Tunable waveguide antenna

Disclosed is a preferably designed to operate with local coils tunable waveguide antenna for a magnetic resonance imaging apparatus (1), wherein the waveguide antenna includes a plurality of metal surfaces (M1, M2, M3, M4, M5, M6, M7, M8, M21, M31, M41), wherein between the metal surfaces (M1, M2, M3, M4, M5, M6, M7, M8, M21, M31, M41) diodes are (D1, D2, D3, D4, D5, D6, D21, D31, D41), wherein metal surfaces are connected in a state are switched through in the diode between the metal surfaces of RF signals via these diodes to each other, wherein metal surfaces are turned off in a state in which diodes between the metal surfaces, for RF signals are unconnected with each other.