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2024-11-12
PIER M
Vol. 130, 49-61, 2024
download: 36
An Intelligent Algorithm Based on the Improved CNN-LSTM for the Detection of Concrete Reinforcement Information
Xuefeng Bai , Ronghua Zhang , Jinxun Le , Boyang Li , Wenying Fu , Shuqing Jia and Wuliang Yin
Reinforced concrete plays a vital role in the construction industry. Therefore, it is necessary to evaluate the parameters such as the number, diameter and protective layer thickness of rebar in concrete during and after the construction process. In this paper, we take the pulsed eddy current detection method as the principle, build the relevant experimental system, collect the data samples about the parameter information of the rebar, and propose an intelligent algorithm based on Convolutional Neural Network with Long Short-Term Memory (CNN-LSTM) based on Convolutional Block Attention Module (CBAM), which is capable of automatically extracting the relevant features of information-rich PECT signals, and the CBAM is introduced into CNN to enhance its feature extraction capability, which improves the accuracy and interpretability of CBAM-CNN-LSTM in predicting rebar information. In order to verify the performance of the method, traditional CNN, LSTM, and CNN-LSTM algorithms were used for comparison, and the prediction results were evaluated by decision coefficient (R2), Explained Variance Score (EVS), Root Mean Square (RMSE), and Mean Absolute Error (MAE). The experimental results show that the method is able to accurately predict the specimen information with good prediction accuracy and stability as the average error of the prediction of the number is reduced by 50% and the average error of diameter and thickness prediction reduced by 20% and 3% after adding the CBAM.
An Intelligent Algorithm Based on the Improved CNN-LSTM for the Detection of Concrete Reinforcement Information
2024-11-06
PIER M
Vol. 130, 37-48, 2024
download: 100
Design of Multiband Metasurface Radome for Leading Wing Edge of Aircraft
Kanathil Meethal Arya , Akshay Manish Aserkar , Shailesh Ashok Patil , Raveendranath Nair and Shiv Narayan
A novel metamaterial-element based frequency selective surface (FSS) is proposed in this paper for multiband radome for airborne application, which exhibits angular stability and polarization independence up to incidence angle, 60˚. The proposed metasurface radome consists of a combination of different patch-type elements in two cascaded layers, forming an electrically thin design suitable for aerospace applications. It operates in the frequency bands, S- (3.3 GHz), C- (4.8 GHz) and X- (9.1 GHz) with high transmission efficiency and good isolation between bands (< -20 dB). An equivalent circuit model of the proposed design is derived and validated with the simulated (based on HFSS) and measured results. Further, a multilayered radome wall configuration is designed using proposed metamaterial-element based FSS that exhibits transmission bandwidths, 220 MHz, 1 GHz, and 1.3 GHz corresponding to S-, C-, and X-bands, respectively w.r.t. -1 dB insertion loss. The structural analysis of multilayered radome wall configuration confirms its suitability for shared aperture antenna integrated to leading wing structure of aircraft.
Design of Multiband Metasurface Radome for Leading Wing Edge of Aircraft
2024-11-06
PIER M
Vol. 130, 29-36, 2024
download: 97
A 2-Port High Isolation Millimeter Wave Dual-Band Antenna Based on SIW Back-Cavity Slot
Mingming Gao , Chang Ge , Jingchang Nan , Chunli Liu , Hongliang Niu and Hang Yuan
To enhance the transmission rate and bandwidth utilization of Multiple-Input Multiple-Output (MIMO) communication systems, a dual-band MIMO antenna for millimeter waves is proposed, which is based on a substrate-integrated waveguide (SIW) and fed by a 50 Ω microstrip line. To achieve the dual-band performance, it employs a modified dual P-shaped slot instead of the conventional single P-shaped slot. The modified slot antenna generates dual-frequency radiation by exciting the primary and mixed modes in the circular resonant cavity. To improve the channel capacity of the system, the antenna is formed into a 2-element antenna, and the isolation of the antenna is improved by pattern diversity and defected ground structure (DGS). The antenna's dimension is 20 x 18.9 x 0.508 mm3. Measured results show that the impedance bandwidth of the antenna is about 26.7 GHz-27.9 GHz and 37.95 GHz-40.92 GHz with peak gain of 5.63 dBi and 6.35 dBi, respectively. In addition, the isolation degree is greater than 30 dB, the envelope correlation coefficient (ECC) less than 0.0002, and the diversity gain (DG) greater than 9.995. The antenna shows the advantages of low profile, dual-frequency radiation, and high isolation characteristics, which are well suited for millimeter-wave wireless communication systems.
A 2-port High Isolation Millimeter Wave Dual-band Antenna Based on SIW Back-cavity Slot
2024-10-27
PIER M
Vol. 130, 19-27, 2024
download: 117
Designing Fabric-Based Broadband Metamaterial Absorbers for Radar Operating Frequency Bands
Baojun Chen , Hao Yuan , Yanjie Ju , Yanbing Xue , Tianyu Jiao , Qinghua Liu and Mengqiu Qian
With the increasing use of radar technology across various fields, electromagnetic pollution has become a growing concern, posing significant risks to human health. Consequently, there is a rising interest in developing wearable, flexible fabric-based absorbers that can efficiently absorb electromagnetic waves. However, the low dielectric constant of fabrics makes it challenging to achieve high absorption rates and broad bandwidth at low frequencies. To address this issue, in this study, we introduce a fabric-based broadband metamaterial absorber using felt as the dielectric substrate. The absorber features a centrosymmetric square block array design, incorporating a PU conductive film as the surface resonant material. By fine-tuning the parameters of each component in the absorber's equivalent circuit and optimizing structural parameters, the absorber achieves an extended bandwidth from 3.92 to 15.25 GHz, with a relative absorption bandwidth of 118.21%. Impressively, in the lower frequency C-band, the absorber maintains an efficiency of over 95%. The absorber was fabricated using the ``cut-transfer-paste patterning method.'' Testing results demonstrate that it is insensitive to incident angle and polarization and retains excellent absorption performance even when being bent.
Designing Fabric-based Broadband Metamaterial Absorbers for Radar Operating Frequency Bands
2024-10-22
PIER M
Vol. 130, 11-17, 2024
download: 151
Compact 8-Port MIMO Antenna for Hot-Spot Applications Based on Embedded Double-Negative Metamaterial Split Ring Resonators
José Alfredo Tirado-Méndez , Arturo Rangel-Merino and Luis Alberto Vasquez-Toledo
This article proposes an 8-port MIMO antenna based on double-negative metamaterial Split Ring Resonators (SRRs) for three-dimensional (3D) non-planar applications, such as hotspots. The antenna features eight radiators arranged orthogonally to each other, placed in two perpendicular planes, operating at 3.5 GHz. Each resonator incorporates six embedded SRRs to enhance the metamaterial behavior, achieving a 40% size reduction compared to a conventional disc monopole at the same frequency. Simulated and measured results demonstrate excellent performance for MIMO applications, with Envelope Correlation Coefficient (ECC) values below 0.001 and Diversity Gain (DG) around 20 dB. The Total Active Reflection Coefficient (TARC) bandwidth is approximately 930 MHz at the -10 dB threshold. The S-parameters indicate excellent electromagnetic isolation between radiators exceeding 20 dB, and a very low cross-polarization level below -30 dB. However, the main limitation of this design is a reduction in gain, an expected result.
Compact 8-port MIMO Antenna for Hot-spot Applications Based on Embedded Double-negative Metamaterial Split Ring Resonators
2024-10-21
PIER M
Vol. 130, 1-10, 2024
download: 184
A Multi-Channel Error Compensation Method for Space-Borne RDBF-SAR
Lu Bai , Wei Xu , Pingping Huang , Weixian Tan and Yaolong Qi
The time-varying amplitude error and phase error in the multi-channel will affect the system performance of Range Digital Beam Forming-Synthetic Aperture Radar (RDBF-SAR), which will lead to the elevation of the side lobes amplitude of the echo signal, thus affecting the quality of space-borne synthetic aperture radar (SAR) images. A multi-channel error compensation method for space-borne RDBF-SAR is proposed in this paper. The echo signals of each channel are aligned in the frequency domain. For the amplitude error, the amplitude error compensation factor is obtained by comparing the amplitude of each channel signal with the amplitude of the reference channel signal. For the phase error, the phase error compensation factor is obtained by conjugate multiplication of the phase of each channel signal and the phase of the reference channel signal. Reduce the amount of calculation by averaging. This method can well compensate the amplitude error and phase error, suppress the elevation of the echo side lobe, and make the synthetic aperture radar image more focused and accurate. Finally, the effectiveness of the method is verified by simulation experiments. Under the simulation conditions in this paper, the amplitude compensation reduces the side lobes pulse compression amplitude by 2~10 dB, and the phase compensation reduces it by -1~9 dB.
A Multi-channel Error Compensation Method for Space-borne RDBF-SAR