This document describes the log-periodic antenna, which is a multi-element directional antenna designed to operate over a wide range of frequencies. It consists of a series of dipole elements of varying lengths positioned along a support boom. Due to the different lengths of the dipole elements, each radiates best at a different frequency, allowing the antenna to operate over a wide bandwidth. The log-periodic antenna has constant characteristics like radiation resistance and gain across its operating frequency range. Common types include the log-periodic dipole array and slot log-periodic antenna. Applications include HF communications, TV reception, and monitoring across various frequency bands.

1. LOG-PERIODIC ANTENNA
BY :
H.P ANUSH
1560547
6BTEC

2. CONTENTS
• INTRODUCTION
• LPDA
• STRUCTURE OF LP ANTENNA
• WORKING OF LP ANTENNA
• RADIATION PATTERN
• POINT OF EXCITATION
• TYPES OF LP ANTENNA
• ADVANTAGES & DISADVANTAGES
• APPLICATION
• CONCLUSION

3. INTRODUCTION
• A log-periodic antenna (LP), also known as a log-periodic array or log-periodic aerial, is a multi-element,
directional antenna designed to operate over a wide band of frequencies.
• It was invented by Dwight Isbell and Raymond DuHamel at the University of Illinois in 1958.
• It is a broadband, multi-element, unidirectional, narrow-beam antenna.

4. LPDA (Log – Periodic Dipole Array )
• The most common form of log-periodic antenna is the log-periodic dipole array or LPDA.
• The LPDA normally consists of a series of dipoles known as "elements" positioned along a support boom lying
along the antenna axis
• LPDA antennas look somewhat similar to Yagi antennas, in that they both consist of dipole rod elements mounted
in a line along a support boom.
• Both LPDA & Yagi Antenna work in a different manner.

5. STRUCTURE OF LP ANTENNA
• Log periodic antenna has an array of dipole which has their length according to logarithmic scale.
• The elements at the back of the array where the elements are the largest is a half wavelength at lowest
frequency of operation.
• It is basically a wideband antenna due to the presence of many dipole elements which are of different length,
radiating in a different frequency.

7. WORKING OF LP ANTENNA
• The construction and operation of a log-periodic antenna is similar to that of a Yagi-Uda antenna.
• The major difference with this antenna when compared to other antenna’s is that it exhibits
constant characteristics over a desired frequency range of operation.
• It has the same radiation resistance and therefore the same SWR. The gain and front-to-back ratio
are also the same.

8. RADIATION PATTERN
• From the Radiation pattern one can say that it has less directivity than compared to other antennas like Yagi-uda.
• But we can obtain wide frequency response than any other antenna‘.
• Here the radiation pattern is shown at 2GHz frequency.

9. RADIATION PATTERN @ 2 GHZ

10. POINT OF EXCITATION
• The single element is provided excitation via these cross connection lines.
• Here in the example taken only one element has provided excitation and other element has no separate
excitation.
• By varying the point of excitation we can change the radiation pattern of log periodic antenna.

11. TYPES OF LP ANTENNA
• There are several forms of log periodic antenna. The exact type that is most applicable for any given application
will depend upon the requirements.
• The main types of log periodic antenna include:
• Log periodic dipole array, LPDA
• Slot log periodic
• Zig zag log periodic array
• Trapezoidal log periodic
• V log periodic

12. ADVANTAGES & DISADVANTAGES
ADVANTAGES
• The antenna design is compact.
• Gain and radiation pattern are varied according to the requirements.
DISADVANTAGES
• External mount.
• Installation cost is high.

13. APPLICATIONS
• Used for HF communications.
• Used for particular sort of TV receptions.
• Used for all round monitoring in higher frequency bands.

14. THANK YOU