This paper describes an accurate design method of coplanar waveguide (CPW) test structures on characterizing dielectric properties of thin films with arbitrary thickness. Current CPW measurement ...method has difficulty in providing accurate dielectric properties of films with extremely small thickness. To address this issue, an optimized algorithm is presented to generate proper geometric parameters of CPW test structures for films with different thickness. To validate the accuracy of the proposed design methodology, various test cases of CPW structures with different dimensions have been designed and implemented, the extracted dielectric properties (e.g., dielectric constant and loss tangent) from the S-parameters of the different test cases are compared to the benchmark results simulated by accurate electromagnetic tool Ansys HFSS. It demonstrates the efficacy of the proposed optimized method on quickly producing correct dimensions of CPW test lines for accurate properties characterization of thin films.
Versatile printing of polymers, metals, and composites always calls for simple, economic approaches. Here we present an approach to three-dimensional (3D) printing of polymeric, metallic, and ...composite materials at room conditions, based on the polymeric vapor-induced phase separation (VIPS) process. During VIPS 3D printing (VIPS-3DP), a dissolved polymer-based ink is deposited in an environment where nebulized non-solvent is present, inducing the low-volatility solvent to be extracted from the filament in a controllable manner due to its higher chemical affinity with the non-solvent used. The polymeric phase is hardened in situ as a result of the induced phase separation process. The low volatility of the solvent enables its reclamation after the printing process, significantly reducing its environmental footprint. We first demonstrate the use of VIPS-3DP for polymer printing, showcasing its potential in printing intricate structures. We further extend VIPS-3DP to the deposition of polymer-based metallic inks or composite powder-laden polymeric inks, which become metallic parts or composites after a thermal cycle is applied. Furthermore, spatially tunable porous structures and functionally graded parts are printed by using the printing path to set the inter-filament porosity as well as an inorganic space-holder as an intra-filament porogen.
This article proposes a filtering structure consisting of two half‐wavelength resonators and two open‐stub loaded resonators, which generates two third‐order passbands. Multiple transmission zeros ...are introduced by the newly developed coupling scheme, resulting in extremely sharp roll‐off desirable for highly selective filters. The proposed structure is applied to design a PIN‐diodes switch‐controlled reconfigurable dual‐band bandpass filter (BPF) with four‐state filtering responses: both passbands ON, both passbands OFF, high‐frequency passband ON, and low‐frequency passband ON. Stepped‐impedance open stubs and one‐end‐grounded coupled lines are studied and employed in the design to suppress unwanted responses. In addition, two filtering structures are placed symmetrically to design a dual‐band balun BPF. Double‐sided parallel‐strip lines are added in the input port of the filter, and their inherent out‐of‐phase feature enables the balun filter to convert unbalanced signal to balanced signal at desired frequencies. The measured results of both fabricated devices agree well with the simulated results. The switchable BPF and balun BPF have two passbands (2.8 and 4.8 GHz) with high selectivity with the minimum roll‐offs from −3 to −15 dB are 1.70 × 103 and 2.71 × 103 dB/decade, respectively. The insertion loss of the switchable BPF is 2.3/2.0 dB and the minimum signal suppressions level OFF state is measured as −18.2 dB. The insertion loss of the balun BPF is 1.8/1.4 dB, and the phase and magnitude imbalances are less than 0.3 dB and 5°, respectively. The excellent performances of the implemented filter and filtering balun successfully demonstrate the advantages and design efficacy of the proposed filtering structure for different applications.
Over the past several decades, wireless communications have been tremendously developed with multiple frequency bands, standards, and functions to provide more convenient communication services. ...Nowadays, commercial wireless devices, especially customer premises equipment, are required for smaller size, higher integration, and higher data rates to meet the ever-increasing demands of communications. The transceiver front ends need to provide high-speed and high-quality communication services without a substantial increase in cost and size. This dissertation aims to develop miniaturized, multifunctional, and reconfigurable RF technologies and to signal integrity improvement solutions for highly integrated systems with high data transfer rates.A promising way to shrink the communication systems is to replace the repetitive and cumbersome discrete RF passive devices with multiband and multifunctional RF components. A filtering structure is first developed in this dissertation to provide a dual-band filtering response with high selectivity. Multiple transmission poles are generated by utilizing half-wavelength and open stub loaded resonators. In addition, a novel coupling scheme is applied to the design to generate multiple transmission zeros, leading to highly selective passband and good out-of-band rejection. This filtering structure is then applied to design a switch-controlled reconfigurable dual-band bandpass filter and a dual-functional filtering balun. The excellent performances of the implemented filter and filtering balun show great superiority and demonstrate the design efficacy of the proposed filtering structure.Besides designing multifunctional or reconfigurable RF components in specific configurations, this dissertation investigates a more flexible solution to facilitate the reconfigurability and miniaturization of the integrated systems. Designing tunable and miniaturized RF components on engineered substrate enabled with ferromagnetic thin films is fully studied in the dissertation. By selectively patterning the ferromagnetic thin films, the engineered substrate provides increased and tunable effective permeability with limited losses. In order to achieve higher permeability, more or thicker ferromagnetic thin film layers are required. The performance of the RF components is dependent on the properties of the engineered substrate. It is critical to develop an accurate model which quickly optimizes and determines the configuration of the ferromagnetic thin film patterns in the engineered substrate for a desired permeability. In this dissertation, a multilayer substrate model is created by thoroughly exploring the impact of different factors on the performance of the engineered substrate, such as pattern dimensions, the number of film layers, film thickness, filling density, etc. To demonstrate the design efficacy of the developed model, a miniaturized and tunable frequency selective surface (FSS) and a performance-enhanced antenna are implemented on the optimized engineered substrate.With the previous designs and techniques, a highly integrated system with multiple frequency bands and multiple functions is achieved. However, a highly integrated system suffers the signal integrity issue due to the far-end crosstalk in high-density traces, especially as the data transfer rates get higher and higher. Adding tabs between the coupled lines is an existing good way to reduce crosstalk. In this dissertation, thin film techniques are applied to further reduce the far-end crosstalk and improve the signal integrity of the highly integrated system. The far-end crosstalk of coupled transmission lines and the tabbed routing structure is thoroughly analyzed, and closed-form formulas are derived to characterize and optimize the performance. Based on the theoretical analysis, practical solutions are developed to further reduce the crosstalk between interconnects, including the application of ferromagnetic thin films and ferroelectric thin films and new interconnect structure with non-uniform signal line tab thickness.
This paper analyzes the far-end crosstalk ( FEXT ) of high-density interconnects and implements new designs of high-performance tabbed lines with significantly reduced FEXT . The FEXT of traditional ...coupled lines with and without integrated tabs are fully analyzed. Closed-form formulas are applied to calculate the capacitance and inductance matrices of the coupled lines and the tabbed routing structures, leading to an accurate evaluation of the far-end crosstalk. Designs in 3D configuration and integration of magnetic and dielectric thin films are proposed to either increase the mutual capacitance or increase the self-inductance within the coupled interconnects for further reduction of FEXT . To validate the proposed designs, structures are implemented on silicon wafers with the standard photolithography process, and their performance in terms of S -parameters and eye diagrams has been characterized and compared. The measured FEXT behaviors of the implemented interconnects show that the proposed designs reduce the FEXT at 10 GHz of the original coupled lines from -10.99 dB to -17.44 dB, -25.19 dB, and -25.58 dB, respectively. This paper provides efficient methods and designs to improve FEXT of high-speed and high-density interconnects.
Abstract
This paper presents a novel efficient heat dissipation concept in electronics with switch controllable thermal and electromagnetic (EM) performance. Besides the traditional implementation of ...heatsinks on the back of the antenna in communication systems, a passive technique by introducing a reconfigurable heatsink that reuses the air space above the antenna for additional heat dissipation channels is proposed. The non-contact heatsink is lifted with a tiny air gap from the antenna and partially connected with the antenna through physical switches/poles that balance the EM performance and heat dissipation efficiency, which eliminates the negative impact of the heatsink on the antenna EM performance. EM effects of heatsink on the antenna in terms of locations of contacts, states of switches, and various dimensions are thoroughly investigated. To demonstrate the design efficacy for optimized thermal efficiency and EM performance, a properly designed heatsink is implemented on the top of a simple patch antenna. The measured results show that good heat dissipation is achieved without deteriorating the EM performance of the antenna, in respect to return loss, gain, and radiation patterns. When the switches are OFF and ON, the reflection coefficient of the antenna is measured as −20.82 dB and −17.56 dB, respectively. In addition, with a 20 mW heat source at the input port of the antenna to mimic the heat generation from the electronics, the temperature of the antenna surface is reduced with the front-integrated heatsink by 7.4 °C and 13.4 °C when the connection switches are turned OFF and ON. The implementation of the front-integrated heatsink on the antenna fully demonstrates the proposed heat dissipation concept which provides an effective way to solve the tradeoff between thermal inefficiency and EM performance.
Hybrid materials based on transition metal carbide and nitride (MXene) nanosheets have great potential for electromagnetic interference (EMI) shielding due to their excellent electrical conductivity. ...However, the performance of final products depends not only on the properties of constituent components but also on the morphology of the assembly. Here, via the controlled diffusion of positively charged poly(allylamine hydrochloride) (PAH) chains into the negatively charged Ti3C2T x MXene suspension, MXene/PAH hybrids in the forms of thin films, porous structures, and fibers with distinguished internal morphologies are obtained. Our results confirm that PAH chains could effectively enhance the oxidation stability and integrity of wet and dry MXene structures. The flexibility to tune the structures allows for a thorough discussion of the relations between the morphology, electrical conductivity, and EMI shielding mechanism of the hybrids in a wide range of electrical conductivity (2.5 to 3347 S·cm–1) and thickness (7.7 to 1900 μm) values. The analysis of thin films shows the direct impact of the polymer content on the alignment and compactness of MXene nanosheets regulating the films’ electrical conductivity/EMI shielding effectiveness. The colloidal behavior of the initial MXene suspension determines the interconnection of MXene nanosheets in MXene/PAH porous assemblies and the final electrical properties. In addition to the internal morphology, examining the laminated MXene/PAH fibers with geometrically different arrangements demonstrates the role of conductive network configuration on EMI shielding performance. These findings provide insights into tuning the EMI shielding effectiveness via the charge-driven bottom-up assembly of electrically conductive MXene/polyelectrolyte hybrids.
In this paper, a novel dual-band balun bandpass filter (BPF) is designed by using double-sided parallel-strip line (DSPSL) with an intermediate conductor plane. Half wavelength resonators and open ...stub loaded resonators are utilized to provide third-order filtering responses in each band. Due to the frequency-independent out-of-phase feature of DSPSL, two balanced outputs are achieved with 180° phase difference. In addition, the proposed coupling topology introduces multiple transmission zeros providing high frequency selectivity and good out-of-band rejection. A well-designed BPF is fabricated and measured with two passbands centering at 2.89 GHz and 4.81GHz, respectively. Good filtering and balun performance are realized from the well-agreed simulated and measured results.
