Dual Band Research Articles

Snow water equivalent retrieved from X- and dual Ku-band scatterometer measurements at Sodankylä using the Markov Chain Monte Carlo method

Abstract. Radar at high frequency is a promising technique for fine-resolution snow water equivalent (SWE) mapping. In this paper, we extend the Bayesian-based Algorithm for SWE Estimation (BASE) from passive to active microwave (AM) application and test it using ground-based backscattering measurements at three frequencies (X and dual Ku bands; 10.2, 13.3, and 16.7 GHz), with VV polarization obtained at a 50° incidence angle from the Nordic Snow Radar Experiment (NoSREx) in Sodankylä, Finland. We assumed only an uninformative prior for snow microstructure, in contrast with an accurate prior required in previous studies. Starting from a biased monthly SWE prior from land surface model simulation, two-layer snow state variables and single-layer soil variables were iterated until their posterior distribution could stably reproduce the observed microwave signals. The observation model is the Microwave Emission Model of Layered Snowpacks 3 and Active (MEMLS3&a) based on the improved Born approximation. Results show that BASE-AM achieved an RMSE of ∼ 10 cm for snow depth and less than 30 mm for SWE, compared with the RMSE of ∼ 20 cm snow depth and ∼ 50 mm SWE from priors. Retrieval errors are significantly larger when BASE-AM is run using a single snow layer. The results support the potential of X- and Ku-band radar for SWE retrieval and show that the role of a precise snow microstructure prior in SWE retrieval may be substituted by an SWE prior from exterior sources.

Sum and difference frequency generation in a valley-photonic-crystal-like topological system

Nonlinear sum frequency generation (SFG) and difference frequency generation (DFG) are fundamental methods to obtain new light sources for various applications. However, most of the on-chip SFG and DFG are based on conventional resonators, lacking robustness against fabrication defects. Here, we demonstrate topologically protected SFG and DFG in a second-order topological photonic system. The mechanism is based on the nonlinear interaction between three high-Q corner modes inside dual topological band gaps. The frequency matching condition for SFG and DFG is precisely satisfied by designing a valley-photonic-crystal-like topological system, which provides more freedoms to tune the corner modes. The topological SFG and DFG are achieved with high conversion efficiency, and the underlying topological physics is revealed. This work opens up avenues toward topologically protected nonlinear frequency conversion, and can find applications in the fields of on-chip single-photon detections and optical quantum memories with robustness against defects.

A synchronization-constraints-based dual bands method of traffic signal optimization

This paper presents a synchronization-constraints-based dual bands method of traffic signal optimization for multiple traffic flows. The synchronization coefficient, traffic volume ratio, synchronization benefit, and their thresholds of traffic flow pair are proposed to select synchronized traffic flow pairs for progression. Then, progression bands of multiple traffic flows can be achieved by merging time windows, combining equivalent phase, and optimizing benefits evaluation index of the synchronized traffic flow pair. The proposed method adopts step-by-step optimization processing, and the combinatorial optimization of signal cycle, phase sequence, and offset is decomposed by performing synchronization and progression. A real-world case is presented to illustrate the application of the proposed method with VISSIM simulations. The results show that compared with the MULTIBAND model and TRANSYT, this method significantly decreased the average delay and average stops along the arterial of the entire traffic system composed of buses and cars.

Exploring the mechanisms of excited-state intramolecular proton transfer in hydroxyphenyl-benzimidazole derivatives: A theoretical perspective

We conducted a comprehensive theoretical exploration for the ESIPT mechanism in a set of HBI derivatives in THF solution (Cpd-A and Cpd-B, and three isomers: Cpd-1, Cpd-2 and Cpd-3), employing time-dependent density functional theory (TD-DFT) methods for the excited-state calculations. An energy scan for the excited-state proton transfer pathway indicates that both Cpd-A and Cpd-B exhibit a low transition barrier from Enol* to Keto*, with the energy of Keto* much lower than Enol* state, which implies a rapid ESIPT process. The high instability of Enol* state contradicts the experimental observed dual emission bands for Cpd-A, where the emission band predominantly contributed from Keto* state. We propose a new mechanism to account for this dual fluorescence phenomenon of Cpd-A, where the overall fluorescence band can be ascribed to the emissions from both Keto* and a stable rotamer of Cpd-A. Calculations suggest that Cpd-A can exist in both syn and anti rotamers, with a relatively low isomerization barrier of 14.0 kcal/mol. The coexistence of two stable isomers in solution gives rise to the phenomenon of dual emission for Cpd-A. Further investigation for the substituent effects on the ESIPT dynamics of three isomers (Cpd-1, Cpd-2 and Cpd-3) indicates that varying substituent positions can have a substantial impact on both ESIPT process and excited-state charge transfer. The methoxy group substitution proximate to the hydroxy functional group decreases the energy barrier for Enol*-Keto* transition, and also promotes a more substantial charge transfer. Our study demonstrates a new mechanism of the dual fluorescence observed for the target HBI derivatives, offering a novel understanding for the ESIPT mechanism in solvent.

Design of a 2×2 dual band 28/38 GHz MIMO antenna in millimeter band for 5G

Design of a 2×2 dual band 28/38 GHz MIMO antenna in millimeter band for 5G

Genetic optimization of terahertz metamaterial absorber for improved absorption and quality factor

Terahertz metamaterial absorbers are typically comprised of an array of sub-wavelength meta-atoms, a dielectric spacer layer and a ground plane. The absorption and quality factor are two of the most important performance metrics for various advanced applications, such as THz communication, sensing, and imaging. However, a large number of structural parameters in the meta-atom make the design approach based on physical intuition and parameter sweep impractical and difficult. In this paper, we report an intelligent design methodology based on the genetic algorithm that facilitates the optimization of an air-spaced terahertz metamaterial absorber to improve its absorption and quality factor. The presented approach starts by randomly generating the size parameters of the meta-atom, and it iteratively obtains the optimized design of the dual narrow band terahertz metamaterial perfect absorber. The quality factor for the two near unity-absorption peaks are 23.8 at 0.5 THz and 60.3 at 0.7 THz, respectively. The device was fabricated using the surface and bulk-micromachining processes, and the measured absorption spectra agrees well with the simulated results. Not limited to this proof-of-concept demonstration, this methodology can be applied to all metamaterial-based photonic systems achieving efficient forward optimization design.

Novel design of a compact tunable dual band wireless power transfer (TDB-WPT) system for multiple WPT applications

Novel design of a compact tunable dual band wireless power transfer (TDB-WPT) system for multiple WPT applications

A High Gain Concurrent Dual-band Low-Noise Amplifier in 130-nm BiCMOS Technology

This paper presents a fully integrated concurrent 15/30-GHz dual-band low-noise amplifier (LNA). The proposed concurrent LNA IC is designed and simulated in 130-nm BiCMOS technology. The new passive LC notch filter is proposed to realize high gain and low noise figure over dual-band frequency, simultaneously. The simulated BiCMOS LNA IC has exhibited peak gains of 30.1/23.7 dB at 15/30-GHz, respectively, with 20-mW power consumption from 1-V supply. The concurrent dual-band LNA achieves noise figure of 2.2/2.9-dB and IIP3 of -18.2/-8.8 dBm at the respective passbands. Therefore, the proposed dual band concurrent LNA IC is applicable to front-end RF receivers for Ku-Band and Ka-Band systems.

Design of a Dual-band Wearable Antenna Operating at 2.45 GHz and 5.8 GHz for Medical Communication Applications

Indonesia's natural demographic which consists of 16,771 islands makes it has many challenges in infrastructure development, especially in the health sector. According to data, Indonesia currently has 10,203 Puskesmas and 2,449 hospitals. In terms of the number of medical personnel, currently in Indonesia there are 124,449 medical personnel. However, of the large number of medical personnel, 61.12% are concentrated in Java and Bali. This inequality causes the need for a technology that makes it easier for medical personnel to provide services to the community. Wireless Body Area Network (WBAN) is one of developed technology that supports telemedical services. In WBAN, wearable antenna is needed as a transmitter to transmit data. In this paper, a compact wearable dual band antenna was designed in ISM frequency band of 2.45 GHz and 5.8 GHz. A combination of rectangular shape radiating structure and cross slot is constructed to achieve dual band frequency. Jeans Textile material with permitivity of 1.7 and thickness of 1 mm is used for fabricating the proposed antenna. The size of antenna is 52.3mm x 58.69mm. The proposed antenna is simulated with and without human body panthom using cst software. The simulations result indicates that antenna resonates at frequency 2.45 GHz and 5.8 GHz with peak gains of 6.92 dBi and 6.5 dBi. SAR values when the proposed antenna simulated at wrist phantom ​​are 0.326W/kg and 1.024W/kg. When simulated at chest phantom, the SAR values ​​are 0.554W/kg and 0.394W/kg. Therefore, The proposed wearable antenna design is well suited for telemedical services.

Litar Setara Dwi Jalur Antena Dwikutub Bersepadu untuk Aplikasi RFID

This paper presents dual band antenna by designing basic dipole antenna integrated with C-shaped patches structure for RFID applications. This C-shaped patch is inspired by E-shapes patch antenna that able to perform multiband frequency. The design of the equivalent circuit started with the fundamental circuit of impedance Zo and Z1 which functioned as a dipole antenna in single band. The parallel RLC circuit of impedance Z2 is added in the circuit as loaded patch has affected the resonating frequency. Variations of C1 and L1 on impedance Z1 effect a gap between the two resonance frequencies without changing the bandwidth by shifting the lower frequency. In addition, the variation of C2 and L2 on the impedance Z2 also affects the ratio between the two resonance frequencies but both frequencies are shifted and the bandwidth changes. Consequently, the dual band is presented at 0.915 GHz (UHF RFID) and 2.4 GHz (ISM RFID) by calculating the value of the resistance, inductance and capacitance. The data from electromagnetic simulation are compared with the data predicted by the antenna circuit modeling. The frequency sampled measurement data may be represented in the form of S-parameter in order to represent dependent data in a time domain simulator in P-SPICE software. The C-shaped design can be independently controlled to perform lower band and upper band by adjusting the width and length of the patch. The performance of the proposed antenna demonstrates the dual band antenna for RFID application with good agreements between measured and simulated results.

Layer-stacked polyaniline/silver nanowire composite film for multicolor electrochromic smart windows with dual-band optical modulation

Dual-band electrochromic smart windows (DESWs) have attracted widely concern for their potential in significantly reducing building energy consumption by selectively controlling near-infrared (NIR) and visible light (VIS) transmittance. However, its monotonous color changes limit its large-scale application. In this study, we designed a DESW based on the layer-stacked polyaniline (PANI)/silver Nanowires (Ag NWs) composite films. When PANI films is stacked layer by layer with Ag NWs, it not only performs dual band regulation, but also exhibits impressive electrochromic performance with rich color conversions (light yellow, yellow-green and blue-black). The four-layer PANI/Ag NWs composite film outperformed the pure single-layer PANI film because of the faster electron transfer, its coloring time and bleaching time at 525 nm were shortened to 6.7 s and 18.0 s, respectively, and the coloring efficiency was increased to 45.5 cm2 C-1. After 2500 cycles, the PANI/Ag NWs films tend to have better cycle stability. Therefore, the incorporation of Ag NWs enhances the electrochromic performance of PANI films, providing valuable insights for advancing single-component organic electrochromic materials.

Metasurface-based polarization-insensitive absorber with dual-band tunable absorption intensity

In this paper, a polarization-insensitive absorber with dual-band tunable absorption intensity is proposed. Two absorption bands are generated by introducing external branches into a ring structure. Since the resistance of the loaded PIN diode changes with bias current, the reflectivity of two absorption bands can be dynamically adjusted from almost 0 dB to less than −10 dB at normal incidence. Inductors are loaded on both sides of the metal structure, which guarantees not only that the units are connected during DC feeding, but also the symmetry of the metal structure in RF band to ensure polarization insensitivity. The mechanisms of dual absorption bands and tunable absorption intensity are revealed through the detailed analysis of resonant modes, equivalent circuit model, surface current, and loss density distribution. A sample prototype has also been fabricated, and the measured results are well consistent with the simulated ones. The proposed absorber has the unique advantage of dynamic tuning of dual-band absorption intensity, making it a versatile choice in modern communication, radar, and stealth systems.

Improvement of rejection band with Defected Microstrip Line and Ground plane Resonators

In this paper first a dual band bandstop filter is proposed using a unique spiral defect at the signal plane for Wi-Fi communication and remote sensing applications. The spiral defects is studied, simulated and measured. Next proposed spiral defect is combined with the hexagonal head defected resonators at ground plane to improve the rejection band. In addition a study is also done to observe the effects of the proposed defects at both signal plane and ground plane. A comparison is done among the response of individual defects filters and combined defect filter. It is observed that later shows improved overall bandwidth with compactness. The proposed combined defect filter with improved stopband displays 92.6% FBW and 112.5 dB/GHz sharpness factor with very compact in size as 0.26 λ0 × 0.25 λ0. All measurement results are in good agreement with the simulated results.

Enhanced Fano resonances in a silicon nitride photonic crystal nanobeam-assisted micro ring resonator for dual telecom band operation

Silicon-based Micro Ring Resonators (MRR) are a powerful tool for the realization of label free optical biosensors. The sharp edge of a Fano resonance in a Silicon Nitride (Si3N4) platform can boost photonic sensing applications based on MRRs. In this work, we demonstrate enhanced Fano resonance features for a Si3N4 Micro Ring Resonator assisted by a Photonic Crystal Nanobeam (PhCN-MRR) operating in the TM-like mode at the O-band wavelengths. Our findings show that the fabricated PhCN-MRR results in increased asymmetric resonances for TM-like mode compared with TE-like mode operation in the C-band. As a result, a versatile and flexible design to realize Fano resonance with polarization dependent asymmetry in the C and O telecom bands is presented.

Metal oxide-mixed polymer-based hybrid electrochromic supercapacitor: improved efficiency and dual band switching

The inclusion of charge storage properties in electrochromic devices (ECDs) has gained much interest and has evolved into a promising emerging energy-related field due to multifunctional smart device applications. Here, an organic–inorganic solid-state asymmetric electrochromic supercapacitor device (ESCD) containing nano-CoTiO3-mixed poly-3-hexylthiophene and WO3 as two electrodes has been designed to study electrochromic and supercapacitor properties. The electrochemical properties of CoTiO3 show a pseudocapacitive-type charge storage capability, which has been utilized to enhance the electrochromic performance of the ESCD with additional charge storage ability. The device shows charge storage properties with fast charging and slow discharging, giving very high coulombic efficiency with a specific capacitance of 6.4 mF cm−2 at 0.2 mA cm−2 current density. The device shows excellent electrochromic supercapacitive properties with a color contrast of ∼50% and a short switching time of ∼1 s at a 515 nm wavelength with excellent cyclic stability. The device exhibits the capability to cut near infrared wavelength (700 nm and 850 nm) and has a potential application as a heat filtering device. Thus, the addition of pseudocapacitive-type materials in ECDs enhances the capacitive performance along with electrochromic properties, which makes ECDs more suitable for real life applications.

Dual-Notched UWB Orthogonal MIMO Antenna with Improved Gain Characteristics Using Frequency Selective Surfaces for Wireless Communication Applications

In this paper, a complementary split ring resonator (CSRR) loaded compact CPW-fed circular shaped monopole UWB antenna with dual band notch characteristics is designed on an FR-4 substrate. The propounded band-notched UWB antenna is integrated with two frequency selective surface layers referred as bandpass frequency selective surface (FSS-1) and reflector (FSS-2) to offer enhanced radiation performance. Bandpass FSS-1 enhances the gain of the antenna by improving directivity and reflector FSS-2 reflects back the backside radiation of the proposed antenna towards the forward direction thereby increasing gain and directivity of the proposed antenna. Furthermore, a two-element orthogonal MIMO antenna is proposed with improved gain using two FSS layers. The complete configuration of the proposed two-element MIMO antenna consists of CSRR-based radiating patches, monopole ground planes and two integrated FSS layers. The proposed MIMO antenna operates in UWB range from 3.46[Formula: see text]GHz to 16.02[Formula: see text]GHz with dual notches at 3.9[Formula: see text]GHz and 7.2[Formula: see text]GHz. Isolation between MIMO elements is greater than 23 dB. Both antennas are fabricated and investigated at 5.9[Formula: see text]GHz for vehicular communications. Maximum gain improvements of 8 dB and 6.4 dB are observed in case of the presented single element and MIMO antenna within the entire operating band due to the integration of dual FSS layers. The diversity performance of the suggested MIMO antenna is investigated by analyzing mean effective gain, envelope correlation coefficient, channel capacity loss and diversity gain parameters. The proposed MIMO antenna is a suitable candidate for vehicular and UWB wireless communication applications.

Compatible camouflage for dual-band guided-laser radar and infrared via a metamaterial perfect absorber.

Laser-guided detector and infrared detection have attracted increasing attention in a wide range of research fields, including multispectral detection, radiative cooling, and thermal management. Previously reported absorbers presented shortcomings of lacking either tunability or compatibility. In this study, a metamaterial perfect absorber based on a Helmholtz resonator and fractal structure is proposed, which realizes tunable perfect absorptivity (α 1.06μ m >0.99,α 10.6μ m >0.99) of guided-laser radar dual operating bands (1.06 µm and 10.6 µm) and a low infrared average emissivity (ε¯3-5μ m =0.03,ε¯8-14μ m =0.31) in two atmospheric windows for compatible camouflage. The proposed perfect absorber provides a dynamically tunable absorptivity without structural changes and can be applied to optical communication, military stealth or protection, and electromagnetic detection.

Dual-band polarization insensitive graphene-based reconfigurable absorber in a terahertz regime.

In this paper, a dual-band graphene-based absorber is structured and investigated in a terahertz frequency domain. The designed absorber contains a plus-shaped graphene sheet, as well as four dual concentric graphene-based rings. It is designed according to the SiO2-based substrate. A dual concentric graphene ring provides more than 90% absorption from 2.36-3.24THz, while a plus-shaped graphene sheet is accountable for absorption from 5.0-5.32THz. The maximum absorption is found at 2.56, 3.08, and 5.16THz with 99.81%, 97.34%, and 99.74%, respectively. The variation in the chemical potential of the graphene material offers re-configurability in the dual absorption bands. Due to the four-fold symmetry of the designed structure, the absorptivity value is approximately constant for various polarizations with a wide incident angle (more than 60°). The aforementioned features of the proposed graphene-based absorber make it appropriate in a terahertz frequency regime.

Metallic waveguide transmitarrays for dual-band terahertz antennas with high gain and low sidelobe levels

The antenna is an indispensable device in terahertz (THz) wireless communication systems. Owing to the high propagation attenuation of THz waves in atmospheric, THz antennas with high gain and low sidelobe levels (SLLs) are in an urgent need. Here, a metal waveguide transmitarry antenna (MWTA) is proposed to realize high gain and low SLLs at dual THz bands simultaneously. At the frequencies of 0.14 and 0.0972 THz, the peak gains are 32 and 28 dBi, the SLLs are both 21 dB lower than the main lobe, and the 3 dB beamwidths are 4.4° and 5.7°, respectively. As a proof of concept, a prototype with a diameter of 48 mm is fabricated and the measured results are in good agreement with the simulations. The proposed MWTA with high gain and low SLLs at dual THz bands holds great application potential in 6G wireless communication, non-destructive testing, and biomedicine.

Filtering wideband omnidirectional patch antenna with four operation states

A filtering wideband omnidirectional patch antenna with switchable dual bands is proposed to fulfil four operation states in this paper. Firstly, five resonant modes of the antenna are simultaneously and simply excited to enable the dual-band operation. Radiation nulls are generated beyond the bands, which improves the frequency selectivity and out-of-band suppression for the antenna. Furthermore, each of the bands could be easily and independently shut off to introduce three additional operating states by etching slots on the ground plane or/and inserting metallic rods at appropriate positions, with rejections of the suppressed bands larger than 10 dB. The radiation states show the characteristics of wide operation bands and broad stopbands. For verification, the prototypes are designed and fabricated. The simulated and measured results show good agreement.