Reconfigurable Linear/Circular Polarization Rectangular Waveguide Filtenna

We introduce a new reconfigurable linear polarization and circular polarization (CP) antenna, based on a rectangular waveguide (RWG) and a novel reconfigurable polarizer. The polarizer consists of two orthogonal apertures. The apertures transform the linear polarization of the dominant mode of the RWG antenna to CP. Each of these apertures is loaded by a p-i-n diode to alter its electrical length. This length difference provides the phase rotation needed to obtain CP. The signal polarization of the antenna can be selected by changing the applied bias voltage of p-i-n diodes as right-handed (RH)/left-handed (LH) CP. We can also achieve linear polarization if both diodes are ON or OFF. The reconfigurable polarizer acts as a bandpass filter, since the apertures can be considered as complementary electrically small resonators. This self-filtering capability is useful for reduction out of band noise in a communication system such as satellite links. The proposed antenna is designed to operate at 2.65 GHz, but the same approach can be applied to other frequency bands. The measurement results show a very good RH/LHCP and they are in good agreement with simulations.