This paper presents the design and characterization of a millimeter-wave (mmWave) power amplifier (PA) with a saturated output power of 11 dBm in a 130 nm SiGe technology. A pseudo-differential single-stage cascode topology is used to obtain a gain of 14 dB at 66 GHz and a small-signal 1 dB-bandwidth from 54 to 76 GHz. The proposed PA exceeds comparable conventional PAs in terms of bandwidth while being more efficient than wideband distributed amplifiers. Within the unlicensed bands between 57 GHz and 66 GHz, the 1 dB-compression point is larger than 9 dBm and the power-added-efficiency (PAE) at compression is larger than 9 %. To achieve optimal performance of the mmWave structures, the effects of patterned ground shields (PGSs) on inductors and transmission lines in the used technology are investigated by measurements.