance and Input
Radiation Resistance
• Directivity and Effective
Aperture

16. HALF - WAVELENGTH DIPOLE
• one of the most commonly used
• radiation resistance - 73 ohms

17. HALF - WAVELENGTH DIPOLE
• electric and magnetic field
component

18. HALF - WAVELENGTH DIPOLE
• Radiation Resistance and Input
Impedance
• Directivity and Effective
Aperture

19. LINEAR ELEMENTS NEAR OR ON INFINITE
PERFECT CONDUCTORS
• antennas radiating into an
unbounded medium
• obstacles introduce alteration of
overall radiation pattern

20. LINEAR ELEMENTS NEAR OR ON INFINITE
PERFECT CONDUCTORS
• Image Theory - virtual sources
for the refletion
• obstacles introduce alteration of
overall radiation pattern

21. LINEAR ELEMENTS NEAR OR ON INFINITE
PERFECT CONDUCTORS

22. LINEAR ELEMENTS NEAR OR ON INFINITE
PERFECT CONDUCTORS

23. LINEAR ELEMENTS NEAR OR ON INFINITE
PERFECT CONDUCTORS

24. LINEAR ELEMENTS NEAR OR ON INFINITE
PERFECT CONDUCTORS

25. LINEAR ELEMENTS NEAR OR ON INFINITE
PERFECT CONDUCTORS

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