Low-loss Dielectric Layer Research Articles

High Speed Transmission Characteristics on Glass Based Interposers

Interposers for system in package will became more and more important for advanced electronic systems. As the industry moves toward HPC (High Performance Computing) for huge data transmission with low power consumption. The major engineering requirements for HPC application are highdensity, high speed data transmission, low loss, precision manufacturing and low cost. On the 2.5D heterogenous package structure, key technology is fine wiring connected with CPU chip and HBM chips. The fine wires needed high speed transmission. This paper presents the demonstration of Glass-based twin type interposers, Glass interposer with fine pitch metalized through via and RDL interposer with low loss dielectrics on Glass carrier. We compare twin types of Interposes fabrication process capability with panel size format 300x400mm. Finally, we compare the transmission characteristics using eye diagram for heterogenous integration application. Glass Interposer has low loss glass via, it is effective vertical interconnection. RDL interposer has low loss dielectric layers, excellent transmission characteristics obtained on fine pitch trace area.

High efficient dual band stacked antennas integrated into rescue helmets for indoor communication

AbstractA dual-band stacked antenna integrated with a rescue helmet is proposed for WLAN applications. The cross slot aperture feeding technique enables the antenna to support dual-band operation at 2.4 and 5 GHz. On the ground plane, two slots are formed, perpendicular to each other and of different lengths. Four dielectric layers of different permittivity are stacked over this cross slot to attain the desired frequency bands. Under free space condition, the radiator yields 7% (2.31–2.48 GHz), 15.87% (5.12–6 GHz) 10 dB return loss bandwidth (BW). The use of low loss dielectric layers on the slots also provides a high antenna efficiency and moderate gain at both frequency bands. The small dimension of antenna encourages its use as a wearable helmet antenna. Antenna performances are observed under wearable condition. For assessing human exposure to RF electromagnetic fields, SAR evaluations are conducted at both 2.4 and 5 GHz WLAN bands.

Custom, spray coated receive coils for magnetic resonance imaging

We have developed a process for fabricating patient specific Magnetic Resonance Imaging (MRI) Radio-frequency (RF) receive coil arrays using additive manufacturing. Our process involves spray deposition of silver nanoparticle inks and dielectric materials onto 3D printed substrates to form high-quality resonant circuits. In this paper, we describe the material selection and characterization, process optimization, and design and testing of a prototype 4-channel neck array for carotid imaging. We show that sprayed polystyrene can form a low loss dielectric layer in a parallel plate capacitor. We also demonstrate that by using sprayed silver nanoparticle ink as conductive traces, our devices are still dominated by sample noise, rather than material losses. These results are critical for maintaining high Signal-to-Noise-Ratio (SNR) in clinical settings. Finally, our prototype patient specific coil array exhibits higher SNR (5 × in the periphery, 1.4 × in the center) than a commercially available array designed to fit the majority of subjects when tested on our custom neck phantom. 3D printed substrates ensure an optimum fit to complex body parts, improve diagnostic image quality, and enable reproducible placement on subjects.

Ultra-broadband and wide-angle terahertz polarization converter based on symmetrical anchor-shaped metamaterial

We propose a reflective terahertz metamaterial linear polarization converter, consisting of three layers: an array of metallic symmetrical anchor-shaped resonators, poly tetra fluoroethylene (PTFE) as a low loss dielectric layer, and a metal surface ground plane. The simulation results show that the proposed metamaterial can convert the linearly polarized waves into the cross-polarized waves with a polarization conversion ratio (PCR) of above 93% in the frequency range of 1.21–2.83 THz and the relative bandwidth is as high as 80.2%. The proposed metamaterial is valid for a wide range of incident angles, and the average polarization conversion ratio remains 93% even though the incident angle reaches 45°. Additionally, we theoretically analyzed the conversion mechanism of achieving a high-efficiency linear polarization conversion in a wide frequency range by calculating the polarization angle and elliptical angle of the reflected terahertz waves. The experiment results using the terahertz time domain spectroscopy (THz-TDS) consist well with the simulation results. Our design will provide an important reference for the practical applications of the metamaterials in polarization manipulation.

Broadband and wide-angle reflective linear polarization converter for terahertz waves

Polarization control of electromagnetic waves has wide applications in the field of communications, imaging, and remote sensing. Recent designs of periodic two-dimensional devices or metasurfaces employed for polarization control are limited in efficiency, bandwidth, and allowable incidence angle. This is attributed to high dissipation in the dielectric material used and to less-optimal device configuration. We propose and experimentally validate a reflective linear polarization converter metasurface with high efficiency, wide bandwidth, and wide acceptance angle in the terahertz regime. Our device is composed of three layers: an array of oriented metallic T-shaped resonators, cyclic olefin copolymer (COC) as a low loss dielectric layer, and a ground plane. For the normal and 45° incidence angles, a fabricated sample shows a bandwidth of 95% and 100%, with the average polarization conversion ratio above 80%, covering a frequency range of 0.38–1.07 and 0.36–1.08 THz, respectively. The wide-angle stability is attributed to a phase difference between a single resonance along the T-shaped resonator and a smooth phase response in the low-loss COC dielectric layer. For broad bandwidth performance, a resonator arm extending to adjacent unit cells introduces the fundamental resonance at a lower frequency, while the packed unit cell size shifts the grating lobe onset to a higher frequency. These design aspects can significantly improve the performance of other metasurfaces operating in any frequency range.

Ultra-broadband wide-angle perfect absorber in the visible regime through a thin grating–insulator–metal structure

A new thin grating-insulator-metal (GIM) structure with ultra-broadband wide-angle perfect absorption is proposed, and a general approach to this kind of multilayered structure is investigated based on the rigorous coupled-wave analysis method and the transfer matrix method. On the basis of this approach, the electromagnetic field distributions in each layer and optical diffraction coefficients are derived theoretically. Compared with a metal–insulator–metal (MIM) structure, the GIM structure consisting of a metal grating on top of a low-loss dielectric layer and a bottom metal layer can achieve a higher absorption with the smaller thickness that attributes to the extraordinary optical transmission of the top grating layer and the cavity resonance of the middle insulator layer. By optimizing the structural and material parameters, the materials from top to bottom are selected as Mn-Al2O3-Mn, whose thicknesses are 10 nm, 65 nm, and 70 nm, respectively. With these optimum parameters, better performance with average absorption over 95% in the visible regime is obtained. Furthermore, this structure retains near-perfect broadband absorption for large incidence angles and different polarizations. The conclusions presented here could have potential applications in optical devices, such as optical displacement detection and visible light absorption.

Low-Profile Ultra-Broadband Log-Period Monopole End-Fire Antenna

This paper proposes an ultra-broadband (2–13 GHz) and low-profile log-period monopole end-fire antenna for the flush-mounted applications. 24 monopoles with a log-period rule are used to cover the whole operating frequency band, and those monopoles are printed on both sides of a low-loss dielectric layer vertically placed over a slot feeding line with wideband microstrip-to-slotline transition. The low profile is realized by bending the parts of the long monopoles so that the overall antenna size is obtained as 40 mm × 100 mm × 13.6 mm. The proposed antenna is fabricated, and the measured results agree with the simulated results very well. The measured results indicate that the proposed antenna can work at the whole 2–13 GHz band with very good end-fire radiation patterns and stable gain performances.

Capacitively Loaded Inverted CPWs for Distributed TRL-Based De-Embedding at (Sub) mm-Waves

In this paper, we present a thru-reflect-line (TRL) calibration/de-embedding kit integrated in the back-end-of-line of a SiGe technology, which allows direct calibration at the first metallization layer, thus moving the reference planes as close as possible to the intrinsic device. The proposed calibration/ de-embedding kit features capacitively loaded inverted CPW lines, allowing to reduce the losses arising from the conducting (i.e., silicon) substrate, by confining the propagating field in the low-loss dielectric layers. The structures have been designed specifically for (sub) mm-wave measurements, as complementary to conventional de-embedding kits used at lower frequencies. A simplified analytical model is presented to support the design of the capacitively loaded CPW lines. Results of a calibration/de-embedding kit, realized using a 130-nm BiCMOS technology are experimentally obtained in the WR-03 waveguide band. Worst case error bounds providing error below 5% in the entire WR3 band are demonstrated. Comparison between direct calibration and de-embedding using calibration transfer from fused silica are provided to highlight the improvements of the proposed approach in the mm-wave bands. Finally, the TRL calibration kit is employed for S-parameter measurements of a heterojunction bipolar transistor and the results are compared to the HiCUM model of the same transistor for verification.

Sputter-deposited low loss Mg2SiO4 thin films for multilayer hybrids

Mg2SiO4 (forsterite) thin films grown by rf magnetron sputtering from a ceramic target have been investigated particularly for thin film hybrids requiring a low loss dielectric layer. Understanding of the processing parameters and their correlations to dielectric properties is the main concern of this work. Fundamental parameters, such as working pressure and post-deposition annealing temperature, were found to influence phase evolution, morphology and dielectric properties. For example, polycrystalline α-Mg2SiO4 could be obtained above the annealing temperature of 500°C regardless of working pressure. The dielectric constant increased gradually while the dielectric loss showed a reverse trend of decrease with raising annealing temperature to 700°C. Dielectric constant of ~6.8 and dielectric loss of ~2.8×10−3 were obtained at 1MHz from the sample annealed at 700°C. A promising planarized thin film structure for fine line multilevel packaging was demonstrated without any significant inter-diffusion and damages between Mg2SiO4 and Pt layers.

Polarization-independent broad-band nearly perfect absorbers in the visible regime

Polarization-independent broad-band absorbers in the visible regime are theoretically investigated. The absorbers are three-layered structures consisting of a lossy dielectric grating on top of a low-loss dielectric layer and a substrate of the same lossy dielectric placed at the bottom. Enhanced absorption in the underlying structure is attained over a broad range of frequency for both TE and TM polarizations. In particular, a nearly perfect absorbance (over 99.6%) is achieved at λ ≈ 600 nm, around which the absorption spectra show a substantial overlap between two polarizations. The enhanced absorption is attributed to cavity resonance and its hybridization with a weakly bound surface wave. This feature is illustrated with the electric field patterns and time-averaged power loss density associated with the resonances.

High-performance low-cost phase-shifter design based on ferroelectric materials technology

A novel approach to ferroelectric phase-shifter design using BaxSr1-xTiO3 (BSTO) films in a multilayer dielectric coplanar waveguide structure is described. By including a low-loss dielectric layer (SiO2) between the coplanar waveguide conductors and a layer of ferroelectric materials, significant reduction in insertion loss can be achieved in conjunction with a threefold increase in figure of merit (°/dB).

Passive filter for increasing directivity in dual polarisation antenna systems

A novel design for a passive microwave filter is presented. The filter consists of a stacked array of low loss dielectric layers, whose permittivity profile alters in a near sinusoidal manner. The radiation property of the filter is investigated for both co- and crosspolarisation and it is shown that the filter acts as an apodiser and a beam shaper.