A tuneable capacitor

A tuneable capacitor comprises at least two parallel and coaxial conductive electrode bodies 101, 103. Each electrode body has a circular array of curved plates 105, 107 extending transversely from the electrode body towards the opposite electrode body, with the array of curved plates extending from one electrode body being radially spaced from the array of plates extending from the opposite electrode body. At least a portion of one of the electrode bodies may be rotatable about a central axis so that the mutual overlap between side surfaces of the curved plates of opposite electrode bodies is varied by the rotation of the portion of the electrode body relative to the opposite electrode body, thereby varying the capacitance with the rotation angle. The circular arrays may comprise several concentric rings of curved plates, with the concentric rings of one electrode body interleaved with the concentric rings of the opposite electrode body.