Advantages and Disadvantages of Log Periodic Dipole Antennas

Antennas are of different kinds and work differently according to the radiation pattern, characteristics, and frequency range. Log Periodic antenna is a type of antenna that contains multiple dipoles with various lengths and spaces. It might look like a Yagi antenna but both of them have some differences.

In a log periodic antenna, the dipole elements reduce in size and have different lengths. In this blog, we will discuss the Advantages and Disadvantages of Log Periodic Dipole Antennas in detail with other things.

Construction of Log periodic antenna

 LPDA or log periodic antenna is constructed by using the different half-wave dipole elements with increasing length. It is designed in such a way that the electrical properties will show periodic repetition with frequency logarithm.

In this antenna, the different dipoles of various lengths and spacing are put together. External excitation in an LPDA is given by using the balanced transmission line. This line is exchanged between the different terminals of the dipole.

The structure of a log Periodic antenna is somewhat similar to the Yagi-Uda Antenna containing a half-wave dipole antenna. The different elements of an LPDA are mounted on one line with the help of a support boom. Both these elements operate differently. Adding elements in a log periodic antenna will increase its frequency response or bandwidth.

Advantages of a log periodic antenna

After discussing the definition and construction of an LPDA, we will now look at the major advantages of this antenna. Some of the major benefits of an LPDA are:

1.     Wide bandwidths

One of the major Benefits of Log Periodic Dipole Antennas is the wide bandwidths. These antennas have broader bandwidths than Yagi antennas and work on HF as well as UHF frequencies. Apart from that, the log periodic antennas are also used for EMC measurements when one needs to scan a wide range of frequencies. These antennas have a similar radiation resistance over their range of frequency

2.     Ratio and gain

Log periodic antenna has the same gain and back-to-front ratio with a high forward gain. A gain of 3 to 6 dB gain over a 2:1 bandwidth works in the case of a log periodic antenna. The feed point impedance in an LPDA is constant.

3.     Simple to use

Using an LPDA is very easy as it contains dipole elements of different lengths. Due to its simple design, it is very comfortable to use a log periodic antenna. You can also make various changes in an LPDA due to a simple design. Besides, the changes also leave a very small impact on the electrical characteristics.

4.     Low SWR

LPDA has a low SWR and it is possible to achieve an SWR level in a log periodic antenna. Using a single LPDA can easily replace multiple Yagi antennas as it acts mostly like Yagi antennas.

5.     Multiple applications

You can use a log periodic antenna for various tasks and applications such as HF/UHF/VHF communication and TV reception. It is mostly used in the areas where you need a strong signal. LPDA is available in various shapes and can be used for two-way communication that needs multiple frequencies.

Disadvantages of a log periodic antenna

Like multiple benefits, the log periodic antenna also has many disadvantages such as:

·        Costly antenna

One of the biggest Disadvantages of Log Periodic Antennas is their cost. These antennas are costlier than other kinds of antennas because of their simple design, multiple dipole elements, and use of good materials to make them. This antenna is mostly used in large commercial and residential areas to gain good signals.

·        Low gain

A log periodic antenna has a lower gain than Yagi antennas of the same size. It also has a low gain per unit of weight or wind load. You will need a large log periodic antenna for better VSWR performance. This performance is not gained in a small LPDA.

·        Multiple elements

We discussed in the above section that an LPDA has multiple dipole elements with different lengths. It will not work effectively for lower frequencies in HF and VHF bands without adding the elements. LPDA cannot be used in any omnidirectional applications as it is a kind of Directional Antenna with a low polarization ratio.

·        Needs a strong platform

Mounting a log periodic antenna on any platform is not easy because of the various dipole elements. You will need a good mounting platform for a log periodic antenna as it has many elements.

Major features of a log periodic antenna

Now, let us have a look at some major features of a log periodic antenna in this section:

Ø The structure in a log periodic antenna must radiate to the short element and be negligible to the right direction to get a unidirectional radiation pattern.

Ø In a single active region, the excitation to the LPDA is offered at a shorter length side. On the other hand, the excitation to LPDA in two active regions is offered at the center of the antenna.

Ø The magnitude and phase of the currents in a log periodic antenna must be proper in the active region to get better radiation patterns.

Ø Log periodic antenna provides both bidirectional and unidirectional radiation patterns depending on the log periodic structures.

Ø You will gain a unidirectional radiation pattern in a structure in a single active region.

Ø Two active regions will provide a bidirectional radiation pattern.

Ø The structure of a log periodic antenna is compact and small.

Final words

These are the major Advantages of Log Periodic Antennas with structure, design, features, and certain disadvantages. A log periodic antenna is similar to a Yagi antenna with certain differences as well. It is widely used for the purpose of high-frequency communication.

Log periodic antennas are also used for TV reception as they contain multiple elements that give good directivity. It can work only in the active region. You can get high-quality log periodic antennas today on the official sites of the manufacturer.