Reduce Insertion Loss Research Articles

Bubble curtain modelling: analytical prediction of piling noise mitigation

In order to mitigate underwater noise caused by pile driving, bubble curtains are widely used during offshore constructions. These form an impedance barrier to the acoustic pressure wave, and the resulting attenuation on the interface of water to bubbly water is the main driver behind the insertion loss that can be achieved. A secondary effect is energy absorption by bubble resonance; however, normal bubble sizes are such that the resonance frequency is considerably higher than the peak in the piling noise spectrum, rendering the resonance contribution to the overall insertion loss relatively small. The broadband insertion loss and sound level reduction spectra of bubble curtains are mainly determined on an empirical basis, comparing actual project data and noise monitoring results across sites. Although several efforts have been made to capture the noise mitigation by bubble curtains in numerical models, there is no straight-forward integrated modelling method available to quantify the influence of individual design and operational parameters. Using a number of assumptions and simplifications, this paper presents an analytical model for the frequency-dependent and broadband insertion loss achieved by bubble curtains, that combines both impedance and resonance effects.

Optimization and Design of Passive Link with Single Channel 25 Gbps Based on High-Speed Backplane

In recent years, with the development of the communication industry, the need to use Ethernet switches to transmit big data has become more urgent, and its protocol standards are iterating towards higher return loss, wider bandwidth, lower impedance fluctuations and insertion loss. Based on the research of high-speed backplane with a single channel 25 Gbps transmission rate, a novel double grounded planar strip coplanar waveguide design is presented, which significantly improved return loss to 20 dB and reduced insertion loss, which meet the loss standard of 100GBASE-KR4. The resonant cavity model of transmission line reference plane is improved by introducing vias and the parameters of vias in the reference plane are studied to reduce the impact of resonance, which improved the transmission −1 dB bandwidth to 60 GHz. Based on equivalent circuit analysis of differential vias’ joint reverse pad, the parameters related to the differential vias are studied, the impedance fluctuation is reduced to 100 ± 3 Ω, which is 70% better than the impedance fluctuation standard (100 ± 10 Ω) of 100GBASE-KR4. After optimizing the mathematical model of strip coplanar waveguide, reference plane and differential vias, we built a simulation model of the backplane passive link which met the 100GBASE-KR4 backplane Ethernet specification. In the actual test, it was found that the optimized model can improve the link performance.

Spectral Characteristics of Square-Wave-Modulated Type II Long-Period Fiber Gratings Inscribed by a Femtosecond Laser.

We study here the spectral characteristics of square-wave-modulated type II long-period fiber gratings (LPFGs) inscribed by a femtosecond laser. Both theoretical and experimental results indicate that higher-order harmonics refractive index (RI) modulation commonly exists together with the fundamental harmonic RI modulation in such LPFGs, and the duty cycle of a square wave has a great influence on the number and amplitudes of higher-order harmonics. A linear increase in the duty cycle in a series of square wave pulses will induce another LPFG with a minor difference in periods, which is useful for expanding the bandwidth of LPFGs. We also propose a method to reduce insertion loss by fabricating type II LPFGs without higher-order harmonic resonances. This work intensifies our comprehension of type II fiber gratings with which novel optical fiber sensors can be fabricated.

Size reduction and performance improvement of a microstrip Wilkinson power divider using a hybrid design technique

In the design of a microstrip power divider, there are some important factors, including harmonic suppression, insertion loss, and size reduction, which affect the quality of the final product. Thus improving each of these factors contributes to a more efficient design. In this respect, a hybrid technique to reduce the size and improve the performance of a Wilkinson power divider (WPD) is introduced in this paper. The proposed method includes a typical series LC circuit, a miniaturizing inductor, and two transmission lines, which make an LC branch. Accordingly, two quarter-wavelength branches of the conventional WPD are replaced by two proposed LC branches. Not only does this modification lead to a 100% size reduction, an infinite number of harmonics suppression, and high-frequency selectivity theoretically, but it also results in a noticeable performance improvement practically compared to using quarter-wavelength branches in the conventional microstrip power dividers. The main important contributions of this technique are extreme size reduction and harmonic suppression for the implementation of a filtering power divider (FPD). Furthermore, by tuning the LC circuit, the arbitrary numbers of unwanted harmonics are blocked while the operating frequency, the stopband bandwidth, and the operating bandwidth are chosen optionally. The experimental result verifies the theoretical and simulated results of the proposed technique and demonstrates its potential for improving the performance and reducing the size of other similar microstrip components.

Optically-reconfigurable phase change material nanoantenna-embedded metamaterial waveguide

Heterogeneous integration of phase change materials (PCM) into photonic integrated circuits is of current interest for all-optical signal processing and photonic in-memory computing. The basic building block consists of waveguides or resonators embedded with state-switchable PCM cells evanescently coupled to the optical mode. Despite recent advances, further improvements are desired in performance metrics like switching speeds, switching energies, device footprint, and fan-out. We propose an architecture using resonant metamaterial waveguides loaded with Ge2Sb2Te5 (GST) nanoantenna, and present a numerical study of its performance. Our proposed design is predicted to have a write energy of 16 pJ, an erase energy of 190 pJ (which is three to four times lower than previous reports), and, an order of magnitude improvement in the write-process figure-of-merit. Additional advantages include lowered ON state insertion loss and GST volume reduction.

Integrated Silicon Fourier Transform Spectrometer with Broad Bandwidth and Ultra‐High Resolution

AbstractAn ultra‐high resolution Fourier transform spectrometer (FTS) realized in silicon photonic platform that can operate with broad band, narrow band as well as a combination of broad band and narrow band signals is reported. The ultra‐high resolution of the spectrometer is achieved by exploiting multiple techniques: a Michelson interferometer (MI) structure to increase the optical path delay (OPD), a hybrid waveguide design to reduce insertion loss, an optimized heater and air trenches to achieve higher thermal efficiency. Moreover, to further increase the OPD of the spectrometer to increase its resolution, a novel multiple interferometers approach is employed which combines balanced MI with N statically imbalanced MIs, thereby increasing the OPD of a single MI by factor of N + 1. An FTS spectrometer consisting of N = 2 such MIs is fabricated and experimentally characterized using unknown broad bandwidth input signal spectra of about 180 nm centered around 1550 nm, a narrow line laser input signal, and a combination of broad and narrow band signals demonstrating spectral resolution of about 0.16 nm.

On the routing and scalability of MZI-based optical Beneš interconnects

Silicon Photonic interconnects are a promising technology for scaling computing systems into the exa-scale domain. However, there exist significant challenges in terms of optical losses and complexity. In this work, we evaluate the applicability of a thermally/electrically tuned Beneš network based on Mach–Zehnder Interferometers for on-chip and inter-chip interconnects as regards its scalability. We examine how insertion loss, laser power and switching energy consumption scale with the number of endpoints. In addition, we propose a set of hardware-inspired routing strategies that leverage the inherent asymmetry present in the switching components. We evaluate a range of network sizes, from 16 up to 256 endpoints, using 8 realistic and synthetic workloads and found very promising results. Our routing strategies offer a reduction in path-dependent insertion loss of up to 35% in the best case, as well as a laser power reduction of 31% for 32 endpoints. In addition, bit-switching energy is reduced by between 8% and 15% using the most efficient routing strategy, depending on the communication workload. We also show that workload execution time can be reduced with the best strategies by 5%–25% in some workloads, while the worst-case increases are at most 3%. Using our routing strategies, we show that under the examined technology parameters, a 32-endpoint interconnect can be considered for the NoC domain in terms of insertion loss and laser power, even when using conservative parameters for the modulator.

Design and Loss Reduction of Multiple-Zeros Dual-Band Bandpass Filter Using SISL

This brief proposed a dual-band bandpass filter (DBBPF) topology realized on substrate integrated suspended line (SISL) platform. In this topology, separated electric and magnetic coupling paths (SEMCP) is firstly applied between two different filter bands to generate additional zeros for better skirt selectivity. The proposed filters, featured with self-packaging advantage, use hybrid spiral structure to realize different electric and magnetic coupling scheme for dual-band, compact size and multiple transmission zeros. In addition, loss reduction approach to reduce both substrate and metal losses is used to achieve insertion loss reduction.

Passband broadening of sub-wavelength resonator-based glide-symmetric SIW filters

Here, we discuss the virtues of glide symmetry for designing low-frequency band-pass periodic filters in substrate integrated waveguide (SIW) technology based on complementary split-ring resonators (CSRRs). Conventional (non-glide) versions of these filters have a narrow passband, due to the fact that this band is below the cutoff frequency of the background waveguide. When glide symmetry is added to the filter configuration, the low-frequency passband is significantly widened, as well as the first stopband. The dispersion properties of both conventional and glide-symmetric periodically loaded waveguides are analyzed and compared with commercial software and an equivalent circuit model. Finally, two prototypes of the proposed glide-symmetric structure have been designed and built, illustrating the potential of this technique to widen the passband and reduce insertion losses of conventional sub-wavelength CSRR-loaded SIW filters.

Transmission-mode all-dielectric metasurface color filter arrays designed by evolutionary search

All-dielectric metasurface (ADM) color filter arrays (CFA) are attractive for replacing conventional organic-dye color filters due to several advantages such as CMOS-compatibility, size scalability, and robustness to degradation. We propose metasurface designs with polygon-shaped unit cells for improving the performance of such filters. Our numerical results predict improvement in color purity for red, green, and blue primary color filters and significant reduction in insertion loss for blue filters as compared to the previously reported designs using simple circular shapes. The proposed differential evolution optimization methodology can be useful for improving the performance of other metasurface spectral filtering structures.

Quality enhancement and insertion loss reduction of a rectangular resonator by employing an ultra-wide band gap diamond phononic crystal

We report on an ‘in plane mode’ band gaps investigation of a novel diamond CRS (circle-rectangle-square) shaped holey phononic crystals in the desired operating frequency ranges. An ultra-wide band gap for diamond in the ‘in plane mode’ is observed. We also investigate an ultra-wide acoustic band gap for a finite one-dimensional (1D) diamond CRS phononic crystal (PnC) in the ‘out of plane mode’, and an ultra-wide acoustic band gap of a finite two-dimensional (2D) diamond CRS phononic crystal (PnC) in the ‘out of plane mode’ based on the FEA (Finite Element Analysis) method. We analyze that the transmission response of diamond in the length extension and width extension manner is more reasonable. Ultra-wide peak attenuations in the transmission spectra of a CRS shaped diamond phononic crystal successfully reveal the complete band gaps. The wide band gap of a CRS shaped diamond phononic crystal and the wide peak attenuation strongly agree in the same frequency region. It is analyzed that when a CRS-diamond phononic crystal is employed for MEMS resonators with different tether widths the quality Q of the resonators improved, and the energy losses decrease with extremely low insertion loss. In addition, it is observed that the vibrational displacement of a resonator is reduced by employing a diamond phononic crystal.

Low-loss and broadband fiber-to-chip coupler by 3D fabrication on a silicon photonic platform

We propose and demonstrate a low-loss fiber-to-chip vertical coupler on the silicon photonic platform by using a 3D two-photon fabrication method. Such a coupler significantly reduces insertion loss, measured to be 1 dB, and provides a wide working wavelength range for both TE and TM polarizations over the entire C-band. Moreover, a large tolerance for misalignment of the coupling fiber, up to 4.5 µm for a 1 dB loss, enables the development of relaxed alignment techniques.

CMOS integrated delay chain for X-Ku band applications

A wideband integrated delay chain chip with 5-bit delay control, maximum delay of 120 ps and 3.9 ps delay resolution, designed and fabricated in 0.18 $$\upmu \hbox {m}$$ CMOS technology is presented. Second-order all pass networks (APN) are used as delay structures in this delay circuit. In the design of the two MSB bits of the fabricated chip, a new design approach is used which allows higher group delay to be achieved with fewer number of passive second-order APN circuits. This would in turn reduce insertion loss of the designed delay control chain. Measurement results of the fabricated delay chain show 12.6–20.5 dB insertion loss and less than 3.3 ps RMS delay error over the intended frequency band from 8 to 18 GHz. The fabricated chip occupies an area of $$1.2\times 2.7$$ mm$$^{2}$$ and has no DC power consumption.

Wideband Waveguide-to-Microstrip Transition for mm-Wave Applications

Introduction. Increased data rate in modern communication systems can be achieved by raising the operational frequency to millimeter wave range where wide transmission bands are available. In millimeter wave communication systems, the passive components of the antenna feeding system, which are based on hollow metal waveguides, and active elements of the radiofrequency circuit, which have an interface constructed on planar printed circuit boards (PCB) are interconnected using waveguide-to-microstrip transition.Aim. To design and investigate a high-performance wideband and low loss waveguide-to-microstrip transition dedicated to the 60 GHz frequency range applications that can provide effective transmission of signals between the active components of the radiofrequency circuit and the passive components of the antenna feeding systemMaterials and methods. Full-wave electromagnetic simulations in the CST Microwave Studio software were used to estimate the impact of the substrate material and metal foil on the characteristics of printed structures and to calculate the waveguide-to-microstrip transition characteristics. The results were confirmed via experimental investigation of fabricated wideband transition samples using a vector network analyzer Results. The probe-type transition consist of a PCB fixed between a standard WR-15 waveguide and a back-short with a simple structure and the same cross-section. The proposed transition also includes two through-holes on the PCB in the center of the transition area on either side of the probe. A significant part of the lossy PCB dielectric is removed from that area, thus providing wideband and low-loss performance of the transition without any additional matching elements. The design of the transition was adapted for implementation on the PCBs made of two popular dielectric materials RO4350B and RT/Duroid 5880. The results of full-wave simulation and experimental investigation of the designed waveguide to microstrip transition are presented. The transmission bandwidth for reflection coefficient S11 < –10 dB is in excess of 50…70 GHz. The measured insertion loss for a single transition is 0.4 and 0.7 dB relatively for transitions based on RO4350B and RT/Duroid 5880.Conclusion. The proposed method of insertion loss reduction in the waveguide-to-microstrip transition provides effective operation due to reduction of the dielectric substrate portion in the transition region for various high-frequency PCB materials. The designed waveguide-to -microstrip transition can be considered as an effective solution for interconnection between the waveguide and microstrip elements of the various millimeter-wave devices dedicated for the 60 GHz frequency range applications.

A Tunable SiGe BiCMOS Gain-Equalizer For X-Band Phased-Array RADAR Applications

This brief presents a compact-size tunable gain-equalizer for X-band phased-array RADAR applications in a 0.25- $ \mu \text{m}$ SiGe BiCMOS technology. An isolated nMOS-based variable resistance was used for the first time to tune the slope of the gain-equalizer. For nMOS, an isolated body created by a deep n-well was utilized to reduce insertion loss due to the substrate conductivity. Furthermore, the power-handling capability of the tunable gain-equalizer was improved thanks to the resistive body-floating technique. The designed tunable gain-equalizer operates in the frequency range from 8 to 12.5 GHz with a measured positive slope of 1 dB/GHz and 1 dB tunable slope. The effective chip area excluding the pads is 0.21 mm2, and the total area including pads is 0.31 mm2. To authors best knowledge, this brief is the first tunable gain-equalizer in SiGe technology presented for X-band phased-array RADAR applications.

Tapered Long-Range Surface Plasmon Polariton Waveguides with a Gap.

We propose tapered long-range surface plasmon polariton (LR-SPP) waveguides with a gap (tapered G-SPPWs) for improved tunneling efficiency in G-SPPWs. The optical characteristics of the fabricated tapered G-SPPWs were experimentally measured and compared with simulation results. The proposed tapered structure can improve tunneling efficiency by reducing insertion loss of the tapered G-SPPWs. The insertion losses of the straight G-SPPW with an 8-µm gap length and a 2-µm SPPW width and the tapered G-SPPW with an 8-µm gap length, a 2-µm SPPW width, a 6-µm taper width, and a 3-µm taper length were measured to be ~1.03 and ~0.74 dB, respectively. The tapered G-SPPW has potential as an efficient plasmonic modulation device element, offering control of the guided SPP through interaction with an applied force in the gap.

High-gain leaky surface acoustic wave amplifier in epitaxial InGaAs on lithium niobate heterostructure

Active surface acoustic wave components have the potential to transform RF front ends by consolidating functionalities that currently occur across multiple chip technologies, leading to reduced insertion loss from converting back and forth between acoustic and electronic domains in addition to improved size and power efficiency. This letter demonstrates a significant advance in these active devices with a compact, high-gain, and low-power leaky surface acoustic wave amplifier based on the acoustoelectric effect. Devices use an acoustically thin semi-insulating InGaAs surface film on a YX lithium niobate substrate to achieve exceptionally high acoustoelectric interaction strength via an epitaxial In0.53Ga0.47As(P)/InP quaternary layer structure and wafer-scale bonding. We demonstrate 1.9 dB of gain per acoustic wavelength and power consumption of 90 mW for 30 dB of electronic gain. Despite the strong intrinsic leaky propagation loss, 5 dB of terminal gain is obtained for a semiconductor that is only 338 μm long due to state-of-the-art heterogenous integration and an improved material platform.

Highly sensitive temperature sensor based on a polymer-infiltrated Mach-Zehnder interferometer created in graded index fiber.

A highly sensitive temperature sensor is proposed and demonstrated based on a UV-curable polymer-infiltrated Mach-Zehnder interferometer (MZI) created in a graded index fiber (GIF). The device was constructed by splicing a half-pitch GIF between two single-mode fibers and creating an inner air cavity in one lateral side of the GIF core by means of femtosecond laser micromachining. The air cavity and the residual GIF core functioned as two interference arms of the MZI. Moreover, the GIF was used as a miniature in-fiber collimator to reduce insertion loss of the air cavity. Experimental results show such an MZI device has a high refractive index (RI) sensitivity of 24611.54nm/RIU (RI=1.545-1.565). Subsequently, thermo-sensitive polymer liquid was infiltrated into the air cavity, then cured with UV illumination, and annealed at 50°C for 12h. The infiltrated MZI exhibits a high temperature sensitivity of -13.27 nm/°C. In addition, this MZI also has excellent thermal stability and repeatability, compact structure, low insertion loss, and high fringe visibility. As such, the proposed MZI could be developed for high-accuracy temperature measurements in many areas such as biomedical or oceanographic applications.

Transition from rectangular waveguide to empty substrate integrated gap waveguide

Empty substrate integrated waveguide (ESIW) is a hollow SIW with its inner dielectric removed to achieve a reduced insertion loss. One of the drawbacks is the top and bottom covers need to be soldered to the middle substrate. Gap waveguide (GW) technology solves the contact issue utilising contactless electromagnetic band-gap (EBG) structures. Therefore, empty substrate integrated GW (ESIGW) is a transmission line having both advantages of ESIW and GW. In this Letter, a wideband transition from rectangular waveguide (RW) to ESIGW is presented. RW is firstly matched to reduced-height RW using E -plane stepped waveguides. Then, a short substrate integrated GW (SIGW) section is introduced between the reduced-height RW and the ESIGW. This section not only serves as an impedance matching component, it also connects the two sides of the ESIGW and maintains the integrity of the substrate. To broaden the bandwidth of the transition, a triangular dielectric is added at the end of the ESIGW. A Ka-band back-to-back prototype of the transition is designed and fabricated. In addition, TRL calibration is used to measure the transmission performance of the ESIGW. The measured results show that the transition works well over the entire Ka-band.

Resonant amplification via Er-doped clad Si photonic molecules: Towards compact low-loss/high-Q Si photonic devices

Silicon photonics routers and band-pass filters employing ring resonators are usually constrained by a trade-off between quality factors and insertion loss, which is even more pronounced in compact designs. Device real estate is another factor to be considered for compactness and cost reduction. We propose an approach to simultaneously reduce insertion losses and increase the quality factor in such devices, while minimizing footprint. This approach consists in replacing the standard SiO2 top cladding of Si devices by erbium-doped Al2O3 films with a single post-processing step. Experimental results confirm the effectiveness of the method, where 1 dB output power increase is observed for a single ring device, in addition to an increase of 5% in the Q factor. In some cases of structures comprised of multiple coupled resonators, i.e., photonic molecules, the observed value of power increase is as high as 2.6 dB, with a Q factor increase of 25% and loss reduction of 3 dB.