COMPACT FREQUENCY-NOTCHED WIDEBAND PLANAR MONOPOLE ANTENNA WITH AN L-SHAPE GROUND PLANE Wang-Sang Lee, Ki-Jin Kim, Dong-Zo Kim, and Jong-Won Yu Department of Electrical Engineering and Computer Science Korea Advanced Institute of Science and Technology (KAIST) 373-1 Guseong-Dong, Yuseong-Gu Taejeon, 305-701, Korea Received 31 January 2005 ABSTRACT: A wideband planar monopole antenna with an L-shape ground plane is presented. The antenna also has a frequency-notching characteristic. By etching a half-wavelength U-shaped slot in the inte- rior of the radiation element, the frequency-notching characteristic has been created. This paper presents the design and experimental results of the proposed antenna. Moreover, the study also investigates the tuning effects of the geometry parameters on the impedance matching. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 340 –343, 2005; Published online in Wiley InterScience (www.interscience.wiley. com). DOI 10.1002/mop.20981 Key words: antennas; planar-monopole antenna; frequency-notched wideband antennas; UWB antennas; L-shape ground plane 1. INTRODUCTION Ultra-wideband antennas are becoming very attractive for future software-defined and reconfigurable wireless systems. Planar monopole and dipole antennas show good promise for use in UWB systems. Despite the FCC’s approval for UWB operation over 3.1 to 10.6 GHz, it may be necessary to notch out portions of the band in order to avoid interference with existing wireless networking technologies such as GPS and wireless LAN systems. As communication devices have become smaller and more compact, due to the greater integration and functionality of elec- tronics and smaller printed-circuit-board configurations, the an- tenna has become a significantly larger part of the overall package volume. Finding space for the antenna without compromising its performance characteristics is increasingly demanding. In this paper, we present a method to achieve frequency- notching characteristics in ultra-wideband planar monopole an- tenna using an L-shape ground plane. The design mainly consists of an ultra-wideband planar monopole antenna and an L-shape ground plane to meet the needs for ultra-wideband operation and antenna-size reduction. Also, both the notch frequency and notch bandwidth can be adjustable by varying the geometry parameters of the etched U-shape slot. 2. ANTENNA DESIGN The configuration of the proposed antenna is shown in Figure 1. The ground plane, which has an inverted L-shape, consists of a horizontal and vertical part. A probe is adopted to excite the antenna in this design. The SMA connector passes through the hole on the center of the horizontal ground plane, and connects with the center of the bottom edge of the monopole. Many new planar monopole-antenna designs for achieving a wideband characteristic, which depend on the antenna size W a  L a , Figure 1 Geometry of the proposed wideband planar monopole antenna with L-shape ground Figure 2 Return losses for the planar antenna with/without vertical ground Figure 3 Simulated and measured VSWR vs. frequency 340 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 46, No. 4, August 20 2005