A wireless communication antenna system includes: a radio-frequency circuit configured to couple to a printed circuit board; a broadside radiator configured and disposed to radiate first millimeter-wave energy at a first boresight away from a broadside surface of the printed circuit board; an end-fire radiator configured and disposed to radiate second millimeter-wave energy at a second boresight away from a side surface of the printed circuit board; and at least one flex cable each including a substrate, the at least one flex cable including a plurality of signal conductors coupled to the radio-frequency circuit; where at least one of the broadside radiator or the end-fire radiator is a cavity radiator; and where respective signal conductors of the plurality of signal conductors are disposed to excite the broadside radiator and the end-fire radiator.