This is the summary notes of the important terms and concepts in Chapter 15 of the book "Electronic Communications System" by Wayne Tomasi. The notes are properly synchronized and concise for much better understanding of the book. Make sure to familiarize this review notes to increase the chance of passing the ECE Board Exam.
ANTENNAS AND WAVEGUIDES
A metallic conductor system capable of radiating and capturing
Couples energy from a transmitter to an antenna or from
antenna to a receiver
A special type of transmission line that consists of a
conducting metallic tube through which high-frequency electromagnetic energy
Electrical energy that has escaped into free space in the form
of transverse electromagnetic waves
The plane parallel to the mutually perpendicular lines of the
electric and magnetic fields.
The ratio of radiated to reflected energy.
Antenna wherein two conductors are spread out in a straight
line to a total length of one quarter wavelength.
Quarter Wave Antenna
Another name for quarter wave antenna.
Vertical Monopole or Marconi
A half-wave dipole.
A special coupling device that can be used to direct the
transmit and receive signals and provide the necessary isolation.
A polar diagram or graph representing field strengths or power
densities at various angular positions relative to an antenna.
Radiation pattern plotted in terms of electric field strength
or power density.
Absolute Radiation Pattern
Radiation pattern plots field strength or power density with
respect to the value at a reference
The primary beam of an antenna.
The major lobes that propagates and receive the most energy.
Lobes adjacent to the front lobe.
The secondary beam of an antenna.
Lobes in a direction exactly opposite the front lobe
The ratio of the front lobe power to the back lobe power.
Front to Back Ratio
The ratio of the front lobe to a side lobe.
Front to Side Ratio
The line bisecting the major lobe, or pointing from the center
of the antenna in the direction of maximum radiation.
Line of Shoot or Point of Shoot
Antenna that radiates energy equally in all directions.
Radiates power at a constant rate uniformly in all directions.
The direction in which an antenna is always pointing.
It is defined as an equivalent transmits power. It stands for
Effective Isotropic Radiated Power.
The equivalent power that an isotropic antenna would have to
radiate to achieve the same power density in the chosen direction at a given
point as another antenna.
Effective Radiated Power
(ERP) or (EIRP)
The power density in space and the actual power that a receive
antenna produces at its output terminals.
Captured Power Density
It describe the reception properties of an antenna
Another name for capture area.
The relationship of captured power to the received power
density and the effective capture area of the received antenna.
It refers to the orientation of the electric field radiated
from the antenna.
The angular separation between the two half-power (-3dB)
points on the major lobe of an antenna’s plane radiation pattern.
The frequency range over which antenna operation is
Another name for antenna input terminal
The feedpoint presents an ac load to the transmission line.
Antenna Input Impedance
The simplest type of antenna.
Another names for elementary doublet
Ø Short Dipole,
Ø Elementary Dipole
Any dipole that is less than one-tenth wavelength
Hertz antenna is name after him and he was the first to
demonstrate the existence of electromagnetic waves.
A single pole antenna one quarter wavelength long, mounted
vertically with the lower end either connected directly to ground or grounded
through the antenna coupling network.
Main disadvantage of Marconi Antenna.
Must be close to the Ground
A technique use to increase the electrical length of an
A coil added in series with a dipole antenna which effectively
increases antenna’s electrical length.
A loading coil approximately increases the radiation
resistance of the antenna.
An individual radiator, such as a half or quarter wave dipole.
Two types of antenna elements
Two Elements of a single antenna
Its purpose is to increase the directivity and concentrate the
radiated power within a smaller geographic area.
Elements that are directly connected to the transmission line
and receive power from the source.
Elements are not connected to the transmission line; they
receive energy only through mutual induction with a driven element.
A parasitic element that is shorter that its associated driven
Radiation pattern depends on the relative phase of feeds.
The simplest type of antenna arrays.
A widely used antenna commonly uses a folded dipole as the
driven element and named after two Japanese scientists.
Typical directivity of a yagi-uda antenna.
7 dB and 9 dB
Formed by placing two dipoles at right angles to each other.
A class of frequency-independent antennas.
A broadband VHF or UHF antenna that is ideally suited for
applications for which radiating circular rather than horizontal or vertical
polarized electromagnetic waves are required.
Modes of propagation:
Antennas having half power beamwidths on the order of 1º or
Three important characteristics:
Ø Front-to Back Ratio,
Ø Side-to-Side Coupling
Antenna that provides extremely high gain and directivity and
are very popular for microwave and satellite communications link.
Two main part
Ø Parabolic Reflector
Ø Feed Mechanism
Parabolic Reflector Antenna
The effective area in a receiving parabolic antenna and is
always less than the actual mouth area.