IEEE Transactions on Antennas and Propagation

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ISSN / EISSN : 0018-926X / 1558-2221
Total articles ≅ 16,936
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, Ka Ma Huang, Chaoyun Song, Yuan Ding, George Goussetis
IEEE Transactions on Antennas and Propagation, pp 1-1; https://doi.org/10.1109/tap.2021.3119045

Abstract:
Traditionally, the signal power is divided equally between dual functions in Wireless Information and Power Transmission (WIPT), which, intuitively, is not an optimal solution since the power sensitivities for communication and charging node pose different constraints for signals. To address this challenge, a two-channel rectenna with an asymmetrical coupler feeding network (ACFN) has been proposed for WIPT under the power and time sharing (PS and TS) schemes. The proposed two-port rectenna consists of a receiving antenna integrated with ACFN where one output port is connected to a rectifying circuit while the other is used for information recovery. Different from the conventional PS scheme with equal division, the proposed rectenna can adjust ratios of power at two outputs. That is, routing high power to the RF-DC port, and transferring low power but of sufficient signal-noise-ratio (SNR) to the port being used for signal demodulation/decoding. As a result, the simulated/ measured maximum RF-DC conversion efficiency of the rectenna can reach up to 73.9%/70.4% for Quadrature Phase Shift Keying (QPSK) modulated signals and 63.9%/60.7% for continuous wave (CW) signals. In addition, good isolation between the two output ports ensures low interference against information decoding.
, Elham Mohammadi, John Booske, Nader Behdad
IEEE Transactions on Antennas and Propagation, pp 1-1; https://doi.org/10.1109/tap.2021.3119095

Abstract:
Antennas operating at the high-frequency (HF) band (3-30 MHz) are often electrically small due to the large wavelength of electromagnetic waves (10-100 m). Passive electrically small antennas (ESAs) have low bandwidth and poor efficiency values, which makes it challenging to radiate instantaneously broadband, high-power signals for applications such as electronic warefare. To address these challenges, we present the design and experimental demonstration of an active, electrically-small antenna capable of transmission over the entire HF band. The proposed antenna consists of a 2-m long dipole integrated with a class-AB push-pull amplifier. The amplifier circuit that drives the antenna is specifically designed to behave as a high-voltage current buffer to the antenna, resulting in ultra-wideband operation. The amplifier uses high-power vertically-diffused MOSFET transistors capable of sustaining the high voltage and current swings that occur at the terminals of the highly-reactive dipole during transmission. A prototype of the antenna is fabricated and characterized in field tests. Experiments demonstrate stable, ultra-wideband operation over the entire HF band. Measurement results show that the proposed active antenna can offer total efficiency improvements of over 15 dB compared to a passive matching scenario. The advantages of this approach over non-Foster impedance matching techniques are also highlighted.
, Puyan Mojabi
IEEE Transactions on Antennas and Propagation, pp 1-1; https://doi.org/10.1109/tap.2021.3119115

Abstract:
This paper presents an electromagnetic inversion algorithm for the design of cascaded metasurfaces that enables the design process to begin from more practical output field specifications such as a desired power pattern or far-field performance criteria. Thus, this method combines the greater field transformation support of multiple metasurfaces with the flexibility of the electromagnetic inverse source framework. To this end, two optimization problems are formed: one associated with the interior space between two metasurfaces, and the other for the exterior space. The cost functionals corresponding to each of these two optimization problems are minimized using the nonlinear conjugate gradient algorithm with analytic expressions for the gradient operators. The numerical implementation of the developed design procedure is presented in detail, including a total variation regularizer that is incorporated into the optimization procedure to favour smooth field variations from one unit cell to the next. The capabilities of the method are demonstrated by converting the produced surface susceptibilities into threelayer admittance sheet models, which are simulated in several two-dimensional (2D) examples.
Hojatollah Zamani, Mohammad Fakharzadeh, , Farokh Marvasti
IEEE Transactions on Antennas and Propagation, pp 1-1; https://doi.org/10.1109/tap.2021.3119100

Abstract:
This communication addresses the focusing problem in the millimeter-wave imaging systems. We categorize the focusing problem into the frequency focusing for wideband systems and the range focusing for narrow-band systems. In an out of focus wideband system, a shifted shadow of the object is present in the reconstruction, whereas for a range out of the focused system, the recovered images are blurred. To overcame these issues, first we theoretically show that the defocusing variations for both categories are bounded. Then, we present a universal formulation for focusing problem, which covers both wideband and the narrow-band systems. As the true focused images are sharp at the boundaries of the objects, our strategy for solving the problem is to maximize a defined sharpness metric. Moreover, we propose an autofocusing zero knowledge algorithm, which concerns with maximizing the sharpness metric from an unknown object, while the exact gradient of the cost function is unknown. The proposed method is suitable for practical applications, since it is simple, fast, and computationally efficient. The simulation results on synthetic and measured data are promising and support our claims that the proposed method increases the quality of the reconstruction.
Gang Ni, , Yanchang Gao, Jingfeng Chen, Ronghong Jin
IEEE Transactions on Antennas and Propagation, pp 1-1; https://doi.org/10.1109/tap.2021.3119046

Abstract:
A general high-efficiency time-modulated module and harmonic beam scanning time-modulated array (TMA) are proposed and investigated in this paper. By introducing the periodically controlled phased-shifters, a significant improvement on theoretical overall efficiency and transmitted bandwidth can be realized in harmonic beam scanning. Then equivalent cascade structure of the general modulation module is proposed for RF circuit simplification and practicability in actual applications. Theoretical derivation and simulation results show that increased efficiency, 100% feeding network efficiency and theoretical overall efficiency tending to 100% without consideration of insertion loss, can be achieved with the increase the phase-shifter states when only a single sideband is utilized. Compared to the existing state-of-the-art harmonic beam scanning TMAs, the proposed TMA exhibits a much higher overall efficiency while keeps a similar hardware complexity. Additionally, with acceptable increase of circuit complexity less than existing works, similar level of the wide transmission bandwidth can also be achieved. To experimentally verify the feasibility of the proposed general design, a 4-bit time-modulated module with reconfigurable states and the corresponding 8-element harmonic beam scanning TMA are fabricated and tested. The experiments on signal transmission and harmonic beam scanning demonstrate the effectiveness of power loss reduction and improvement in transmitted bandwidth with the increase of modulation phase states.
Bin Xi, Yu Xiao, , Zhixi Liang, Shao Yong Zheng, Zengping Chen, Yunliang Long
IEEE Transactions on Antennas and Propagation, pp 1-1; https://doi.org/10.1109/tap.2021.3119048

Abstract:
A periodic mirror-reflected circular-polarized (CP) leaky wave antenna (LWA) with dual beam-scanning in dual polarization types is reported in this paper. The unit cell of the proposed antenna consists of two oblique stubs that are orthogonally separated (90°) to create a circular polarization. In order to achieve better CP (axial ratio (AR) < 3dB) and beam-scanning characteristics for the periodic CP antenna, a new method of adding a groove at the junction of stubs within the unit cell is introduced. To realize dual beam-scanning in dual circular polarization, a metal via is added at the end of the antenna to generate a mirror reflection. A mirror-reflected structure is fabricated and measured. The measured results show that the right-handed CP (RHCP) scanning range of the incident beam is -31°~-8° and 5°~-14°, and the left-handed CP (LHCP) scanning range of the corresponding reflected beam is 31°~6° and -6°~-15°. The measured results are in good agreement with the simulated ones.
, Puyan Mojabi
IEEE Transactions on Antennas and Propagation, pp 1-1; https://doi.org/10.1109/tap.2021.3119049

Abstract:
This paper augments existing gradient-based inverse scattering algorithms to enable the design of reflectionless lossless permittivity profiles within a given design domain that can transform an input incident field into an output field of desired characteristics. These desired characteristics are often some user-defined far-field performance criteria such as main beam directions, null directions, and half-power beamwidth (HPBW). To this end, two extra steps will be performed prior to the inverse scattering step. Firstly, an inverse source algorithm inverts the desired far-field performance criteria to infer a set of equivalent surface currents on a boundary close to the design domain. These equivalent currents are then converted to a set of fields values that constitute the required aperture fields. Secondly, these aperture fields are scaled such that the input incident power to the design domain is approximately equal to the output power leaving the design domain. Finally, the desired scattered fields are formed and then inverted by an inverse scattering algorithm to reconstruct a lossless reflectionless dielectric profile within the design domain. We also show that the inverse scattering algorithm can employ appropriate regularization methods, in particular a binary regularization term, to facilitate the physical implementation of reconstructed dielectric profiles.
Priyashantha Tennakoon, Chandika B. Wavegedara
IEEE Transactions on Antennas and Propagation, pp 1-1; https://doi.org/10.1109/tap.2021.3119036

Abstract:
This paper proposes a generalized three dimensional (3D) geometry-based stochastic model (GBSM) channel model with an arbitrary center point of the scatterer distribution. In the proposed channel model, scatterers are assumed to be Gaussian distributed about an arbitrary point within a spheroidal shell having the transmitter and the receiver located at its focal points. Exact closed-form expressions are obtained for the joint probability density function (PDF) of the angles of arrival (AoAs) and time of arrival (ToA), and the marginal PDF of ToA. Moreover, approximate closed-form expressions are derived for the marginal PDFs of AoAs in the elevation and azimuth planes. The accuracy of the analytically derived AoA and ToA PDFs are verified by comparing with the PDFs obtained using computer and ray-tracing simulation. Furthermore, we study the characteristics of the analytically-derived AoA and ToA PDFs for different propagation scenarios. By choosing the center point and standard deviation of the scatterer distribution appropriately, our proposed 3D channel model can be used to evaluate the performance of wireless communication technologies and systems in indoor environments.
Peng-Yu Feng, , Ka Fai Chan, Shiwen Yang, Chi Hou Chan
IEEE Transactions on Antennas and Propagation, pp 1-1; https://doi.org/10.1109/tap.2021.3119044

Abstract:
This paper presents a design concept of integrative transmitarray antenna (TAA) with gain-filtering and low-scattering characteristics. The integrative TAA element combines a bandpass frequency-selective surface (FSS) element and a square dielectric post with antireflection pyramidal structures (SDPP), achieving the simultaneous control of in-band transmitted waves and out-of-band reflected waves. The FSS element provides the phase-shifting and gain-filtering capabilities around the center operating frequency f0. Meanwhile, the SDPP elements with different heights are utilized to reduce the scattering cross section (SCS) based on the phase cancellation principle. To realize wideband and wide-angle SCS reductions, also to mitigate the in-band radiation degradation, the optimal SDPP arrangement is determined with subarray segmentation. In the experiment, a 42×42-element integrative TAA is designed. Against only the FSS TAA, the simulated results show that loading the optimal SDPP array can realize the scattering reduction in a 10:1 bandwidth up to 60°, including ~5 dB/~10 dB SCS reductions in 0.5~1.5f0/1.5~5f0, respectively. Moreover, the integrative TAA achieves gain-filtering responses with out-of-band suppression levels higher than 20 dB. After fabricating the FSS TAA and the SDPP array by the technologies of standard PCB fabrication and 3-dimensional printing, respectively, the proposed design is further demonstrated by experiments.
Lifeng Wu, , Qiangming Cai, Zhipeng Zhang, Jun Hu, Zaiping Nie
IEEE Transactions on Antennas and Propagation, pp 1-1; https://doi.org/10.1109/tap.2021.3119096

Abstract:
In this paper, a fast high-order volume surface integral equation (HOVSIE) formulas solver will be presented to fast calculate the wideband electromagnetic (EM) scattering of anisotropic medium-metallic composite objects. Firstly, in the HOVSIE, the equivalence volume and surface current vectors are discretized by the high-order hierarchical vector basis functions (HVBFs), which can reduce unknowns and facilitate the calculation of the broadband EM scattering. Secondly, a fast wideband algorithm, i.e., the hybrid multilevel accelerated Cartesian expansion-multilevel fast multipole algorithm (MLACE-MLFMA), is integrated to accelerate the matrix-vector multiplication in the iterative solution. At last, in order to improve the iterative convergence, a simple overlapping domain decom-position method (ODDM) based preconditioner is also employed in the proposed HOVSIE enhanced by the MLACE-MLFMA. Summarily, three advantages can be found here: 1) more flexible calculation of the wideband EM scattering; 2) less memory occupation; 3) better iterative convergence. The accuracy, efficiency and flexibility will be demonstrated in the numerical examples.
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