A new Fabry-Perot resonator (FPR) antenna fed by an L- probe is proposed for mobile applications that require relatively low antenna gains. The proposed antenna consists of two parallel metal plates that are perpendicular to the ground plane. Its resonance frequency can be controlled by changing the separation between the parallel plates, as similar to that of the FPR. A probe resonance near the FPR mode is utilized to widen the impedance bandwidth. To reduce the cross polarization, a groove is introduced to each parallel plate. Ansoft HFSS was used to simulate the antenna, and a prototype operating in K-band was fabricated to verify the simulation. Reasonable agreement between the measured and simulated results is observed. The prototype has a 10-dB impedance bandwidth of 5% and the maximum gain of 11.1 dBi. The proposed antenna is simple and, more importantly, not too tiny to fabricate even at millimeter-wave frequencies. © 2006 IEEE.