Technology is hardware that enables fundamental research and wealth creation.
Technology comprises devices and subsystems. These combine to make complete systems for many and varied applications, satisfying the needs of end users.
Millimetre wave devices comprise: antennas, transmission lines (waveguides & coaxial cables), quasi-optical passive components (polarisers, waveplates, delay lines, phase shifters), mixers, amplifiers, filters and detectors. These devices exploit in one way or another the linear and non-linear electrical characteristics of materials.
The cost and performance of technology together with the political and economic drivers of the application will determine whether systems will be developed. A natural evolution of all technology is for performance to rise and costs to fall. When performance outweighs costs, technology development snowballs, usually for a particular application. When systems are taken up for production in large numbers by industry, device costs fall by several orders of magnitude. When this happens large profits can be made and further spin-out applications evolve.
Sufficiently advanced technology is indistinguishable from magic. - Variant of Clark's 3rd law.