Reviewer b) Secondary Electrical Constants of

Transmission Line (Characteristic

Type of transmission line Impedance, Propagation Constant)
Wired transmission line ANTENNA
Wireless transmission line
antenna is a mettalic conductor system
Transmission line- metallic conductor capable of radiating and capturing
system used to transfer electrical energy from electromagnetic energy.
one point to another point using electric Transmit end: "Converts electrical energy to
current flow. electromagnetic waves."
GUIDED - are those with some form of Receive end: "Captures electromagnetic
conductor that provides a conduit in which waves and converts them into electrical
electromagnetic signals are contained.
energy."
UNGUIDED - are those wireless systems. The WAVEGUIDE
signal of it are emitted then radiated through
air or a vacuum - metallic conductor system used to
transfer electrical energy from one
Standing Waves point to another point using electric
combination of two waves moving in opposite current flow.
directions, each having the same amplitude RADIOWAVES
and frequency.
- metallic conductor system used to
2 types of standing waves
transfer electrical energy from one
Matched Line. All the incident power is point to another point using electric
absorbed by the load. current flow.

Unmatched or mismatched Line. some of the Basic Antenna

incident power is absorbed by the load, and - passive reciprocal device that it
some is returned to the source. cannot actually amplify a signal, at
Traveling Waves least not in the true sense of the word;
transmit and receive characteristics
Incident Wave - the wave traveling from the and performance are identical (i.e.,
source to the load gain, directivity, frequency of
Reflected Wave - The wave that bounces back operation, bandwidth.
from the load toward the source.
Characteristics of a Transmission Line a) Transmit antenna
a) Electrical Properties (wire conductivity & - must be capable of handling high
insulator dielectric constant) powers
b) Physical Properties (wire diameter & - constructed with materials that can
conductor spacing) withstand high voltages and currents,
such as metal tubing
Primary Electrical Constants of Transmission
Line (Distributed Parameters - R, L, C, G b) Receive antenna
- produce very small voltages and currents
- constructed from small-diameter wire - ratio of the power radiated by an antenna to
the sum of the power radiated and the power
Diplexer dissipated, or the ratioof the power radiated
- a special coupling device used to direct the by the antenna to the total input power.

transmit and receive signals and provide the N= Prad/Pin x100

necessary isolation. Directive gain

- is the ratio of the power density
radiated in a particular direction to
- Standard antennas have no active thepower density radiated to the
components (diodes, transistors, same point by a reference antenna,
FETs, and so on); therefore, they are assuming both antennasare radiating
passive and reciprocal. the same amount of power.
antenna coordinate system Power gain
- is a spherical coordinate system used - is the same as directive gain except
todescribe the directional thatthe total power fed to the antenna
characteristics of electromagnetic is used (i.e., antenna efficiency is
waves radiated or received by an taken into account). It is assumed
antenna. that the given antenna
Near and Far Fields and the reference antenna have the
same input power and that the
reference antenna is loss¬
less (T) = 100%).
Near Fields
Effective isotropic radiatedpower (EIRP) is
▪ refers to the field pattern that is close to the
defined as an equivalent transmit power
antenna
ERP (effective radiated power)
▪ sometimes called as induction field
- is the equivalent power that
Far field
anisotropic antenna would have to
▪ refers to the field pattern that is at great radiate to achieve the same power
distance density in the chosen di¬rection at a
given point as another antenna.
▪ Sometimes called as radiation field
capture area of an antenna
Radiation resistance
- is an effective area and can be
- is somewhat “unreal” in thatit cannot described as follows.A transmit
be measured directly. Radi¬ation antenna radiates an electromagnetic
resistance is an ac antenna wave that has a power density at the
resistance and is equal to the ratio receive antenna’s location in W/m2.
ofthe power radiated by theantenna to
the square ofthe current at its A receiving antenna exposed to the
feedpoint. electromagnetic field will have radio-
frequency voltage and current induced in it,
Antenna Efficiency producing a corresponding radio-frequency
- power at the antenna’s output terminals. In
principle, the power available at the
antenna’s output terminals (in watts) is the
captured power. BALANCED TRANSMISSION WIRE
- Balanced transmission lines use two
Conductors carrying equal and
polarization of an antenna opposite
Currents, forming a differential signal.
- refers simply to the orientation of the The
electric field radiatedfrom it. An Signal is measured as the potential
antenna may be linearly (generally Difference between the wires.
either horizontally or vertically
polarized, as¬suming thatthe antenna UNBALANCED TRANSMISSION LINES
elements lie in a horizontal or vertical
- Use single-ended signal transmission,
plane), elliptically, or
circularlypolarized. where one wire carries the signal
while the other is grounded.
Antenna beamwidth
A BALUN
- is simply the angular separation
between the two half-power ( — 3 - (Balanced to unbalanced) is a device used
dB)points on the major lobe of an to connect a balanced transmission line to an
antenna’s plane radiation pattern, unbalanced load or viceVersa.
usually taken in one of the“principal” Transmission line losses
planes.
- This refer to the energy dissipated as
Antenna bandwidth electricity travels from generation
- is vaguely defined as the frequency sources to consumers, primarily due
range over which antenna operation is to the resistance of conductors, and
“satisfactory.” Bandwidth is normally can range from 5-10% over long
taken as the difference between the distances if not mitigated.
half-powerfrequencies (difference
between the highest and lowest
frequencies of operation) but
sometimes refers to variations in the
antenna’s input impedance.
Antenna input impedance
- is simply the ratio of the antenna’s
input voltage to input current.
The elementary doublet
- is an electrically short dipole and is
often referred to simply as a short
dipole, elementary dipole, or Hertzian
dipole.