Low-loss Substrate Research Articles

Super Low Profile 5G mmWave Highly Isolated MIMO Antenna with 360∘ Pattern Diversity for Smart City IoT and Vehicular Communication

This study introduces a planar folded super low profile 5G mmWave monopole antenna for small IoT devices with superior efficiency and gain. Low-loss Rogers RT-5880 substrate material has been utilized to achieve higher efficiency, gain, and diversity performance in a relatively compact size. The unit element planar monopole antenna has been designed within 6.15×5.13×0.8mm3 with a partial ground. Four unit element antenna was orthogonally arranged on alternating sides of the substrate plane with narrow inter-component spacing in the multiple input multiple output (MIMO) system. The integration of the double negative (DNG) metamaterial array on the antenna led to a cumulative improvement in the overall performance of the antenna, which includes gain, efficiency, and isolation. The minimum isolation of the antenna increased by 11 dB with substrate-loaded metamaterial. The proposed MIMO antenna model with substrate-loaded metamaterial demonstrates 8 GHz instantaneous bandwidth (33.1 GHz - 41.1 GHz), 0.001 envelope correlation coefficient (ECC), diversity gain (DG) greater than 9.99 dB, channel capacity loss (CCL) less than 0.2bits/s/Hz, and a total active reflection coefficient (TARC) of 25 dB, which suggests that the diversity characteristics of the MIMO antenna system is impressive. Moreover, a densely packed 12-element antenna model has been introduced in this study with 360∘ pattern diversity, capable of receiving signals from any direction. Three 4-element MIMO systems have been arranged in an architecture to develop the 12-element MIMO system, and the size of the 12-element MIMO architecture is 15×15×15mm3. Despite having this compact size and dense packing, the 12-element MIMO antenna model shows similar diversity performance as the 4-element antenna model. Analog equivalent circuit models or resistor-inductor-capacitor (RLC) equivalent systems for the antenna models were created. A concept of a 128-element massive MIMO antenna has been presented to support the end devices, creating an application scenario of an IoT-interconnected smart city.

Reconfigurable and polarization-dependent optical filtering for transflective full-color generation utilizing low-loss phase-change materials

All-dielectric metasurface, which features low optical absorptance and high resolution, is becoming a promising candidate for full-color generation. However, the optical response of current metamaterials is fixed and lacks active tuning. In this work, we demonstrate a reconfigurable and polarization-dependent active color generation technique by incorporating low-loss phase change materials (PCMs) and CaF2 all-dielectric substrate. Based on the strong Mie resonance effect and low optical absorption structure, a transflective, full-color with high color purity and gamut value is achieved. The spectrum can be dynamically manipulated by changing either the polarization of incident light or the PCM state. High transmittance and reflectance can be simultaneously achieved by using low-loss PCMs and substrate. The novel active metasurfaces can bring new inspiration in the areas of optical encryption, anti-counterfeiting, and display technologies.

Extraction method for superimposed coherent transition radiation using Fresnel reflection in a ring-type resonator

To generate terahertz pulses with a high peak power, a pulse train of coherent transition radiation (CTR) is superimposed by circulating it in a ring-type resonator at an L-band electron linear accelerator facility at the Kyoto University Institute for Integrated Radiation and Nuclear Science. By extracting the superimposed CTR pulses from the ring-type resonator via Fresnel reflection on a low-loss parallel substrate, we show that the cavity loss can be suppressed without being affected by the wavenumber of the CTR pulses. The power of the superimposed CTR pulse is increased to approximately four times that of a CTR generated by plane mirrors in the resonator at a wavenumber of 8.5cm−1, where the diffraction loss of the resonator is lower. Using shorter electron bunches to generate CTR pulses with higher wavenumbers increases the amplification factor caused by superposition and allows CTR pulses with a higher peak power to be generated.

Optimisation of asymmetries in mm-wave single-element fractal antenna for gain-bandwidth enhancement

ABSTRACT In this study, a low-loss substrate was used to create an Asymmetric Irregular Hexagonal Fractal (AIHF) mm-wave antenna. The antenna consists of an Asymmetric Defected Ground Structure (ADGS) attached to the bottom of a 0.55λ0 ×0.40λ0 ×0.032λ0 mm3 substrate and an Irregular Hexagonal Fractal (IHF) patch on top of the substrate. The proposed fractal technique is unique and based on fractal-slot 3-stage iterations. The IHF patch is created by etching seven fractals arranged symmetrically about the y-axis, one of which has a central 1/3rd (scaling) iteration factor and six hexagonal fractals that are 1/9th of the parent 0th order iteration. On the patch, these fractal slots are evenly spaced out. By etching an Asymmetric Cascaded Double Dumbbell (ACDD) slot on the ground plane, an ADGS is created. With this etching in the patch and ground, a gain of > 5.0 dBi for a −10 dB S11 bandwidth of 4.655 GHz (32.84–37.215 GHz), a recorded peak gain of 13.4 dBi is at 33.55 GHz and an average radiation efficiency of 87.75% is achieved. Using the High-Frequency Structure Simulator (HFSS), the width of ADGS, the position of ACDD on ADGS, and the dimensions of etched fractals are optimised through a pattern search parametric iterative technique. These results are validated using the Vector Network Analyser (VNA), and the Anechoic Chamber and it is revealed that they agree well with the simulated results. The designed AIHF antenna’s RLC electrical equivalent circuit modelling is presented along with evaluated R, L, and C values.

A unique SWB multi-slotted four-port highly isolated MIMO antenna loaded with metasurface for IOT applications-based machine learning verification

This study introduces a MIMO antenna system incorporating an epsilon negative Meta Surface (MS). The system’s architects intended for it to have a large usable frequency range, high gain, narrow inter-component spacing, and superior isolation properties with four elements of MIMO antenna that are strategically organized in an orthogonal arrangement and a compact form factor measuring 41 × 41 × 1.6 mm3, utilizing a low-loss Rogers RT5880 substrate. The architecture of the antenna is characterized by integrating a multi-slotted radiating patch, a partial ground plane, and an epsilon-negative Meta Surface. This integration is done by a 7 × 7 Metamaterial array at the back of the MIMO antenna with a dimension of 41 × 41 × 1.6 mm3, resulting in a collective enhancement of the antenna’s overall performance by affecting the phase, amplitude, electromagnetic field and reducing the backward radiation. The separation between the Meta-surface and the MIMO antenna is established at a distance of 6 mm. The antenna’s exceptional super wideband performance is increased from 2–19 GHz to 1.9–20 GHz after using the MS. Moreover, isolation increases from 20 dB to 25.5 dB, Realized gain from 4.5 dBi to 8 dBi, and radiation efficiency from 77% to 89% across the operational bandwidth. The MIMO antenna exhibits remarkable diversity characteristics, as indicated by an envelope correlation coefficient (ECC) of <0.004, a diversity gain (DG) surpassing 9.98 dB, a channel capacity loss (CCL) below 0.3, and a total active reflection coefficient (TARC) measuring 12 dB. Furthermore, a circuit analogous to a resistor–inductor–capacitor (RLC) system is constructed, and four regression methods from the field of machine learning are employed to validate the gain and efficiency achieved. Notably, the linear regression model exhibits exceptional performance, achieving an accuracy of 99%. The MIMO antenna design demonstrates significant potential for many applications in the Internet of Things (IoT), specifically focusing on Vehicle-to-Everything (V2X) communications. These highlight its appropriateness for emerging IoT sectors.

On-Chip Circularly Polarized Circular Loop Antennas Utilizing 4H-SiC and GaAs Substrates in the Q/V Band.

This paper presents a comprehensive assessment of the performance of on-chip circularly polarized (CP) circular loop antennas that have been designed and fabricated to operate in the Q/V frequency band. The proposed antenna design incorporates two concentric loops, with the outer loop as the active element and the inner loop enhancing the CP bandwidth. The study utilizes gallium arsenide (GaAs) and silicon carbide (4H-SiC) semiconductor wafer substrates. The measured results highlight the successful achievement of impedance matching at 40 GHz and 44 GHz for the 4H-SiC and GaAs substrates, respectively. Furthermore, both cases yield an axial ratio (AR) of less than 3 dB, with variations in bandwidths and frequency bands contingent upon the dielectric constant of the respective substrate material. Moreover, the outcomes confirm that utilizing 4H-SiC substrates results in a significantly higher radiation efficiency of 95%, owing to lower substrate losses. In pursuit of these findings, a 4-element circularly polarized loop array antenna has been fabricated for operation at 40 GHz, employing a 4H-SiC wafer as a low-loss substrate. The results underscore the antenna's remarkable performance, exemplified by a broadside gain of approximately 9.7 dBic and a total efficiency of circa 92%. A close agreement has been achieved between simulated and measured results.

DEFECTED GROUND SQUARE PATCH EDGE TRUNCATED POLARIZATION RECONFIGURABLE ANTENNA

In this paper, a polarization reconfigurable antenna is reported. The proposed antenna operates in linear and circular polarization. Linear polarization is obtained using a square patch antenna and circular polarization is realized by truncating the diagonal corners of the square patch. Wideband circular polarization is obtained using two triangular defects to the ground plane beneath the truncated edge. To implement polarization reconfigurability, two pin diodes are placed on the truncated edges. These pin diodes electronically transform the proposed structure into square or truncated square patches resulting in linear or circular polarizations respectively. The proposed antenna operates in the 4.75 to 3 GHz band with circular polarization and the 4.75 to 1 GHz band with linear polarization. The antenna exhibits a higher peak gain of 7.7 dBi due to a low-loss foam substrate with the main lobe at 0&amp;deg;. A prototype of the antenna is developed and tested.

Low Loss/Low CTE Semiconductor Carrier Packaging Thin Core Material

There is an ever-increasing need by semiconductor/packaging companies for the introduction of a low loss, ultra-low Coefficient of Thermal Expansion chip carrier packaging substrate core material that provides a cost-effective method for producing thin core build up with very dense core vias. This low loss, low CTE flip-chip substrate core is well suited to multi-layer, RF, and applications requiring a system-in-package approach. This paper discusses a novel substrate core material using a build-up film dielectric layer in conjunction with glass fiber weave. Key properties include low loss (Df&lt;0.002), a CTE from 5 - 10 ppm/C, extremely high thermal reliability, and low modulus. An advantage of using glass fiber weave instead of Invar, for instance, is the extremely low CTE that can be achieved while still maintaining a non-conductive power or ground plane. Multilayer circuits using PTFE can suffer from extremely high lamination temperatures, high cost, and low overall yields due to the inability of the soft material to go through a desmear process. Substrate core materials have the primary benefit that they offer stability and increased reliability of many subsequent build-up microvia layers. As monolithic semiconductors are replaced by chiplets, there is a growing need to package many types of chiplets without losing the signal integrity performance of a monolithic semiconductor on a single IC package. An extremely low loss substrate core offers the potential benefit that unique chiplet packaging architectures can be designed with the lowest possible dielectric losses due to the multichip interconnect strategy.

Realization of Miniatured Wi-Fi 6E Bandpass Filters on a Low-Loss Organic Substrate

Realization of Miniatured Wi-Fi 6E Bandpass Filters on a Low-Loss Organic Substrate

Electrical Performance Analysis of High-Speed Interconnection and Power Delivery Network (PDN) in Low-Loss Glass Substrate-Based Interposers.

In this article, electrical performance analysis of high-speed interconnection and power delivery network (PDN) in low-loss glass substrate-based interposers is conducted considering signal integrity (SI) and power integrity (PI). The low-loss glass substrate is a superior alternative to silicon substrate in terms of high-speed signaling and fabrication yield. However, the low-loss of the substrate is vulnerable to power/ground noise in the PDN since the low-loss property of the substrate cannot suppress the noise naturally. In this article, an in-depth electrical performance analysis is conducted based on various measurements and simulations to fully benefit the advantages of the low-loss glass substrate. First, the fabrication process and test vehicles for the analysis are explained. Using the test vehicles, the electrical performance of the glass interposer's high-speed interconnection is compared with those of silicon and organic interposers. The insertion loss, eye-diagrams, and signal bandwidths of three interposer channels are compared and analyzed based on electromagnetic (EM) and circuit simulations. Also, the electrical performance of the through glass via (TGV) channel is measured and compared with through silicon via (TSV) channel. The high-speed interconnection of the glass interposer showed better performance for most of the parameters which is more suitable for maintaining the SI. Even though the low-loss of the glass substrate ensured the SI, power/ground noise issues in the PDN must be analyzed and solved. In this article, various cases inducing the power/ground noise in the PDN are considered, simulated, and measured. To solve the issues, ground TGV design and electromagnetic bandgap (EBG) design are proposed for an efficient broadband suppression of the noise generated in the glass interposer PDN.

Ultra-Wideband Fractal Ring Antenna for Biomedical Applications

In this paper, an efficient, coplanar waveguide (CPW)-fed printed circular ring fractal ultra-wideband (UWB) antenna is presented for biomedical applications. In UWB technology, short-range wireless communication is possible with low transceiving power, a characteristic that is particularly advantageous in the context of microwave and millimeter-wave (mmWave) medical imaging. In the proposed antenna configuration, the UWB response is achieved by introducing wedged slots in the radiating patch, designed on a low-loss substrate. A CPW partial ground plane is truncated from the edges to optimize the antenna impedance. Experimental results indicate the antenna’s robust performance across the frequency range of 3.2–20 GHz. The well-matched measured and simulated results confirm our contribution’s employability. Furthermore, a time-domain study offers valuable insights into how the antenna responds to transient signals, highlighting its responsiveness and adaptability to biomedical applications.

A Low-Loss Via-Free Ridge Air-Filled Substrate Integrated Waveguide on Printed Circuits Board for mmWave Application

A Low-Loss Via-Free Ridge Air-Filled Substrate Integrated Waveguide on Printed Circuits Board for mmWave Application

Optically transparent conformal ultra-broadband metamaterial absorber based on ITO conductive film

An optically transparent metamaterial absorber with polarization insensitivity and wide-angle absorption is proposed. The absorber, which consists of an indium tin oxide resistive film and a low-loss substrate, is optically transparent and conformal. By tuning the reflection response of the frequency-selective surface and the thickness of the spacer layer, the whole structure achieves an absorption of more than 97% in the range of 6.54–18.66 GHz. Numerical simulation results show that the absorber can still maintain an absorption rate of more than 85% in a wide range of oblique incidence angles from 0° to 60°. In addition, the intrinsic physical mechanism of the absorber is elucidated using the impedance matching theory and the distribution of surface currents. The ratio of dielectric loss and ohmic loss is also quantitatively analyzed. Finally, the reflection and transmission coefficients of the sample were measured in a microwave anechoic chamber, which showed a good agreement with the simulation results. This design uses a low-resistivity resistive film as a frequency-selective surface, which was rarely involved in previous studies, and provides a new idea for future design and application.

An LTCC-Based Antenna Array for D-Band Terahertz Communication

<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> </i> — In this letter, a novel patch antenna array with via and slot loading based on low-loss substrate integrated waveguide (SIW) feeding network is investigated for D-band applications. The radiating patch element is designed with vias and modified geometry for good broadband impedance matching response and high radiation gain. The feeding network provides the same magnitude and in-phase excitation for the radiating elements in the array. To verify the proposed array design, a 4×4 array prototype is implemented by low-temperature co-fired ceramic (LTCC) fabrication method and tested. The proposed dual resonance concept is validated by the good agreement between the simulated and measured results. The measurement results of the fabricated prototype show that the proposed design can achieve an 12.5% bandwidth with | <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> |< -10 dB (150 to 170 GHz) and realize a maximum gain of 16.8 dBi at 166 GHz. With the combined advantages of wideband, low fabrication difficulty and stable broadside radiation, the proposed array antenna is considered as a promising candidate for future D-band terahertz phased array communication.

Extraction of Graphene's RF Impedance through Thru-Reflect-Line Calibration.

Graphene has unique properties that can be exploited for radiofrequency applications. Its characterization is key for the development of new graphene devices, circuits, and systems. Due to the two-dimensional nature of graphene, there are challenges in the methodology to extract relevant characteristics that are necessary for device design. In this work, the Thru-Reflect-Line (TRL) calibration was evaluated as a solution to extract graphene's electrical characteristics from 1 GHz to 65 GHz, where the calibration structures' requirements were analyzed. It was demonstrated that thick metallic contacts, a low-loss substrate, and a short and thin contact are necessary to characterize graphene. Furthermore, since graphene's properties are dependent on the polarization voltage applied, a backgate has to be included so that graphene can be characterized for different chemical potentials. Such characterization is mandatory for the design of graphene RF electronics and can be used to extract characteristics such as graphene's resistance, quantum capacitance, and kinetic inductance. Finally, the proposed structure was characterized, and graphene's resistance and quantum capacitance were extracted.

Wideband Analysis and Prolongation of Surrounding TGVs Shielding Structure in 3-D ICs

Through glass vias (TGVs) with low substrate loss are subjected to signal distortion issues. This letter proposes a wideband scalable model for assessing signal reliability and rationalizing 3-D integrated design in glass interposers. The established equivalent circuit model is derived for extracting the parasitic parameters of the signal transmission unit, and the relevant variables stem from the geometric dimension parameters. The result of comparative analysis uncovers that the simulation results are in excellent accordance with the analytical model. Furthermore, seven crosstalk shielding topologies are proposed, and their noise suppression ability is analyzed. Such the shielding structures can not only reach the insertion loss (IL) performance below 0.15 dB but also achieve the crosstalk suppression capability exceeding 60 dB even at 40 GHz. Feasible strategies are proposed to trade off IL, noise isolation (NI), and occupied area in order to match suitable application scenarios, which can provide a reference for layout design.

Compact Low-Loss Half-Mode Substrate Integrated Waveguide Filter With Controllable Transmission Zeros

Two novel planar filters with controllable mixed electromagnetic couplings are developed in this brief for C band operation. They are implemented with the half mode substrate integrated waveguide (HMSIW) technology. Owing to the half mode SIW cavity, both of the filters exhibit a compact size. The size of filter I is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.53\,\,{\boldsymbol{\lambda }}_{\mathbf {0}} \times 0.30 {\boldsymbol{\lambda }}_{\mathbf {0}}$ </tex-math></inline-formula> , while the size of filter II is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.47\,\,{\boldsymbol{\lambda }}_{\mathbf {0}} \times 0.28 {\boldsymbol{\lambda }}_{\mathbf {0}}$ </tex-math></inline-formula> . ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\boldsymbol{\lambda }}_{\mathbf {0}}$ </tex-math></inline-formula> represents the wavelength in the free space at the center frequency). A wide passband response with a quasi-elliptic characteristic and good out-of-band rejection is realized due to the transmission zeros (TZs) introduced by the etched slot structures on the top metal layer. By modifying the dimensions of the structure, the strength of the electric and magnetic coupling can be independently controlled, and consequently the position of TZs is controllable to achieve desired stopband response with high selectivity. As a validation of the concept, one prototype is fabricated and tested. Excellent agreement is observed between the simulated and measured results.

Low‐Loss Anisotropic Image Polaritons in van der Waals Crystal α‐MoO3 (Advanced Optical Materials 21/2022)

Monocrystalline gold flakes serve as an atomically-flat low-loss substrate for the highly confined mid-infrared “image polaritons” stemming from hybridization of polaritons with their mirror image in the metal. By leveraging the physical properties of the gold flakes, the strongly anisotropic image phonon polaritons are rigorously studied in a biaxial van der Waals crystal α-MoO3 (see article number 2201492 by Min Seok Jang and co-workers). Notably, the image phonon polaritons provide approximately twice stronger field confinement yet longer lifetime compared to the phonon polaritons on a dielectric substrate.

Experimental demonstration of multiple Fano resonances in a mirrored array of split-ring resonators on a thick substrate

This work demonstrates the first experimental observation of multiple Fano resonances in the terahertz range in a system based on an array of mirror-symmetric split-ring resonators deposited on low-loss and low-refractive index polytetrafluoroethylene (PTFE) substrate. For the first time, selective surface activation induced by laser technology has been used to deposit a copper layer on a PTFE substrate with the further application of standard mask lithography for metasurface manufacturing.

Design of Power/Ground Noise Suppression Structures Based on a Dispersion Analysis for Packages and Interposers with Low-Loss Substrates.

In this study, power/ground noise suppression structures were designed based on a proposed dispersion analysis for packages and interposers with low-loss substrates. Low-loss substrates are suitable for maintaining signal integrity (SI) of high-speed channels operating at high data rates. However, when the power/ground noise is generated in the power delivery network (PDN), low-loss substrates cannot suppress the power/ground noise, thereby causing PDN-induced crosstalk and various power integrity (PI) issues. To solve these issues, noise suppression structures generating electromagnetic bandgap were proposed and designed. The mechanism of the proposed structures was examined based on a proposed dispersion analysis. The proposed structures were designed and fabricated in glass interposer test vehicles, and the effectiveness of the structures on power/ground noise suppression was experimentally validated by measuring the noise suppression band. The proposed dispersion analysis was also verified by comparing the derived noise stopband edges ( and ) with electromagnetic (EM) simulation and experimental results, and they all showed good agreement. Compared to EM simulation, the proposed method required smaller computational resources but showed good accuracy. Using the proposed dispersion analysis, various power/ground noise suppression bands were designed considering the applications and design rules of packages and interposers. With measurements and EM/circuit simulations, the effectiveness of the designed structure in maintaining SI/PI was verified. By adopting the designed structures, the noise transfer properties in the PDN were suppressed in the target suppression frequency band, which is key for PI design. Finally, it was verified that the proposed structures were capable of suppressing power/ground noise propagation in the PDN by analyzing PDN-induced crosstalk in the high-speed channel.