GaN is a transformational technology that has set new levels of performance in the RF world. Being a wide band gap material, it naturally allows higher power levels for RF output power (and PAE) at frequencies up through W-band. Some of the narrow band examples allow platforms to have agile multi-beam capabilities not realizable with TWTA’s, while some wide band PA examples used as drivers shrink the transmitter size by >30%. Examples of the linearity characteristics of NGC’s GaN process will be shown, which allows minimal backoff for complex modulation transmission. High frequency design challenges with GaN will be discussed, and discrete examples of K through W-band will be shared, including the most recent published data. Some aspects of reliability will be presented, as well as packaging and thermal challenges.