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Design of Nonuniformly Spaced Antenna Arrays Using Orthogonal Coefficients Equating Method
(Společnost pro radioelektronické inženýrství, 2022-12) Khalaj-Amirhosseini, M.
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.
Direct Coupled Wave Removal for GPR Data Based on SVD in the Wavelet Domain
(Společnost pro radioelektronické inženýrství, 2022-12) Chen, D.; Xiang, A.; Xiong, S.; Wang, L.; Guo, L.
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.
Design of Bifurcated Beam using Convex Bent Array Feed for Satellite Mobile Earth Station Application
(Společnost pro radioelektronické inženýrství, 2022-12) Tengah, Z.; Abd Rahman, N. H.; Yamada, Y.; Abd Rashid, N. E.; Pasya, I.; Aris, M. A.; Dinh, N. Q.
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.
Uncooperative Emitter Localization Based on Joint Sensor Selection and Semidefinite Programming
(Společnost pro radioelektronické inženýrství, 2022-12) Cao, L.; Zhang, J.; Liu, Y.; Zhu, Y.; Deng, J.; Chen, G.
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.
Design of Dual-Mode Loop Resonator-Based Microwave Diplexers with Enhanced Performance
(Společnost pro radioelektronické inženýrství, 2022-12) Zhu, Z. L.; Li, J. L.
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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