Log-Periodic Antenna


A Log-Periodic Antenna is a type of directional antenna commonly used in wireless communications which features a particular design to achieve a very wide bandwidth. Its design consists of multiple elements gradually increasing or decreasing in size in a logarithmic manner, positioned along a longitudinal axis. This unique structure allows it to have gain and directivity across a wide range of frequency bands.


The phonetic pronunciation would be: “Lahg-Peer-ee-ah-dik An-ten-uh”

Key Takeaways

Sure, here are three main takeaways about Log-Periodic Antenna:“`html

  1. The Log-Periodic Antenna is a multi-element, directional, antenna designed to operate over a wide band of frequencies. It displays an operational pattern that repeats over a logarithmic scale, hence its name.
  2. One of the main features of a Log-Periodic Antenna is its frequency independent behavior. This means the antenna’s impedance and radiation characteristics remain constant across its operational frequency range. This feature makes it suitable for broadband applications in various fields like communications and radio and television broadcasting.
  3. Log-Periodic Antennas usually exhibit a bidirectional radiation pattern, i.e., they transmit and receive power in two opposite directions with equal strength. However, they can be made unidirectional by placing a reflective screen behind the antenna.



The term “Log-Periodic Antenna” is important in technology, mostly in communication fields, due to the antenna’s unique ability to operate over a wide range of frequencies. This is highly beneficial in various applications that require frequent adjustment or wide coverage of frequencies, such as television and radio broadcasting, frequency scanning, and spectrum management. Unlike other types of antennas that are efficient at a specific frequency, the Log-Periodic Antenna ensures consistent performance across the entire desired frequency band and this makes it an efficient, versatile and valuable communication tool. Its design concept also proves to be remarkably useful in dealing with electromagnetic compatibility and interference assessments.


A log-periodic antenna, in the realm of radio broadcasting and communication systems, serves a crucial function. It is fundamentally employed for transmitting and receiving signals over a broad range of frequencies. This extensive frequency spectrum makes it particularly suitable for various applications that require consistent performance across diverse frequencies, such as television broadcasting, frequency scanning systems, and advanced telecommunications. It’s a multi-element, directional, narrow-beam antenna that’s capable of delivering or picking up signals in a specific direction, minimizing unwanted interferences from other directions and enhancing signal strength.The primary purpose of log-periodic antennas is to provide an inherently frequency-independent antenna, essentially meaning that the antenna gain, radiation pattern, and impedance are preserved within the overall frequency range of the antenna. This makes it a preferred solution in radio communications, acting as a ‘one-size-fits-all’ antenna solution for various applications. Specifically, these antennas are extensively used in wide-band communications, both in research facilities or for commercial use, including ham radio, broadband internet, and also in radar and surveillance systems where wide bandwidth, reliable gain, and consistent beam direction are crucial.


1. TV reception: A log-periodic antenna is commonly used for TV reception. It’s a type of directional antenna that allows TV reception to pick up signals from a specific direction, filtering out unwanted signals from other directions. This type of antenna can deliver high-quality pictures even from long distances.2. Communication Satellites: Many satellite communication systems use log-periodic antennas. These antennas are designed to work within a wide range of frequency bands, which make them ideal for communication satellites that need to transmit and receive signals in various frequency bands. 3. Radio Stations: In the broadcasting industry, log-periodic antennas are used at AM/FM radio stations. These antennas are perfect for these applications because of their wideband capabilities and directional properties which helps to broadcast the signal to a larger target area.

Frequently Asked Questions(FAQ)

**Q1: What is a Log-Periodic Antenna?**A: A Log-Periodic Antenna is a type of directive antenna developed for a wide frequency band, where its radiation characteristics such as input impedance and gain repeat periodically as the logarithm of the frequency.**Q2: How does a Log-Periodic Antenna work?**A: Log-Periodic Antennas work on the principle of a logarithmically-spaced frequency that aids in receiving a much wider bandwidth. They achieve this by forming an array of dipole elements of varying lengths.**Q3: What are the advantages of using a Log-Periodic Antenna?**A: Log-Periodic Antennas are flexible, meaning they can operate over a broad frequency band. They also have a consistent radiation and impedance pattern over their frequency range.**Q4: Are there any disadvantages to using a Log-Periodic Antenna?**A: Yes, one disadvantage is they can be larger than other types of antennas. They also can have a lower gain compared to other high gain antennas within their frequency range.**Q5: Where are Log-Periodic Antennas typically used?**A: They are often used in scenarios where a wide range of frequencies is essential. This includes telecommunication infrastructure, radios, and the field of research like radio astronomy.**Q6: What is the design principle of a Log-Periodic Antenna?**A: The design of a Log-Periodic Antenna is based on a logarithmically scaled sequence of radiating elements. This allows the antenna to perform consistently in a wide range of frequencies.**Q7: Can Log-Periodic Antennas be used for transmitting and receiving?**A: Yes, Log-Periodic Antennas are bi-directional, meaning they can serve as both a transmitting and receiving antenna. **Q8: How does the periodicity of a Log-Periodic Antenna affect its performance?**A: The periodicity of the antenna’s elements contributes to its frequency independent performance. Consequently, its electrical properties repeat periodically as the logarithm of the frequency.**Q9: What are the typical elements of a Log-Periodic Antenna?**A: A Log-Periodic Antenna generally consists of a series of half-wave dipole elements arranged along its axis, a feedline, and a support structure to hold these components.**Q10: How do you determine the size of a Log-Periodic Antenna?**A: The size of the antenna is generally determined by the range of frequencies it needs to cover. Lower frequencies require longer elements and hence cause the antenna to be bigger.

Related Tech Terms

  • Directional Radiation Pattern
  • Frequency Bandwidth
  • Feeding Network
  • Antenna Gain
  • Dipole Elements

Sources for More Information

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