Abstract: A travelling wave stripline antenna array adapted for use as a frequency-swept antenna, comprising a pattern of conducting material on an insulating substrate with a conducting backing, the pattern comprising a feeder strip and a plurality or radiating antenna elements each in the form of a strip attached to and extending tranversely away from the feeder strip, and having an open circuit termination at its free end. At least some, and preferably all, of the strips are formed with a longitudinal slot extending from the opposite side of the feeder strip and terminating before the open circuit end of the strip, so that each slotted strip behaves as a phase shifter as well as a resonant radiating antenna element.