We propose a periodically modulated metasurface (MTS) capable of producing two-sided electromagnetic (EM) beams with frequency controlled beam reconfiguration. The beam forming functionality is realized through the leaky wave conditions of the periodic structure, and the beam reconfiguration at a quadrature azimuth angles is triggered by switching between the two operating frequencies. The MTS is formed using a periodic homogeneous array of split ring resonators (SRR) with anisotropic characteristics. The electromagnetic bandgap (EBG) properties and leaky wave conditions of the individual SRRs are combined to produce both beam-forming and beam-reconfiguration functionality. The subwavelength SRR unit cells are designed such that they satisfy leaky-wave theory at 1.8 GHz to form a two-sided beam along azimuth angles 00 and 1800, and create a complete electromagnetic bandgap (EBG) at 2.6 GHz to form a two-sided beam along angles 900 and 2700 at 2.6 GHz. Both the TE and TM mode response of the individual SRRs is taken into consideration during the design process. The MTS structure is synthesized and evaluated using full-wave EM simulator, and is validated with experimental results.

We propose a metasurface structure integrated at the aperture of a flanged rectangular waveguide to produce dual-beam radiation. The dual beams are anti-parallel in an orientation and perpendicular to the boresight direction. The metasurface is backed by a dielectric slab to produce a substrate integrated waveguide-like response above the flange. The metasurface is engineered to limit the boresight emission from the waveguide aperture, as well as to allow symmetric wave splitting between the metasurface and waveguide flange. A lens-like end texturing involving surface tapering and electromagnetic bandgap (EBG) cells is utilized to enhance the beam directivity at end fire from the flange. The dual-beam radiation exists for all frequencies between 10.5 GHz and 12.4 GHz. The proposed design is modeled via full-wave simulation in commercial software, then validated through the measurement of a fabricated prototype.

The effect of using a superstrate dielectric layer on an on-head matched antenna for biomedical diagnosis applications is investigated. Two on-head matched antennas are considered with different length meandered lines ensuring operation around 0.9 GHz frequency. The first antenna’s conductive radiating structure is in direct contact with the head phantom, whereas the second one utilises a 0.5 mm thick superstrate layer on top of the conducting layer as a buffer. The lateral dimensions of both antennas are held constant at 30 × 30 mm². The electric and magnetic field distribution is analysed and the power penetration, 50 mm inside the head phantom, is derived from the electromagnetic field surrounding the antennas. Both homogeneous and inhomogeneous head phantoms are considered while evaluating the antennas in terms of their reflection coefficient, current distribution, electric field, magnetic field, specific absorption rate (SAR) and power penetration inside the head. The antennas are fabricated and measured utilizing an inhomogeneous phantom to validate the proposed performance improvement using a superstrate. It is shown that the superstrate antenna achieves a ~8 dB increase in power penetration inside the head phantom along with a 0.0731 W/kg decrease in SAR compared to the antenna without a superstrate.