Inductively Loaded Shorted Patch Antenna With Reduced Size M. S. Ruiz Palacios, M. J. Martinez Silva Universidad de Guadalajara, Jalisco, México Abstract— A shorted patch antenna with inductive loading for size reduction is presented. To improve input matching characteristics, a small inverted L antenna is appended at the shorted side of the patch. The transmission line model of the structure is used for predicting input impedance of the antenna. A design example is carried out for the 2.4 GHz ISM band. Calculated S11 parameter is compared and agrees well with simulation results. A near omnidirectional radiation pattern is obtained with a gain of 1.26dBi. An area reduction of approximately 80% was obtained respect to the rectangular patch antenna. I-INTRODUCTION Antenna size is of main concern for many wireless applications. Many techniques have been used for size reduction of patch antennas A technique of inductively loading is applied to a shorted air dielectric patch antenna. In order to improve input matching characteristics, a small inverted L wire antenna is appended to the short circuit side of the patch. A transmission line model is used in the development of this antenna. A design example for the 2.4 GHz ISM band is presented. II. ANTENNA DEVELOPMENT The geometry of the proposed antenna is shown in figure 1. This is obtained from the basic half wavelength rectangular patch antenna when we: a) Apply a short circuit along the middle of the length of the basic patch; b) Reduce the width of the patch by half; c) Introduce notches between the feed point and the radiating edge of the patch (this leads to a smaller distance between this two points); d) Introduce a notch next to the feed point on the shorted side of the patch and connect an inverted L antenna next to the notch, this produces an impedance frequency dependence that is useful to get resonance from the patch. Fig. 1. Inductively loading shorted patch antenna with an inverted L antenna. A. Transmission Line Model The transmission line model of the antenna in fig. 1 is presented in fig. 2. Input Impedance is given by Fig. 2. Impedance performance. B. Notch inductance A notch on a microstrip is considered a discontinuity, and produces an equivalent series inductance than can be calculated using C. Inverted L Antenna In order to obtain better performance of input impedance of the patch, an inverted L antenna is appended to the patch. This adds flexibility in the selection of other parameters of the antenna and acts as an additional radiator. III. A 2.4 GHZ ANTENNA DESIGN AND SIMULATION Using dimension shown in table 1 on an electromagnetic simulator, and after an optimization procedure to adjust central frequency and minimum reflection coefficient following changes were obtained: W S =30mm, b 1 =7mm, b 2 =7mm, c=8.75 and d=16.3mm. Simulation results are shown in fig. 5 and 6. As a design example, in this section an antenna for 2.4 GHz (ISM) band is calculated, based on the transmission line model. Dimensions obtained are shown in table 1, and impedance performance of each reference plane is shown in fig. 3. V. CONCLUSION In this work a small antenna with omnidirectional pattern characteristics at a frequency of 2.4GHz was developed. It was proved that the transmission line model can be adapted to new design problems; for example, in this work a wire antenna is appended to a patch antenna. This facilitates adjusting antenna parameters. The results were satisfactory and it is attractive to use this technique in the design of broadband or multi-band antennas. Fig. 2. Transmission line model of proposed antenna. Table 1. Dimensions of the antenna. Fig. 5. magnitude of S11 (simulation-optimized) Fig. 6. 3D pattern (simulation) Construction and Measurements The antenna was constructed and input impedance was measured as shown in the figures REFERENCES [1] S Pinhas and S. Shtrikman, “Comparison between computed and measured bandwidth of quarter-wave microstrip radiators,” IEEE trans. Antennas Propagat, Vol. 36, November 1988, pp [2] V. Zachou, G. Mayridis, C. G. Christodoulou and M. T. Chryssomallis, “Transmission Line Model Design Formula for Microstrip Antennas with Slots,” Proceedings of the Antennas and Propagation Society International Symposium, IEEE Page(s): Vol.4 [3] RongLin Li, G. DeJean, M. M. Tentzeris and J. Laskar, “Development and Analysis of a Folded Shorted-Patch Antenna With Reduced Size,” IEEE Trans. Antennas Propagat, Vol. 52, No. 2, February [4] A. Holub and M. Polivka, “A Novel Microstrip Patch Antenna Miniaturization Technique: A Meanderly Folded Shorted-Patch Antenna,” Proceedings of the 14th Conference on Microwave Techniques, 2008, Page(s):1 - 4 [5] C. A. Balanis, “Antenna Theory, Analysis and Design,” (3rd Edition), Wiley-Interscience, Cap. 11 [6] K.C. Gupta, Ramesh Garg and Rakesh Chadha, Computer-Aided Design of Microwave Circuits, Artech House, 1981, pp [7] A. D. Wunsch and S. P. Hu, “A Closed-Form Expression for the Driving-Point Impedance of the S. M. Metev and V. P. Veiko, Laser Assisted Microtechnology, 2nd ed., R. M. Osgood, Jr., Ed. Berlin, Germany: Springer-Verlag, 1998.