A highly sensitive temperature sensor based on a polymer cavity of a Fabry-Perot interferometer (FPI) is experimentally demonstrated. The interferometer gives ease in fabrication, and it can be formed by the induction of a thermos-sensitive polymer layer in between two single mode fibers (SMFs). The polymer is used as an FPI cavity for temperature sensing. Due to high thermal expansion coefficient (TEC) and thermos-optic coefficient (TOC) of polymer make the interferometer highly sensitive to ambient temperature. The maximum temperature sensitivity of 2.2209 nm/°C for the polymer FPI cavity of 40.61 µm in the ambient temperature range of 28°C to 34°C is obtained. The proposed sensor shows the advantages of high sensitivity, compactness, simple fabrication, and low cost. Thus, it may become a part of various practical applications in the field of environmental science and engineering sciences.

This paper proposes a novel miniaturized bandpass filter by loading a stepped-impedance resonator (SIR). Owing to the intrinsic characteristic of SIR, a third-order bandpass filter with SIR is presented, which has a size reduction of 38% compared with the conventional hairpin-line filter. On account of the electrical tape gap effect of a defected ground structure (DGS), further miniaturization is realized by introducing a pair of complementary split-ring resonator (CSRR) DGSs. Besides, frequency selectivity and out-of-band rejection can be improved by adding CSRR DGS and source-load (S-L) coupling structures, which produce two transmission zeros at two side band of passband respectively. The results show that the passband range is 3.4-3.6 GHz, and the final size is reduced by 50.3%.

The concept of ultra-wideband (UWB) reconfigurable mmWave/THz microstrip antenna with a newfangled gold radiating patch with two PIN diodes installed on a benzocyclobutene (BCB) polymer is presented. The reconfigurable types of the proposed antenna are frequencies, bandwidths (BWs), and beams reconfigurations. This reconfigurable antenna was designed and simulated with the time-domain based on a FIT solver at the CST MWS solver, while the comparison was with the frequency-domain based onthe FEM solver at the CST MWS solver. The simulation results obtained from both solvers were in fair agreement, supporting the proposed antenna design. These antennas may be used in cellular communication at mmWave/THz band for beyond 5G.

In order to investigate the influence of different magnetization modes on the electromagnetic performance of magnetic gear, four models of magnetic gear with different magnetization modes are established. The finite element method is used to simulate the four models and compare their performances. The distribution of magnetic flux lines, air gap magnetic field, harmonic distribution, static torque and dynamic torque are calculated, respectively. The simulation results show that the coaxial magnet gear with Halbach array has larger air gap flux density amplitude, smaller air gap harmonic content and higher output torque than the other three kinds of magnetic gears.

Double-stator switched reluctance motors (DSSRMs) acquire attention because of their high torque/power generating capability compared to conventional and segmented rotor switched reluctance motors. One of the main limiting performance indices of such motors for industrial applications is its high torque ripple. This paper proposes a 12/10/12 pole DSSRM with an angular shift of half of the stroke angle between inner and outer stators. The respective phase windings of the inner and outer stators are parallelly excited with the same phase angle shift to reduce the torque ripple. Each rotor segment is constructed with a pair of half rotor segments that are isolated from each other through the insertion of a non-magnetic isolator between them. Firstly, the design hypothesis for a low torque ripple DSSRM has been presented; thereafter, some geometric modifications have been suggested and investigated to obtain a nearby response in the proposed DSSRM. The calculation of the width of the non-magnetic isolator, modification in the pole height of outer stator and modification in the arc angles of rotor segments/stator poles are discussed in detail. The effectiveness of the proposed motor is investigated through a 2D finite-element modelling and simulation in ANSYS/MAXWELL software. Simulation results show that the torque ripple is significantly reduced by 74.9% in the proposed DSSRM compared to the baseline DSSRM.

This paper presents a multifunctional metasurface based reflective polarization converter, to convert the polarization of incident electromagnetic wave in three adjacent frequency bands. In the first band linear to circular polarization conversion and in the remaining two bands linear to orthogonal polarization conversion is achieved. The designed metasurface consists of two circular split rings and a star-shaped split resonator which is fabricated on a metal-backed dielectric substrate. From the simulation results, it is evident that the orthogonal linear polarization conversion band is observed at 9.2 GHz and 12.8 GHz with a polarization conversion ratio of more than 92%. Similarly, it is identified that the same metasurface converts the incident linear polarized wave to circularly polarized wave at 7.3 GHz. Furthermore, the proposed metasurface maintains the handedness of the circularly polarized incident wave at 9.2 & 12.8 GHz frequency upon reflection. The proposed multifunctional polarization converter has a simple planar geometry and low profile which can be used in many applications, such as reflector antennas, imaging systems, remote sensors, and radiometers.

In this paper, a 3-port compact MIMO antenna is designed using Characteristics Mode Analysis (CMA). It consists of three antenna elements. Ant-1 is 45˚ tilted, and Ant-2 and Ant-3 has L-bend transitions. Ant-2 is 1/4th, and Ant-3 is 1/2 in size w.r.t. Ant-1. To improve 10-dB impedance bandwidth and isolation > 17 dB, fractal slot is etched at bottom, and deformity in antenna structures has three distinct modes. Ant-1 operates in UWB mode from (4.8-10.6) GHz with 75.32% IBW, and Ant-2 and Ant-3 operate in wide-band mode from (8.1-10.8) GHz with 28.57% IBW and from (7.2-9.8) GHz with 30.58% IBW. CMA is utilized to investigate the anonymous behaviour of antenna, predicts modal significance (MS), characteristics angle (CA) and eigen values (EV). From these parameters bandwidth potential, radiation energy source and Q-factor are estimated. For investigations first six modes are swept in modal navigator, where dominant modes are traced as ideal antenna resonant modes, and unwanted modes are neglected. The antenna gain is (3-7) dBi with ECC < 0.08. The proposed antenna is fabricated and measured for validation. From the outcomes, it is found suitable for UWB, air traffic and defense tracking, meteorological, amateur satellite, maritime vessel traffic controlling, and X-band satellite applications.

A coplanar waveguide (CPW) fed multiple-input multiple-output (MIMO) ultra-wideband (UWB) antenna with high isolation and dual band-notched characteristic is proposed. The antenna consists of two orthogonal circle patches. An annular SRR slot and a rectangular SRR slot are added on the patches to produce two notched bands. High isolation is successfully acquired by adopting a double Y-shaped branch between the two radiation elements. By cutting the fractional substrate, the antenna size has been reduced by 31.4 percent. The measured results show that the working bandwidth of the antenna covers 2.36-12 GHz, and at the same time, the notched bands cover 3.37 GHz-3.98 GHz and 4.71 GHz-5.51 GHz. The isolation is better than 21 dB. The paper also studies the radiation pattern, peak gain, and envelope correlation coefficient (ECC) of the UWB MIMO antenna.

In this paper, a Q-band GaAs low noise amplifier (LNA) for satellite communications is presented. The LNA is designed using common-source (CS) topology, self-biased configuration and current-reused technology. Simultaneous noise and input matching are achieved by employing source series inductance. The current-reused LNA is fabricated in a 90 nm GaAs pseudomorphic high electron mobility transistor (pHEMT) process. On-wafer measurement results show that the LNA features a small-signal gain of 23.8~24.5 dB, noise figure (NF) of 2~2.1 dB, and output 1-dB compression point (OP1 dB) of 6.6~8 dBm over 36~42 GHz, while consuming 10.9 mA with a supply voltage of 5 V. The chip size is 1.6×0.8 mm² including all RF and dc pads.

Wheat, canola, and pasture are three of the major vegetation types studied during the Soil Moisture Active Passive Validation Experiment 2012 (SMAPVEX12) conducted to support NASA's Soil Moisture Active Passive (SMAP) mission. The utilized model structure is integrated in the SMAP baseline active retrieval algorithm. Forward lookup tables (data-cubes) for VV and HH backscatters at L-band are developed for wheat and canola fields. The data-cubes have three axes: vegetation water content (VWC), root mean square (RMS) height of rough soil surface and soil permittivity. The volume scattering and doublebounce scattering of the fields are calculated using the distorted Born approximation and the coherent reflectivity in the double-bounce scattering. The surface scattering is determined by the numerical solutions of Maxwell equations (NMM3D). The results of the data-cubes are validated with airborne radar measurements collected during SMAPVEX12 for ten wheat fields, five canola fields, and three pasture fields. The results show good agreement between the data-cube simulation and the airborne data. The root mean squared errors (RMSE) were 0.82 dB, 0.78 dB, and 1.62 dB for HH, and 0.97 dB, 1.30 dB, and 1.82 dB for VV of wheat, canola, and pasture fields, respectively. The data-cubes are next used to perform the time-series retrieval of the soil moisture. The RMSEs of the soil moisture retrieval are 0.043 cm³/cm³, 0.082 cm³/cm³, and 0.082 cm³/cm³ for wheat, canola, and pasture fields, respectively. The results of this paper expand the scope of the SMAP baseline radar algorithm for wheat, canola, and pastures formed and provide a quantitative validation of its performance. It will also have applications for the upcoming NISAR (NASA-ISRO SAR Mission).

The use of invasive weeds optimization in the synthesis of antenna arrays has become popular in the last few years. This optimization method is robust, simple and can be easily improved. Like other stochastic algorithms, IWO suffers from premature convergence and other drawbacks. To overcome these problems, a dynamic IWO is proposed and used for synthesizing two antenna array topologies (linear and circular array). This proposed method tries to achieve an optimal array pattern by acting on the amplitude excitation of elements in the non-uniform circular array and their positions on the array to obtain an array pattern with deep nulls in some directions of interferences and low side lobe level. For the linear array, the nulls control can be achieved by acting on the relative amplitude excitation of each element in the array for an optimal inter-element spacing. This proposed method improves the performance greatly and allows to achieve a maximum reduction in side lobe level in band Nulls with an acceptable dynamic range ratio (DRR). To show the performance of the proposed method, for each topology, our results are compared to other results of the literature.

Owing to its all-day and all-weather imaging capabilities, high-resolution spaceborne synthetic aperture radar has shown great potential for the effective monitoring of wide-area, ultra-high-voltage (UHV) transmission lines. Scattering characteristics of UHV power lines in 3-m-resolution TerraSAR-X images is analyzed in this paper. First the study area and structure of the UHV transmission line are introduced. Then, the data processing method is described, which includes the preprocessing of TerraSAR-X images and target feature extraction. Finally, the scattering characteristics of the UHV power line are analyzed, and the analysis results demonstrate that the UHV power line can be visible in a TerraSAR-X image only when the angle between its extension direction and the azimuth of the sub-satellite ground track is within ±15°. Furthermore, besides the span length, the spatial location of the UHV power line in a TerraSAR-X image is also influenced by the angle between its extension direction and the azimuth of the sub-satellite ground track, as well as by the height difference between adjacent pylons.

This paper presents two size-miniaturized quarter mode (QM) and eighth mode (EM) substrate integrated waveguide (SIW) bandpass filters (BPFs), which are embedded with a novel frequency-dependent coupling (FDC) structure. The proposed FDC is implemented as a composition of balanced folding lines and inductive iris. One additional transmission zero (TZ) introduced by FDC between two cavities leads to higher frequency selectivity and better out-of-band rejection. Higher order modes suppression appears by combining the loaded paired open stubs on feeder lines with FDC technique, achieving a wide stopband. Meanwhile, the circuit dimension is further reduced by symmetrically cutting SIW. To validate the novel approach, the frequency-dependent coupling matrix (CM) is implemented to determine characteristics of the proposed structure in theory, QM- and EM-SIW BPFs loaded with FDC have been designed, fabricated and measured. Experimental results illustrate the characteristics of miniaturization and good performance. All results are in good agreement.

In this research project, the hardware implementation of a Field-Programmable Gate Array (FPGA) based Fast Fourier Transform (FFT) will be carried out by using Verilog Hardware Description Language (HDL). Since FFT serves as the core for the Range Doppler Algorithm (RDA) in Synthetic Aperture Radar (SAR) processing, it is of paramount importance to evaluate the algorithm and its computational complexity for the design of an efficient FFT hardware architecture. The design process and Verilog hardware description language which is used to describe and model a digital FPGA-based SAR processor will be introduced. Detailed explanation of the hardware implementation for FFT and Inverse Fast Fourier Transform (IFFT) in SAR processing are thus presented. The performance evaluations of the proposed processors including the comparison of the proposed processor with MATLAB-based processor, timing considerations of the processor, and lastly the hardware resources usage considerations are delivered at the end of this paper.

In this paper, new fractal curves are designed, simulated, and implemented for passive UHF RFID application. 5-, 6-, 7-, and 8-sides polygon fractal loops are proposed and implemented in this work based on the 2nd iteration. It is shown that increasing the number of sides can improve the performance and minimize the size of the fractal antenna. The designed fractal loop antennas have been compared with other fractal loop antennas published previously, and the recent antennas show a better performance. The designed antennas are fabricated using PCB technology, and the antenna parameters are measured experimentally and compared to CST simulations. There is an acceptable agreement between the simulated and measured results. The effect of different materials on antenna performance is also studied.

In this paper, the performance analysis of a dual-hop reconfigurable intelligent surface (RIS)-aided power line communication (PLC) system is presented under different relay transmission protocols. The relay is assumed to be decode-and-forward (DF) or amplify-and-forward (AF) relaying protocol. It is also assumed that the RIS link is subjected to Rayleigh fading while the PLC link undergoes Log-normal fading with the influence of additive background and impulsive noise. To evaluate the system performance, the end-to-end cumulative distribution function for both relaying protocols are derived. Based on these, the analysis expressions for the system outage probability and average bit error rate (ABER) are derived under DF and AF relaying protocols. To gain further insight about the system performance, the asymptotic analysis for the derived expressions is obtained at high signal-to-noise ratio regime. The findings illustrate the significant impact of the number of RIS elements and impulsive noise on the overall system performance. In addition, the accuracy of the analytical results is justified through Monte-Carlo simulations.

By combining the method of moments and the compressive sensing theory, a rapid scheme for analyzing the electromagnetic scattering problems over a wide incident angle has been developed, by which the calculation times of traditional method of moments can be decreased efficiently. To further reduce the calculation times, the matrix splitting technique is proposed to establish a new scheme in this paper. The basic principle is elaborated in detail, and the effectiveness of the new scheme is verified by numerical results.

A non-invasive thermometry approach for monitoring core (internal) tissue temperature using microwave radiometry is presented. We detail the design and analyses of a microwave antenna capable of detecting core temperature at depth. Performance of the radiometer with a printed dipole antenna is evaluated at frequency of 1.4 GHz in a multilayer 3D computational structure consisting of skin, fat, and muscle. To study this approach, a human tissue model was constructed with skin, fat, and deep muscle tissues having electrical properties at working frequency of 1.4 GHz. One of the main challenges is the Radio Frequency (RF) interface; hence, frequency selection will be important. Moreover, the antenna must be designed for characteristics in close proximity of biological medium in the selected frequency band. The Specific Absorption Rate (SAR) and volume loss density have been used to determine the amount of absorbed power in each tissue layer and thus emitted power from each tissue layer. This approach has been designed to detect thermal emissions radiated from tissue up to 23 mm deep. We present the numerical analysis of 3D tissue-layer power emission and temperature sensing by a microwave radiometric antenna from a single frequency band of 1.4 GHz. Computed results show that this method senses the internal temperature in each tissue layer.

In this article, we present a compact and efficient diametrically-fed dual port fractal UWB MIMO antenna for portable handheld wireless devices. The electromagnetic behaviour on conducting body is analyzed through classical approach based characteristics mode analysis (CMA). Their intrinsic characteristics are explored on the basis of (a) modal surface current distributions, (b) narrow/broad bandwidth capability and (c) radiation potentials. Concurrent analysis is persuaded on diametrically-fed dual port fed fractal conducting surface, that provides interesting facets on the combinatory effect of electromagnetic performance and physical behaviour on metallic radiator, metallic ground planes (unconnected/connected) and combination of two aforementioned metallic compact geometries. Theoretical insights are investigated for essential/non-essential modes existing in proposed geometry. The investigation through CMA also gives plethoric information on the feed location of antenna on modal surface currents and similar trends to capture its radiation potentials on the current nulls existing in the physical body. A broad classification of modes is explained, covering the CMA modal dynamics such as (a) characteristics angle (CA), (b) eigen values (EV) and (c) modal significance (MS). These additive parameters in general reflect the resemblance of Q-factor≈B.W. for narrowband/wideband traits, electrically/magnetically coupled energy behaviour and radiative potential for far-field propagation. Thus, in a nut-shell, it can be inferred that `CMA provides physically intuitive guidance for the analysis and designing of antenna structures'. To support the findings highlighted in this particular study, a concise review about the theory of characteristic modes and the practical examples that use such concepts are taken into consideration.

A novel circularly polarized (CP) square slot antenna for covering the universal ultrahigh-frequency (UHF) radio frequency identification (RFID) band is proposed. The antenna uses low-cost FR4 material as the dielectric substrate and coplanar waveguide (CPW) to feed. Circularly polarized radiation can be realized by embedding two symmetrical rectangular grounded planes with L-shaped slits in opposite corners of the square slot. The widened vertical tuning stub at the end of the signal line fed by CPW can improve the CP and impedance matching operation, and finally realizes broadband characteristic. The measured 10 dB impedance bandwidth and 3 dB axial ratio (AR) bandwidth are 1250 MHz (710-1960 MHz) and 180 MHz (840-1020 MHz), respectively. The measured peak gain is about 3.4 dBi in the whole UHF RFID frequency band (0.84-0.96 GHz). The dimension of the CP square slot antenna is 116×116 ×1.6 mm³. The proposed antenna has the advantage of simple structure, is easy to be processed, can exhibit dual CP radiation characteristic, and covers the broadband frequency range, which can be applied to the UHF RFID handheld reader environment.