Search Results (3)

A novel reflective metasurface (RMS) is proposed in this paper. The MS measures 128 × 128 × 2.794 mm³ and consists of a six-layer vertically stacked structure, with a liquid crystal (LC) cavity in the middle layer. A dual fan-shaped direct current (DC) bias circuit is designed to minimize the interaction between the radio frequency (RF) signal and the DC source, allowing control of the LC dielectric constant via bias voltage. This enables multi-band operation to improve communication capacity and quality for x-band devices. The polarization conversion (PC) structure employs an orthogonal anisotropic design, utilizing logarithmic functions to create two pairs of bowtie microstrip patches for linear-to-circular polarization conversion (LCPC). Simulation results show that for x-polarized incident waves, with an LC dielectric constant of ε_r = 2.8, left- and right-handed circularly polarized (LHCP and RHCP) waves are achieved in the frequency ranges of 8.15–8.46 GHz and 9.84–12.52 GHz, respectively. For ε_r = 3.9, LHCP and RHCP are achieved in 9–9.11 GHz and 9.86–11.81 GHz, respectively, and for ε_r = 4.6, they are in 8.96–9.11 GHz and 9.95–11.51 GHz. In the case of y-polarized incident waves, the MS reflects the reverse CP waves within the same frequency ranges. Measured results show that at ε_r = 2.8, the axial ratio (AR) is below 3 dB in the frequency ranges 8.16–8.46 GHz and 9.86–12.48 GHz, with 3 dB AR relative bandwidth (ARBW) of 3.61% and 23.46%, respectively. For ε_r = 4.6, the AR < 3 dB in the frequency range of 9.78–11.34 GHz, with a 3 dB ARBW of 14.77%. Finally, the measured and simulated results are compared to validate the proposed design, which can be applied to various applications within the corresponding operating frequency band. Full article

A compact and triple-band polarization converting reflective type metasurface (PCRM) with a high polarization conversion ratio (PCR) is proposed for strategic wireless antenna-integrated applications. The unit cell of the metasurface is composed of S- and G-shaped patches separated with a parasitic gap and the grounded via is connected to the full ground plane. The unit cell is etched on an FR4 substrate (dielectric constant, ε_r = 4.4, loss tangent, tan δ = 0.02), with compact dimensions of 10 mm³ × 10 mm³ × 1.6 mm³. This structure provides a resonance at 5.2 (ISM), 6.9, and 8.05 GHz (X-band) frequencies. The designed unit cell structure is studied for Transverse Electric (TE)/Transverse Magnetic (TM) incident waves and their responses to the various incident angles. The corresponding PCR is calculated, which shows 92% in the lower frequency band (5.2 GHz), 93% in the second frequency band (6.9 GHz), and 94% in the high-frequency band (8.05 GHz). The total efficiency of the structure shows 83.2%, 62.95%, and 64.6% at the respective resonance bands. A prototype of the proposed PCRM with 3 × 3 unit cells is fabricated to validate the simulated results. The experimental data agrees with the simulation results. The compactness, triple-band operation with a high PCR value of more than 92% makes use of the designed metasurface in wireless antenna-integrated applications at ISM and X-bands. Full article

The use of the millimeter wave (mmWave) spectrum and further exploration of sub-mmWave has led to a new era in wireless communication, as the need for higher data rates grows. High frequencies, on the other hand, incur a higher path loss, requiring an increase in antenna gain requirements. Metasurfaces, which emerge as a promising technology for mitigating path loss effects by utilizing two dimensional (2D) arrays of engineered meta-atoms resembling metamaterials that control the surface’s electromagnetic response have been introduced. Currently, metasurfaces are primarily considered as passive reflecting devices in wireless communications, assisting conventional transceivers in shaping propagation environments. This paper presents an alternative application of metasurfaces for wireless communications as active reconfigurable antennas for next generation transceivers. A framework that demonstrates the design process of a metasurface antenna structure was introduced and further used to design a 4 × 4 array and its reconfigurable counterpart. In contrast to conventional phased array antennas, a reconfigurable metasurface (RMS) antenna does not require phase-shifters and amplifiers, which leads to reduced cost. Instead, each individual element achieves reconfigurability by shifting the resonating frequency using semiconductor devices such as PIN diodes. The proposed metasurface antenna is designed to operate at a frequency of 28 GHz and 40 GHz. In addition, an increase in gain and directivity was observed when diodes were added to the metasurface antenna array. However, due to PIN diodes being connected to metallic strips in the metasurface antenna array, loss can occur due to power dissipation, which results in a decrease in radiation efficiency. Full article