10. J.L. Lawson, Yagi design, 1982. 11. B.M. Reljic, Analysis of waves propagating along uniform ladder array consisting of metallic cylindrical rods, In: TELFOR Conference Proceedings 2003, Vol. 1, pp. 53-56. 12. Ansoft HFSS, Software and User’s Manual. 13. B. Kolundzija, S. Ognjanovic, T, Sarkard, WIPL-D, Wipl-D Ltd., 2004. 14. B.M. Kolundzija and B.M. Reljic, Plate modeling of wire structures, In: Proceedings of 1997 IEEE International Syposium and URSI North. American Radio Science Meeting, pp. 1789-1793. © 2007 Wiley Periodicals, Inc. WIDEBAND PATCH ANTENNA FED BY PRINTED MEANDERING STRIP Hau-Wah Lai and Kwai-Man Luk Department of Electronic Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong; Corresponding author: hwlai@ee.cityu.edu.hk Received 8 June 2007 ABSTRACT: A printed meandering strip (PMS) is proposed for feeding a patch antenna. It is demonstrated that the impedance matching of the antenna can be further improved by using a higher order PMS. A patch antenna fed by a first order meandering strip has an impedance band- width of 22% [standing wave ratio (SWR)  1.5], cross polarization level of less than 25 dB and a gain of 9 dBi. The measured impedance bandwidths of a second order PMS and a third order PMS are 12% (SWR  1.2) and 8% (SWR  1.1), respectively. They have an aver- age gain of about 9 dBi and cross polarization levels are low in level. All measurements have been confirmed by simulation. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 188 –192, 2008; Published online in Wiley InterScience (www.interscience.wiley. com). DOI 10.1002/mop.23047 Key words: wideband patch antenna; low cross polarization level; probe feed; RFID base station 1. INTRODUCTION Microstrip patch antenna is low profile, has ease of fabrication and low material cost; however, they have narrow impedance band- width. Several wideband feeding techniques [1– 4] have been proposed to widen the impedance bandwidth. They are suitable for modern wireless communication systems. Recently, a new feeding mechanism, named meandering probe, has been proposed to in- crease the impedance bandwidth and suppress the cross polariza- tion of the patch antenna [5]. It has low backlobe radiation and symmetric radiation patterns in the two principle planes [6]. The impedance bandwidth of the meandering probe fed patch antenna can be further enhanced to 37% [standing wave ratio (SWR)  1.5] with the use of stacked parasitic patch structure [7]. It shows that meandering probe is a very good feeding mechanism for patch antenna. This article demonstrated that using higher order meandering probe could further improve the impedance matching of a patch antenna. To simplify the difficult constructing process, the higher order meandering probe is fabricated on a printed circuit board and forming a printed meandering strip (PMS). The proposed higher order PMS fed patch antenna is suitable for a wireless communi- cation system requiring very good matching. One of the typical examples is the RFID reader, which requires the SWR of the antenna less than 1.2. 2. PMS FED PATCH ANTENNA 2.1 Antenna Geometry The geometry of the PMS fed patch antenna (Antenna 1) is shown in Figure 1. The center frequency f c of the antenna is designed at f 0  1.82 GHz ( 0  165 mm). The patch of Antenna 1 is made of a 0.3-mm thick copper patch of width W  70 mm (0.43 0 ) and Parameters W L Hp dL H g h t Values/mm 70 60 16.5 40 16.5 2 12.5 1.5 (0.427λ0) (0.366λ0) (0.101λ0) (0.244λ0) (0.101λ0) (0.122λ0) (0.76λ0) (0.009λ0) Soldering between the PMS the patch Finite Microwave Substrate (εr=4.6) Patch Foam Spacer x z y L W GL GW Finite Ground Plane Connect to SMA Launcher t (a) (b) h g dL L H h g Finite Ground Plane PMS with 2mm width Finite Microwave Substrate SMA launcher Soldering point Patch y z x s1 s2 Finite Ground Plane (c) Soldering point W H PMS with 2mm width Finite Microwave Substrate SMA launcher Patch t x z y K Figure 1 Geometry of PMS fed patch antenna. (a) Perspective view (b) Side view (c) Front view (*All dimensions are shown in mm). [Color figure can be viewed in the online issue, which is available at www. interscience.wiley.com] Figure 2 Simulated and Experimental results of SWR and Gain against frequency of the PMS fed patch antenna. Measured ——— Sim- ulated 188 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 50, No. 1, January 2008 DOI 10.1002/mop