Saturday, 1 August 2015

Dipole antenna

Dipole antenna

Dipole antenna used to transmit and receive signals of fixed frequency. Although the usual measurements are used in wideband antenna, but the venue and the measurement antenna attenuation coefficients are required to use a dipole antenna. Dipole antenna in the frequency range 30MHz ~ 4GHz. Which is a set of precise VHAP and UHAP dipole antenna is especially suitable for measuring site attenuation and antenna factor. Meanwhile, the antenna for the Japanese VCCI standards organizations designated only dedicated antenna anechoic chambers and open-field site attenuation measurement and the like. The antenna is used by many laboratories, as antenna standard laboratories.

Vertical antenna is actually a dipole antenna. Dipole antenna consists of two conductors, each 1/4 wavelength, i.e., the total length of a half wavelength of the antenna. So dipole antenna, also called half-wave dipole. The transducer can be a dipole antenna horizontal position, vertical position may be. Its pattern to the feeding point of symmetry. Feed point in the center of the half-wave vibrator. Feed point impedance is purely resistive, approximate 75Ω (approximately 73Ω). If the two 1/4 wavelength resonator extended and then folded back to the center, and joined together, then it became a folded dipole antenna, referred to as folded vibrator.

Folded dipole antenna impedance is purely resistive approximate 300Ω (about 290Ω), shows a high input impedance, high impedance transmission antenna feeder parallel constitute use in many occasions. The dipole antenna straight up, perpendicular to the ground, then a vertical antenna. If the "remove" the lower part of the 1 / 4λ oscillator, the asymmetrically vertical antenna. Common vertical antenna are asymmetric antenna, isotropic in the horizontal direction.
A special.This antenna has a special name called Marconi antenna. R7000 receiver and other antenna configurations belong to this antenna.