With the increase of system complexity in wireless communications, higher requirements on miniaturization and integration are put forward for future antennas. Antennas of different frequency bands ...need to be placed together to achieve multiple communication goals. However, when a large-sized antenna operating at a low-band (LB) is used alongside a small-sized antenna operating at a high-band (HB), the radiation from the former can block the latter, thereby impacting the overall functioning of the antenna system. In this work, we propose a novel method for designing electromagnetic (EM) transparent antennas based on Drude metasurfaces. A dipole antenna made of Drude metasurfaces can maintain the radiation pattern of nearby HB antenna without compromising on radiation performance compared to the conventional metal-based one. An interconnected metasurface is designed to ensure low surface conductivity at HB yet high surface conductivity at LB, thus providing low radar cross section (RCS) compatible with the HB antennas. A prototype of the EM transparent dipole antenna is experimentally demonstrated and microwave measurements verify its capabilities in strong radiation and suppressing scattering at the LB and HB, respectively. Our results demonstrate an alternative way of solving EM blockages in multiband antenna systems by replacing conventional antennas with Drude-type meta-antennas.
A cavity-backed slot-antenna (CBSA) pair is designed in a shared cavity inserted with the multifunctional metasurface diaphragms (MSDs). The CBSA pair is co-polarized and in-band, and meanwhile ...exhibits the good features of a wide working band, good in-band decoupling, and enhanced out-of-band filtering performance, which are rarely achieved in other reported CBSAs. The customized MSDs in this design can introduce desired reflection/transmission properties and provide shorting paths in the cavity, which play an important role in adjusting the frequencies of the resonance modes to expand the working bandwidth, allowing proper transmission magnitudes and phases at different frequency points to enable the high isolation level, and generating filtering responses to introduce the radiation nulls (RNs) and enhance the out-of-band suppression. The proposed CBSA pair was analyzed, and then fabricated and measured. The total electrical size at the lowest working frequency <inline-formula> <tex-math notation="LaTeX">\text{f}_{L} </tex-math></inline-formula> is <inline-formula> <tex-math notation="LaTeX">0.76\times 0.58\times 0.16\lambda _{L} ^{3} </tex-math></inline-formula>. The overlapped fractional impedance bandwidth is <inline-formula> <tex-math notation="LaTeX">\sim </tex-math></inline-formula>11.1%. The peak realized gain (RG) reaches 6.4 dBi, and the isolation is greater than 15 dB. The three introduced RNs guarantee the out-of-band suppression level is better than 14.6 dB in 6-15 GHz. The proposed CBSA pair is a good candidate for the compact, co-polarized, in-band, and high-efficiency multiple-input-multiple-output (MIMO) CBSAs.
The hot carrier injection (HCI) reliability of n-type FinFETs in ring oscillators (ROs) is investigated with consideration of the circuit-level time-varying electrothermal effects in the ROs. The ...oscillating voltages and electrical power in a nine-stage RO are captured by circuit simulation in Cadence with its layout that is designed and verified based on FreePDK15. Spatial temperature response is obtained by heat conduction simulation with finite element analysis in the 3-D integrated structure that is accordingly constructed from the layout of the RO, where the heat generation is extracted from the Cadence simulation. With the obtained ac stress voltages and transient temperature, the HCI-induced threshold voltage shift (TVS) of n-type FinFETs under the circuit-level time-varying electrothermal effects is successfully predicted. The impacts of electrical and thermal parameters of the RO, including the supply voltage and thermal surrounding, on the electrothermal response and HCI reliability of FinFETs are also revealed.
•Sensor devices based on a configuration of HZSM-5 zeolite films printed Pd-WO3 sensing film were prepared.•The selectivity of Pd-WO3 sensors is considerably improved by the printing of HZSM-5 ...zeolite films.•Selective detection of CO and methanol is achieved by printing with HZSM-5 and Pt/HZSM-5 films on the top of sensing layers.
In the present study, gas sensors based on Pd-loaded WO3 sensor layers were prepared and coated with zeolite films to improve the selectivity. The sensing behavior of such sensors was characterized using different single gases and mixtures to assess their selectivity. We observed that the selectivity of sensors based on Pd-WO3 can be significantly tailored towards specific target gases by adding a printed zeolite film. The use of an HZSM-5 zeolite film made the Pd-loaded WO3 sensor highly sensitive to CO, with a response of around 10 at 100 ppm CO. When Pt-modified HZSM-5 zeolite film was used, same sensor became sensitive to methanol, with a detection limit of 0.5 ppm even in the presence of high concentration of CO. Interestingly, the Pt-modified HZSM-5 film caused the catalytic conversion of CO, which resulted in a p-type response to CO. In addition, in the presence of methanol such a p-type response to CO was also observed in pure WO3 sensor. Based on the power-law response to oxygen, it is proposed that the resistive responses of all tested sensors were highly dependent on the oxygen content, indicating that oxygen adsorbates on the surface were involved in the fundamental sensing mechanism, which is the same process as conventional gas sensors. The present study showed that the configuration of Pd-WO3 sensing layers coated with zeolite films is viable for tailoring the selectivity of gas sensors.
For charge injection from an electrode into a trap-filled dielectric slab, its current-voltage (<inline-formula> <tex-math notation="LaTeX">{I} </tex-math></inline-formula>-<inline-formula> <tex-math ...notation="LaTeX">{V} </tex-math></inline-formula>) characteristics are governed by the Mark-Helfrich (MH) law. By matching the experimentally measured <inline-formula> <tex-math notation="LaTeX">{I} </tex-math></inline-formula>-<inline-formula> <tex-math notation="LaTeX">{V} </tex-math></inline-formula> characteristics to a right <inline-formula> <tex-math notation="LaTeX">{I} </tex-math></inline-formula>-<inline-formula> <tex-math notation="LaTeX">{V} </tex-math></inline-formula> model, one can characterize the microscopic properties of the dielectric like its carrier mobility and traps distribution. The original MH law was developed for a bulk solid and may not be valid for modern ultrathin dielectrics used in 2-D electronics. Here, we revise the MH law for an ultrathin trap-filled dielectric of length <inline-formula> <tex-math notation="LaTeX">{L} </tex-math></inline-formula> biased with a voltage of <inline-formula> <tex-math notation="LaTeX">{V} </tex-math></inline-formula>. Our model suggests a new scaling of the current line density: <inline-formula> <tex-math notation="LaTeX">\mathcal {J}_{\text {2-D}} \,\,\propto \,\,{}{({V}}/{\alpha {L}{)}} \text {exp}{(} - {(\beta {l}}/{l+{1}}{)}{)} {}^{l+{1}} </tex-math></inline-formula>, where <inline-formula> <tex-math notation="LaTeX">\alpha </tex-math></inline-formula> = (2.8, 2.03) and <inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula> = (1.02, 0.94) are numerical values for two different geometrical (edge, strip) contacts, respectively. Using this 2-D ultrathin MH law, we demonstrate that the estimated carrier mobility can be significantly different from the traditional MH law. Under the same material properties, our model also highlights that strip contact geometry will always lead to a larger current flow than edge contact geometry. Thus, the developed model should be useful for the characterization of the ultrathin dielectrics used in 2-D materials-based electronics, organic semiconductors, and thin-film electronics.
This paper presents the analysis and design of a miniaturized polarization insensitive metamaterial absorber (MMA) for suppression of the electromagnetic interference (EMI) at microwave frequency ...range. The proposed MMA consists of a periodic array of double split ring structures printed on an FR4 substrate with a thickness of 0.07 λ 0 . The simulated results derived from CST indicate that the absorption ratio of the MMA is over 90% with a wide frequency range from 8.3 GHz to 11.3 GHz for a normal incident electromagnetic (EM) wave. To understand the EM wave absorption mechanism, an equivalent circuit model of the MMA unit cell is constructed to investigate the absorbing characteristics, and the electric field and surface current distributions are analyzed at absorption peaks.. Both equivalent circuit model (ECM) and measured results show good agreement. What's more, the measurement data shows that the radiated electric field of the patch antenna at 1 meter is significantly reduced at 10 GHz while loading with the MMA. A maximum suppression of 18 dBμν/m is achieved at 10 GHz. As the proposed absorber possesses good ability on electromagnetic radiation absorption, it could be well applied on printed circuit board (PCB) level EMI suppression.
It is the pursuit of a multiple-input-multiple-output (MIMO) system to approach and even break the limit of channel capacity. However, it is always a big challenge to efficiently characterize the ...MIMO systems in complex space and get better propagation performance than the conventional MIMO systems considering only free space, which is important for guiding the power and phase allocation of antenna units. In this article, an electromagnetic-information-theory (EMIT)-based model is developed for the efficient characterization of MIMO systems in complex space. The group-<inline-formula> <tex-math notation="LaTeX">T </tex-math></inline-formula>-matrix-based multiple scattering fast algorithm, the mode-decomposition-based characterization method, and their joint theoretical framework in complex space are discussed. First, key informatics parameters in free EM space based on a dyadic Green's function are derived. Next, a novel group-<inline-formula> <tex-math notation="LaTeX">T </tex-math></inline-formula>-matrix-based multiple scattering fast algorithm is developed to describe a representative inhomogeneous EM space. All the analytical results are validated by simulations. In addition, the complete form of the EMIT-based model is proposed to derive the informatics parameters frequently used in EM propagation, by integrating the mode analysis method with the dyadic Green's function matrix. Finally, as a proof-or-concept, microwave anechoic chamber measurements of a cylindrical array are performed, demonstrating the effectiveness of the EMIT-based model. Meanwhile, a case of image transmission with limited power is presented to illustrate how to use this EMIT-based model to guide the power and phase allocation of antenna units for real MIMO applications.
Modern antenna systems face serious problems of mutual coupling, which will cause electromagnetic compatibility problems such as pattern distortion. This article presents an innovative methodology ...for adaptive mutual coupling compensation based on the efficient characterization of coupled antenna arrays (CAAs), especially for nonuniform configurations. As a data-driven methodology, efficient characterization of CAAs is conducted firstly to simplify the analysis of mutual coupling by utilizing the characteristic modes of individual antenna elements, resulting in a more efficient data-collection process with reduced computational time. More importantly, this efficient characterization approach is applicable to any antenna spacing and excitation distribution, providing a new physical perspective to reveal mutual coupling. Furthermore, to realize adaptive mutual coupling compensation, this article employs a conditional generative adversarial network to address the challenges of high dimensional data loss and nonunique input-output mapping. The proposed methodology is demonstrated through its implementation in a real-world engineering scenario and provides a comprehensive solution for adaptive mutual coupling compensation. In other words, it avoids time-consuming full-wave simulations, complex neural network processing, and repetitive iterations.
With the rapid development of wireless communication, the requirements of high-integration and low-cost radio frequency (RF) front-end modules in mobile phones result in more usage of ...silicon-on-insulator field effect transistors (SOIFETs) for the manufacturing of RF switches. However, the nonlinear behavior of SOIFET switches in off -state always produces unwanted harmonics distortion interference when they are excited by a large signal. In this article, we simplify the well-known physics-based surface potential model to an interelectrode nonlinear capacitance (INC) model since it adequately describes the harmonic effects produced by the transistor. The INC model, referred to as the coarse model, cannot match the behavior of the real switch, since many parameters of the switch cannot be accurately determined. This article proposes a novel dynamic neuro-space mapping network model, referred to as the fine model, to optimize the INC model. The proposed model takes advantage of the high accuracy of the fine model and the fast speed of the coarse model. Ultimately, the proposed method can accurately predict the harmonics interference for SOIFET switches in the complex RF front-end environment and provides an intuitive guideline under the design stage to prevent EMI problems.
In this letter, a novel low-profile dual-band and dual circularly polarized (CP) microstrip antenna is proposed. The antenna consists of two circular eccentric rings (CECRs) with different sizes. The ...two eccentric rings each work as a single-band circular polarization radiator and are simultaneously excited by an arc-shaped strip. A lumped equivalent circuit model is developed to analyze the operation mechanism of the antenna. In order to simplify the design procedure, empirical formulas are derived based on the physical parameters of the antenna. The proposed structure has been examined by both simulation and experiment, and both results agree very well.
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