Very high peak power levels at microwave frequencies can be generated from several semiconductor devices (Gunn diodes, l.s.a. mode devices, TRAPATTs, etc.), but some of these devices are only a little removed from laboratory devices, and are limited in frequency. The Gunn device is the most practical and proven device, but, at 16 GHz, is only capable of powers of about 10 W peak. A simple technique is described that results in the addition of the powers and which does not degrade the other parameters, such as r.f. risetime.