An active integrated antenna (AIA) which consists of a T-shaped microstrip-line-fed slot antenna is proposed. Since the designed antenna has an electromagnetically coupled feedback loop, it can easily solve the problem of DC isolation between a radiator and amplifier. The fabricated parallel-feedback antenna oscillator shows stable oscillation at a frequency of 10.05 GHz. The measured effective isotropic radiated power (EIRP) is 37.79 m W, and the cross-polarization levels are at least -15-dB lower than those of co-polarization for all directions. (c) 2005 Wiley Periodicals, Inc.