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December 2022, Volume 31, Number 4 [DOI: 10.13164/re.2022-4]

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Q. Ma, H. Tie, B. Zhou [references] [full-text] [DOI: 10.13164/re.2022.0455] [Download Citations]
Compact LTCC Balun using L-C Embraced Structure for 128 MHz 3T MRI Applications

A compact lumped-element balun is proposed for 128 MHz frequency 3 Tesla (T) magnetic resonance imaging (MRI) applications. The miniaturization is achieved by the inductor-capacitor (L-C) embraced structure, which places vertically-interdigital-capacitor (VIC) inside spiral inductor for higher integration. The L-C surrounded structure only takes up one element’s area without increasing the number of substrate layers. The balun is built on a 10-layer thickness low temperature co-fired ceramic (LTCC) substrate and has the smallest reported size of only 0.007×0.008 × 0.0009 λg. Moreover, the proposed balun also has a 2nd-order harmonic suppression of 32 dB. Furthermore, comparisons and discussions are also implemented.

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  17. Microwave Office, Applied Wave Research Corporation, El Segundo, CA.
  18. AXIEM, Applied Wave Research Corporation, El Segundo, CA.

Keywords: Compact; balun; LTCC; MRI

A. Oncu, A. G. Aydin, Y. Erdogan, A. Akdogan [references] [full-text] [DOI: 10.13164/re.2022.0460] [Download Citations]
Mode-S Radar Interrogation Algorithm Design for Dense Air Traffic Environment

The increasing trend in air traffic density will continue in the near future with the addition of different aerial vehicles. Before the Mode-S protocol, Mode A and Mode C were in use; however, the Mode A/C configuration was only usable in sparsely dense air traffic. One of the useful features of Mode-S is the ability of probabilistic interrogation. However, there has not yet been a sophisticated algorithm for many close aircraft. Considering a futuristic air environment with a swarm of drones and airbuses equipped with transponders, we utilized the probabilistic interrogation feature of Mode-S and designed an algorithm. The proposed algorithm is able to collect close aircraft information in a relatively short time. There has also been created a high-level Mode-S uplink and downlink communication simulator in order to exchange all-call communication and record the algorithm’s performance in terms of time and number of interrogations sent.

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Keywords: Garbling, lockout, Mode-S, stochastic interrogation

L. Zou, X. Wang, L. Zhang, H. Gao [references] [full-text] [DOI: 10.13164/re.2022.0468] [Download Citations]
Enhanced SIMO Radar System Based on Time-Frequency Correlation for Target Localization Applications

This study developed a novel S-band radar system for planar location applications. High-resolution range imaging and target angle estimation were achieved by using a stepped frequency continuous wave (SFCW) signal and single input multiple output (SIMO) architecture with a linear sparse array layout, respectively. An improved time-frequency method was utilized to link the independent range profile and angle spectrum results to obtain the plane positions of the targets. The radar hardware was composed of the antenna array with one transmit element and five receive elements, an RF transceiver, and a signal processing component. Under the proposed waveform parameters and signal processing scheme, a 16-ms process cycle, 0.3-m ranging error, and 0.4° angle estimation error for target positioning were achieved in field tests. These results demonstrate the effectiveness and advantages of the proposed radar system.

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Keywords: Planar location radar, SIMO system, stepped frequency waveform, range-angle correspondence, moving target indicator, sparse array

D. Song, Q. Chen, K. Li [references] [full-text] [DOI: 10.13164/re.2022.0477] [Download Citations]
An Adaptive Sparse Constraint ISAR High Resolution Imaging Algorithm Based on Mixed Norm

Based on the sparsity of inverse synthetic aperture radar (ISAR) signal, in this paper, a novel high resolution imaging algorithm is proposed. In this method, an optimal ISAR signal model based on mixed norm is established by using compressed sensing theory. The high-resolution ISAR image with short coherent accumulation time is realized by solving the optimization model. The main advantages of the proposed approach are: The model makes use of the l2,0 mixed norm to realize faster convergence and improve the computational speed of the model solution obviously. Moreover, according to the result sparsity of each iteration under arbitrary noise, the regularization coefficient in the model can be adjusted adaptively, which avoids the complex process of repeated attempts, otherwise, the optimal coefficient needs to be estimated and attempted by the statistical characteristics of the noise and signal. The effectiveness of the proposed method is verified by simulated and measured data.

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Keywords: Inverse Synthetic Aperture Radar (ISAR), mixed norm, regularization coefficient, sparse constraint

A. N. Yadav [references] [full-text] [DOI: 10.13164/re.2022.0486] [Download Citations]
Tunable Balanced-to-Unbalanced In-Phase Power Divider: Theoretical Analysis and Design

This paper presents a tunable power divider (PD) which is balanced at the input port and unbalanced at the output ports. This tunable balanced-to-unbalanced (TBU) PD divides the power either equally or in specific ratio by varying capacitance in the circuit. The complete theoretical study is presented for this type of PD. The analysis is based on the impedance matching of all the ports and isolation requirements of the two unbalanced output ports. By changing the capacitance, different power dividing ratio (PDR) can be achieved. The theoretical results are obtained from the design equations of the proposed PD. The reflection coefficient of the unbalanced ports are better than 10 dB with fractional bandwidth of 21.5%. The isolation between the two output unbalanced ports is achieved better than 15 dB with fractional bandwidth of 23.5%. The proposed PD shows the in-phase characteristic between the two output signals.

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Keywords: Tunable power divider, balanced-to-unbalanced, differential mode, microwave circuit

C. Chen, F. F. Yang, C. L. Zhao, H. J. Xu [references] [full-text] [DOI: 10.13164/re.2022.0496] [Download Citations]
Distributed Reed-Solomon Coded Cooperative Space-Time Labeling Diversity Network

This paper proposes a distributed Reed-Solomon coded cooperative labeling diversity (DRSCC-LD) scheme over the Rayleigh frequency-flat fast fading channel to further improve the BER performance. The non-binary Reed-Solomon (RS) code with more consecutive roots is applied at the relay to provide additional redundancy. As a novel diversity technique, labeling diversity (LD) with three different mappers is employed in the proposed DRSCC-LD scheme utilizing 16-QAM and 64-QAM, respectively, which may achieve diversity gain and greatly decrease the error floor (EF). Besides, a reduced-complexity detection algorithm based on a variable signal subset (RC-VSS) is proposed to lower the complexity of detection at both relay and destination. The proposed critical SNR-assisted (CSA) joint decoding algorithm then collaborates with the joint detection based on the RC-VSS algorithm to improve the overall BER performance. Theoretical analysis and Monte Carlo simulated results reveal that the proposed DRSCC-LD scheme clearly outperforms its corresponding non-cooperative RS coded scheme by a gain of more than 7 dB and the existing schemes by a margin of more than 3.5 dB under the identical conditions, respectively.

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Keywords: Reed-Solomon (RS) code, distributed coded cooperation, labeling diversity (LD), detection algorithm, joint decoding algorithm

L. Ge, Z. Wang, L. Qian, P. Wei, F. Gao, M. Li [references] [full-text] [DOI: 10.13164/re.2022.0510] [Download Citations]
Improved Phase Noise Compensation in OFDM Systems

Phase noise (PN) consists of common phase error (CPE) and inter carrier interference (ICI). In an OFDM symbol, CPE has the same impact on each subcarrier, which is easy to be suppressed. However, ICI destroys the orthogonality of subcarriers, which is difficult to be eliminated. Therefore, an additional method is needed to be performed in the OFDM receiver to compensate the ICI. The interpolation method is considered an effective way to eliminate the ICI caused by PN in the OFDM system. To enhance the accuracy of the PN estimation and compensation, we propose a linear method, LI-ICI-EE1 method based on LI-ICI-E1. Multiple interpolation slopes are first calculated by selecting multiple pairs of observation samples, then the slope with the maximal linear fitting degree based on the least square (LS) criterion is selected to improve the LI precision. Furthermore, to improve the estimation accuracy of PN in the LI-ICI-EE1, we propose a Shrinkage-based on LI-ICI-E1 method named SLI-EE1, which is implemented by adding an l2 norm penalty term to the error function. At last, to optimize the low accuracy of LI-ICI-EE1 and SLI-EE1 when the PN compensation problem is a high-order problem, we propose a non-linear method Shrinkage-based Third-order Lagrange method named STL. Simulation results show that the improved methods have better BER performance.

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Keywords: Channel estimation, phase noise, orthogonal frequency division multiplexing, shrinkage technique, third-order Lagrange method

A. Kovalova, L. Hudcova, R. Roka [references] [full-text] [DOI: 10.13164/re.2022.0520] [Download Citations]
Optical Ray Transfer Matrix Model of the Turbulent Cells Cascade

The paper offers a new approach to modeling atmospheric turbulence consisting of turbulent cells whose size is larger than the optical beam width. Particular turbulent cells are approximated by an optical element matrix. The ray transfer matrix method is presented, through which the optical elements can be described in the matrix form. A deflection simulation was performed that indicated the behavior of the optical beam by passing through the optical element. Furthermore, the calculation of the deflection vector is described together with a cascade model of turbulent cells. The matrix calculation for the cascade of optical elements is also expressed.

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Keywords: Atmospheric turbulence, matrix optics, cascade of turbulent cells, ABCD matrix, reciprocity

Z. L. Zhu, J. L. Li [references] [full-text] [DOI: 10.13164/re.2022.0527] [Download Citations]
Design of Dual-Mode Loop Resonator-Based Microwave Diplexers with Enhanced Performance

In this paper, a dual-mode loop resonator based circuit topology is studied for microwave diplexer applications. Several diplexers, with dense and sparse channel separations, are further discussed based on the introduced topology, featuring capable of controlling transmission zeros flexibly. Hence microwave diplexers with high selectivity and good channel isolation can be realized by placing transmission zeros of the channel filters at the desired channels. With the use of the proposed topology, the achieved center frequency ratio between two channels can be from 1.03 to 1.35 with good isolations, high selectivity and compact size. The demonstration diplexers are realized on PCB processes, but can be implemented with other media including MMIC. Experimental validations on the developed demonstrator are presented in the paper, and measured responses match well the full-wave electromagnetic simulated results. The developed UMTS diplexer demonstrator achieves the measured minimum passband insertion losses of 2.55 and 2.7 dB with return losses better than 15 dB and channel isolations over 40 dB at the two channels.

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Keywords: Microwave diplexer, dual-mode resonator, loop resonator, microstrip resonator

Y.-Y. Won, S. M. Yoon [references] [full-text] [DOI: 10.13164/re.2022.0533] [Download Citations]
Simultaneous Wireless Transmission Based on Visible LED of On-Off-Keying and Discrete Multitone Signal Using Sparse Compressive Sampling and Derivative-Subtractive Sampling

We propose a technique for simultaneously transmitting two signals with different waveforms (non-return-to-zero on-off keying (NRZ-OOK) signal and discrete multi-tone (DMT) signal) in an optical wireless link based on visible light emitting diode (LED). A sparse compressive sampling technique is proposed to reduce the length of the DMT signal encoded by quadrature phase shift keying (QPSK) symbols and a derivative-subtractive sampling is proposed to separate the NRZ-OOK signal and the DMT signal from the mixed signal (NRZ-OOK + DMT). It is possible to reduce the length of the DMT signal up to 38% using the sparse compressive sampling technique. A 37.6-Mb/s transmission capacity (NRZ-OOK: 10 Mb/s, QPSK symbols: 20 Mb/s + 7.6 Mb/s) is achieved over 10 ­MHz bandwidth.

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Keywords: Derivative-subtractive sampling, discrete multi-tone, optical wireless transmission, sparse compressive sampling, white light emitting diode

Z. Tengah, N. H. Abd Rahman, Y. Yamada, N. E. Abd Rashid, I. Pasya, M. A. Aris, N. Q. Dinh [references] [full-text] [DOI: 10.13164/re.2022.0541] [Download Citations]
Design of Bifurcated Beam using Convex Bent Array Feed for Satellite Mobile Earth Station Application

For multibeam operation at the satellite mobile earth station and telecommunication base stations, a cylindrical lens antenna with multi-feed is a promising candidate due to the simple antenna configuration and good scanning performance to produce multi beams. However, efficient illumination at the lens surface is critical. Previously, the present antennas were used; however, a significant ta-pered distribution is observed, resulting in under-illumination at the lens edges. The feed positions are re-quested to be placed near the lens to achieve a slender lens form. Therefore, the feed radiation pattern should have high radiations at the wide-angle region. This paper proposes a bifurcated beam array antenna to alter the amplitude distribution. This method is expected to improve the radiation pattern coverage area. In designing a bifur-cated beam antenna, the important parameter is to ensure that the separated beams have the same current phase excitations at each radiating element and a precise patch arrangement to achieve the targeted radiation pattern. The differences in surface current will affect the radiation patterns due to the significant interference and cancella-tion effects which will contribute to high losses. This pa-per forms the array by a convex bent array with the same phase excitation for all patch elements. The feed perfor-mances are also verified by the good agreement between simulated and measured results. An improved aperture distribution is demonstrated for array feed having 0.7λo spacing compared to the tapered distribution by a single patch design with the hyperbolic lens through detailed analysis and comparative study. By changing the spacing distance of the convex bent array, many radiation patterns are observed, such as strong radiation in the wide-angle region, the uniform radiation level in a wide-angle region, and the tapered radiation pattern. Thus, many aperture distributions of center-dip, uniform and tapered, are achieved.

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Keywords: Multi-beam, satellite mobile earth station, cylindrical lens antenna, bifurcated beam, convex bent array

L. Cao, J. Zhang, Y. Liu, Y. Zhu, J. Deng, G. Chen [references] [full-text] [DOI: 10.13164/re.2022.0553] [Download Citations]
Uncooperative Emitter Localization Based on Joint Sensor Selection and Semidefinite Programming

Radio emitter localization based on Received Signal Strength (RSS) is promising in large-scale Internet of Things (IoT) and wireless sensor networks (WSNs) for its low hardware and computation costs. To improve its local-ization accuracy and reduce the system energy consump-tion, we propose an improved RSS localization algorithm based on the joint sensor selection and semidefinite pro-gramming (SDP). An initial position estimate is first ob-tained using RSSs available at a random set of sensors. A refined sensor set is then selected to complete the sec-ond estimation by analyzing the geometric structure of sensing network. Performance of the method is evaluated in terms of localization accuracy and execution time, and compared with existing methods. Extensive simulations demonstrate that the proposed approach achieves a locali-zation accuracy of approximately 1.5 m with 8 to 10 sen-sors. The method outperforms the second-order cone pro-gramming (SOCP) and the least squared relative error (LSRE)-based SDP algorithms in terms of both the loca-tion and the transmit power estimation accuracy.

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Keywords: Received signal strength, sensor selection, semidefinite programming, least squared relative error

D. Chen, A. Xiang, S. Xiong, L. Wang, L. Guo [references] [full-text] [DOI: 10.13164/re.2022.0564] [Download Citations]
Direct Coupled Wave Removal for GPR Data Based on SVD in the Wavelet Domain

This paper presents a new algorithm of the singular value decomposition (SVD) in the wavelet domain for ground penetrating radar (GPR) to remove direct coupled waves. In fact, direct coupled waves commonly disturb the reflecting waves from underground targets. Besides, the amplitude and energy of direct coupled waves are large, which reduces the resolution of the images to the targets and adversely affects the subsequent image interpretation work. The GPR signal is decomposed into several levels by Wavelet to obtain approximation components and detailed components of each level. The information of targets is contained in big eigenvalues of detail components, while the direct coupled waves are contained in small ones. Therefore, the SVD in the wavelet domain can reduce the misjudgment of effective signals and improve the signal to noise ratio (SNR) of GPR signals. The simulated and field GPR data show that the SVD in the wavelet domain denoising method has better results for direct coupled wave removal than the traditional methods, which validates the effectiveness of the proposed denoising method.

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Keywords: Singular value decomposition, wavelet domain, ground penetrating radar, direct coupled waves, SNR

M. Khalaj-Amirhosseini [references] [full-text] [DOI: 10.13164/re.2022.0572] [Download Citations]
Design of Nonuniformly Spaced Antenna Arrays Using Orthogonal Coefficients Equating Method

Orthogonal Coefficients Equating (OCE) method as an analytic method is proposed to synthesize nonuniformly spaced antenna arrays to have array factors nearly equal to that of a previously designed uniformly spaced antenna arrays. In this method, the orthogonal coefficients of array factors of nonuniformly space array are equated to those of uniformly space array. To this end, three orthogonal functions including Chebyshev polynomials, Legendre polynomials and exponential functions are discussed. Some examples are brought to verify the performance of the OCE method for all three orthogonal functions.

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Keywords: Nonuniformly spaced arrays, uniformly spaced arrays, orthogonal coefficients equating, Chebyshev polynomials, Legendre polynomials, exponential functions.