Worst-case Insertion Loss Research Articles

Crosstalk-Aware Automatic Topology Customization and Optimization for Wavelength-Routed Optical NoCs

Optical network-on-chip (ONoC) is an emerging upgrade for electronic network-on-chip (ENoC). As a kind of ONoC, wavelength-routed ONoC (WRONoC) shows ultrahigh bandwidth and ultralow latency in data communication. Manually designed WRONoC topologies typically reserve all to all links. This causes the waste of resources. Topology customization for each individual communication network can save resources, but requires automation for efficient design. The state-of-the-art design automation method is not efficient and does not support crosstalk analysis and signal-to-noise ratio (SNR) optimization. Moreover, the state of the art does not consider the physical locations of the data sending/receiving ports, causing unavoidable detours and crossings in the physical layout. In this work, we present FAST+: an automatic topology customization and optimization method. Compared with the state of the art, FAST+ operates much more efficiently and proposes a concrete router-level crosstalk-analysis method and a novel SNR optimization algorithm. This work also provides solutions to avoid detours and crossings in the physical layout. When SNR optimization is not enabled, experimental results show that FAST+ runs thousands times faster than the state of the art on average while providing multiple better or equally good topologies regarding resource usage and the worst case insertion loss. When SNR optimization is enabled, FAST+ provides <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.75\times $ </tex-math></inline-formula> better worst case SNR on average after the optimization while not sacrificing resource usage and the worst case insertion loss.

Micromachined Subterahertz Waveguide-Integrated Phase Shifter Utilizing Supermode Propagation

In this work, we propose a new concept of phase shifting by tuning the coupling distance between two parallel silicon slabs that support the propagation of an in-phase supermode. A prototype device was implemented in the 220-330-GHz band by integrating the micro-electro-mechanical system (MEMS)-actuated phase-shifting mechanism, based on two moveable parallel-coupled high-resistivity silicon slabs, inside a metallized hollow rectangular waveguide in silicon-on-insulator (SOI) micromachining technology. The prototype device has been characterized to a maximum continuous phase tunability of 550° with a maximum insertion loss of 1.87 dB achieved at 330 GHz. A maximum figure-of-merit (FOM) of 375°/dB is achieved at around 320 GHz, which presently is the highest FOM value reported for any phase shifter in the subterahertz (sub-THz) frequency range. The bandwidth covers the whole waveguide band with an average and worst case insertion loss of 1.94 and 2.5 dB, respectively, a worst case insertion-loss variation of 0.7 dB and a phase error better than 4° for all phase states. A large displacement of MEMS electrostatic comb-drive actuators that are co-fabricated in the micromachined waveguide platform is achieved by a driving voltage of 50 V. The prototype footprint is 7.3 ×5.3 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Bi-Directional Benes With Large Port-Counts and Low Waveguide Crossings for Optical Network-on-Chip

We propose a new variant of the Benes network using a merge-replace-fold approach. It is to realize a large port-count optical switch with low waveguide crossings. A bidirectional switch is built instead of a unidirectional switch. Compared to the classical Benes, it requires the same number of switches but far fewer intersections. The novel designs enable a 24-percentage reduction in waveguide intersections. Moreover, it has a worst-case insertion loss of 12.01 dB and a comparable crosstalk level of −13.67 dB between the neighbouring paths. Thus, it offers an energy-efficient way to solve the optical on-chip design problem in a bidirectional manner.

Ultralow Loss and High Extinction Ratio TM-Pass Polarizer in Silicon Photonics

TM-pass polarizers are pivotal components of photonic integrated circuits (PICs), especially those intended for biosensing applications. In the literature, several silicon TM-pass polarizers have been proposed, designed and experimentally demonstrated, but their insertion loss is not compatible with the current trend of silicon photonics aimed at exponentially increasing the component density within PICs. Herein, we propose and design a TM-pass polarizer whose insertion loss is carefully minimized to 0.05 dB at wavelength 1.55 μm by utilizing a combination of an asymmetric directional coupler and a mode evolution section. The adoption of appropriate technical solutions makes this record insertion loss value compatible with a high extinction ratio equal to 38 dB. With a device footprint of only 2.5 × 20 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , the design exhibits an insertion loss less than 1.7 dB and extinction ratio better than 30 dB over a large bandwidth of 200 nm. The design assumes the constraints of a typical silicon photonics open-access technological process and a standard 220 nm silicon-on-insulator (SOI) wafer. A very low sensitivity of the achieved performance to reasonable fabrication inaccuracies is demonstrated, with a worst-case insertion loss of only 0.32 dB at wavelength 1.55 μm.

Frequency and Bandwidth Tunable mm-Wave Hairpin Bandpass Filters Using Microfluidic Reconfiguration With Integrated Actuation

Microfluidically reconfigurable radio-frequency (RF) devices in general have been found attractive for low-loss, wide-frequency tunability and high-power-handling capabilities. Recently, integrated actuation of the microfluidically reconfigurable devices has been proposed for compact mm-wave device applications. This article for the first time introduces microfluidically reconfigurable frequency- and/or bandwidth-tunable bandpass filters (BPFs) operated at the mm-wave band with integrated actuation. The BPFs consist of coupled hairpin resonators. Frequency tuning is achieved by capacitively loading the resonators. Bandwidth tuning is achieved by creating varying capacitive loading among the resonators to control the interresonator couplings. The capacitive loading mechanisms are realized using the selectively metallized plates (SMPs) that can be repositioned within the microfluidic channels. The microfluidic channels are located directly above the stationary metallizations of the filter. Piezoelectric bending actuators placed under the filter's ground plane provide the SMP motion capability. The BPFs perform with the worst-case insertion loss of 3.1 dB. Frequency-tuning capable filters operate within 28-38-GHz band. Fractional bandwidth tunability varies from 7.8% to 16.7% at 38 GHz and 7.6% to 12.5% at 28 GHz for the filter that is capable of both tuning mechanisms. The filters are characterized to handle 5 W of the continuous RF power without needing thick ground planes or heat sinks. In addition, the frequency-tuning speed is characterized to be 285 MHz/ms.

Optimization of high-channel count, switch matrices for multinuclear, high-field MRI.

Modern magnetic resonance imaging systems are equipped with a large number of receive connectors in order to optimally support a large field-of-view and/or high acceleration in parallel imaging using high-channel count, phased array coils. Given that the MR system is equipped with a limited number of digitizing receivers and in order to support operation of multinuclear coil arrays, these connectors need to be flexibly routed to the receiver outside the RF shielded examination room. However, for a number of practical, economic and safety reasons, it is better to only route a subset of the connectors. This is usually accomplished with the use of switch matrices. These exist in a variety of topologies and differ in routing flexibility and technological implementation. A highly flexible implementation is a crossbar topology that allows to any one input to be routed to any one output and can use single PIN diodes as active elements. However, in this configuration, long open-ended transmission lines can potentially remain connected to the signal path leading to high transmission losses. Thus, especially for high-field systems compensation mechanisms are required to remove the effects of open-ended transmission line stubs. The selection of a limited number of lumped element reactance values to compensate for the for the effect of transmission line stubs in large-scale switch matrices capable of supporting multi-nuclear operation is non-trivial and is a combinatorial problem of high order. Here, we demonstrate the use of metaheuristic approaches to optimize the circuit design of these matrices that additionally carry out the optimization of distances between the parallel transmission lines. For a matrix with 128 inputs and 64 outputs a realization is proposed that displays a worst-case insertion loss of 3.8 dB.

Variable High Precision Wide D-Band Phase Shifter

This paper proposes a new concept of designing compact high precision millimeter-wave wideband variable phase shifters. The phase shifter is implemented with a stacked shim with extremely short length of 0.9 mm and two waveguide flange adaptors with length of 0.5 mm. High precision phase shifting is achieved over entire D-band (110-170 GHz) by rotating the shim 90 degrees from aligned to perpendicular with consistent impedance matching performance. In addition, a glide-symmetric holey electromagnetic bandgap (EBG) structure is adopted to avoid wave leakage from the gap between the shim and the flange adaptors. A proof-of-concept (PoC) demonstrator is designed, manufactured, and tested. The measured results show that the designed stacked shim phase shifter with embedded EBG structure ensures return loss higher than 10 dB across 110-170 GHz with a 75 mu m airgap between waveguide flanges. The studied phase shifter provides a 0.88ffi phase shifting with each degree of mechanical rotation. The fabricated PoC phase shifter has a worst-case insertion loss of 0.92 dB and a return loss of 20 dB across the entire 110-170 GHz band and a maximum phase shift of 30 degrees. At 10 degrees phase shifting, the measured insertion loss is lower than 0.52 dB, and return loss is higher than 23 dB, respectively.

A Sub-THz Rectangular Waveguide Phase Shifter Using Piezoelectric-Based Tunable Artificial Magnetic Conductor

An analog phase shifter operating at 240 GHz and implemented within a rectangular waveguide is presented in this paper. The phase shifter relies on mechanically actuating a tunable perfect magnetic conductor (PMC) inside an upright rectangular waveguide supporting a modified TE10 mode. The PMC boundary condition is realized using a metallic strip suspended slightly above the short wall of the rectangular waveguide. It is shown analytically and numerically that vertically actuating the metallic strip changes the dispersion relation of the modified TE10 mode leading to a controllable phase shift. The proposed structure is designed using full-wave simulations and optimized for minimal losses. It is then fabricated using standard silicon microfabrication techniques including photolithography, deep reactive ion etching, and metal sputtering. The actuation is done through an external piezoelectric actuator that is assembled with the microfabricated structure to form a single unit. The phase shifter shows a measured phase shift of 380° with worst case insertion loss of 3 dB leading to an excellent figure of merit (FoM) of 127°/dB. To the best of our knowledge, this is the best reported FoM for all passive phase shifters operating beyond 60 GHz.

Reliable and Compact 3- and 4-Bit Phase Shifters Using MEMS SP4T and SP8T Switches

This paper presents radio frequency (RF) micro-electromechanical system-based 3- and 4-bit phase shifters using single-pole-four-throw (SP4T) and single-pole-eight-throw (SP8T) switches. The design is fabricated on $635~\mu \text{m}$ alumina substrate using a surface micromachining process. SP4T and SP8T switches demonstrate measured return loss of >16 dB, worst case insertion loss of 1.66 dB, and isolation of >13.6 dB up to 40 GHz. Total area of the SP4T and SP8T switches is 0.98 mm2 and 1.66 mm2, respectively. Switches are capable of handling 1 W of incident RF power and can sustain up to 1 billion cycles at 85°C. Finally, 3- and 4-bit phase shifters deliver measured return loss of >12 dB, average insertion loss of 1 billion cycles with 0.1 W of power in cold switching. In addition, phase shifters also worked satisfactory up to >400 million cycles with 0.5 W of power at 85 °C in hot switching condition. Devices were enclosed within a low-cost package and characterized them systematically. [2017-0104]

Extensive performance evaluations of RF MEMS single-pole-multi-throw (SP3T to SP14T) switches up to X-band frequency

This work presents wide range of compact and reliable single-pole-multi-throw (SPMT) radio frequency (RF) microelectromechanical system (MEMS) switches where the M (output) varies from 3 to 14 throws. The single dc-contact switch dimensions are 0.144 mm × 0.29 mm which are fabricated on 635 µm alumina substrate using a surface micromachining process. SPMT switching networks demonstrate a measured return loss of more than 14 dB, a worst case insertion loss of ~1.76 dB and isolation of ~14.5 dB up to 12 GHz. The maximum area of the fabricated SPMT switch is ~1.2 mm2. The SPMT switches are capable of handling 1 W of RF power up to >1 billion cycles at 25 °C, and sustained even up to >80 million cycles with 0.5 W at 85 °C. To the best of our knowledge, this is the first reported wide range of MEMS SPMT switches and their respective performance evaluations in the literature that has undergone extensive measurement stages.

Systematic measurements of high isolation DC – 20 GHz miniature MEMS SPDT switch

ABSTRACTA systematic measurement procedure of high isolation single‐pole‐double‐throw (SPDT) switch utilizing six metal contact switches using micro electromechanical systems (MEMS) is presented in this paper. A complete measurement procedure of a MEMS DC‐contact is outlined here including profile analysis, mechanical, electrical, switching/release time, temperature stability, power handling, intermodulation, IIP3, S‐parameter and reliability. Measured return loss of better than 20 dB with worst case insertion loss of 1.67 dB and isolation greater than 42 dB have been experimentally obtained from the SPDT switch up to 20 GHz within 1.25 mm2 area. Switch demonstrates temperature stability up to 70°C temperature and 0.1–1 W of RF power handling. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1154–1159, 2016

Tunable directional coupler for RF front‐end applications

A tunable directional coupler for radio frequency (RF) front-ends of handheld mobile devices is presented. The coupler is implemented in a 0.13 μm bulk RF-CMOS technology with all elements monolithically integrated on a single die. A digitally-tuned termination network at the isolated port of the coupler is realised solely with RF-switch transistors using the channel resistance of a metal-oxide-semiconductor (MOS) device. The fine-tuned termination network allows the coupler to achieve a directivity of over 25 dB in the whole cellular frequency range from 699 MHz up to 2.7 GHz. The worst-case insertion loss in the transmitted path is 0.15 dB at 2.7 GHz.

Multimode Polymer Waveguide Components for Complex On-Board Optical Topologies

Multimode polymer waveguides are an attractive transmission medium for board-level optical links as they provide high bandwidth, relaxed alignment tolerances, and can be directly integrated onto conventional printed circuit boards. However, the performance of multimode waveguide components depends on the launch conditions at the component input, complicating their use in topologies that require the concatenation of multiple multimode components. This paper presents key polymer components for a multichannel optical bus and reports their performance under different launch conditions, enabling useful rules that can be used to design complex interconnection topologies to be derived. The components studied are multimode signal splitters and combiners, 90°-crossings, S-bends, and 90°-bends. By varying the width of the splitter arms, a splitting ratio between 1% and 95% is achieved from the 1 × 2 splitters, while low-loss signal combining is demonstrated with the waveguide combiners. It is shown that a 3 dB improvement in the combiner excess loss can be achieved by increasing the bus width by 50 μm. The worst-case insertion loss of 50 × 100 μm waveguide crossings is measured to be 0.1 dB/crossing. An empirical method is proposed and used to estimate the insertion losses of on-board optical paths of a polymeric four-channel optical bus module. Good agreement is achieved between the predicted and measured values. Although the components and empirical method have been tailored for use in a multichannel optical bus architecture, they can be used for any on-board optical interconnection topology.

Fabrication-Tolerant Four-Channel Wavelength-Division-Multiplexing Filter Based on Collectively Tuned Si Microrings

We demonstrate a robust, compact and low-loss four-channel wavelength-division multiplexing (WDM) filter based on cascaded double-ring resonators (2RR) in silicon. The flat-top channel response obtained by the second-order filter design is exploited to compensate for the detrimental effects of local fabrication variations and their associated phase errors on the ring-based filter response. Full wafer-scale characterization of a cascaded, four-channel 2RR filter with channel spacing of 300 GHz shows an average worst-case insertion loss below 1.5 dB and an average worst-case crosstalk below -18 dB across the wafer, representing a substantial improvement over a first-order based ring (1RR) design. The robust 2RR filter design enables the use of a simple collective thermal tuning mechanism to compensate for global fabrication variations as well as for global temperature fluctuations of the WDM filter, the WDM laser source, or both. Highly uniform collective heating is demonstrated using integrated doped silicon heaters. The compact filter footprint of less than 50×50 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> per channel enables straightforward scaling of the WDM channel count to 8 channels and beyond. Such low-loss collectively tuned ring-based WDM filters can prove beneficial in scaling the bandwidth density of chip-level silicon optical interconnects.

High Resolution Tunable MEMS Phase Shifters for Radar Phased Array Antenna

The paper proposes a high resolution tunable MicroElectroMechanical Systems (MEMS) phase shifters for radar phased array antenna to steer the beam. Two phase shifters are considered the first is a switched line phase shifter; the second is a reflection type phase shifter. The resolution of the designed phase shifters is two degree phase shift using 8 bit control circuitry. The proposed circuit is based on dividing the tuning range into coarse and fine tuning sections which change the phase by 30o and 2o steps respectively to achieve the desired phase. A microstrip phase shifters have been designed at 3 GHz suitable for surveillance radar applications. The development of RF MEMS switches over the past years has enabled system designers to consider replacing the GaAs phase shifters with RF MEMS phase shifters. MEMS phase shifter exhibit excellent characteristics, including low insertion loss and low DC power consumption. The designed phase shifters are simulated and tested using Advance Design System circuit simulation package (ADS) and the results demonstratedusing the graphics capability of Matlab Program. The results show that the worst case insertion loss is less than 0.17 dB and 0.05 dB for switched line and reflection type phase shifters respectively. The return loss for the two proposed phase shifters is less than -60 dB.

Design of CWDM multiplexers based on series coupled ring resonators: analysis, potential and prospects on MEMS fabrication technologies

New designs for a 1 × 4 and a 1 × 8 CWDM multiplexers based on cascaded groups of series coupled ring resonators (Little et al. in J Lightwave Technol 15:998–1005, 1997; IEEE Photon Technol Lett 10:2263–2265, 2004; Hryniewicz et al. in IEEE Photon Technol Lett 12:320–322, 2000) are presented. Compared to other integrated optical alternatives such as MMI phasars (Paiam and MacDonald in Appl Opt 36: 5097–5108, 1997), cascaded Mach–Zehnder interferometers (Wang and He in J Lightwave Technol 23:1284–1290, 2005) and cascaded AWG (Dragone in IEEE Photon Technol Lett 3:812–815, 1991; Uetsuka in IEEE J Sel Top Quant Electron 10:393–402, 2004), the proposed circuits offer superior performance in their very sharp roll-off factor that exceeds 0.75, their reduced crosstalk level that lies below −60 dB and their negligible insertion loss for the 1 × 4 design. For the 1 × 8 design, the worst case insertion loss is 4 dB. However, the performances obtained exhibit passband ripples in the order of 5 dB, and besides, they are not very tolerant to fabrication errors. Being designed for SOI technology, the proposed circuits are compact as the circuit areas are 130 × 130 and 90 × 150 μm2 for the 1 × 4 and 1 × 8 designs, respectively. They also have a high potential for MEMS tunability.

Optimization and Implementation of Impedance-Matched True-Time-Delay Phase Shifters on Quartz Substrate

In this paper, design equations for true-time-delay microelectromechanical (MEM) phase shifters comprised of impedance-matched slow-wave unit cells are presented. The input to these equations requires only the specification of the maximum frequency of operation (fmax) and substrate dielectric constant (epsi r). The basis of the design methodology is to maximize the phase shift versus insertion loss performance. Experimental data for three 1-bit devices that are 11.44-mm long (fmax=12 GHz), 4.6-mm long (fmax=50 GHz), and 3.12-mm long (fmax=110 GHz) shows a maximum phase deviation of 3% compared to predicted performance, with S11 less than -19 dB from 1 to 110 GHz. The worst case insertion loss is 0.9 dB for fmax=12 GHz, 1.16 dB for fmax=50 GHz, and 2.65 dB for fmax=110 GHz. The MEM beams are actuated using high-resistance SiCr bias lines with typical actuation voltage around 30-45 V

Optical and mechanical performance of a novel magnetically actuated MEMS-based optical switch

A novel magnetically actuated 8/spl times/8-port MEMS-based fiber-optic switch is described. Fiber-to-fiber insertion loss measurements of six 8/spl times/8 switch units show average and worst-case insertion loss of 1.3 dB and 2 dB, respectively. Low insertion loss is achieved through a unique MEMS design that uses anisotropically etched single-crystal silicon sidewalls to provide a global mechanical alignment stop for an array of MEMS mirrors. This alignment surface produces a uniform and repeatable mirror angle across the mirror array. Mirror misalignment is attributed to the surface roughness of the silicon sidewalls. Repeated interferometric measurements of the mirrors of 24 8/spl times/8 switch units show repeatability of the mirror angle of 3/spl times/10/sup -3/ degrees, while the uniformity of the mirror angle across the MEMS array is 2/spl times/10/sup -2/ degrees, in agreement with the angular error predicted from measurements of sidewall surface roughness. In turn, the average repeatability and uniformity of the insertion loss are 0.01 dB and 1 dB, respectively, in agreement with predictions based on the interferometric measurements. Finally, the unique dynamics of the magnetic actuation and electrostatic addressing scheme are described. Measurements show that fast switching can be achieved by driving the mirrors with a magnetic pulse that is faster than the mechanical resonant frequency of the mirror, relying on an electrostatic clamping force to capture the mirror as it overshoots the magnetic field angle. This actuation scheme is shown to result in switching times of 8.5 ms to 13.5 ms, but requires accurate control of the kinetic energy of the mirror.

Pigtailed tree-structured 8/spl times/8 LiNbO/sub 3/ switch matrix with 112 digital optical switches

We report on integrated optics Ti:LiNbO/sub 3/-based 8/spl times/8 switch matrices. The matrix design uses a tree structure with 112 digital optical switches as switch elements. The matrix, which has been pigtailed and packaged in an open package for convenient system demonstrator use, exhibits a worst case insertion loss of less than 15 dB. >

Liquid crystal 1 × N optical switch

The design, experimental results, and analysis of a 1 x N ferroelectric liquid-crystal optical switch based on polarization rotation are reported. The switch is broadband and tolerant to errors in the ferroelectric liquid-crystal tilt angle and cell thickness. Moreover, the cross talk in the switch is noncumulative and independent of the switch size N. The results of an experimental 1 x 4 switch are presented. The switch has a signal-to-cross-talk ratio ranging from 21.6 to 37.1 dB, a switching time of 50 microsec, and a worst-case insertion loss of 3.5 dB.