Dream Catcher ME1310 Руководство - Страница 3
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1.
Introduction
An antenna radiation pattern is a representation of the field strength or power intensity versus the
antenna orientation angle. For a receiving antenna, the antenna radiation pattern shows the received
signal level at various directions (angles). Similarly, for a transmitting antenna, the antenna radiation
pattern shows its field strength at various directions at a constant distance. The antenna radiation pattern
of most antennas is valid when receiving and transmitting.
An antenna radiation pattern may consist of several lobes. Most of the power is concentrated in the main
lobe. The 3-dB beamwidth is the angle between two points, which are 3 dB lower than the main lobe
maximum. Figure 1 illustrates the radiation pattern lobes together with different power points and
beamwidth.
Figure 1 – Radiation pattern lobes
The antenna radiation pattern is usually shown in two planes. For a dipole antenna, its H-plane antenna
radiation pattern will be plotted if both antennas are placed vertically, while its E-plane antenna radiation
pattern will be plotted if both antennas are placed horizontally. The E-plane radiation pattern is defined as
"the plane containing the electric field vector and the direction of maximum radiation", and the H-plane
radiation pattern is defined as "the plane containing the magnetic field vector and the direction of
maximum radiation".
With advancement of mobile telecommunication technology, it is crucial to measure the radiation pattern
of an antenna in full spherical format, or also known as 3D radiation pattern. Typically, antenna
manufacturers do not provide 3D radiation pattern but only in H-planes and E-planes radiation patterns.
This will not create any issue if the antenna is used for large macro cells or long-distance communication.
However, as microcells or picocells deployments are getting more and more common for indoor mobile
communication, the knowledge of antenna radiation field strength for the angles in between H-plane and
E-plane has become an imperative requirement. For path loss measurement and antenna efficiency
measurement, it is essential to measure and build a 3D radiation pattern.
ME1310 Antenna and
Lab 1 - 3/18
Propagation (3D)