Advantages of Log Periodic Antenna | disadvantages of Log Periodic Antenna
This page covers advantages and disadvantages of Log Periodic Antenna. It mentions Log Periodic Antenna advantages or benefits and Log Periodic Antenna disadvantages or drawbacks. It also describes Log Periodic Antenna basics.
What is Log Periodic Antenna?
The Log periodic antenna consists of array of dipoles having different lengths and spacings. The array is feed from two-wire line which is transposed between each of the dipole pairs. The array is fed from narrower end maximum radiation is achieved as shown in the figure-1.
The following is the mathematical equation which can be used in design of Log periodic antenna.
➨ R1/R2 = R2/R3 = R3/R4 = τ = l1/l2 = l2/l3 = l3/l4
τ is design ratio and it is less than 1.
Two lines drawn to join the opposite ends of dipoles are straight and convergent forming an angle α. Typical values of τ and α are 0.7 and 30 degrees respectively.
Refer Antenna tutorial >> and Log Periodic Antenna basics >>.
LPDA (Log Periodic Dipole Array) antenna is of two types.
• LPDA Straight type
• LPDA Vee type
Benefits or advantages of Log Periodic Antenna
Following are the benefits or advantages of Log Periodic Antenna:
➨The radiation resistance and pattern of the antenna do not depend on frequency.
➨10:1 Bandwidth can be achievable with simple design. The wide bandwidth is great advantage of this antenna compare to YAGI and other antenna types.
➨Low to moderate gains can be obtained.
➨It offers uni-directional and bi-directional radiation patterns. It is highly directional antenna.
➨It can be used for HF/VHF/UHF communication as well as for TV reception.
➨It is available in wide variety of shapes.
➨It is used for two way communication requiring multiple frequencies.
Drawbacks or disadvantages of Log Periodic Antenna
Following are the disadvantages of Log Periodic Antenna:
➨Log periodic antenna requires higher number of elements for lower frequencies in HF/VHF bands.
➨The antenna offers lower gain compare to YAGI antenna having same size.
➨They are not used for omni-directional applications.
➨They have low polarization ratio.
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