Directivity of an antenna embedded inside a Fabry–Perot cavity: Analysis and design

✍ Scribed by H. Boutayeb; K. Mahdjoubi; A.-C. Tarot; T. A. Denidni

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 173 KB
• Volume: 48
• Category: Article
• ISSN: 0895-2477
• DOI: 10.1002/mop.21249

✦ Synopsis

and the values of the feeding line impedances are in the range 140 Ͻ Z 0 (Ohms) Ͻ 400.

Thus, we can improve the input matching by adjusting the antenna's dimensions, but at the expense of the bandwidth. To demonstrate this statement, in Figure 11 we present the values of ͉⌫͉ of the antenna for case 4 with square loops with the parameters L l /L d ϭ 0.225, d 4 /L d ϭ 0.05, and d 5 /L d ϭ 0.02. This antenna has a smaller bandwidth in comparison with the antenna in Figure 10, but its bandwidth (B ϭ 55.6%) is larger then the bandwidth of the antennas presented in [10] (B ϭ 17%), where the authors used combinations of the electric dipoles only.

4. CONCLUSION

In this work, we have presented some preliminary results concerning antennas which are a combination of electric and magnetic dipoles with single feeding that possess an increased bandwidth. The electromagnetic coupling between the orthogonal electric and magnetic dipoles modifies the input impedance of the antenna. Varying the loop antenna's dimensions and their positions with respect to the electric dipole, it is possible to obtain better input matching in comparison with the isolated electric dipole and a combination of the electric dipoles, and consequently, larger bandwidth. These rather simple antennas can theoretically achieve the 80% to 90% bandwidth. Applying some optimization techniques such as the genetic algorithm (for example), we hope to further improve the frequency characteristics of such antennas.