In this paper, an unequal Filtering Power Divider (FPD) adopting a novel dual-band resonator and inter-digital feeding lines structure is presented. By integrating the resonator and modifying coupling mode, filtering and unequal power distribution are all achieved on the base of the deformed Wilkinson power divider. Two sets of cascading resonators operating at 2.45/4.44G with the same structure are proposed for WIFI and other application. Keeping with the unchanged coupling mode, the unequal ratio of 2:1 is arrived by adjusting the strength of coupling. The two resonant frequencies can be adjusted independently to ensure the flexibility of the design. For verifying the theoretical designs and simulated results, a fabricated FPD is exhibited, analyzed and measured. The simulated results are in good agreement with the measured ones with slight variations.
In order to reduce the multipath fading caused by the reflection of various obstacles in short-distance communication, this paper designs a quaternion MIMO millimeter wave antenna working at 28 GHz. The antenna design adopts an inverted trapezoidal radiation patch and a slotted trapezoidal ground plate structure, so that the S11 of the antenna is lower than -10 dB in the frequency band of 24~32 GHz. By using a 1×2 array structure as the unit of MIMO antenna, the gain of the antenna at 28 GHz is 7.5 dBi. The isolation degree of each port is lower than -25 dB by orthogonal placement of each unit. The performance of the antenna is tested by the physical production test. The actual test results show that the operating bandwidth of the antenna is consistent with the simulation results. The gain at 28 GHz is slightly lower than the simulation results by 0.1 dBi, and the isolation of each port is lower than -18 dB, which is 7 dB away from the simulation results but still meets the requirement of -15 dB for MIMO communication. The measured results show that the antenna can be used in MIMO short-distance communication system.
This work aims for nonionizing radiation assessment to reduce Specific Absorption Rate (SAR) in the IEEE SAM phantom using MIMO antenna. The traditional copper material MIMO is designed with mode characteristics and validated for 2.4 GHz in this experiment. The MIMO antenna, when placed near SAM phantom and SAR, is estimated. Copper-based antennas are replaced by nanomaterial-based antennas, such as graphene, multi-walled carbon nanotube (MWCNT), and single walled carbon nanotube (SWCNT), to study SAR behavior. SAR is reduced using Nanomaterial based antenna in which SWCNT significantly reduces SAR up to 66 percent using Altair's Feldberechnung für Körper mit beliebiger Oberfläche (FEKO).
In this paper, we devise a phased array antenna with liquid crystal material, employing a 10×10 uniform rectangular array. The phase of the phased array antenna is controlled by loading bias voltage on the liquid crystal layer, and the FoM (figure-of-merit) of the phase shifter can attain 70.6°/dB. The phased array antenna works at 16 GHz and employs a microstrip circular patch as the radiation unit. The proposed phased array can achieve a gain of 23.1 dBi, and its beam scanning range reaches ±45° in simulation experiment. The preliminary measurement results demonstrate that the performance of the proposed antenna is basically consistent with simulation results.
A wideband, compact and flexible conformal circularly polarized antenna (CCPA) with ground plane is proposed in this letter. It consists of a polygonal patch, two V-shaped coupling feed lines, a phase-shift transmission line and two layers of metallic ground planes. Two resonant modes are generated by cutting one vertex of the octagonal patch to broaden the operational bandwidth. An L-shaped ground plane is designed on the back of the top substrate. This configuration can obtain a relatively compact phase shifter on the one hand and make the coupling branches and octagonal patch share one ground plane on the bottom, improving the thickness of the antenna which yields wide bandwidth on the other hand. The CCPA can own good performances both in the planar and cylindrical carriers. Under the cylindrical conformal circumstance, the measured |S11| and axial ratio (AR) bandwidth reach 12.05% (5.5 GHz-6.205 GHz) and 8.93% (5.67 GHz-6.2 GHz), respectively. The measured gain is 8.5 dBic with 3 dB gain bandwidth covering the whole operational band.
This letter presents a wideband polarization reconfigurable antenna based on liquid metal (LM) switches. It consists of single-fed crossed bowtie dipoles, a parasitic element grounded via a metallic post, a dual-cavity-backed reflector and liquid metal switches. The two arms of one dipole are loaded with two symmetrical identical slots, and on top of the slots, two sets of fixed-length movable liquid metal columns filled in polytetrafluoroethylene (PTFE) tubes are attached as switches. The altering between linear polarization (LP) and circular polarization (CP) can be achieved by changing the positions of the liquid metal switches. The dual-cavity structure is applied to obtain unidirectional radiation and enhance the circularly polarized performance. A prototype with overall size of 127 × 127 × 57 mm3 is designed and fabricated. The measured results indicate that the impedance bandwidth (IBM) of the antenna is from 1.06 to 2.46 GHz (79.54%) and the axial ratio bandwidth (ARBW) is from 1.39 to 1.91 GHz (31.52%) for CP state. In addition, the IBW for LP state is from 1.06 to 2.30 GHz (73.81%). Moreover, the peak gains can reach 7.73 dBic in CP state and 9.21 dBi in LP state.
Micro-variation monitoring radar based on the differential interference principle can monitor objects prone to micro deformation. However, it is easily affected by human and environmental factors to cause the radar image to loss coherence in the long-term monitoring work, thus affecting the normal monitoring of radar. Therefore, it is of great significance to study the change detection method of micro-variation monitoring radar images, which can provide reference information and quantitative analysis for monitoring work. In this paper, a method of landslide area identification and detection based on micro-variation radar image is proposed. Based on the radar coherence coefficient image of time series, the difference image is produced by logarithmic ratio cumulation. The difference map is decomposed and denoised by wavelet transform, and then the final difference map is produced by reconstructing the processed wavelet coefficients. Finally, the improved K-means is used to cluster the difference map to get the change detection result image. The actual monitoring data of a mining area is used for variation detection. The results show that the proposed method retains the detailed information of the change area and removes a lot of noise. The difference map is easier to cluster, and the clustering result is more accurate.
A novel compact composite right/left-handed (CRLH) substrate integrated waveguide (SIW) based leaky wave antenna (LWA) is proposed. Mushroom-inspired unit cell is utilized to achieve CRLH transmission property as well as energy leakage. Periodically loaded metallic vias, which act as an internal 1:2 power divider, are along the center line of the SIW structure, leading to a compact antenna size. The LWA can be regarded as an antenna array whose two elements are excited by two newly produced quasi-TE10 modes, respectively, and therefore, the antenna peak gains are enhanced. Good agreements are obtained between the simulated and measured results. Continuous beam scanning feature indicates that the proposed design is a balanced frequency scanning work operating in Ku-band.
This paper proposes a conformal multiple band four port MIMO antenna for next generation vehicular communications in the extended UWB. The single element consists of a monopole antenna resembling a U-shaped structure with two branches folded and complimentary to each other. It uses coplanar waveguide feeding with a defected ground structure. The antenna is printed on a Kapton Polyamide flexible substrate having a thickness of 0.25 mm. The antenna has dimensions of 0.8λ x 0.8λ x 0.001λ. It resonates at 2.6 GHz, 3.9 GHz and 5.6 GHz which are used in vehicular communications, and can be used in sub-6 GHz 5G applications. It also provides band notches at 2.1 GHz, 3.5 GHz and 4.5 GHz which enables it to mitigate the interferences from any narrow band devices operating in that range. All MIMO parameters are simulated and compared with the measured results, and are found to be in good agreement. The designed antenna can be mounted at any position of the vehicle as it has a conformal structure.
Nanostructure based perovskite solar cell with high performance is the emphasis of study in current work keeping in view the improvement in cell efficiency. In the first part of the study, a plane-layered solar cell is studied by adding a 1D photonic crystal at the bottom of the cell in order to facilitate the photon rotation process. However, in the second part of the study, it is observed that addition of grating enhances the light absorption due to photons trapping. Following that, the light absorption of three different structures is compared. The observations reveal that short-circuit current density (Jsc) is found to be -39.93 mA/cm2, which is 87.29% higher than that for a planar structure exhibiting the Jsc value as -21.32 mA/cm2. Ultimately, the efficiencies of these perovskite solar cells based on nanostructures are observed to be significant as well. For the proposed solar cell structure, an 87.24% improvement in the power conversion efficiency (PCE) is observed i.e., from 14.03% for the planar structure to 26.27%.
An ultra-wide band (UWB) antenna with C-band and X-band notches for wireless communication is presented. The designed structure is printed on a material of ``Rogers 4350B'' with εr = 3.66, tanδ = 0.0037 and a thickness of 0.508 mm. This structure is designed to operate at a UWB range starting from 3.3 GHz up to 10.15 GHz with a stopband range from 6.75 GHz to 8.5 GHz. The rejected bands are the upper C-band (6.75 GHz-8 GHz) and the uplink X-band of the satellite (space to earth) from 7.25 GHz to 7.75 GHz. The overall antenna size is optimized, and its dimensions are 21 × 30 × 0.508 mm3. The antenna gain varies from 2.1 to 4.2 dBi at the passband, and its total radiation efficiency is 96.4%. The suggested structure is designed and simulated using CSTMWS software. Moreover, a prototype of the proposed structure is fabricated and measured. The fabrication process was done using photolithography techniques, and the measurements were done using an R&S vector network analyzer. Good agreement is achieved between the simulated and measured results.
This work proposes and experimentally evaluates a single layer bandpass frequency selective surface (FSS) that resonates at X-band (8-12 GHz). The metal plate of the unit cell has a half-Jerusalem cross slot of size 0.15λ0, where λ0 is the wavelength corresponding to 10 GHz centre frequency. The effects of unit cell parameters on filter response are analyzed through parametric analysis. The results reveal that the proposed bandpass FSS exhibits good polarization stability and angular stability at oblique angles up to 45˚. Furthermore, negligible frequency deviations in both TE and TM polarizations have also been achieved using this structure. A prototype of the bandpass FSS was fabricated on an FR4 substrate to validate the proposed design which includes 10×10 elements in a dimension of 45 mm × 45 mm × 1.6 mm. Measurements show that the bandpass FSS has a fractional bandwidth of 40% centered at 10 GHz from 8 GHz to 12 GHz. The unique feature of the proposed filter is its ability to operate in the whole X band (8-12 GHz) by tuning the filter elements.
The rapid development of telecommunication systems has promoted the research of electromagnetic metamaterial absorbers. Based on the equivalent circuit theory, this paper proposes and designs a broadband absorption absorber based on electromagnetic metamaterials, which adopts a sandwich structure with an overall absorber thickness of 3.234 mm. The results show that the absorber has an absorption rate of more than 90% in the X-, Ku-, and K-bands (8.06 GHz-18.46 GHz) for the incident angle varying in the range of 0-50°. The absorption rate is higher than 90% for TE and TM mode electromagnetic waves and electromagnetic waves with polarization angle in the range of 0-50°. The absorber still has good absorption characteristics. The study shows that the absorber has small size, thin thickness, and broad angle broadband absorption characteristics.
This paper presents a novel microstrip three-mode filtering power divider (FPD) with high frequency selectivity and high isolation, which integrates only a single resonator and a resistor to realize the dual functions of the power division and filtering. In order to further improve its frequency selectivity and obtain wide upper stop band, three open stubs are loaded into the input and output ports of the filter power divider. The measured and simulated results show that the range of S11 < -10 dB is 1.86~2.1 GHz; the relative bandwidth of 3 dB is 17.9%; the in-band isolation is higher than 26 dB; and it has a relatively simple topology.
We study two array antennas to expand a 3 dB axial ratio bandwidth. Each array is located at a quarter wavelength above the ground plane and analyzed using the moment method. First, we use paired spiral elements fed by balanced parallel lines to avoid unwanted radiation from the feedline. It is found that the antenna shows an axial ratio bandwidth of 30%. Next, the elements are separated and fed by a single feedline to simplify the feed system. It is revealed that the antenna can radiate a circularly polarized wave under a feedline radiation of less than -16 dB. The frequency responses show that an axial ratio < 3 dB and VSWR < 2 are obtained in a bandwidth of 21%, where the gain is more than 13.3 dBi. The simulated results are verified with experimental ones.