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Vol. 179, 95-100, 2024
download: 243
Dispersion Compensation for Spoof Plasmonic Circuits
Wenyao Zou , Wen Xuan Tang , Jingjing Zhang , Shanwen Luo , Facheng Liu , Haochi Zhang , Yu Luo and Tie-Jun Cui
Spoof surface plasmon polariton (SSPP) transmission lines (TLs) provide a possible way to confining transmitted signals in deep subwavelength scale. SSPP TLs can suppress the mutual coupling between adjacent channels and improve the signal integrity, providing a promising alternative to conventional transmission lines. However, SSPP structures generally possess strong chromatic dispersion (i.e. signals at different frequencies propagate with different velocities), resulting in significant pulse distortion. Such drawback greatly hampers the practical application of SSPP TLs, especially in the long range transmission. To tackle this bottleneck problem, we propose a dispersion-compensation mechanism, where a section of judiciously designed TL with an opposite-dispersion characteristic is added to the SSPP circuit to achieve minimized total dispersion of the link within a broad frequency range. The experimental results indicate an impressive improvement of 72.46% for the SSPP transmission line in the stability of the circuit group delay after applying the dispersion compensation approach. This hybrid transmission line has high transmission efficiency without inducing group delay dispersion of the signals. Our design scheme can be easily extended to other frequency band, offering a possible solution to high-performance signal transmission in future integrated circuits.
Dispersion Compensation for Spoof Plasmonic Circuits
Vol. 179, 83-94, 2024
download: 243
Wave Manipulation with mmWave Wide Bandwidth and Extensive Spatial Coverage Using 1-Bit Reconfigurable Intelligent Surface
Saiful Islam , Van Linh Pham , Tae Hwan Jang and Hyoungsuk Yoo
We present an advanced approach to wave manipulation utilizing mmWave wide bandwidth, enhanced gain, and extensive spatial coverage through a 1-bit stacked patch reconfigurable intelligent surface (RIS). The RIS was designed on a four-layer board based on RO4350B, featuring a stacked patch on the front and phase-shifter components with a biasing line on the back of board. This sophisticated RIS comprises 400 elements, with a total array size of 100 × 100 mm2, providing a remarkable bandwidth of 7.02 GHz to cover the n257 band. Through a meticulous blend of simulations and real-world implementation, we emphasize the adaptability of the RIS in steering beams, maintaining a minimum gain variation and ensuring the gain of 21.03 to 15.17 dBi up to ±80˚ beam steering on normal incidence. Our study explores various beam manipulation scenarios, including near-to-far-field, far-to-far-field, and far-to-near-field transformations. The successful fabrication of the proposed RIS, combined with communication performance tests across the n257 band, underscores the practical applicability and robust performance of the system in real-world scenarios, thereby ensuring link throughput. The comprehensive investigation provides valuable insights into the design, simulation, fabrication, and performance evaluation of mmWave RIS. The successful integration of theoretical insights with empirical validations positions the present study at the forefront of mmWave innovation, with significant implications for the future of various research and wireless communication technologies.
Wave Manipulation with mmWave Wide Bandwidth and Extensive Spatial Coverage Using 1-bit Reconfigurable Intelligent Surface
Vol. 179, 71-81, 2024
download: 182
Design of High-Performance Antenna System for High-Speed Railways
Wenrui Zheng and Hui Li
In this paper, a systematic and efficient method is proposed to collectively synthesize the pattern for multiple antennas on high-speed railways (HSRs) based on pixel structures and N-port network, achieving an overall omnidirectional circularly polarized (OCP) pattern over a broad elevation angle. The integration of flush-mounted antennas not only enhances communication quality but also eliminates the undesired aerodynamic drag. Network parameters and radiating features of the N-port network based on the pixel structures are firstly retained through full-wave simulations. Subsequently, without resorting to extra simulations, the configurations of multiple antennas are precisely synthesized through numerical calculations. The beam direction and beam width of each element can be automatically adjusted, promoting a seamless omnidirectional radiation feature. Following the approach, the proposed antenna thoroughly cover the 5G N41 band (2.515-2.675 GHz), delivering omnidirectional, high-gain, right-hand CP radiation throughout the entire 160 MHz band from θ = 50˚ to 100˚. The averaged CP gains and ARs reach 6.09 dBi and 2.36 dB, respectively, within the target region. The antenna system was validated experimentally, with the measured results agreeing well with the simulated ones. Such radiating characteristics perfectly match the established base stations antennas.
Design of High-performance Antenna System for High-speed Railways
Vol. 179, 61-69, 2024
download: 269
Fabricated Magnetic-Dielectric Synergy FE@Carbon Microspheres by Spray-Pyrolysis with Excellent Microwave Absorption in C-Band
Hao Zhu , Zhuolin Li , Mengqiu Huang , Lei Wang , Yongsheng Liu , Yuxiang Lai and Renchao Che
The development of materials with excellent absorption properties in the C-band through the utilization of the magnetoelectric coupling effect holds great potential within the field of absorption research. However, there are still several challenges. To address these challenges, Fe@Carbon (Fe@C) microspheres were successfully fabricated using spray-drying followed by pyrolysis. The average size of the Fe@C microspheres is 3.6 µm with uniform dispersion, where iron nanoparticles (NPs) are tightly anchored with the carbon matrix to tune the microwave absorption properties. Synthesized Fe@C microspheres exhibit remarkable electromagnetic wave absorption capability within the C-band (4-8 GHz), covering a bandwidth of 2.8 GHz. Also, the Fe@C microsphere exhibits a minimum reflection loss of -48.11 dB at 4.5 mm thickness and 6.88 GHz. Systematic analysis has uncovered that the integration of large-sized magnetic carbon structures, high-density confinement of magnetic units, and robust magnetic coupling are crucial for enhancing the magnetic loss dissipation. This study introduces a novel approach for the preparation of electromagnetic absorbing materials, providing inspiration for further exploration of the mechanism behind low-frequency magnetic loss.
Fabricated Magnetic-dielectric Synergy Fe@Carbon Microspheres by Spray-Pyrolysis with Excellent Microwave Absorption in C-band
Vol. 179, 49-59, 2024
download: 475
Multi-Characteristic Integrated Ultra-Wideband Frequency Selective Rasorber
Dengpan Wang , Xingshuo Cui , Dan Liu , Xiaojun Zou , Guang-Ming Wang , Bin Zheng and Tong Cai
Frequency selective rasorbers (FSRs), especially those with ultra-wideband and hybrid characteristics, are of great significance in modern stealth technology and applications. However, currently available FSRs have issues with limited transmission bandwidth and single operating characteristics. Here, a novel strategy is proposed to design multi-characteristic integrated FSRs with ultra-wide and high-efficiency passband via spoof surface plasmon polariton (SSPP). The designed FSR exhibits the characteristics of absorption-transmission (AT), transmission-absorption (TA), and absorption-transmission-absorption (ATA), which consists of AT resistive sheets, TA SSPP slow-wave structures, and ultra-wideband bandpass frequency selective surface (FSS). The top lumped-resistor-loaded resistive sheet and the bottom multi-layer cascaded FSS form an AT FSR which is demonstrated by equivalent circuit model (ECM). Middle dispersion gradient SSPP structure that generates SSPP on the periodic array is an independent TA FSR while the working principle is based on k-dispersion control and energy distribution. Thus, the transition band between the transmissive and absorptive bands is narrowed while the crosstalk between absorber and transmission is avoided. For verification, a prototype is fabricated and experimentally demonstrated. Measured results manifest the validity and feasibility of the FSR with an ultra-wide -1 dB transmission band from 8.9 to 16.4 GHz (59.3%) and two 85% absorption bands covering 2.2-6.4 GHz (97.7%) and 17.6-26 GHz (38.5%). Our work provides a novel method for the design of ultra-wideband multi-characteristic FSR and stimulates its application in broadband electromagnetic stealth, shielding and compatible devices.
Multi-characteristic Integrated Ultra-wideband Frequency Selective Rasorber
Vol. 179, 37-47, 2024
download: 455
Theoretical Analysis on Generating Composite-Orbital Angular Momentum Beam
Zhixia Wang , Zelin Zhu , Shilie Zheng , Xiaonan Hui and Xianmin Zhang
For orbital angular momentum (OAM) based practical applications in radio frequency, inherent puzzles of traditional OAM carrying waves will be encountered inevitably, such as the inherent dark zone in the beam center and severe beam divergence. To solve the problem, some specific beams which are directional beams with high gain, and retain the vorticity and orthogonality of conventional OAM carrying beams have been put forward. They are termed as composite-orbital angular momentum (c-OAM) beam for the first time in this paper. Continuous arc source model (CASM) and discrete arc source model (DASM) are proposed to generate c-OAM beams which are composed of several OAM waves with different weights. Mathematical models of CASM and DASM are demonstrated, and the field expressions are derived. Numerical simulations are conducted to analyze the characteristics of the c-OAM beams, including directivity, vorticity, orthogonality, etc., and certify validity of the proposed model. In all, CASM and DASM are capable of generating c-OAM beams which are more suitable for OAM property based practical applications. Since beamforming is one of the key technologies in 5G systems, c-OAM beams are beneficial to be applied in current communication systems.
Theoretical Analysis on Generating Composite-Orbital Angular Momentum Beam
Vol. 179, 19-36, 2024
download: 851
Fast Calculations of Vector Electromagnetics in 3D Periodic Structures Based on Multiple Scattering Theory and Broadband Green's Function
Leung Tsang , Tien-Hao Liao , Shurun Tan , Xiaolan Xu , Xuyang Bai and Rouxing Gao
We have developed a fast method of using Multiple Scattering Theory-Broadband Green's Function (MST-BBGF) for band field calculations. In this paper, we successfully extended the method to the vector electromagnetic case of 3D periodic structures. In the MST-BBGF approach, the broadband transformation to vector spherical waves for 3D is derived using the Broadband Green's function. The band eigenvalue problem is expressed in terms of the single scatterer T matrix which is independent of the periodic lattice nor the Bloch vector. For the first five bands, the dimension of the KKR eigen equation is merely 6, as 6 vector spherical waves are utilized for the scattered waves. We make extensive comparisons of the results with the commercial software COMSOL in both accuracy and computation efficiency. The CPU requirementon a standard laptop for the MST-BBGF method is merely 0.309 seconds for the first 5 bands. The MST-BBGF method is accurate and is at least two orders of magnitude faster than commercial software COMSOL. In the band field calculations, we employ the approach of extended coefficient to use the low order eigenvector of 6 to extend to 240 vector spherical wave coefficients without the need of re-calculating the eigenvalue nor the eigenvector of the KKR equation. The extended coefficients approach gives accurate band field solutions for the entire (0,0,0) cell.
Fast Calculations of Vector Electromagnetics in 3D Periodic Structures Based on Multiple Scattering Theory and Broadband Green's Function
Vol. 179, 1-18, 2024
download: 1152
Information-Theoretic Measures for Reconfigurable Metasurface-Enabled Direct Digital Modulation Systems: an Electromagnetic Perspective
Xuyang Bai , Shurun Tan , Said Mikki , Erping Li and Tie-Jun Cui
The fusion of electromagnetic (EM) waves and information theory in wireless and waveguide communication technologies has enjoyed a remarkable revival during the last few years. In particular, unlike traditional transceiver systems, the recently proposed information metasurface system directly links the controllable binary array sources with the scattered EM waves, making the combination of EM and information theories highly desirable and natural. Moreover, a traditional linear channel matrix cannot be directly used for such scattering reconfigurability enabled communication system, making the information characterization of such system a great challenge. In this paper, EM information characteristics of a direct digital modulation (DDM) system enabled by programmable information metasurface, also known as reconfigurable intelligent surface (RIS), are analyzed, in which RIS is used as a modulator of the illuminating field, while the scattered far-field amplitudes are measured and effectively treated as the received quantities. The posterior probability for a specific source coding pattern, conditioned over a given measured scattering fields, is obtained through the Bayesian analysis technique, from which the average mutual information (AMI) is obtained to estimate the RIS observation capability along any particular direction. The averaged receiver mutual information (ARMI) is then introduced to characterize the generated field correlation structures along different observation directions. Based on ARMI, the joint observation capability is also analyzed. Furthermore, the suggested techniques are employed in a noisy environment, and a code selection scheme is put forth to achieve efficient information transmission. The proposed configuration is validated through a simulated experiment. As a comprehensive evaluation of the system's performance, the channel capacity of the system is derived, and a set of relevant influencing factors are identified and analyzed from four different perspectives: 1) the observation direction, 2) the size of RIS, 3) potential joint observations in multiple directions, and 4) the noise level. The proposed method, together with the various related performance measure metrics introduced therein, are expected to provide the research community with guidelines for analyzing and designing the current and future RIS-based communication systems, which can also be extended to other aspects in the growing field of the EM information theory.
Information-theoretic Measures for Reconfigurable Metasurface-enabled Direct Digital Modulation Systems: An Electromagnetic Perspective