Polarization-insensitive Archimedes'-spiral-shaped ultrathin metamaterial absorbers for microwave sensing application.

This work has developed and simulated a planar complementary Archimedes-based metamaterial absorber with the goal of its application in refractive index sensing. Unlike designs that employ multiple layers or numerous resonators within a single unit cell, our proposed absorber adopts a more streamlined approach. It consists of three layers, with an FR4 dielectric substrate sandwiched between two copper layers. It's important to note that the absorption characteristics of this design are polarization-dependent. This polarization dependence arises from the asymmetrical resonance behavior observed in both the x and y directions. The absorber exhibits impressive absorption rates at various resonance frequencies, namely 98.5% at f1 = 8.49 GHz, 77.1% at f2 = 8.88 GHz, 88.7% at f3 = 9.3 GHz, 98.2% at f4 = 9.87 GHz, 99.7% at f5 = 10.65 GHz, 83.4% at f6 = 11.58 GHz, and 99.9% at f7 = 12.24 GHz. Furthermore, the article explored the refractive index sensing capabilities of this structure by introducing a 1 mm analyte layer on top of the patch structure. Through refractive index sensing analysis, we've determined that this absorber-based sensor yields an impressive high-quality factor value of 84.5, highlighting its remarkable sensitivity and precision. A more profound comprehension of the physical mechanisms in action has been attained by examining the distribution of surface currents. Furthermore, the behavior of the absorber has been investigated under varying polarization and incident angle conditions, ranging from zero degrees to sixty degrees. The thorough characterization establishes this absorber as a promising choice for microwave sensing applications.

Simulation of the microwave five-band a perfect metamaterial absorber for the 5G communication .

This study proposes a five-band perfect metamaterials absorber (MMA) for 5G communication in the K- and Ka-bands of the microwave range. The MMA design is based on a folded arms resonator (FAR) with a novel shape, forming the fundamental unit of the absorber. This absorber demonstrates a reasonably wide range of absorption capabilities for 5G communication in the K and Ka bands of the microwave region. The absorptivity of the MMA was examined for both normal and oblique incidence of waves in the frequency range of 20-26 GHz. According to a theoretical analysis, five absorption peaks at resonance frequencies of 20.38, 21.75, 23.1, 24.22 and 25.12 GHz exhibit absorption rates of 97.8%, 92.9%, 97.2%, 99.3% and 96.8%, respectively. The overall average absorption rate is 95.53%, taking into account the presence of two perfect absorption peaks. By adjusting the structural parameters, it is possible to influence the absorption peaks and resonant wavelengths. Additionally, the absorber demonstrates a high level of symmetry, resulting in insensitivity to TE mode polarisation angle and incident angle. The fractal resonators exhibited a capacitive effect at lower frequencies, while the SRRs demonstrated a capacitive effect at higher frequencies. This MMA design is expected to have practical applications in 5G communication technology.

The Emirates Mars Mission (EMM) Emirates Mars InfraRed Spectrometer (EMIRS) Instrument.

The Emirates Mars Mission Emirates Mars Infrared Spectrometer (EMIRS) will provide remote measurements of the martian surface and lower atmosphere in order to better characterize the geographic and diurnal variability of key constituents (water ice, water vapor, and dust) along with temperature profiles on sub-seasonal timescales. EMIRS is a FTIR spectrometer covering the range from 6.0-100+ µm (1666-100 cm-1) with a spectral sampling as high as 5 cm-1 and a 5.4-mrad IFOV and a 32.5×32.5 mrad FOV. The EMIRS optical path includes a flat 45° pointing mirror to enable one degree of freedom and has a +/- 60° clear aperture around the nadir position which is fed to a 17.78-cm diameter Cassegrain telescope. The collected light is then fed to a flat-plate based Michelson moving mirror mounted on a dual linear voice-coil motor assembly. An array of deuterated L-alanine doped triglycine sulfate (DLaTGS) pyroelectric detectors are used to sample the interferogram every 2 or 4 seconds (depending on the spectral sampling selected). A single 0.846 µm laser diode is used in a metrology interferometer to provide interferometer positional control, sampled at 40 kHz (controlled at 5 kHz) and infrared signal sampled at 625 Hz. The EMIRS beamsplitter is a 60-mm diameter, 1-mm thick 1-arcsecond wedged chemical vapor deposited diamond with an antireflection microstructure to minimize first surface reflection. EMIRS relies on an instrumented internal v-groove blackbody target for a full-aperture radiometric calibration. The radiometric precision of a single spectrum (in 5 cm-1 mode) is <3.0×10-8 W cm-2 sr-1/cm-1 between 300 and 1350 cm-1 over instrument operational temperatures (<∼0.5 K NE Δ T @ 250 K). The absolute integrated radiance error is < 2% for scene temperatures ranging from 200-340 K. The overall EMIRS envelope size is 52.9×37.5×34.6 cm and the mass is 14.72 kg including the interface adapter plate. The average operational power consumption is 22.2 W, and the standby power consumption is 18.6 W with a 5.7 W thermostatically limited, always-on operational heater. EMIRS was developed by Arizona State University and Northern Arizona University in collaboration with the Mohammed bin Rashid Space Centre with Arizona Space Technologies developing the electronics. EMIRS was integrated, tested and radiometrically calibrated at Arizona State University, Tempe, AZ.