dB Coupling Research Articles

Measurement of end-face reflection property of micro-nano fibers

The end-face reflection property of micro-nano fiber (MNF) is one of its important transmission features, which plays remarkable roles in a variety of practical applications of MNF. In this paper, we propose a novel method to study the MNF end-face reflection property using an optical circulator, which overcomes the deficiencies of the direct measurement relying on a 3 dB coupler. On the basis of this method, we further introduce the aerogel fixing and power compensation techniques to effectively eliminate the errors caused by MNF pigtail floating, the light source output instability and internal loss. Therefore, the whole experimental design improves the measurement accuracy. The MNF end-face reflections with respect to the diameter of MNF and the wavelength of the guided light are investigated. The experimental results are in good agreement with simulation results, showing that this new approach is reliable for measuring the reflectivity of specific MNF. This detailed investigation on the end-face reflection versus various factors will be conducive to the constructions of versatile micro-nano scale devices based on the MNF, such as the MNF lasers, MNF amplifiers, MNF couplers and MNF filters.

Compact and Closely Spaced Metamaterial MIMO Antenna With High Isolation for Wireless Applications

This letter presents a design of a two-element multiple-input-multiple-output (MIMO) metamaterial-based antenna. The two antenna elements operate at 5.8 GHz for wireless applications. The two antenna elements are designed employing only one left-handed unit cell. The reduction of mutual coupling between the two antenna elements is achieved by using a simple defected ground structure between them to limit the surface waves between them. The distance between the two antenna elements is only 1.8 mm (0.034 λ0). The designed antenna elements have better than -45 dB coupling isolation between the two inputs. Moreover, the proposed MIMO antenna has the advantage of compactness (its size is only 2.36 × 2.6 cm2). The design represents size reduction of more than 50% compared to conventional patch antennas operating at the same frequency. The proposed MIMO system has -55 dB correlation coefficient between its two elements.

Broadband focusing grating couplers for suspended-membrane waveguides

We propose and demonstrate broadband focusing grating couplers for suspended-membrane waveguides on silicon-on-insulator both in near-infrared (near-IR) and in mid-IR wavelength range. Finite-difference time-domain simulation predicts ∼100 nm 3dB bandwidth with -1.7 dB coupling efficiency for an apodized grating in near-IR. -3.5 dB maximum coupling efficiency and ∼90 nm 3dB bandwidth are realized experimentally. In mid-IR, -5.5 dB maximum coupling efficiency from a uniform focusing grating is measured at 2.75μm, and ∼500 nm 3dB bandwidth is predicted theoretically.

All planar compact size microstrip CRLH arbitrary coupling directional coupler

A new compact size microstrip arbitrary coupling directional coupler (DC) based on the coupled line composite right/left handed (CL-CRLH) unit cell is proposed. The coupler is patterned on a single metal layer, does not use vias, and occupies 45 × 11 mm2 area. Its bandwidth is 400 MHz centered around 2.4 GHz and it provides −3 dB coupling coefficient. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:115–119, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27270

A Low-Cost Wideband 77-GHz Planar Butler Matrix in SIW Technology

This communication presents a low-cost 77-GHz switched-beam slot antenna array driven by a Butler matrix. In the proposed configuration, four broadband couplers are combined and crossovers are effectively avoided. In this case, the overall circuit and beamforming network losses are considerably reduced. A 4 × 4 planar SIW Butler matrix is designed and demonstrated for integrated beamforming network applications, which exhibits about 7 degrees phase error and ±0.75 dB coupling imbalance over 11% bandwidth. This experimentally prototyped matrix is integrated with a four-array slot antenna on the same substrate. An alternating displacement of the slots in subsequent radiating waveguides is proposed to save the arrangement of the input ports and to achieve broadband performances. Measured radiation patterns are in good agreement with simulated counterparts over the proposed 77-GHz frequency range.

Chip-scale parametric amplifier with 11 dB gain at 1550 nm based on a slow-light GaInP photonic crystal waveguide

We report on a chip scale parametric amplifier based on a GaInP photonic crystal waveguide. The amplifier operates with both pump and signal in the 1550nm wavelength range and offers an on-chip gain of 11dB (5dB including the 6dB coupling losses) when pumped at only 800mW. It enables us, therefore, to incorporate the many advantages of parametric amplification within photonic chips for optical communication applications.

Design and analysis of optical coupler with a stable splitting ratio based on cascaded multistage directional couplers

An optical 3 dB coupler based on cascaded three-stage directional couplers is proposed. The optical coupler with a finite impulse response on optical power is able to provide a stable 50% splitting ratio. The influence of the waveguide gap, width of each waveguide, and coupling length on the performance of the proposed coupler is illustrated. The numerical analysis and results show the reported coupler with less sensitivity to such fabrication variations. The proposed optical coupler could also be designed with any stable splitting ratio for optical communication applications.

Apodized focusing subwavelength grating couplers for suspended membrane waveguides

We demonstrate an apodized focusing subwavelength grating (SWG) for suspended membrane waveguides on silicon-on-insulator. Finite-difference time-domain simulation predicts −1.7 dB coupling efficiency and a 3 dB bandwidth of ∼50 nm for the transverse-magnetic mode apodized SWG, which has 98% field overlap with propagation mode in the single mode fiber. A modified phase matching formula is proposed to design the focusing apodized SWG. Better than −3.0 dB coupling efficiency and a 3 dB optical bandwidth of ∼50 nm is demonstrated experimentally.

High-Efficiency SOI Fiber-to-Chip Grating Couplers and Low-Loss Waveguides for the Short-Wave Infrared

We report on high-efficiency silicon-on-insulator (SOI) grating couplers and low-loss single-mode optical waveguides operating in a short-wave infrared. A -3.8 dB coupling efficiency from a standard single-mode fiber to an SOI waveguide at 2.1 μm is obtained experimentally. Single-mode waveguide losses in the short-wave infrared below 0.6 dB/cm are reported.

Wideband subwavelength gratings for coupling between silicon-on-insulator waveguides and optical fibers

We propose and experimentally demonstrate a novel subwavelength grating coupler on silicon-on-insulator, for coupling to optical fibers with a wide optical bandwidth. Theoretical analysis and design optimization of the coupler are described. About 73 nm 1 dB bandwidth was experimentally demonstrated with -5.6 dB coupling efficiency. Better than -3.4 dB efficiency with 86 nm 1 dB bandwidth is predicted for these structures with optimized buried oxide thickness.

Implementation of load resilient ion cyclotron resonant frequency (ICRF) systems to couple high levels of ICRF power to ELMy H-mode plasmas in JET

The paper summarizes the continuous developments made to the ion cyclotron resonant frequency (ICRF) system at JET in order to improve the reliability of the power coupled to plasma. It details the changes and improvements made to the system so that more power is coupled during ELMy plasmas as well as increasing the power density to demonstrate reliable operation in the range of the requirements for ITER. Results obtained using the conventional matching (stubs and trombones) system, 3 dB couplers and the conjugate-T scheme with variable matching elements outside the wave launching structure (external conjugate-T) and inside the wave launching structure (ITER-like antenna) are described. The presence of the three different approaches to load resilient ICRF systems at JET creates a unique opportunity to compare these methods under very similar plasma conditions and to assess the results of ICRF power delivery to ELMy plasmas, an important issue for ITER. The impact of the availability of increased levels of reliable ICRF power on plasma physics studies in JET is illustrated.

CMOS compatible integration of Si/SiO_2 multilayer GRIN lens optical mode size converter to Si wire waveguide

We present a CMOS compatible mass manufacturable, compact Si/SiO(2) multilayer GRIN lens mode size converter from standard single mode fiber to 300 nm-thick Si waveguide. The fiber-to-GRIN lens coupling loss is 2.6 ± 0.3 dB (coupling efficiency: 51~60%) with optimized focal length of 11.6~11.8 μm and Si/SiO(2) multilayer thickness of 7.4 μm.

Multi-Layered Ring Log-Periodic Antennas Array Design for GPS Systems

The objective of the present study is the design of log periodic ring printed antennas array witch generates circular polarization with wide band by single feed linearly polarized elements for GPS systems. The radiating elements have been fed by magnetic coupling through a slot. The circular polarization is achieved by having a basic 2 ×2 sub-arrays with unique element angular and phase arrangement, both the element angular orientation and feed phase are arranged in the 0°, 90°, 180 and 270° fashion. The purpose of different angular orientations of the patches is to generate two orthogonally polarized fields, while -3dB coupler is used to provide the required amplitude and phase delays for circular polarization generation. This uniquely formed array has the capability of generating excellent circular polarization. An association of the coupler with the antennas has been established. This work is completed using the moment’s method of Momentum software. Good performances of adaptation and polarization were obtained. The simulation results are then presented and discussed.

Tunable graphene Q-switched erbium-doped fiber laser with suppressed self-mode locking effect

Self-mode locking effect in a wideband tunable graphene-based passively Q-switched erbium-doped fiber laser has been observed experimentally. Q-switching is achieved by using graphene as a saturable absorber, while a tunable bandpass filter with a narrow bandwidth is used to obtain wideband tunability. We propose to suppress the modulation on each pulse from self-mode locking by introducing three subring resonators constructed with three 3 dB couplers into the laser ring cavity. Moreover, the laser output characteristics with respect to pump power are studied in detail. A stable Q-switched erbium-doped fiber laser with a tunable range from 1522 nm to 1568 nm is demonstrated experimentally.

Wideband Printed MIMO/Diversity Monopole Antenna for WiFi/WiMAX Applications

A novel printed diversity monopole antenna is presented for WiFi/WiMAX applications. The antenna comprises two crescent shaped radiators placed symmetrically with respect to a defected ground plane and a neutralization lines is connected between them to achieve good impedance matching and low mutual coupling. Theoretical and experimental characteristics are illustrated for this antenna, which achieves an impedance bandwidth of 54.5% (over 2.4-4.2 GHz), with a reflection coefficient <;-10 dB and mutual coupling <;-17 dB. An acceptable agreement is obtained for the computed and measured gain, radiation patterns, envelope correlation coefficient, and channel capacity loss. These characteristics demonstrate that the proposed antenna is an attractive candidate for multiple-input multiple-output portable or mobile devices.

Single etch grating couplers for mass fabrication with DUV lithography

Surface grating couplers enable efficient coupling of light between optical fibers and planar waveguide circuits. While traditional grating designs require two etch steps for efficient coupling to silicon-on-insulator waveguides, recently proposed subwavelength structured gratings can achieve the same coupling efficiencies with a single etch step, thereby significantly reducing fabrication complexity. Here we demonstrate that such couplers can be fabricated on a large scale with ultra-violet lithography, achieving a 5 dB coupling efficiency at 1,550 nm. Through both simulations and experiments we give physical insight on how pattern fidelity impacts the performance of these couplers, and propose strategies to deal with inevitable process variations.

A Millimeter Wave Six-Port Network Using Half-Mode Substrate Integrated Waveguide

A novel six-port network based on half-mode substrate integrated waveguide (HMSIW) is proposed. In this design, a HMSIW hybrid 3 dB coupler and a -90° phase shifter are designed as fundamental building block of six-port network. By combining four HMSIW couplers and one phase shifter, a HMSIW six-port network at 29–32 GHz is constructed. The six-port network is fabricated and measured. Measurement results agree well with simulation, and show good balance and phase relationship between ports.

Substrate integrated coaxial line 3 dB coupler

A compact substrate integrated coaxial line (SICL) 3 dB coupler is proposed, designed, fabricated and measured. Compared with some available reports of substrate integrated waveguide 3 dB couplers, this SICL coupler maintains good performance but with a remarkable 80 reduction in size.

3 dB桥误差对能量倍增器性能的影响

3 dB桥误差对能量倍增器性能的影响

DESIGN AND IMPLEMENTATION OF AN ULTRA-WIDEBAND SIX-PORT NETWORK

This paper presents a six-port network over an ultra- wideband (UWB) of 2{8GHz. Its key component is the six-port junction, which consists of a Wilkinson power divider and three 3-dB quadrature couplers. This six-port junction is accomplished in a low dielectric constant substrate (Rogers RT/duroid 5880). Multi-section impedance transformation is applied in the power divider, and the quadrature coupler is realized by using two 8.34dB couplers in tandem. An ultra-wideband operation of the six-port junction is verifled by full electromagnetic simulations and measurements. The results show that the designed devices exhibit good performance across 2{8GHz band: the return losses at input ports are higher than 15dB, the insertion losses from input ports to the remaining ports are 7:2dB § 1:7dB, the isolation between two input ports is greater than 20.5dB, and the maximum phase difierence compared with the theoretical behavior between two test ports is 10 - . For the manufactured six-port junction, a six-port phase measurement system and a calibration technique based on support vector regression (SVR) are introduced. Results show that the SVR model can achieve a mean phase error of 1.5274 - .