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Why are loop antennas used?
Loop antennas feature simplicity, low cost and versatility. They may have various shapes: circular, triangular, square, elliptical, etc. They are widely used in communication links up to the microwave bands (up to ≈ 3 GHz). They are also used as electromagnetic (EM) field probes in the microwave bands.
What are the field components of loop antenna?
A loop antenna consists of a wire loop of arbitrary shape fed by an input current Iin. A circular loop, as shown in Figure 6.15, is the shape most commonly used. The radius of the loop, R, could be electrically small or large.
What are the advantages of using ferrite loops?
One of the advantages of using a ferrite in the antenna is that it brings the radiation resistance of the overall antenna to a reasonable level. This is of considerable importance in any antenna and hence circuit design. The ferrite rod antenna can be considered as a very small loop antenna.
Which way do I point my antenna loop?
The polarization of the loop antenna will be vertically or horizontally polarized depending upon the feed position. The vertical polarization is given at the center of the vertical side while the horizontal polarization is given at the center of the horizontal side, depending upon the shape of the loop antenna.
How is a loop antenna different from an electrical antenna?
Magnetic vs. electrical antennas. The small loop antenna is known as a magnetic loop since it behaves electrically as a coil (inductor). It couples to the magnetic field of the radio wave in the region near the antenna, in contrast to monopole and dipole antennas which couple to the electric field of the wave.
How does a ferrite loop antenna increase efficiency?
To increase the magnetic field in the loop and thus its efficiency, while greatly reducing size, the coil of wire is often wound around a ferrite rod magnetic core; this is called a ferrite loop antenna.
Where is the feed point for a loop antenna?
The loop antenna feed point does not matter too much – it can be anywhere along the loop perimeter. Note that a balun may be needed, so that the cable that connects the radio (transmitter or receiver) to the loop does not influence the current distribution on the loop antenna.
What kind of loop antennas are used for EMC testing?
Low frequency loop antennas for EMC testing (1 kHz to 30 MHz typically) come in conbinations of active, passive and shielded models with and without built-in preamplifiers. Conduct emissions and immunity testing typical for military standards and more.