We have integrated a microwave oscillator with a zeroth‐order resonance antenna to build an active oscillating antenna using the coplanar waveguide technology. In this design, the antenna is electrically small and the oscillator has an excellent phase noise performance of 92.5 dBc/Hz. Also, 16.11 dBm (40.83 mW) of effective isotropic radiated power is radiated with high direct current to radio frequency efficiency (27.2%), which is much higher than many other active oscillating antenna designs. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1240–1243, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27543