An apparatus is described incorporating an interposer having a cavity for a portion of an antenna structure, having conductor through vias, a top Si part having interconnection wiring and having pads for electrically mounting an integrated circuit chip thereon, wherein the top Si part mates with the interposer electrically and mechanically. The interposer and top Si part may be scaled to provide an array of functional units. The invention overcomes the problem of combining a high efficient antenna with integrated circuit chips in a Si package with signal frequencies from 1 to 100 GHz and the problem of shielding components proximate to the antenna and reduces strain arising from mismatching of TCEs.