The Type 23 fittings that suppress self-generated radar clutter

What are the round white objects on the forward and aft superstructure of a Type 23 frigate?

They help suppress reflections and clutter from the ship's own structures so its radar receives a cleaner picture.

The fittings are identified as deflectors that control unwanted radar reflections from the ship's own structures. Nearby superstructure and missile installations can create repeated reflections and disturb the radar picture. Even when the system recognises a return as coming from its own ship, the associated clutter still needs to be reduced. The example leads into the Type 23's origins as a relatively inexpensive frigate and the long service demanded of the design.