The increasing frequency of applications poses new challenges to radio architectures, which must overcome the increasing losses of the propagation channel, compensated by the orientation and focusing of the radiated electromagnetic wave. In most cases, the solutions to be implemented require the implementation of high performance passive functions that are difficult to integrate in active front-end chips, although this does not rule out placing them close together, in the same package, by exploiting dedicated technologies or even the packaging itself.

The Butler matrix is an example of a beamforming system based solely on the use of passive circuitry. The figure below shows an example of a 4x4 Butler matrix designed to operate around 28GHz, recently produced in collaboration with 3DiS Technologies. The use of this company's 3D technology process results in an extremely compact Integrated Passive Device (IPD) (0.9 mm²) and low insertion loss (1.3 dB).