The invention relates to a flat screen (E) that comprises an active pixel matrix (M), an electrode that is common to said pixels (C), and a conductive strip (R) preferably in the form of a ring that is connected to said common electrode and at least partially surrounds said active matrix, characterized in that at least one slot (F) defining an antenna is formed in said conducting strip. The invention also relates to a portable apparatus that comprises: such a flat screen (E); an electronic board including a floorplan (PM) parallel to the flat screen and electrically connected to the conductive strip of the same; a means for generating and/or detecting electric radiofrequency signals; and an excitation port (P) for the slot antenna (F) installed in the flat screen, and connected to said means for generating and/or detecting electric radiofrequency signals.