A tunable dual-band miniaturized monopole antenna

Summary form only given. The rapid growth of the market for wireless communication devices demands more flexibility in coordinating different wireless standards and devices while maintaining a small device profile. This has produced a need for compact antennas with frequency tunability across multiple operating bands. Many techniques have been developed to produce miniaturized antennas, including the use of slots and high-permittivity dielectrics. At the same time, techniques for producing tunable multi-band antennas have been devised. These include the loading of a multi-resonance structure, such as a multi-branch monopole or a planar inverted F antenna, with varactor diodes. However, such tuning techniques typically result in limited size reduction or increased manufacturing complexity. In this paper, a technique of producing miniaturized, tunable, planar monopole antennas is presented. Miniaturization of the antenna is achieved by optimizing the geometry of a pixelated metallic patch surrounding a monopole antenna through a genetic algorithm. Full wave simulations using HFSS have been employed to demonstrate that tuning of the miniaturized antenna can be achieved by varying the capacitance of an appropriate varactor diode placed at a proper location. As a result, an ultra-compact monopole antenna that fits into hemisphere of 5.3 mm radius, which is equivalent of λ /22 at 2.1 GHz, is realized. A prototype antenna with integrated DC bias has been fabricated and measured to demonstrate the feasibility of the proposed design. It is seen that by varying the capacitance of the varactor diode, two resonance frequencies can be continuously tuned simultaneously. The tuning range of the antenna covers multiple frequency bands for WLAN and WiMAX, which makes it suitable for wireless applications. The radiation patterns and efficiency of the antenna will be measured and validated through simulations.