  Meeting the ever increasing demand for transmission capacity in wireless
networks will require evolving towards higher regions in the radiofrequency
spectrum, reducing cell sizes as well as resorting to more compact, agile and
power efficient equipment at the base stations, capable of smoothly interfacing
the radio and fiber segments. Photonic chips with fully functional microwave
photonic systems are promising candidates to achieve these targets. Over the
last years, many integrated microwave photonic chips have been reported in
different technologies. However, and to the best of our knowledge, none of them
have fully integrated all the required active and passive components. Here, we
report the first ever demonstration of a microwave photonics tunable filter
completely integrated in an Indium Phosphide chip and packaged. The chip
implements a reconfigurable RF- photonic filter, it includes all the required
elements, such as lasers, modulators and photodetectors, and its response can
be tuned by means of control electric currents. This demonstration is a
fundamental step towards the feasibility of compact and fully programmable
integrated microwave photonic processors.
