Log Periodic Dipole Array Antenna


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LPDA Antenna


Contents


Introduction

Abstract:Simulation of LPDA Antenna using FDTD.
Log period dipole array (LPDA) antennas exhibit relatively uniform input impedances, VSWR, and radiation characteristics over a wide range of frequencies. In essence, log periodic arrays are a group of dipole antennas of varying sizes strung together and fed alternately through a common transmission line. The log periodic antenna works the way one intuitively would expect. Its “active region,” – that portion of the antenna structure which is actually radiating or receiving radiation efficiently – shifts with frequency. The longest element is active at the antenna’s lowest usable frequency where it acts as a half wave dipole. As the frequency shifts upward, the active region shifts forward. The upper frequency limit of the antenna is a function of the shortest elements. The LPDA antenna is fed from a single port that feeds the shortest (highest frequency) half dipole element.


Figure 1: Designed LPDA Antenna

Design Challenges

Accurate simulations of critical antenna design parameters such as gain, radiation patterns, and impedance of the antenna are important for LPDA antenna structures. In this example, a 200 MHz to 1.0 GHz LPDA antenna design is created. Due to the broad bandwidth, FDTD simulation method is preferred, since a single simulation will capture the broadband response.


Figure 2: FDTD Mesh with Conformal Meshing applied on LPDA

Results

Figure 3 shows a steady state E-field plot on the horizontal plane at 500MHz.

Figure 3: Steady state E-field on horizontal plane at 500MHz

Figure 4 shows the LPDA gain for Theta = 90 deg.

Figure 4: Gain vs. Phi at 200MHz, 500MHz and 1GHz

Figure 5 shows the LPDA gain for Phi = 90 deg.

Figure 5: Gain vs. Theta at 200MHz, 500MHz and 1GHz

Conclusion

In this example, the design and simulation of LPDA antenna is demonstrated.

Reference

1. The ARRL Antenna Book, The American Radio Relay League, Newington, CT, 1991.
2. R. H. DuHamel and D. E. Isbell, “Broadband Logarithmically Periodic Antenna Structures,” 1957 IRE National Convention Record, Part 1.
3. R. L. Carrell, “The Design of Log-Periodic Dipole Antennas,” 1961 IRE International Convention Record, Part 1.
4. J. A. Hamadameen, “Analysis, design, and simulation of a Log Periodic Antenna for Mobile Communication bands,” WSEAS Trans. On Communications, Issue 5, Volume 7, 2008
5. J. Salsburg, “The Log Periodic Dipole Array,” self-published, www.salsburg.com
6. Glen Dash, Ampyx LLC, GlenDash@alum.mit.edu, Designing Log Periodic Antennas.

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