Electromagnetic wave, spectrum, & antenna basics

Antenna feed impedance

Antenna feed impedance When a signal source is applied to an RF antenna at its feed point, it is found that it presents a load impedance to the source. This is known as the antenna "feed impedance" and it is a complex impedance made up from resistance, capacitance and inductance. In order to ensure the optimum efficiency for any RF antenna design it is necessary to maximise the transfer of energy by matching the feed impedance of Read More


Antenna directivity and gain

Antenna directivity and gain RF antennas or aerials do not radiate equally in all directions. It is found that any realisable RF antenna design will radiate more in some directions than others. The actual pattern is dependent upon the type of antenna design, its size, the environment and a variety of other factors. This directional pattern can be used to ensure that the power radiated is focussed in the desired directions. It is normal Read More


Antenna polarization

Antenna polarization Polarisation is an important factor for RF antennas and radio communications in general. Both RF antennas and electromagnetic waves are said to have a polarization. For the electromagnetic wave the polarization is effectively the plane in which the electric wave vibrates. This is important when looking at antennas because they are sensitive to polarisation, and generally only receive or transmit a signal with a par Read More


Antenna Resonance & Bandwidth

Antenna Resonance & Bandwidth Two major factors associated with radio antenna design are the antenna resonant point or centre operating frequency and the antenna bandwidth or the frequency range over which the antenna design can operate. These two factors are naturally very important features of any antenna design and as such they are mentioned in specifications for particular RF ntennas. Whether the RF antenna is used for broadcasting Read More


Antenna Basics and Electromagnetic Waves

Antenna Basics  and  Electromagnetic Waves Radio signals are a form of electromagnetic wave, and as they are the way in which radio signals travel, they have a major bearing on RF antennas themselves and RF antenna design. Electromagnetic waves are the same type of radiation as light, ultra-violet and infra red rays, differing from them in their wavelength and frequency. Electromagnetic waves have both electric and magnetic c Read More





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