the TSNU-PSTD uses only 35.6% of the computational space of its corresponding uniform version. For a more complicated geometry, the TSNU-PSTD may save more computational memory and time in comparison with the conventional PSTD. 4. CONCLUSIONS In this study, we have investigated the polynomial and cubic spline interpolations for an evaluation of the space transformation factors du/dx, dv/dy, and dw/dz, and applied the algorithms in to a wave propagation problem and a scattering analyses. We find that both the polynomial approach at degrees 2 through 4 and the cubic spline interpolation method yield results at a similar level of accuracy. Our simulations also confirm that computation errors occur for higher degree polynomial cases. ACKNOWLEDGMENT This work was partially sponsored by the SCCC under Grant 18300 KA04. REFERENCES 1. Q.H. Liu, The PSTD algorithm: A time-domain method requiring only two cells per wavelength, Microwave Opt Technol Lett 15 (1997), 158 –165. 2. Q.H. Liu, Large-scale simulation of electromagnetic and acoustic measurements using the pseudospectral time-domain (PSTD) algo- rithm, IEEE Trans GRS 17 (1999), 917–926. 3. G.-X. Fan, Q.H. Liu, and J.S. Hesthaven, Multidomain pseudospectral time-domain simulations of scattering by objects buried in lossy me- dia, IEEE Trans GRS 40 (2002), 1366 –1373. 4. Q.H. Liu, G.-X. Fan, G. Zhao, and Y. Zeng, The PSTD methods for computational electromagnetics, In: B. Beker and Y. Chen (Eds.), Recent research developments in microwave theory & techniques, Research Signpost, Kerala, 2002, pp 89 –111 5. X. Liu and Y. Chen, Applications of transformed-space non-uniform PSTD (TSNU-PSTD) in scattering analysis without the use of the non-uniform FFT, Microwave Opt Technol Lett 38 (2003), 16 –21. 6. W.K. Leung and Y. Chen, Transformed-space non-uniform PSTD algorithm, Microwave Opt Technol Lett 28 (2001), 391–396. 7. Q. Li and Y. Chen, Pseudo-spectral time-domain analysis using an initial-condition excitation for elimination of Gibbs phenomena, Chin J Electron 9 (2000), 92–95. 8. Q. Li, Y. Chen, and D. Ge, Comparison study of the PSTD and FDTD methods for scattering analysis, Microwave Opt Technol Lett 25 (2000), 220 –226. 9. W.H. Press, S.A. Teukolsky, W.T. Vetterling, and B.P. Flannery, Numerical recipes in C, 2nd ed., Cambridge University Press, Cam- bridge, 1992. 10. J.P. Berenger, A perfectly matched layer for the absorption of elec- tromagnetic waves, J Comput Phys 114 (1994), 185–200. 11. S.D. Gedney, An anisotropic perfectly matched layered-absorbing medium for the truncation of FDTD lattice, IEEE Trans Ant Prop 44 (1996), 1630 –1639. 12. K.S. Kunz and R.J. Luebbers, The finite difference time domain method for electromagnetics, CRC Press, Boca Raton, 1993. 13. R.J. Luebbers, D. Ryan, and J. Beggs, A two-dimensional time domain near zone to far zone transformation, IEEE Trans Ant Prop 40 (1992), 848. 14. K. Umashankar and A. Taflove, Computational electromagnetics, Ar- tech House, London, 1993, Section 6.7. © 2006 Wiley Periodicals, Inc. SHORT-CIRCUITED MICROSTRIP ANTENNAS FOR MULTIBAND WIRELESS COMMUNICATIONS J. S. Roy, N. Chattoraj, and N. Swain Electronics and Communication Engineering Department International Centre for Wireless and Mobile Communication Birla Institute of Technology Mesra, Ranchi 835215, India Received 25 April 2006 ABSTRACT: The investigations on short-circuited microstrip patch antennas, which are able to generate multiple resonance frequencies in the wireless communication bands, are reported. In these antennas, by properly choosing the positions of shorted posts, good impedance matching can be obtained. The multifrequency nature of the shorted patch, theoretically obtained using IE3D software, is verified by mea- surement. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2372–2375, 2006; Published online in Wiley InterScience (www. interscience.wiley.com). DOI 10.1002/mop.22019 Key words: microstrip antenna; short-circuited; multifrequency; gain; wireless communication 1. INTRODUCTION The increasing use of wireless communication systems demands the antennas for different systems and standards with properties Figure 6 (a) The grid width x(i) vs. the grid index i. (b) Space transformation factor du/dx(i) vs. the grid index i (u = 1 m) 2372 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 48, No. 12, December 2006 DOI 10.1002/mop