J Comput Electron DOI 10.1007/s10825-014-0640-6 Fractal antenna for multi-frequency applications using PIN diode Sumit V. Rakibe · Sonali D. Sahu · S. V. Khobragade © Springer Science+Business Media New York 2014 Abstract This paper presents the design and the analy- sis of a conformal fractal tree reconfigurable antenna having adaptive multi beam radiation patterns and adaptive opera- tion frequency characteristics. The proposed antenna covers some service bands such as: WiMAX (2.400–2.483) GHz, m- WiMAX (3.4–3.6) GHz and WLAN (5.15–5.825) GHz and operates some other frequencies between 2 and 10 GHz. The designed antenna is by using PIN diode switches. For biasing the diodes on the antenna characteristics is presented in the results. Keywords Reconfigurable antenna · Pin Diode · Computer Simulation Technology Microwave Studio Suite 2013 · Fractal Tree antenna 1 Introduction In radar and modern communication systems the demand on multi-functional antennas is increasing. The requirements for these antennas are the abilities to have multi radia- tion patterns, adapting the operation frequency and polar- ization, keeping the physical dimensions and positioning S. V. Rakibe (B)· S. V. Khobragade Department of Electronics and Telecommunication Engineering, Dr. Babasaheb Ambedkar Technological University, Lonere, Raigad, India e-mail: sumit.rakibe@gmail.com S. V. Khobragade e-mail: svkhobragade@dbatu.ac.in S. D. Sahu Department of Electronics and Telecommunication Engineering, MGM’s College of Engineering and Technology, Kamothe, Navi Mumbai, India e-mail: sonali.1108@gmail.com unaltered. Reconfigurable antennas with switching capabil- ity used as a multiple input multiple output (MIMO) sys- tem have been used in recent years to full these require- ments. By means of switches with compatible antenna ele- ments the antenna and its feed structure can be physi- cally reconfigured to provide radiation pattern, frequency band and polarization diversity so they have more advan- tage to compare with conventional antennas [1]. The most prevalent implementation about reconfigurable antenna is related to the operation frequency [2] since it might be the easiest feature to alter. Polarization and pattern recon- figurable antennas are also attractive since they can pro- vide diversity features which leads to an increased sig- nal to noise ratio and therefore a higher quality of ser- vice of whole systems [3–5].PIN diodes are generally used more than transistors and switches as switching devices for RF and microwave front-end communication systems since they have several crucial properties such as low inser- tion loss, good isolation, low power handling and low cost [6]. Although a reconfigurable antenna can take many shapes we will focus on fractal tree antennas in this work. In termi- nology, fractal means broken or irregular fragments which were originally entitled by Mandelbrot [7] to describe a fam- ily of complex shapes that possess an inherent self-similarity in their geometric structure. As a result of small investiga- tion in the environment a lot of example for fractal shapes can be seen as trees, clouds, galaxies, leaves, and much more. Fractal tree structures can be applied into antenna design to produce multiband characteristics [8–10]. Fractal trees studied here are also known as fractal canopies and Pythagoras trees. Although these have several features common with other fractals such as Koch curves, their branching nature offers a significant variation, and is expected to cause some difference in antenna performance. 123