In this paper, we present a circularly polarized antenna with an integrated feeding network which can be mounted on a portable terminal for satellite communications according to the IMT-2000 standard. The radiating element and the feeding system were optimized in order to reduce their size using different software packages. The behavior of the radioelectric characteristics of the antenna realized on finite substrates and mounted on a portable terminal is reported and compared to the theoretical case. Good results are obtained compared to the requirements of the IMT-2000 standard. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 18: 161–166, 1998.