This work reports on designing and experimentally evaluating an asymmetric metasurface absorber (MA) for wide-band and polarization-insensitive operation in the C- and partial X-bands. As the core building block of the radio frequency (RF) subsystem, a unit-cell has been proposed, comprised of a dual-cut square-ring resonator (SRR) and a square patch placed above an FR4 substrate backed by a copper plate, inherently anisotropic. This arrangement efficiently converts linearly-polarized waves to cross-polarized reflected waves, achieving an 80% conversion efficiency over a wide bandwidth (BW) of 4.72–8.49 GHz. The reflected cross-polarized waves are also inhibited by strategically incorporating just three resistors on the top surface. Therefore, the polarization converter (PC) is transformed into an MA. In contrast to previously known MAs that depended on structural symmetry to maintain stable absorption performances across all polarization angles, this newly proposed asymmetric MA breaks that constraint. It achieves consistent absorption irrespective of variations in the polarization angle of the normal incident waves. The full-wave simulations have resulted in over 80% absorption, closely resembling the initial PC’s reflected BW. This MA has a compact assembly with a size of 0.22λ × 0.22λ and a thickness of 0.07λ. Absorption outputs are experimentally evaluated, resulting in more than 80% absorption, covering almost the entire C-band. This device can be used in different applications, such as radar cross-section assessments and energy-harvesting front-ends.

High transmission efficiency metasurface unit cells have been designed based on surface electric and magnetic impedances derived from Huygens’ principle. However, unit cells for low transmission loss (<1 dB) over a wide transmission phase range require at least three metallic layers, which complicates the unit cell design process. In this paper, we introduce high-efficiency Huygens’ metasurface unit cell topologies in double-layer FR4 printed circuit board (PCB) by implementing surface electric and magnetic current using the top and bottom metallic patterns and via drills. Eleven unit cells were optimized for wide phase coverage (−150° to 150°) with a low average transmission loss of −0.82 dB at 10 GHz. To demonstrate the high-efficiency of the designed unit cells, we designed and fabricated two focusing lenses with dimensions of near 150 × 150 mm (5λ × 5λ) to focus a spherical beam radiated from short focal distances (f = 100 and 60 mm). The fabricated focusing lens showed 12.87 and 13.58 dB focusing gain for f = 100 and 60 mm at 10 GHz, respectively, with a 1 dB fractional gain bandwidth of near 10%. We expect that the proposed focusing lens based on high-efficiency double-layer metasurface unit cells can help realize compact and high-gain focusing lens-integrated antenna systems.

The authors design and experimentally analyse an anisotropic metasurface for the simultaneous conversions of linear cross and circular polarisations in the C and partial X bands. The proposed compact structure utilises a dual‐cut square‐ring resonator and a square patch on an FR4 substrate above a ground plane. The full‐wave simulations exhibit over 92% efficiency in cross‐conversion over a fractional bandwidth (BW) of 52.3%. The proposed metasurface efficiently converts linear to circular polarisation in two different bands, achieving left‐hand circularly polarised and right‐hand circularly polarised efficiencies exceeding 93% and 89%, respectively. The compact unit‐cell with dimension 0.22 λ × 0.22 λ attains stable polarisation transformation efficiency rates exceeding 80% up to 40° incident angles. The design is adaptable for efficient wide BW across both lower and higher (millimetre‐wave) frequencies through scaling. A prototype of the proposed polarisation converter (PC) was realised and validated effectively in measurements, aligning well with simulations. This PC features a novel and simple structure with multifunctional wideband operation, stable incident angle output, polarisation insensitivity, and scalability, making it an efficient front‐end for various radio frequency applications, including polarisation control and polarisation transformers.

A tunable transmission Huygens' metasurface implemented in compact double-layer PCB is presented. The unit cells consist of electric and magnetic dipoles where the phase responses are independently controlled by an off-the-shelf PIN diode and varactors, respectively. The DC bias lines are embedded in double metallic layers and highly resistive resistors and DC blocking capacitors are used to reduce cell-to-cell and RF-DC coupling. The metasurface unit cell structures are designed for proof of concept at 10 GHz. For efficient transmission with multiple phases, the optimum pairs of ON-OFF states of the PIN diode and capacitance of the varactors are investigated. The final unit cells with electronic tuning cover transmission phase states from -90°to +150° with average loss of -3 dB.