In this research, the potential of L-band SAR data is evaluated for tropical peatland forest biomass estimation using polarimetric features and field data. For this, ALOS-2 full polarimetric data are acquired over central Kalimantan, Indonesia. Total 54 sampled plots (20 m x 20 m) were established in the study site; diameter at breast height (DBH) and tree species of every tree were collected in each plot. Locally developed allometric equations were used to convert field data to biomass and plot level biomass, and the upscaling factor was applied to upscale plot level biomass to standard tones per hectare scale. Backscattering coefficient (σ_o) was computed for HH, HV, VH and VV polarization. Similarly, eigen decomposition was performed to extract: entropy (E), alpha (α), and anisotropy (A); also diversity indices were computed. Yamaguchi decomposition was performed to extract scattering behavior of forest in central Kalimantan. All polarimetric parameters were upscaled to one-hectare scale. Field data were divided into training plots (70 percent → 42 plots) and validation plots (30 percent → 12 plots). Nonlinear regression analysis was performed between polarimetric parameters and training plots. Perplexity, Shannon index, entropy, Gini Simpson index, index of qualitative inversion, Reyni entropy (order 2), σ_HV, alpha, σ_VV, and volumetric scattering component were found significantly correlated (ranging R² from 0.67 to 0.49) with the field data. The corresponding nonlinear model was inverted, and biomass maps were computed for the individual model. The resultant biomass maps were validated using validation set of referenced measurements. Perplexity, Shannon index, entropy, Gini Simpson index, index of qualitative inversion, Reyni entropy (order 2), σ_HV, alpha, σ_VV and volumetric scattering exhibited a significant correlation between field biomass and predicted biomass computed using developed model. R² for validation ranges from 0.95 to 0.81 with RMSE ranging from 13.59 Mgha^-1 to 25.63 Mgha^-1. The estimated biomass in study site ranges from 49.31 Mgha^-1 to 290.60 Mgha^-1.

Wide bandwidth and high gain designs of sectoral microstrip antennas gap-coupled with parasitic arc shape patches are proposed. In 1800 MHz frequency band, optimum response with bandwidth of more than 50% and peak gain of 10 dBi is obtained for 30° sectoral angle employing two gap-coupled arc shape patches. Further gap-coupled variations of slot cut single arc shape patch with 60° sectoral patch is presented. This design yields bandwidth of above 930 MHz (~53%) with peak gain of more than 10 dBi. The comparison for the proposed gap-coupled sectoral variations with reported antennas is presented. Proposed gap-coupled sectoral configurations are single layer and thus simple in design and yet offers bandwidth and gain of larger than 50% and 10 dBi, respectively.

Tunneling of microwave radiation through a symmetrical trilayer ENG-ferrite-ENG is considered, where ENG refers to a medium of negative permittivity. Such trilayer is an example of a magnetically controlled structure that under certain conditions allows a complete (or perfect) tunneling of the incident radiation. In this paper, the general conditions of the perfect tunneling are analyzed, and the transmissive properties of the structure are studied numerically. It is demonstrated that a broad passband, in which the structure is almost completely transparent, may be obtained both above and below the frequency of the ferromagnetic resonance. The bandwidth can be effectively controlled by an external field that is magnetizing the ferrite layer.

A reconfigurable antenna with on-demand single-band or dual-band rejection capability for ultra-wideband (UWB) applications is presented. A modified monopole structure is integrated with a U-shaped slot and an open-ended slot to realize band-rejection. The antenna operates in four modes: a full UWB (3.1-10.6 GHz) coverage antenna, a UWB antenna with a single-band WiMax or wide local area network (WLAN) rejection, and a UWB antenna with dual-band WiMax/WLAN rejection. On-demand single and dual-band rejections are implemented by controlling two slots using two PIN diodes. Thus, the adopted control technique is quite easy and requires low operating power. Details of the design process and reconfiguration mechanism are presented. The band-rejection performance is explained by return loss and surface current distribution at single-band mode. A prototype is built on a Rogers substrate and tested to validate the performances. The antenna exhibits stable radiation characteristics and almost flat gain responses across the whole band, while significantly gain reduction is achieved at the rejected bands. Therefore, this antenna is suitable for high-performance UWB systems in WiMax/WLAN dense environments with the aim to improve signal quality, system capacity, and communication efficiency.

In this paper 8000 rpm generators with the magnetic cores made of amorphous low-coercivity material and electrotechnical steel were designed. The sizes of the magnetic cores of generators were calculated analytically. Computer simulations of the generators under study were carried out to obtain a complete pattern of the magnetic field distribution in the magnetic cores and to estimate the generator losses. Experimental models of the generators were also made, which were studied at no load and with load. A special bench with a torque sensor was used for experimental studies.

In this paper the design of asymmetric wideband printed dipole antenna is presented along with measured results. The wide bandwidth covering 0.8-4 GHz is achieved using inset feeding technique. This paper also presents the techniques for achieving good omni-directional radiation patterns over the wide frequency band with deviation from omni-directionality within ±2.5 dB. This design offers more than 5:1 impedance bandwidth (for VSWR≤2.2:1), with good radiation efficiency and omni-directionality. The comparison study of symmetrical and asymmetrical printed dipole antennas with and without inset feed is presented in this paper. Thus, the proposed antenna finds a wide range of applications in trans-receive modes in today's wireless devices.

In the development of hand gesture based Human to Machine Interface, the Doppler response feature extraction method plays an important role in translating hand gesture of certain information. The Doppler response feature extraction method from hand gesture sign was proposed and designed by combining time and frequency domain analysis. The extraction of the Doppler response features at the time domain is developed by using cross correlation, and the time domain feature is represented by using peak value of cross correlation result and its time shift. The Doppler response feature of frequency domain is extracted by employing a discriminator filter determined by the frequency spectrum observation of Doppler response. The proposed method was employed as a pre-processing for Continuous Wave (CW) radar output signals, which is able to relieve the pattern classification of Doppler response associated with each hand gesture. The simulation and laboratory experiment using HB 100 Doppler radar were performed to investigate the proposed method. The results show that the combination of all three features was capable of differentiating every type of hand gestures movement.

Regarding the increasing application of terahertz technology, the interest in using two-wire waveguides is getting more and more popular due to their favorable propagation properties. Therefore, a more accurate analysis of these structures is very important. In this paper, a simple analysis of the guided waves in a two-wire waveguide based on Bipolar Coordinate System (BCS) has been investigated. The structure under study is two infinite perfect electric conductor (PEC) cylinders in z direction, whose axes are positioned at a distance d from each other. The solution of TE and TM modes is sought by the aid of electromagnetic formulation, and an analytical expression is proposed for electromagnetic fields and cutoff wave numbers, which have not been present in any of the previous studies. In this study, for the first time a BCS has been used to formulate two-wire waveguide problem, and the validity range of the answer is discussed. The values of the cutoff wave numbers are calculated for the first few modes of TE and TM, using both the proposed method and Finite Difference Method (FDM). The precise correspondence of the obtained values with the proposed method with those of FDM, along with the high speed and simplicity in implementation, introduces the present method as an appropriate candidate for analyzing transmission lines using parallel cylinders.

In this paper, the implementation of convolution perfectly matched layer (CPML) with good absorbing property is proposed for the symplectic multi-resolution time-domain (SMRTD) method, and a side-wall vault-top tunnel model is established by using the equidistant equation. The radian of the tunnel can be selected in the range of 0-π/2 according to actual needs. The absorbing performances of perfect matched layer (PML) and CPML are compared in the proposed tunnel model. In addition, based on the straight tunnel model and curved tunnel model with different radians, the characteristic of field cross-section distribution of electromagnetic pulse (EMP) propagation excited by TE₁₀ mode is studied.

This paper presents the first coupled-line coupler that provides independent power division ratios at dual bands. In contrast with previous dual-band coupled-line couplers, the power division ratios k²(f₂) and k²(f₂) at each band (f₁ and f₂) can be independently controlled in order to satisfy the requirements of various communication protocols at different bands. Moreover, it has a compact size due to the usage of coupled lines rather than transmission lines. Explicit design equations and design guide of the coupler are provided. In this letter, one prototype of the proposed coupler is simulated, fabricated, and measured. It provides power division ratios k²(f₁)=4 dB at f₁=1 GHz and k²(f₂)=8 dB at f₂=2.4 GHz. The measured result agrees well with the simulation.

Wireless technology has significant improvement in features enhancement of device applications. It is highly desirable to operate multiple applications from a single device. A compact size antenna is presented for a variety of IoT based applications, such as home automation, surveillance, satellite communication, vehicle tracking, and medical instruments. This article explores an analytical solution of ultra-large band frequency characteristics of a compact size, trident shape, fractal patch antenna. The overall structure has dimension 18x12x1.6 mm³. This antenna exhibits the multi-edge radiating effects of fractal structure with the help of ground optimization technique. The design evolution consists of a performance measure of the antenna with varying characteristics of the EBG patterns with respect to fractal structure. The design is validated by fabricating the antenna on an FR4 (4.2) substrate, and the return loss & radiation characteristics are measured. The measured |S₁₁| has the impedance bandwidth of 1.59-13.31 GHz and sustainable radiation characteristics. This miniaturized antenna is compatible with the GSM, GPS, Bluetooth, Wi-Fi, WLAN, Wi-MAX, ISM, and other UWB spectrums. The gain of the antenna is 2.52 dBi for the complete operating range. Therefore, the proposed antenna is highly compatible with various wireless devices associated with IoT applications.

A compact square patch band-pass filter is proposed in this paper. The dual-mode filter is designed based on a square patch resonator with a complementary split ring resonator (CSRR) split to be used as a perturbation element. The CSRR split is properly embedded in the square patch resonator to perturb electric current distribution on this patch and thus to simultaneously excite a pair of degenerate modes. Using the proposed CSRR elements, the band-pass filter is designed with miniaturized size, and two transmission zeros in stopbands are achieved to improve the selectivity of the filter. The influence of the CSRR elements on the band-pass filter is analyzed in detail. The proposed dual-mode filter is then fabricated and measured. Good agreement over a wide frequency range is achieved between the simulated and measured results. Moreover, in order to further investigate the characteristic of the dual-mode patch filters with CSRR perturbation, a dual-mode filter with a rectangular ring slot is presented for comparative study.

With reference to the mask-constrained power synthesis of shaped beams through fixed-geometry antenna arrays, we elaborate a recently proposed approach and introduce an innovative effective technique. In particular, the proposed formulation, which can take into account mutual coupling and mounting platform effects, relieson a nested optimization where the external global optimization acts on the field's phase shifts over a minimal number of `control points' located into the target region whereas the internal optimization acts instead on excitations. As the internal optimization of the ripple is shown to result in a Convex Programming problem and the external optimization deals with a reduced number of unknowns, a full control of the shaped beam's ripple and sidelobe level is achieved even in the case of arrays having a large size and aimed at generating large-footprint patterns. Examples involving comparisons with benchmark approaches as well as full-wave simulated realistic antennas are provided.

A novel embeddable miniature near-field reader antenna is designed for Ultra-High Frequency (UHF) Radiofrequency Identification (RFID) applications in the healthcare sector. The antenna spans 45 mm (length) x 20 mm (width) x 1.6 mm (thick) in size. The antenna is tuned for UHF RFID region-2 frequencies, 902 to 928 MHz. The antenna's -15 dB return loss bandwidth is 140 MHz. The antenna has very low far-field gain, and thus false reads of undesired tags are eliminated. The antenna can read both near-fields, and far-field tags as its magnetic field distribution on its surface are uniform with no dead zones. This miniature, light weight antenna is easy to embed and suitable for niche applications like surgical instrument tracking, dental instrument inventory, etc. The antenna's immunity towards proximity metal assets makes it more suitable for healthcare applications.

Datacenters become an important part of technical infrastructure. The Datacom traffic grows exponentially to satisfy the demands in IT services, storage, communications, and networking to the growing number of networked devices and users. High bandwidth and energy efficient optical interconnects are critical to improve overall productivity and efficiency in data centers. Mega-data centers are expected to address the power consumption and the cost in which optical interconnects contribute quite a large part. Silicon photonics is a promising platform to offer savings in power and potential increase in bandwidth for Datacom. Several modulation techniques are developed in silicon photonics to reduce the optical mode volume or enhance the light matter effectto further improve the modulation efficiency. Many other materials such as III-V and LiNbO₃ are integrated on silicon photonics to maximize the optical link performance. This paper reviews several modulation techniques for Datacom, from VCSEL direct modulation to silicon photonics modulators then to hybrid silicon modulators.

Layered molybdenum disulphide (MoS₂) can efficiently emit photoluminescence (PL) excited by visible light. However, one-photon PL of MoS₂ for bioimaging purposes suffers from strong autofluorescence and ion-induced PL quenching. Herein, we report single layer chitosan decorated MoS₂ nanosheets as nonbleaching and nonblinking optical nanoprobes under near infrared femtosecond laser excitation and their applications for two photon luminescence (TPL) and second harmonic generation (SHG) bioimaging. The TPL can resist the ion-induced quenching by the cellular membrane. The proposed TPL and SHG of singlelayer MoS₂ show great potential for real-time, deep and multiphoton bioimaging.

In this paper, a three-port pattern diversity antenna with a Fabry-Perot cavity (FPC) using a partially reflective surface (PRS) for 5.2 GHz Wireless Local Area Network (WLAN) access points is proposed. The topology of three coaxial-fed circular patch antennas provides an initial beam tilt of 15˚. The PRS aperture, at a height of approximately λ/2, is then shaped in such a way for the antenna to radiate at 0˚, +25˚, -25˚, which results in total coverage of 90˚. The antenna system has an impedance bandwidth of 2% ranging from 5.16 GHz-5.25 GHz (90 MHz bandwidth), covering the IEEE 802.11a band, for a gain of 10 dBi throughout the band and across the ports. The shaped PRS structure provides a gain enhancement of 4.5 dB. The mutual coupling between any two ports in the three-port antenna system is less than 17 dB for a port-to-port distance of 0.67λ.

An improved wideband cavity-backed antenna and a planar phased array with wideband wide-angle impedance matching (WAIM) are provided in this paper. A step-shaped cavity is applied in the antenna, so the relative bandwidth of VSWR < 2 can be improved to more than 52% without increasing the cavity profile. Furthermore, a planar phased array constructed by the cavity-backed antenna can work with a wide-angle scanning range of ±60° at both E- and H-planes. Due to the wide-angle scanning range, the impedance matching for the phased array will be unstable in the required wideband. Consequently, the matching layer with metamaterials has been loaded on the phased array. The VSWR is controlled within 2 in E-plane and 3.5 in H-plane during the scanning range of ±60° in wide bandwidth.

In this paper, an efficient Transmission Line Matrix (TLM) approach based on the shift operator (SO) has been developed to model electromagnetic wave interactions with gyroelectric media. The main idea of this technique is to formulate the electric current density vector components by introducing the equivalence between time differential operator ϑ/ϑt and discrete time shift operator z. A concise formulation of voltage sources modeling the frequency dispersive properties of gyroelectric media is then deduced and implemented. Numerical simulations illustrate the Faraday rotation phenomenon in time domain, and in the frequency domain, reflection and transmission coefficients of left hand circular polarization and right-hand circular polarization waves are also calculated. A comparison of SO-TLM scheme with five other approches according to the criteria of accuracy and CPU time is presented. Numerical experiments show that SO-TLM provides the most accurate and fastest results.

Fibre Bragg Gratings (FBGs) offer several advantages including their immunity to electromagnetic fields making them excellent in situ sensors for feature extraction in electrical machines condition monitoring. However, the pre-requisite of bonding FBGs circumferentially on either the machine cast frame or stator windings can introduce undesired sensing characteristics. This is because the FBG relies on adhesives as the transfer medium for any sensed parameter between the machine and sensor. Whilst FBG sensors rely mainly on wavelength shift, an intolerably low signal-to-noise ratio will result in difficulty in measuring such shifts. As a complementary signature, differential optical power can be combined with wavelength shift to broaden the feature extraction capability of FBG sensors. This makes power level (dBm) an important sensing parameter for FBG sensors. The effect of varying number of bonding points on transmitted optical power is investigated using unstripped and stripped bare fibres as well as an actual FBG sensor. Increasing the number of bonding points beyond an optimum number has been observed to significantly attenuate the optical signal power level and quality for a given dynamic range. Hence, as the number of bonding points is increased, the level of attenuation should be closely monitored to ensure that the optimum number is not exceeded if excellent and accurate FBG sensing characteristics are to be realised.