Compact and planar active integrated antenna arrays with a high power multi-stage amplifier were developed with effective heat sink mechanism. By attaching an aluminum plate to the backside of the creased amplifier circuit board, effective cooling can be achieved. The nonlinear behavior of the amplifier agrees well with the simulation based on the Angelov model. The high power amplifier circuit consisted of the three-stage amplifier and operated with an output power of 4W per each element at 5.8GHz. The 32-element active integrated antenna array stably operated with the output power of 120W under the effective heat sink design. With a weight of 4kg, the weight-to-output power ratio and the volume-to-output power ratio of the antenna array are 33.3g/W and 54.5cm³/W, respectively. Wireless power transmission was also successfully demonstrated.