1136 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 51, NO. 5, MAY 2003 selected for simulating diffraction fields since the geometry of the plate and the ECCD array is symmetrical. We investigate the possibility to reduce sidelobes of the ECCD array by mounting a finite reflected plate below the array. It is well known that dipoles with infinite ground plane can achieve the maximum gain if the height of dipoles over the ground is 0.25 wavelength. Extensive calculations in this paper have indicated that a finite reflected plate with an appropriate size can also achieve the same effects for increasing gain and reducing sidelobes as an infinite plate. It has been observed from Fig. 5 that the height of 0.25 wavelengths actually achieves a greatly reduced sidelobes as well as the maximum gain. This is because the diffraction by finite edges of the plate is quite small, compared to reflection from the surface of plate. The total scattering field over the above half-space of a finite plate is almost equal to the sum of two parts, one is from the direct radiation of antennas and the other from full reflection due to the ground plate. The above results are just desired for some radars to increase gain and to block ground clutter signals. Based on the above simulations, we adopt a 22 by 24 planar ECCD array to the LTR shown in Fig. 6. The LTR is a 1.36-GHz pulse-mod- ulated monostatic Doppler radar with an active phased array system, where the antennas consists of two rectangular arrays, they are perpen- dicularly superimposed corresponding to two linear polarization. The configuration of each array is the same as that mentioned in Section III. The nominal peak power is 2 kW (the maximum average power is 400 W), which is produced by 24 solid state power amplifiers (transmitter modules). The LTR has been successfully operated at the Shigaraki MU radar observatory of Kyoto University for the lower atmosphere obser- vation. V. CONCLUSION An efficient analysis procedure is presented for exactly modeling the far field of ECCD element. One of its advantages is that one need not handle infinite integrals raised [1] for the process is based on Pock- lington type of formulation that only involves closed form of Green’s functions in free space. This allows the proposed analysis process in this paper to be easily applied to various ECCD elements with different lengths and radii of circular pipe. Owing to its advantages of simply constructed and clear physical meanings, the procedure in this paper, compared to available methods from other literatures, can also be more easily applied in engineering. The equivalent model derived from the analysis for the ECCD ele- ment can result in the simplification for the computation of the radiation pattern of the ECCD under some special conditions, and therefore can increase computation efficiency. It is fully novel configuration in the ECCD application to mount a large ECCD planar array over a finite metallic reflected plate with a suitable height so as to achieve reduced radiation sidelobes of array antenna. The uniform physical theory of diffraction, being hybrid with the proposed method for the ECCD element, has handled successfully the scattered far field of this system, the proposed height for ECCD array antenna over the plate is practical useful. The proposed ECCD array configuration in the LTR is only a start for ECCD array application. Authors believe that the related configuration can also be expected to application in other fields, such as based station antennas for wireless communications. ACKNOWLEDGMENT This work has benefited from the input of Mitsubishi Electric Corpo- ration (MELCO), Kanagawa, Japan. The authors are grateful for useful discussions with Dr. Miyashita of MELCO. REFERENCES [1] H. Miyashita, H. Ohmine, K. Nishizawa, S. Makino, and S. Urasaki, “Electromagnetically coupled coaxial dipole array antenna,” IEEE Trans. Antennas Propagat., vol. 47, no. 11, pp. 1716–1725, Nov. 1999. [2] H. Miyashita, “Study on analytical modeling of anatenna arrays for im- plementation of efficient design procedure,” Ph.D. dissertation, Radio Science Center for Space and Atmosphere, Kyoto University, ch. 2, May 2000. [3] L. L. Tsai, “A numerical solution for the near and far fields of an annular ring of magnetic current,” IEEE Trans. Antennas Propagat., vol. AP-20, pp. 569–576, Sept. 1972. [4] E. Yamashita, Analysis Methods for Electromagnetic Wave Prob- lems. Norwood, MA: Artech House, 1996, Physical Optics by Makoto Ando, ch. 4. [5] A. K. Bhattacharyya, High Frequency Electromagnetic Techniques: Re- cent Advances and Applications. New York: Wiley, 1995. Radar Cross Section of Stacked Circular Microstrip Patches on Anisotropic and Chiral Substrates V. Losada, R. R. Boix, and F. Medina Abstract—Galerkin’s method in the Hankel transform domain (HTD) is applied to the determination of the radar cross section (RCS) of stacked cir- cular microstrip patches fabricated on a two-layered substrate which may be made of a uniaxial anisotropic dielectric, a magnetized ferrite or a chiral material. Concerning the case of stacked patches printed on magnetized ferrites, the results show that substantial RCS reduction can be achieved inside the tunable frequency band where magnetostatic mode propagation is allowed. It is also shown that both the frequency and the level of the RCS peaks obtained for circular patches fabricated on anisotropic dielectrics or chiral materials may be substantially different from those obtained when substrate anisotropy or substrate chirality are ignored. Index Terms—Anisotropic media, chiral media, ferrites, microstrip an- tennas, scattering. I. INTRODUCTION Although the standard configuration for a microstrip antenna in- volves one single conductor patch, two stacked conductor patches are sometimes employed for obtaining either dual-frequency operation [1] or increased bandwidth operation [1], [2]. Concerning the topic of scat- tering from microstrip antennas, we should say that as the radar cross section (RCS) of military platforms is reduced by geometrical shaping and the use of composite radar absorbing materials, the scattering from the antennas mounted on such structures may give the most impor- tant contribution to the overall RCS. Bearing in mind that microstrip antennas are very suitable for use on aircraft vehicles owing to their light weight and conformability, different results were published in the past for the RCS of single microstrip antennas both on conventional isotropic dielectric substrates [3] and nonconventional substrates with dielectric and magnetic anisotropy [4], [5]. The feeding and radiation Manuscript received September 28, 2001; revised January 28, 2002. This work was supported by the El Centro de Investigación Científica y Tecnológica (CICYT), Spain under Grant TIC98-0630. V. Losada is with the Microwaves Group, Department of Applied Physics, E.U.I.T.A., University of Seville, 41013, Sevilla, Spain. R. R. Boix and F. Medina are with the Microwaves Group, Department of Electronics and Electromagnetism, College of Physics, University of Seville, 41012 Sevilla, Spain (e-mails: boix@us.es; medina@us.es). Digital Object Identifier 10.1109/TAP.2003.811528 0018-926X/03$17.00 © 2003 IEEE