A waveguide antenna (200) is disclosed, comprising: a first plurality (220) of slots (222,224), for producing a beam having a first radiation pattern (301) at a first resonant frequency (f1); and a second plurality (230) of slots (232, 234), for producing a beam having a second radiation pattern (302) at a second resonant frequency (f2). A method of operation of the waveguide antenna (200) is also disclosed, comprising: operating the transceiver at a first frequency (f1) to detect objects in a first field of view; and operating the transceiver at a second frequency (fa) to detect objects in a second field of view