log periodic antenna
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Designing of 200MHz to 1000MHz Log Periodic Antenna
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MUHAMMAD ILYAS SAEED-UR-RAHMAN SAJID ALI TUFAIL AHMED
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Engr. Sardar Ali
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Antenna Introduction Log periodic Antenna Parameters of LP Antenna Calculations of our Antenna Construction of LP Antenna Advantages of LP Antenna Applications
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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
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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.
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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).
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l : Length of elements(l),L: Length of antenna(L),d: Spacing b/w the elements,C: Coaxial feed line,
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Bandwidth
Directivity
Gain
Polarization
Impedance
LPA ParametersLPA Parameters
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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.
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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).
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Radiation Pattern: Radiation pattern shows us that how an
Antenna transmit and receive EM energy in different directions.
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There are two types of LP Antenna.
LPDA Straight type
LPDA Vee type
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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.
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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
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Distance b/w two consective elements D1=0.09λ Di+1=0.7Di
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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
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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.