Half-Wave Dipole

half-wave dipole [′haf ¦wāv ′dī‚pōl]

(electromagnetism)

dipole antenna

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Half-Wave Dipole 

a radiator of electromagnetic waves that consists of a straight thin conductor or of a slot in the metal wall of a wave guide. The length of the conductor or slot is equal to approximately half the radiator’s operating wavelength. Half-wave dipoles are used, for example, as simple antennas for radio communication and as receiving antennas for television (Figure 1). They are also used as radiating elements of antenna arrays in communication and radar systems.

To the gap in the center of the dipole there is connected a feeder, or transmission line, which is either a balanced line or an unbalanced line with a balancing unit. The feeder connects the

Figure 1. Simple television antenna: (1) half-wave dipole, (2) feeder, (3) support, (λ) operating wavelength; the broken line shows the distribution of the current / along the dipole

dipole to the transmitter or receiver. The radiation pattern of a half-wave dipole is a circle in a plane perpendicular to the axis of the dipole and a symmetrical figure eight in a plane containing the axis. The front-to-rear ratio of a half -wave dipole is 1.64. The radiation resistance is ~ 73 ohms.