In the present work, broadband millimeter wave (mmW) receiver and transmitter circuits for wireless communication in the frequency range around 240 GHz are investigated. The absolute available bandwidths in the mmW frequency range allow high data rates and thus potentially close the technological gap between fast but wired and the comparatively slow and wireless communication. For this purpose, monolithic integrated millimeter wave mixer circuits (MMICs) are designed and analyzed, based on the metamorphic high electron mobility transistor, developed at the Fraunhofer Institute for Applied Solid State Physics (IAF). To simplify the signal generation of the local oscillator, subharmonic mixer circuits are of special interest. Together with other building blocks, these circuits are then integrated in multifunctional receiver and transmitter MMICs for wireless digital communication. These active transmitter and receiver MMICs form the functional core of a 240 GHz radio link, which is able to transmit data with up to 40 Gbit/s in a single-input single-output configuration. As part of a long range demonstrator, they allowed the transmission of up to 24 Gbit/s over a distance of 1.1 km.