The invention claimed is:1. A controllable phase control element (1) for electromagnetic waves havinga drive unit,a holder, andat least two polarizers, whereinthe at least two polarizers are mounted on the holder;each polarizer is designed for converting a circularly polarized signal into a linearly polarized signal, and the drive unit is connected to the holder in such a way that the polarizers can be rotated; andwherein the holder can be rotated about an axis which is located in the propagation direction of an incident wave.2. The controllable phase control element of claim 1, wherein the polarizers are mounted on the holder perpendicularly to the propagation direction of an incident wave and parallel to one another.3. The controllable phase control element of claim 1, wherein at least one of the polarizers and the holder has a form that is rotationally symmetrically to the axis of rotation of the holder.4. The controllable phase control element of claim 1, wherein the polarizers are designed as meander polarizers or as septum polarizers.5. The controllable phase control element of claim 1, wherein the holder has a shaft, and this shaft is connected to the drive unit.6. The controllable phase control element of claim 1, wherein the holder consists of a plastic.7. The controllable phase control element of claim 1, wherein the holder consists of closed-cell foam.8. The controllable phase control element of claim 1, having an axially symmetrical form.9. The controllable phase control element of claim 1, wherein the drive unit includes an electric motor or a piezoelectric motor.10. The controllable phase control element of claim 1, wherein the drive unit includes an actuator, which contains electroactive materials.11. The controllable phase control element of claim 1, having an angular position transmitter, which determines the angular position of the holder.12. The controllable phase control element of claim 1, wherein the holder is mounted in a cylindrical waveguide.13. The controllable phase control element of claim 12, wherein the holder is fixedly connected to the waveguide, and the waveguide is connected rotatably and is connected to the drive unit located outside the waveguide in such a way that the drive unit can rotate the waveguide and the interior holder.14. The controllable phase control element of claim 1, wherein the polarizers each comprise at least one polarizer pair, located parallel to one another, and the spacing of these pairs is substantially shorter than the wavelength.15. The controllable phase control element of claim 1, wherein the spacing of the polarizers amounts to approximately have the wavelength.16. The controllable phase control element of claim 1, wherein the holder is a dielectric packing material, which is metallized on its outside.17. The controllable phase control element for electromagnetic waves of claim 1, having two additional polarizers, which are mounted in the propagation direction of an incident wave upstream and downstream, respectively, of the polarizers, and each of the additional polarizers is designed such that it can convert a circularly polarized signal into a linearly polarized signal.18. The controllable phase control element of claim 17, wherein at least one of the polarizers is designed rotatably and has a drive unit with which it can be rotated independently of the holder.19. An antenna having a controllable phase control element of claim 1, wherein the controllable phase control element is inserted into a feed structure of the antenna.
