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In this work, an ultra‐wideband double slot Vivaldi antenna (DSVA) loaded with a novel wideband nonresonant metasurface is proposed to enhance the gain. The semi‐elliptical slots are etched on both sides of the ground plane of the DSVA to improve the current distribution. In addition, the nonresonant metasurface composed of WiFi‐shaped unit cells could maintain a stable high refractive index in the operating bandwidth of 1−18 GHz, which could bend the outgoing wave to the end‐fire direction. Both the original antenna and the proposed antenna are simulated, fabricated, and characterized. The measured results are in good accordance with the simulated ones. The return losses of both antennas are less than −10 dB in the frequency range of 2−13.4 GHz, while the gain of the proposed antenna is improved from 13.6 to 16.3 dBi with a maximum gain enhancement of 3.1 dB. [ABSTRACT FROM AUTHOR]

A novel design of circularly polarized broadband slot antenna with high gain, low profile, and low radar cross‐section (RCS) is proposed by employing polarization conversion metasurface (MS). By introducing sawtooth corner‐truncated square MS with diagonal gaps, a compact circularly polarized antenna composed of 4 × 4 unit cells is presented. It is found that a smaller MS slot antenna can achieve an impedance bandwidth of 42.9% (3.7–5.72 GHz) and a 3‐dB axial ratio (AR) bandwidth of 22.8% (4.55–5.72 GHz). Simultaneously, the MS can realize polarization conversion. The MS and its orthogonal units were arranged in a chessboard‐type pattern and applied as the radiator of a larger MS slot antenna, which was fed by a sequentially rotated feeding network. In addition, owing to the anti‐phase cancellation and scattering, the 5‐dB average RCS reduction can be obtained within the frequency range from 3.8 to 6.9 GHz. For verification, the proposed larger circularly polarized antenna was fabricated and tested. The operating bandwidth was measured as 44% (3.78–5.91 GHz) with a 3‐dB AR bandwidth of 39.6% and a high gain of 10.3 dBic. Furthermore, the larger antenna produces a useful RCS reduction from 3.7 to 6.7 GHz. The simulated and measured results are in good agreement. [ABSTRACT FROM AUTHOR]

This article presents a novel method for the forward modeling and inverse design of a class of Schiffman phase shifters using deep neural networks (DNNs). Since DNNs are capable of mapping the highly nonlinear correlations between inputs and outputs, we constructed a fully connected DNN to predict the electromagnetic (EM) responses of Schiffman phase shifters given their physical dimensions. Based on this fast and accurate modeling tool, a cascaded inverse design DNN was then built and trained to achieve instant on-demand phase shifter designs. This approach is versatile and can be easily modified to accomplish different design goals. To demonstrate its efficacy, we trained two DNNs to realize Schiffman phase shifter designs with different bandwidths (40% and 60%) and arbitrary phase shift targets (0°–180°). Simulation results and experimental verifications substantiate that their performances are comparable with the state-of-the-art designs. Moreover, we discussed the proposed methods’ potential in dealing with design tasks that are nonintuitive and beyond the scope of the existing approaches. We envision that this DNN approach can be extended to the design of various EM components including but not limited to antennas, filters, power dividers, and frequency selective surfaces (FSS). [ABSTRACT FROM AUTHOR]

This article presents the design of Fermi antenna array with improved gain for radar respiration measurement. A six-element Fermi antenna array working at 5.8 GHz is optimally designed and integrated with the respiration radar system. Specifically, to easily feed the antenna array as well as reduce the total size of the array system, a feeding network based on 0-degree phase shifters is used along with suitable impedance transformers. The whole system is proposed to function as a radar sensor for respiration rate measurement, which is known as a promising noncontact and noninvasive approach for lung cancer radiotherapy. The measurement results verify the improved performance of the proposed system for radar respiration measurement in motion-adaptive lung cancer radiotherapy. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1649-1654, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26871 [ABSTRACT FROM AUTHOR]

This paper presents an improved two-antenna microwave passive direction finding system inspired by the human auditory system. By incorporating a head-like scatterer between two monopole antennas, both phase and magnitude information can be utilized to estimate the direction of arrival (DOA) of a microwave signal, thus eliminating ambiguities associated with phase wrapping at high frequency, just like human ears. In addition, better DOA sensitivity is demonstrated with the incorporation of the head-like scatterer. Both numerical modeling and experimental results of a simple X-band two-monopole configuration with symmetric and asymmetric scatterers are presented. [ABSTRACT FROM PUBLISHER]

A low-profile, compact and easily integrated antenna for RF/microwave applications is presented in this article. The designed antenna works around 430 MHz and can be easily scaled to other frequencies. Metamaterial-inspired slot loop antennas are used as the radiating elements. To shrink the total size of the antenna, periodical structures are loaded to the original slot loop. It is found that with this modification, the total size of the antenna is reduced and the impedance matching of the antenna is improved. To further improve the performance of the proposed antenna, a floating ground plane and a parasitic slot were added, made possible by the multilayered structure of the antenna. As a result, the bandwidth and gain of proposed antenna are increased. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:219-223, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25654 [ABSTRACT FROM AUTHOR]

A narrow beam monopole antenna is realized by embedding the antenna within a periodic metallic wire array. The 2D wire array is designed to have an effective index of refraction smaller than unity (neff < 1) at the X-band frequencies (8–12 GHz), within which the antenna operates. The narrow beam effect due to the low refractive index of the wire medium is demonstrated in both simulation and experiment. Measured antenna properties including return loss and radiation pattern are in good agreement with simulation results. This simple and straightforward antenna design methodology can be applied at any microwave frequency. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2341–2345, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23653 [ABSTRACT FROM AUTHOR]

This paper presents a holographic formation of compound photonic crystal and nano-antenna templates through a reflective optical element based laser interference. The reflective optical element consists of four Si facets where a circularly polarized single beam impinges at the Brewster angle and is reflected into four linearly s-polarized beams for the inference lithography. By tuning the phase delay in one of the interfering beams, dual-lattice photonic crystal, and nano-antenna templates are fabricated and compared with theoretic simulation. The design conditions for the nano-antenna formation are discussed. [ABSTRACT FROM AUTHOR]