<p>A microwave antenna (10) is formed from a stack of generally planar elements (14-22) forming an array of horns (12) communicating with waveguides (38). The generally planar elements (14-22) are of metallised plastics. Each of these elements (14-22) has a given overall thickness which is constituted by a membrane of relatively small thickness formed (typically by vacuum forming) into a corrugated shape.</p>
