WavePropagationandAntenna
TransmissionLines(1/2)
March, 2019
Department of Electrical Engineering
Balochistan UET Khuzdar

Wave Propagation and Antenna
 Transmission Lines
 Transmission line
 A transmission line is a connector which transmits energy from one
point to another.
 The study of transmission line theory is helpful in the effective usage
of power and equipment.
 There are basically four types of transmission lines
 Two-wire parallel transmission lines
 Coaxial lines
 Strip type substrate transmission lines
 Waveguides
 While transmitting or while receiving, the energy transfer has to be
done effectively, without the wastage of power.
 To achieve this, there are certain important parameters
which has to be considered.
2

Wave Propagation and Antenna
 Transmission Lines
 Transmission line
 There are basically four types of transmission lines
 Two-wire parallel transmission lines
 Coaxial lines
 Strip type substrate transmission lines
 Waveguides
3

Wave Propagation and Antenna
 Transmission Lines
 Transmission line
 There are basically four types of transmission lines
 Two-wire parallel transmission lines
 Coaxial lines
 Strip type substrate transmission lines
 Waveguides
4

Wave Propagation and Antenna
 Transmission Lines
 Circuit concepts
• Electric I current is a measure of the charge flow/ movement.
• Voltage V is the difference of electrical potential between two points
of an electrical or electronic circuit.
• Impedance Z = R + jX is a measure of opposition to an electric
current.
5

Wave Propagation and Antenna
 Transmission Lines
 Lumped and Distributed Element Systems
• Lumped element system
• The current and voltage along a transmission line may be considered
unchanged (which normally means the frequency is very low). The
system is called a lumped element system.
• Distributed element system
• The current and voltage along a transmission line are functions of the
distance from the source (which normally means the frequency is
high), thus the system is called a distributed element system.
6

Wave Propagation and Antenna
 Transmission Lines
 Transmission Line Model
7
 If we divide the transmission line into many (almost infinite) short
segments of length ∆𝑧, which is much smaller than the wavelength of int
erest, each segment can then be represented using a set of lumped ele
ments.

Wave Propagation and Antenna
 Transmission Lines
 Transmission Line Model
8
 To make the analysis easier, the equivalent circuit of the segment of the tra
nsmission line is simplified in the below figure, where
R = R1 + R2 and L = L1 + L2.