A Millimeter-Wave Orthomode Transducer for Circularly Polarized Radiation

Abstract

Communication systems operating at millimeter frequency bands have become a necessity to enable the support of a larger number of end-users with higher data rate and better resolution. Such communication systems should rely on circularly polarized based transceivers in order to ensure efficient transmission and reception of information while minimizing the propagation losses that occur when operating at millimeter-wave frequency bands. Accordingly, one block that is needed in any millimeter-wave based transceiver chain is the Orthomode Transducer (OMT). This device is responsible for splitting the circularly polarized received wave into 2 orthogonal linear components, a vertical and a horizontal component. The OMT can also combine two linearly polarized waves into one circular component. In this work, groove gap waveguide technology is employed to build an OMT that operates between 28 GHz and 32 GHz, respectively. Additionally, a reconfigurable phase shifting mechanism is achieved by altering the electrical distance of the propagating wave within the structure. Such alteration ensures that the fundamental TE10 mode is maintained while enabling that the overall OMT is fed by a circular waveguide operating with the fundamental TE11 mode. The phase reconfiguration is obtained by mechanically reconfiguring the grooves of the structure that have an interchangeable pin configurations at the bottom waveguide plate.

The structure is fabricated using 3D metal printing process. The fabricated prototype operates over the desired millimeter-wave band, between 28 GHz and 32 GHz. A close agreement is obtained between the theoretical and measured response in terms of matching, isolation and phase reconfiguration between the various ports of the proposed structure.