Designing of 200MHz to 1000MHz Log Periodic Antenna
MUHAMMAD ILYAS SAEED-UR-RAHMAN SAJID ALI TUFAIL AHMED
Engr. Sardar Ali
Antenna Introduction Log periodic Antenna Parameters of LP Antenna Calculations of our Antenna Construction of LP Antenna Advantages of LP Antenna Applications
An antenna is a conductor capable of transmitting and receiving electromagnetic waves.
As a transmitter ◦ radiates electromagnetic energy into space
As a Receiver ◦ collects electromagnetic energy from space
A transmitting antenna can also be used for reception and vice versa. In two-way communication, the same antenna can be used for transmission and reception.
This property of transmit/receive EM waves is known as antenna reciprocity.
Definition A log-periodic antenna is a broadband, multi-
element, unidirectional antenna, that has impedance and radiation characteristics that are regularly repetitive as a logarithmic function of the excitation frequency.
The individual components are often dipoles, as in a log-periodic dipole array (LPDA).
l : Length of elements(l),L: Length of antenna(L),d: Spacing b/w the elements,C: Coaxial feed line,
Bandwidth
Directivity
Gain
Polarization
Impedance
LPA ParametersLPA Parameters
Bandwidth: The bandwidth of an antenna is the
range of frequencies over which it is effective, usually centered around the resonant frequency.
Directivity: Directivity show us that how well an
antenna Transmit and receive EM waves in particular direction.
Gain: Gain is the comparison of TX and RX Em
waves. Gain of Log Periodic antenna is very high.
Polarization: LP antenna has linear polarization.
Impedance: As the electric wave travels through the
different parts of the antenna system,it may encounter differences in impedance.
SWR: The ratio of maximum power to minimum
power in the wave can be measured and is called the standing wave ratio (SWR).
Radiation Pattern: Radiation pattern shows us that how an
Antenna transmit and receive EM energy in different directions.
There are two types of LP Antenna.
LPDA Straight type
LPDA Vee type
log periodic offers reasonably good gain over an extremely wide range of frequencies.
It is also highly directional.
log-periodic provides a very wide bandwidth as compared to yagi-uda antenna’s.
Frequency range: 200MHz – 1000MHz Design factor: 0.8 Longest element: λ/2=3*10^8/200*10^6=0.75m Limiting Factor: λ/2=3*10^8/1000*10^6=0.15m Length of other element is li+1=*li
Distance b/w two consective elements D1=0.09λ Di+1=0.7Di
Equipments: Aluminium pipe (0.25diameter) accoording
to calculations.
Aluminium wire for connection b/w the elements.
End caps
70Ω Coaxial cable + BNC connector
Wood Boom
ReferencesReferences
Kraus john D, Antennas, second edition
NOWATZKY,D .: Logarithmisch periodische Antennen. Technische Mitteilungendes (http://home.tonline.de/home/Dieter.Nowatzky/doc.htm)
R. L. Carrell, “The Design of Log-Periodic Dipole Antennas,” 1961 IRE International Convention Record, Part 1.
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