Efficiency improvement and cross-polarization reduction of single-fed frequency-scan leaky wave microstrip antennas by using an M-shape metasurface as the WAIM layer

Increasing the efficiency and reducing the cross polarization of a single-fed leaky wave antenna by using a wide-angle impedance matching (WAIM) layer are studied in this paper. A wideband serial-fed patch array on a two layer substrate is employed as the leaky wave array. Dimensions of the patch array are optimized for the lowest reflection coefficient between 6 GHz and 7 GHz. The proposed antenna is indeed a frequency-scan antenna in this frequency range. Miniaturization of the proposed leaky wave microstrip antenna is achieved by using circular lines instead of straight lines between the patches. Reducing the separations between the array elements (microstrip patches) led to the sidelobe level reduction of the radiation patterns. Further improvements on the antenna results are obtained by using an anisotropic metasurface WAIM layer. The proposed metasurface layer is composed of printed M-shape unit-cells on a thin substrate, leading to the gain enhancement, sidelobe level reduction, cross-polarization reduction and reflection coefficient reduction of the antenna. Finally, the predicted results are validated by using experimental results, indicating good agreements. As a result, the performance improvement of the antenna by using the WAIM layer is observed in the simulations and measurements, clearly. (C) 2020 Elsevier GmbH. All rights reserved.