A novel approach to suppress mutual coupling (MC) between two patch antennas is presented in this letter. A parasitic isolator, which is printed between the two patches, controls the polarization of ...the coupling field to reduce the antenna coupling. Furthermore, a defected ground structure is employed to suppress the cross-polarization (XP) level. There exists a tradeoff between the MC reduction and XP improvement in this approach. As an example, a two-element patch array with an optimized isolator is fabricated and measured. The measured results show that, at the resonant frequency, the achieved isolation enhancement and XP level are 19.6 dB and -13.2 dB, respectively.
A miniaturized broadband planar monopole multiple‐input‐multiple‐output (MIMO) antenna is proposed for the 3.5 GHz frequency band of the Long‐Term Evolution Advanced application. Two novel broadband ...metamaterial split‐ring resonator units are used to reduce the mutual coupling of the MIMO antenna, also expanding the antenna impedance bandwidth. The size of the whole antenna is 47.5 mm × 40 mm × 1.6 mm (1.15λg × 0.97λg × 0.039λg) and the center distance between the two antenna elements is only 0.25λ0. The measured results agree well with the simulated ones. The measured 10‐dB impedance bandwidth is 3.35 to 3.78 GHz (12.3%), and the isolation is up to 15 dB within the bandwidth.
In recent years, the matrix enhancement and matrix pencil method (MEMP) as well as the forward-backward MEMP (FBMEMP) have been successfully applied to reduce the number of antenna elements in the ...single-pattern planar arrays. This article aims to extend the MEMP and FBMEMP to the synthesis of sparse planar arrays with multiple patterns. The generalized MEMP (GMEMP) first constructs an enhanced matrix for each target pattern according to their data samples, respectively, and then these enhanced matrices are used to form a composite Hankel block matrix. After that, two sets of poles corresponding to two sets of reconstructed location coordinates can be extracted from the principal eigenvectors of the composite Hankel block matrix by the matrix pencil method. The randomized singular value decomposition and Hankel matrix decomposition method are used to accelerate the above extraction process. Then, we make use of improved matching algorithm to pair the two sets of position coordinates to obtain 2-D coordinates. Finally, we use the least-square method to obtain the excitations of sparse planar array elements, which makes the reconstruction process of multiple patterns more stable and accurate. Apart from the above, the GMEMP is also extended to the synthesis of multiple shaped-beam patterns using the generalized forward-backward matrix enhancement and matrix pencil method (GFBMEMP). A series of representative numerical examples show that the proposed methods can reduce the number of elements in the planar arrays efficiently while maintaining the accuracy of all the patterns to be synthesized.
A wide-beam antenna and a planar phased array with wide-angle scanning performance based on image theory are proposed. To solve the wide-angle scanning problem, a summative evaluation of basic types ...of carrier-based antennas is given and the antenna types available for wide-angle scanning arrays or end-fire arrays are pointed out. Afterward, a wide-angle scanning array with an artificial magnetic conductor (AMC) ground is proposed. The main beam direction of the array can scan from -89° to 90° in the H-plane with a gain fluctuation less than 3 dB and the scanning 3-dB beamwidth can cover a range from -105° to 105°. An excellent wide-angle scanning performance from the broadside direction to the end-fire direction can be obtained by the proposed method, which can be used to guide the design of wide-angle scanning arrays.
We propose a novel method to extend the scanning range of planar phased arrays based on a phase gradient metasurface. The phase gradient metasurface is developed by the generalized Snell's law, which ...can irregularly tailor the direction of propagation of the traversing electromagnetic waves. The proposed transmission gradient phase metasurface (TGPMS) uses bidirectional expansion of the scanning range in a phased array application. The TGPMS consists of periodic and multilayer subwavelength elements that contribute to a wide range of transmission phase shift and multiple incident angular stability. The design is verified experimentally with a compact microstrip phased array that is integrated with the proposed TGPMS. Results demonstrate that the TGPMS extends the scanning range of the integrated array symmetrically, from -36°, 38° to -56°, 60°. The proposed TGPMS has additional desirable characteristics, such as high transmission, polarization insensitivity, tunable transmission phases in a wide range, and transmission phase stability for waves incident at different angles.
Determining a good initial structure in the inverse design of electromagnetic devices based on topology optimization method is an important problem that has been relatively little studied. In this ...letter, a method for constructing the initial structure of a multi-frequency nanophotonic device by combining time reversal theory and principal component analysis is proposed, and the inverse design of two-dimensional 1×2 and 1×3 wavelength demultiplexers is taken as examples. The results show that the iterative optimization converges to a better figure of merit after using the proposed method, compared to classical and single-frequency initial structures. The proposed method also shows good adaptability when the design target changes.
Shaping the intensity distribution of radiated electromagnetic (EM) fields in a given bounded target area is a challenging problem in EMs. Although some approaches have been explored for this ...purpose, most are limited to the synthesis of plane-wave fields or point-focused fields. In this communication, a field-shaping method based on angular spectrum projection and the linear superposition principle is presented. The proposed method allows radiated electric fields to be shaped with different desired intensity patterns in a given limited target area with the use of the same antenna array. Via this method, all element excitations of the antenna array can be analytically calculated, and not only is the element excitation computational time reduced, but the real-time control of shaped fields is also made possible. Full-wave simulations were carried out to illustrate the 1-D and 2-D electric field shaping within a small given target area. In the 1-D case, three types of shaped fields with different desired distributions are demonstrated. In the 2-D case, three kinds of origin-symmetric shaped fields with different intensity distributions are illustrated. Finally, shaped fields with more complicated 2-D intensity distributions, like "I"- and "X"-shaped patterns, are demonstrated, and are achieved directly by applying the linear superposition principle to multiple point-focused fields with spatially overlapping focal spots.
The deepening research of physics-informed neural networks (PINNs) demonstrates the advantages of this method to electromagnetic inverse design. Some studies have deeply embedded the physics ...information into the neural networks, obtaining better solution performance and providing a new way for the PINN electromagnetic inverse design problems. This article explores PINN with embedded analytical models (EAM-PINN) to design waveguide devices. We first develop a multilayer dielectric-loaded rectangular waveguide model and derive its <inline-formula> <tex-math notation="LaTeX">{S_{21}} </tex-math></inline-formula> parameter expressions. Considering the inevitable limits of the <inline-formula> <tex-math notation="LaTeX">{S_{21}} </tex-math></inline-formula> response achievable by the waveguide model, we propose a method to solve the model bounds based on the interior point method to determine the number of dielectric layers. To improve the solution effect of PINN, we also present a hard constraint method based on the activation function. Then, we embed the <inline-formula> <tex-math notation="LaTeX">{S_{21}} </tex-math></inline-formula> parameter expressions, as an <inline-formula> <tex-math notation="LaTeX">{S_{21}} </tex-math></inline-formula> analytical model, into the traditional PINN framework, reducing the scale of loss functions. We also theoretically analyze the performance of EAM-PINN and summarize its parameter selection scheme. The EAM-PINN implements three inverse design cases: a known analytical solution retrieving, a bandpass filter, and a dispersive delay line. Finally, we conclude the advantages of EAM-PINN compared to various current methods and validate our inverse design results through simulation. We find that EAM-PINN has high solving efficiency and strong stability, which can realize the inverse design of complex microwave devices, showing the great potential of this method.
In this communication, a novel artificial neural network (ANN) model is proposed to describe the antenna performance with various parameters. In this model, three parallel and independent branches ...are involved for three different performance parameters. Meanwhile, a data-classification technique of support vector machine is also included to classify geometrical variables into the proper categories. Once the geometrical variables are input, the ANN model can simultaneously obtain S-parameter, gain, and radiation pattern from the independent branches. The validity and efficiency of this proposed model are confirmed with a Fabry-Perot resonator antenna example.
A broadband polarization reconfigurable rectenna is proposed, which can operate in three polarization modes. The receiving antenna of the rectenna is a polarization reconfigurable planar monopole ...antenna. By installing switches on the feeding network, the antenna can switch to receive electromagnetic (EM) waves with different polarizations, including linear polarization (LP), right-hand and left-hand circular polarizations (RHCP/LHCP). To achieve stable conversion efficiency of the rectenna (n r ) in all the modes within a wide frequency band, a tunable matching network is inserted between the rectifying circuit and the antenna. The measured n r changes from 23.8% to 31.9% in the LP mode within 5.1-5.8 GHz and from 22.7% to 24.5% in the CP modes over 5.8-6 GHz. Compared to rectennas with conventional broadband matching network, the proposed rectenna exhibits more stable conversion efficiency.
