This paper describes the design of a planar antenna array system with pattern reconfiguration in the azimuthal plane. The antenna array system is designed based on four antenna units where each unit is composed of two printed Yagi-Uda elements that radiate in directional beams over a dedicated sector, thus ensuring maximum isolation with neighboring units. The various units are fed on demand through a reconfigurable structure that is composed of four reconfigurable feeding networks and a one-to-four power divider. The feeding structure distributes the required power to the various radiating units through the activation of the two integrated PIN diodes along each of the four reconfigurable feeding networks. Such activation results in 15 reconfigurable radiation patterns that cover four orthogonal sectors over a fixed operating frequency, at 5.8 GHz. Each antenna unit is designed to exhibit a gain of 9 dBi with a half-power beamwidth of 44 ο and a sidelobe level of -16 dB. The antenna array is fabricated and tested, where the measured results validate the predicted simulated data.
This paper discusses the design of a high gain right-hand circularly polarized millimeter-wave frequency reconfigurable antenna array. The 16-element antenna array is designed to reconfigure its operating frequency over both K-and Ka-bands. More specifically, the reconfigurability is ensured through the integration of a modified ring resonator along with the array's sequentially rotated stacked feeding network. The ring resonator is designed to reconfigure its operating frequency over four distinct bands with center frequencies at 25 GHz, 26 GHz, 27.75 GHz and 29 GHz, respectively. Such integration enables the proposed millimeter-wave antenna array to exhibit unique radiation characteristics by maintaining circular polarization with an Axial Ratio (AR) < 1 dB in a fractional bandwidth of 37.5% between 21.2 GHz and 31 GHz. A Figure of Merit that takes into account the array's axial ratio, sidelobe levels and fractional bandwidth is developed to highlight the unique performance of the presented millimeter-wave circularly polarized array in comparison to available work in the literature. The fabricated antenna array shows good agreement with the simulated data where it is found that the measured realized gain exceeds 12 dBic with sidelobe levels of less than -17.5 dB over the various frequency bands of the frequency reconfigurable antenna array.
Surface acoustic wave devices have been fabricated on a GaAs 100 substrate to demonstrate the capability of 2D Raman microscopy as an imaging technique for acoustic waves on the surface of a piezoelectric substrate. Surface acoustic waves are generated using a two-port interdigitated transducer platform, which is modified to produce surface standing waves. We have derived an analytical model to relate Raman peak broadening to the near-surface strain field of the GaAs surface produced by the surface acoustic waves. Atomic force microscopy is used to confirm the presence of a standing acoustic wave, resolving a total vertical displacement of 3 nm at the antinode of the standing wave. Stress calculations are performed for both imaging techniques and are in good agreement, demonstrating the potential of this Raman analysis.
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