In this paper, two microstrip antennas with a U-slot on the patch are presented for base station applications to provide simultaneous communications for uplink and downlink respectively. The intended antennas are expected to operate in triple bands, i.e., to cover GSM and LTE bands. The three designated bands for uplink antenna are from 823 MHz to 830 MHz for lower band, 1.738 GHz to 1.761 GHz for middle band and 2.321 GHz to 2.355 GHz for upper band. Similarly, the antenna which is designed for downlink operates in three bands from 872 MHz to 880 MHz for lower band, 1.81 GHz to 1.85GHz for middle band, and 2.338 GHz to 2.375 GHz for upper band. These frequency band(s) satisfy the requirements of GSM850, GSM1800, and LTE2300 bands. Comparisons among designed, simulated and measured results are presented. Isolation parameters and the Envelope Correlation Coefficient (ECC) values of Multiple Input Multiple Output (MIMO) antenna in all specified bands are also presented.
Study of Global Navigation Satellite System (GNSS) for various non-navigational applications is gaining importance day by day. Very recently, India's Navigation with Indian Constellation (NavIC) is a new entry in GNSS systems available worldwide such as GPS, GLONASS, Galileo and Beidou. One of the important non-navigational applications is the study of soil moisture with GNSS. NavIC is very much different from widely used and globally available GPS system. Therefore, in this paper we have analyzed and developed an algorithm for soil moisture retrieval with NavIC Carrier to Noise (C/No) ratio. Information of soil moisture is very beneficial for various applications such as groundwater estimation, management of agricultural, drought monitoring and prediction, weather forecasting and flood forecasting. Amplitude of multipath Carrier to Noise (C/No) ratio from the NavIC receiver at L−band has been utilized to determine the soil moisture from the smooth bare soil surface. The analyses of sensitivity of soil moisture have been carried out by observing the NavIC multipath data and measurement of in situ soil moisture content. The algorithm development focuses on the retrieval of multipath amplitude from the interference pattern created at the receiver due to direct signal and reflected/multipath signal. The 1st, 2nd, and 3rd order polynomials have been analyzed to detrend the signal before fitting it with sinusoidal variation. It was observed that the multipath amplitude retrieved after detrending the C/No data with the 1st order polynomial provides better correlation with observed soil moisture than the 2nd and 3rd order polynomials. An empirical relationship between multipath amplitude and soil moisture has been developed. This developed empirical relationship is capable of providing soil moisture with known multipath amplitude. The retrieved soil moisture with developed algorithm is in good agreement with observed soil moisture with RMSE of 1.43%. Obtained results indicate the promising potential for the estimation of soil moisture with NavIC C/No ratio.
A methodology for designing planar spiral antennas with a feeding network embedded within a dielectric is presented. To avoid a purely academic work which may not be manufactured with available standard technologies, the approach takes into account manufacturing process requirements by choice of used materials in the simulation. General design rules are provided. They encompass amongst others, selection criteria for dielectric material, aspects to consider when sketching the radiating element design, as well as those for the implementation of the feeding network. A rule of thumb, which may be helpful in the determination of the antenna supporting substrate's height, has been found. The appeal of the method resides in the fact that it eases up the design process and helps to minimize errors, saving time and money. The approach also enables the design of compact and small-size spiral antenna as antenna-in-package (AiP), and provides the opportunity to assemble the antenna with other RF components/systems on the same layer stack or on the same integration platform.
A novel CPW-fed circular polarized slot printed monopole antenna for 5G application is presented. The proposed slot monopole antenna occupies a small area of 0.23λo x 0.35λo x 0.019λo, and the wavelength has been obtained for the center frequency of 3.4 GHz to 3.8 GHz range. First, two square slots are inserted on either side of the feed line and to provide two orthogonal electric fields, a spiral stub is embedded in one of the slots. In order to improve the axial ratio bandwidth of the proposed antenna, it is possible to etch another spiral stub on the other side of the feed line. The proposed antenna provides circular polarized radiation such that the reflection coefficient bandwidth (below -10 dB) is about 1.4 GHz (from 2.9 GHz to 4.3 GHz) or 38.89%, and the axial ratio bandwidth below 3 dB is about 400 MHz, from 3.4 GHz to 3.8 GHz. This is 11.1% at center frequency of 3.6 GHz. This antenna covers the useful frequency bandwidth for 5G application. Simulation and measurement results are presented.
Magnetic materials are found naturally in certain terrestrial and extra-terrestrial geological settings and can influence subsurface mapping and fluid transport and content estimations. With the advent of magnetic nanoparticle research there is also the possibility that these will be inputted in the environment on purpose, as research and industrial applications, or inadvertently as contaminants. The presence of magnetic materials is usually not considered in electromagnetic response modeling of saturated or partially saturated porous materials. This is because relative magnetic permeability of most natural materials is close to one, and thus should not affect propagation velocity calculations. The objective of this study was to investigate the effect of magnetic mineral inclusions on the velocity of propagation of an electromagnetic signal on porous materials saturated with water and its influence on volumetric water content estimation. The effective relative dielectric permittivity and magnetic permeability terms were modeled using Maxwell-Garnett, Polder-van Santen, Lichtenecker and Looyenga effective medium approximation equations. Data from three nonmagnetic soils saturated with water to varying degrees was used for preliminary model evaluations. The effect of magnetic minerals was tested by mixing magnetic sand with quartz sand at different proportions and measuring propagation velocity under fully water saturated conditions using Time Domain Reflectometry (TDR). Propagation velocity decreased with increasing magnetic volume fraction, while the effect of increasing magnetic fraction on attenuation factor was not markedly distinct. Water content estimations using models not accounting for magnetic inclusion substantially overestimated volumetric water content in saturated porous media.
A traditional magnetic resonant coupling wireless power transfer (MRC-WPT) system is highly sensitive to the distance between transmitting and receiving coils. The transfer performance deteriorates at short distance due to magnetic over-coupling and magnetic weak-coupling at long distance which also results in the decrease of power. In order to improve the power transfer ability, this paper presents an MRC-WPT system with a novel design of resonant loops. Unlike the conventional system in which the receiving coil is identical with the transmitting coil, the receiving coil in the proposed system is different from the transmitting coil in terms of distance between turns. Theoretical equivalent models are presented to investigate the impact of the mutual inductance on the transfer efficiency. Based on numerical simulation, it is found that relatively more uniform mutual inductance can be obtained with the proposed resonant loops. With the proposed MRC-WPT system, the results show that the power transfer ability at short and long distances is improved. The average transfer efficiency is enhanced about 10% compared with the conventional system. Furthermore, the sensitivity of the proposed MRC-WPT system to lateral and angular misalignments is studied and compared with the conventional system. An experimental prototype of the proposed MRC-WPT system is designed for validation. The results show that the performance of the proposed MRC-WPT system outperforms the conventional system without adding any complicated control circuits.
The aim of this paper was to propose and design a photonic crystal drop filter based on ring resonators and study its properties numerically. This structure is constituted in a two-dimensional square lattice. The resonant wavelengths of the PCRR proposed are λ = 1.553 μm, and the extraction efficiency exceeds 99% with a quality factor of 5177. To study the all-optical OR and XOR logic gate function, we calculated the electric field distribution of the 2D photonic crystal for the 1.553 μm signal light. In order to have a large selectivity of filtering and also of having a fast switching in the field of nonlinearity, we increase the number of ring resonators, and the latter are used for designing all optical logic gates which work using the Kerr effect equal to 10-6 m2/w.
Design of a harmonically tuned RF Power Amplifier (PA) with enhanced efficiency and gain is presented in this letter. It makes use of a tri-band impedance transformer as a two-port output network for facilitating concurrent optimum fundamental and harmonic impedances at the drain terminal. The design is augmented by analytical formulations and analysis to identify the optimal impedance matching scenario at the fundamental, second harmonic, and third harmonic. A thorough analysis reveals that the proposed PA design scheme is very simple while maintaining the performance obtained from the load-pull. A prototype operating at a frequency of 3.5 GHz is developed on RO5880 using 10W GaN HEMT. An excellent agreement between the measured and the EM simulated results validates the proposed design technique.
An antenna array formed by four PIFA elements located very close to each other, with low inter-element matching for MIMO applications is proposed. The antenna array consists of four F-inverted wideband radiators, with a fractional bandwidth around 56%, spaced one to each other by a very short distance (< 0.065 λ0) at a centre frequency of 2.55 GHz. The operational bandwidth goes from 1.88 to 3.15 GHz considering the Sii < -10 dB at each port. Moreover, the coupling among ports reaches values below Sij < -10 dB and getting values less than -30 dB at 1.8 GHz, just by employing an uncomplicated technique implemented by a neutralization line between elements. The antenna array gain goes from 2 dB to 6 dB over the operating bandwidth. Concerning MIMO figures of merit, the radiation pattern of each element is orthogonal to each other. The Envelope Correlation Coefficient is below 0.04 at the designed frequency, reaching a peak around 0.082 at 1.8 GHz, but still achieving the requirement for MIMO operation (less than 0.5). The Total Active Reflection Coefficient (TARC) is almost convergent at the design frequency, showing low dependence on random signals at different elements, and finally, the diversity gain reaches values close to 20 dB, making the array suitable for MIMO access point applications.
In this research work a compact patch antenna which is reconfigurable for frequency is presented. Frequency reconfigurability is achieved by the use of two PIN diodes. Antenna operates over four frequencies, i.e., for WiMax (4.94 GHz), WLAN (5.35), and C-Band (6.25 and 6.83 GHz) applications. The overall dimension of antenna is 25×25 mm2, and an FR-4 substrate having dielectric constant of 4.4 and thickness 1.6 mm is used to fabricate the prototype of the proposed antenna. Different resonant frequencies are obtained by cutting a ∏-slot and a U-slot in radiating patch and by modifying ground slot with a modified slotted structure. One diode is used in ground, and another PIN diode is used on the patch at an appropriate position. Maximum gain of 3.91 dBi and stable radiation characteristics and VSWR < 2 are obtained at the operating bands in simulation and measurement. The antenna elicits its novelty through compactness, portability for communication devices through combination of only two PIN diode switching in cellphones, tablets PCs, and other satellite communication devices operating in C-band as per FCC standard. A prototype of antenna is fabricated, and the measured and simulated parameters are in good agreement.
This paper presents a new multi-band stopband filter loaded by a shorted metamaterial circuit. Firstly, two filters loaded by stubs and open ring resonators (ORRs) are studied and compared. The ORRs allow more effects in terms of miniaturization by a shifting toward low frequencies and rejection bandwidth (57.34%). To improve the filter efficiency, coupled split ring resonators (SRRs) are used. The final filter is characterized by a miniaturized size of 18.8 x 40 mm2, wide rejection bandwidth, high selectivity level and multiple resonances over S, C, X and Ku bands. L-C equivalent circuit model filter and other characteristics are investigated. A prototype of the filter with coupled SRRs has been fabricated and measured. Good matching among EM-simulation, equivalent circuit modelling, and measured results are achieved.
An efficient nature inspired algorithm based on particle swarm optimization (PSO) is presented in this paper for the optimal design of planar multi-layered radomes for multiband applications. Material layer sequence and thickness profile are the two critical factors determining the position of pass bands in the frequency range of operation as well as the transmission performance in those bands. These design aspects have to be appropriately optimized to achieve the desired performance, and it becomes a daunting task for radome designers when a comparatively large database of suitable materials is available in the solution space. Even though commercially available software packages provide options (like particle swarm optimization (PSO), genetic algorithm (GA) etc.) for the optimization of thickness profile, they do not have the functionality for optimizing the position of a specific material inside the multi-layered radome wall configuration. In this regard, the proposed PSO-based algorithm automatically chooses suitable materials from the predefined database and optimizes the thickness for each layer, in order to achieve superior transmission in user defined pass bands. Furthermore, the superiority of the indigenously developed algorithm over the optimization techniques available in full wave simulation software (FEKO) w.r.t. accuracy and computational efficiency is also established using suitable case studies and validations. Although PSO has been used in the context of radomes, its application for the simultaneous optimization of material layer sequence and thickness profile of multi-layered radomes is not reported in literature to the best of our knowledge.
There is complex electromagnetic interference in the substation. In order to improve detection accuracy, a digital lock-in amplifier is used in the detection of the grounding grid. This paper introduces the principle of non-destructive testing of grounding grid based on electromagnetic method. Firstly, the distribution characteristics of surface magnetic induction intensity at different frequencies are obtained by CDEGS simulation. At the same time, it describes the principle and structure of an orthogonal vector type digital lock-in amplifier in detail. In order to realize the high-precision grounding grid detection system, the hardware circuit of the digital lock-in amplifier is designed by FPGA and analog-to-digital converter. The digital lock-in amplifier algorithm is implemented in the FPGA. Finally, the digital lock-in amplifier is tested. The test results show that when the signal-to-noise ratio of the signal to be tested is -20 db, the signal amplitude measurement error is less than 3%. The designed digital lock-in amplifier is applied to the actual grounding grid detection, and the topology and corrosion of the grounding network can be detected. Therefore, the digital lock-in amplifier can be effectively applied to non-destructive testing of grounding grid.
The coaxiality of the transmitter and receiver has a significant impact on the efficiency in a wireless power transfer system. In order to keep high system efficiency, a novel coil structure is studied in this paper. Several plane coils are crossed to make up a three-dimensional coil structure in the transmitter, which will make sure the system in the state of strong magnetic field coupling. In the theory part, the magnetic field equation of different relationships between transmitter and receiver is deducted in detail. In the simulation part, the performance of the three-dimensional coil structure has been studied. The simulation results show that the new coil structure can generate a rotating magnetic field, and the rotating magnetic field will keep the system in the state of the strong magnetic field coupling in the simulation model. In the experimental part, the three-dimensional coil structure has been compared to a plane coil structure. The experimental results show that the efficiency of the three-dimensional coil structure is increased above 10% in the misalignment situation. The simulated and experimental results show that the new three-dimensional coil structure has a better performance in the misalignment situation than the plane coil structure in a wireless power transfer system.
In this paper, a compact modified hexagonal spiral resonator-based tri-band patch antenna with an octagonal slot is presented for Wi-Fi/WLAN applications. The proposed antenna is designed on a low-cost FR4 substrate with a dielectric constant of εr=4.4 and loss tangent δ=0.02. The tri-band operations have been achieved by the a Modified Hexagonal Complementary Spiral Resonator (MHCSR) and an Octagonal slot. The loading of the MHCSR at the bottom of the substrate is to cover the 900MHz (IEEE 802.11ah) band, and an Octagonal slot on top of the 5 GHz (IEEE 802.11a/h/j/n/ac/ax) rectangle patch is to cover the 2.4 GHz (IEEE 802.11b/g/n/ax)band. The prototype of the proposed antenna is fabricated and tested to validate the simulation results. The measured impedance bandwidth is 105 MHz at 900 MHz, 160 MHz at 2.4 GHz, 18 0MHz at 5 GHz. The designed antenna has a compact size with overall dimensions of 0.054λ0 x 0.066 λ0 x 0.0048 λ0 (18 x 22 x 1.6 mm3). The 82.2% reduction in size has been accomplished as compared to a conventional patch antenna at 900MHz (lower resonance frequency). The waveguide setup method has been used to validate a negative permittivity property of the MHCSR. The parametric analysis of the proposed antenna had been carried out using the Ansoft HFSS19 software.
The sensitivity of dual-polarized Sentinel-1 backscatter towards biophysical parameters (height and biomass) of wheat and mustard crop was investigated. The plant height and biomass observations categorized into three groups, were useful in understanding the sensitivity across a particular biomass and height range whose significance was determined using a statistical measure (student's t-test). The crop parameters were retrieved only for the C-band sensitive biomass (< 5 Kg m-2) and height (< 160 cm for mustard and < 80 cm for wheat) range considering the saturation of signals at advanced crop stages and based on the detailed investigation. The sensitivity towards the mustard plant height becomes very weak as the crop proceeds to a height > 190 cm. A low RMSE (11.50 cm) was observed when the retrieval was done for height < 160 cm. The cross-polarized responses were more sensitive to crop biomass than co-polarized responses mainly due to the dominant depolarization of the transmitted power. An early saturation was found at co-polarized VV (4 Kg m-2) as compared to cross-polarized VH (6 Kg m-2) particularly for planophiles like mustard and little later in the case of erectophile such as wheat. The backscatter response was found to be sensitive at early crop stages for both the crop geometry, and hence retrieval of biophysical parameters at these stages can yield better accuracy than the overall retrieval. The retrieval of wheat height resulted in a low RMSE of 9.25 cm when the retrieval was carried out for crop height < 80 cm. Retrieval was attempted using the simplistic logarithmic model which can find ways in the operational application using wide swath dual-polarized datasets.
This paper describes the design and development of a highly directive planar end-fire array using arc dipoles as the array elements. The inter element spacing, shape and size of the array elements are optimized for maximum directivity and gain. The array is printed on a substrate whose dimensions are also optimized for better performance. The overall length of the proposed six element array is 1.9λ, giving directivity and gain values as 12.0 dBi and 10.2 dBi respectively at 5.8 GHz.
In this paper, a highly directive small-cell waveguide antenna array for point to point wireless communication in E-band radio frequency systems is presented. The antenna array is designed and dedicated for the paired bandwidths 71-76 and 81-86 GHz. It is composed of 32 x 32 horn elements with a total surface of ~100 x 100 mm2 to achieve a directivity ≥38 dBi, narrow beam (~2°) and low-level sidelobe ≤-26 dB. A compact stepped horn antenna element (SHE) (6.6 mm) is designed. It is 25% smaller than a standard horn element (in the same band) keeping the same aperture surface (3.4 x 3.4 mm2). Layer-by-layer micromachining process is employed for the fabrication. A compact feeding network (25 mm) is realized using ridged waveguide technique with a cut-off frequency of 55 GHz, much lower than standard WG one in the same band. A bow-tie multi-section waveguide polarizer rotator (±90°) is optimized and associated with the WG transitions to re-phase the fields applied to SHE elements. Electric discharge machining (EDM) process was used to manufacture a 4×4 sub-array prototype including the entire WG power-feed network. The antenna is characterized in an anechoic chamber, and experimental results are compared to 3-D electromagnetic simulations with good agreements over the two bands.
Characterization of the human body channel is a necessity to pave way for practical implementation of intrabody communication (IBC) in body area networks (BAN). In this paper, a circuit-coupled finite element method (FEM) based model is proposed to represent the galvanic coupling type IBC on human arm. In contrast with other models for IBC, both the finite element method and the parasitic capacitances between electrodes are taken into account in the modeling. To understand the characteristics of IBC, simulations with multiple frequencies, excitation voltages, channel lengths and values of parasitic capacitors are carried out using the model. The current density and electric field distribution in different human tissues reveal an insight into signal transmission path through the human body intuitively. The body channel gain presents a band-pass property after adding the parasitic capacitances into the model, while it performs an increasing characteristic with the frequency before the adding. Finally, a galvanic coupling IBC measurement setup is fulfilled, and the outcome shows a good agreement with the proposed model. It is indicated that the parasitic capacitances are the major factors to cause the band-pass and affect the bandwidth, and they should not be neglected in the real IBC applications.
This paper proposes a hybrid, compact, low profile, and multi-port antenna system for Cognitive Radio (CR). This system consists of a CPW fed sensing UWB monopole (2-11 GHz) and three NB antennas, out of which one is standalone (7.355 GHz); one is dual-band (5.834 GHz and 8.786 GHz); and the other is reconfigurable (3.863 GHz, 4.664 GHz, 5.2 GHz, and 6.13 GHz) using switching mechanism. This antenna system exhibits less than -15 dB isolation over the operating band. The system is simulated using CST Microwave Studio, and a prototype is fabricated to verify the results. The simulated results are in good agreement with measured ones. The proposed antenna is suitable to operate in C-band, ISM/WLAN/Military application, mid-band 5G, maritime radio navigation, X-band satellite communication, and public safety wireless communications.