An upgraded version of the complementary stripslot radiating element is reviewed. The original radiating element
consists in a microstrip-fed slot in transmission configuration. In the proposed modification, the slot is backed by a cavity in order
to obtain unidirectional radiation. The presence of this cavity changes the behavior of the slot. A new equivalent circuit is
used to propose a design methodology for broadband operation. Two array designs are simulated and implemented: a phased
array and a log-periodic array. Promising experimental results verify the unidirectional radiation and the wide bandwidth of
these antennas.