A bidirectional left-hand circularly polarized antenna using dual rotated patches

In this article, we have proposed a multilayer bidirectional circularly polarized antenna for underground communications. The proposed antenna consists of two slot-coupled back-to-back arranged rotated patches and a microstrip feed-line. Identical left-hand circular polarization is achieved in both front and back directions to avoid the undesired polarization mismatch for point-to-point connection. A prototype of the proposed antenna is built to validate the design strategy. The measured data, including S-parameter, axial ratio, radiation pattern, and gain, agree well with the simulation results.