Browse Topic: Waveguides

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Evaluation of Local and Global Diagnostics for the Integration of Stochastic Time Series Models and Variational Autoencoders: Experimental Assessment on a Full Scale Helicopter BladeF-0080-2024-13715/7/2024
In this work, a unified framework integrating global and local SHM methods for structural health monitoring (SHM) of rotorcraft structures is proposed. This framework integrates both "local" ultrasonic-guided wave-based and "global" vibration-based SHM schemes for tackling damage detection, identification, and quantification under uncertainty. The local SHM is completed by training a variation of variational auto-encoder (MMD-VAE) along with feed-forward neural networks (FFNN). The compressed latent space vector obtained during the training process is applied to achieve both signal reconstruction and state prediction. In terms of the global model, functionally pooled auto-regressive models with exogenous excitation (VFP-ARX) models are applied including to capture low-frequency vibrations. The complete experimental evaluation and assessment of the proposed framework are presented for an Airbus H125 helicopter blade under both low-frequency vibrations and ultrasonic guided waves for SHM
Fan, Yiming, Kopsaftopoulos, Fotis, Forrester, David, Zhou, Peiyuan
Compact Infrared SpectrometerTBMG-384732/1/2021
Mobile phones can do almost anything. With these devices, it might even be possible to ascertain a beerā€™s alcohol content or how ripe a piece of fruit is. The infrared spectrometers used today for chemical analyses generally weigh several kilograms and are difficult to integrate into a handheld device.
Soft Prosthetic Hand Feels Surroundings via Stretchable Optical WaveguidesTBMG-372007/1/2020
Fluid-powered soft actuators have shown potential in applications such as prosthetics and orthotics due to their natural motion. Robots using these actuators require stretchable sensors that can be embedded in their bodies for sophisticated functions; however, these sensors usually rely on the electrical properties of materials and composites to measure a signal and many suffer from hysteresis, complex fabrication, environmental instability, and material incompatibility with soft actuators.
Moving Precision Communication, Metrology, Quantum Applications from Lab to ChipTBMG-368785/1/2020
The field of photonic integration ā€” the area of photonics in which waveguides and devices are fabricated as an integrated system onto a flat wafer ā€” is relatively young compared to electronics. Photonic integration has focused on communications applications traditionally fabricated on silicon chips, because these are less expensive and more easily manufactured.
Optical Gyroscope-on-a-ChipTBMG-363654/1/2020
Gyroscopes are devices that help vehicles, drones, and wearable and handheld electronic devices know their orientation in three-dimensional space. Originally, gyroscopes were sets of nested wheels, each spinning on a different axis. But in a cellphone, a microelectro-mechanical sensor (MEMS) measures changes in the forces acting on two identical masses that are oscillating and moving in opposite directions. These MEMS gyroscopes are limited in their sensitivity, so optical gyroscopes have been developed to perform the same function but with no moving parts and a greater degree of accuracy using a phenomenon called the Sagnac effect.
Direct-Write Quantum Calligraphy in Monolayer SemiconductorsTBMG-346216/1/2019
In contrast with conventional light-emitting diodes (LEDs) that emit billions of photons simultaneously to form a steady stream of light, a single photon emitter (SPE) generates exactly one photon on demand, with each photon indistinguishable from another. These characteristics are essential for photon-based quantum technologies under development. In addition, such capabilities should be realized in a material platform that enables precise, repeatable placement of SPEs in a fully scalable fashion compatible with existing semiconductor chip manufacturing.
Programming Light on a ChipTBMG-346066/1/2019
Microwave signals are ubiquitous in wireless communications but interact too weakly with photons. A technique was developed to fabricate high-performance optical microstructures using lithium niobate, a material with powerful electro-optic properties. The new integrated photonics platform can store light and electrically control its frequency (or color) in an integrated circuit. The platform draws inspiration from atomic systems and could have a wide range of applications including photonic quantum information processing, optical signal processing, and microwave photonics.
Uncertainty Quantification of Guided Waves Propagation for Active Sensing Structural Health MonitoringF-0075-2019-146165/13/2019
Guided-wave-based acousto-ultrasound structural health monitoring (SHM) methods have attracted the interest of the SHM community as guided waves can travel long distances without significant dissipation and are capable of detecting small damage sizes of several types. However, when subject to changing environmental and operational conditions (EOC), guided-wave-based methods may give false indications of damage as they exhibit increased sensitivity to varying EOC. In order to improve the reliability and enable the large-scale applicability of these methods, and to build a robust SHM system, it is necessary to quantify the uncertainty in guided wave propagation due to changing EOC. In this paper, a rigorous investigation on the uncertainty involved in the propagation of Lamb waves due to the variation in temperature and material properties of nominally-identical structures has been performed both numerically and experimentally. A high fidelity finite element model is established to study
Ahmed, Shabbir, Kopsaftopoulos, Fotis
Switch Controls Light on a Nanoscale for Faster Information ProcessingTBMG-3311110/1/2018
Photons, or units of light, are faster than electrons and could, therefore, process information faster from smaller chip structures. A switch was designed that bypasses a tendency for the unwanted absorption of light when using surface plasmons, or light coupled to oscillations of free electron clouds, to help confine light to a nanoscale. Even though plasmonics downsizes light, photons also get lost, or absorbed, rather than transferred to other parts of the computer chip when they interact with plasmons.
Conformal Metasurface Coating Eliminates Crosstalk and Shrinks WaveguidesTBMG-3309110/1/2018
Researchers have developed a method to simultaneously control diverse optical properties of dielectric waveguides by using a two-layer coating, each layer with a near-zero thickness and weight.
Researchers Create Precision Optical Components with Inkjet PrintingTBMG-328819/1/2018
Researchers have developed an inkjet printing technique that can be used to print optical components such as waveguides. Because the printing approach can also fabricate electronics and microfluidics, it could advance a variety of devices such as optical sensors used for health monitoring and lab-on-a-chip devices that integrate and automate multiple laboratory functions onto a chip.
Tech Briefs: September 201818AERP099/1/2018
Enhanced SATCOMs for Unmanned Aerial Systems The Bus Too Tough to Die Combating Infrared Threats on the Battlefield Optical Interconnect Design Challenges in Space High-Performance Computing for the Next-Generation Combat Vehicle Merging Antenna and Electronics Boosts Energy and Spectrum Efficiency Integrated Magneto-Optical Devices for On-Chip Photonic Systems Development of magneto-optical (MO) materials could lead to a range of nonreciprocal optical devices for emerging standardized photonic integrated circuit (PIC) fabrication processes. Low Power Optical Phase Array Using Graphene on Silicon Photonics Electrostatic doping of 2D materials embedded in waveguides could enable ultrafast devices with unprecedented power. Spatial Resolution and Contrast of a Focused Diffractive Plenoptic Camera New technology captures spectral and spatial information of a scene in one snapshot while raising pixel counts and improving image quality. Ultracompact, High-Speed Field-Effect Optical
Ultracompact, High-Speed Field-Effect Optical ModulatorsTBMG-329079/1/2018
The major goals of this research project included two parts. First, an ultracompact plasmonic electro-optical (EO) modulator was to be developed and investigated for efficient intensity modulation. Second, an ultracompact and high-speed EO modulator based on a dielectric platform was to be developed for straightforward integration with existing CMOS technology. Both modulators were targeted to facilitate next-generation interconnects for integrated photonic circuits.
Ultracompact, High-Speed Field-Effect Optical Modulators18AERP09_109/1/2018
Conductive oxides-based modulator devices could provide promising candidates for ultra-compact and ultra-fast optical interconnects in future integrated photonic circuits. Army Research Office, Research Triangle Park, North Carolina The major goals of this research project included two parts. First, an ultracompact plasmonic electrooptical (EO) modulator was to be developed and investigated for efficient intensity modulation. Second, an ultracompact and high-speed EO modulator based on a dielectric platform was to be developed for straightforward integration with existing CMOS technology. Both modulators were targeted to facilitate next-generation interconnects for integrated photonic circuits. This work performed on this project explored novel conductive oxide-based slot waveguides based on the unique properties of indium-tin-oxide (ITO). This research was one of the first experimental attempts to demonstrate optical modulators at nanoscale, and one of the first systematic
Hirschman, Karl
Verification of Discrete and Packaged Photonic Device Technology ReadinessARP6318 (Current)8/20/2018
This document is intended for discrete and integrated digital, wavelength division multiplexing (WDM), and analog/radio frequency (RF) photonic components developed for eventual transition to aerospace platforms. The document provides the reasons for verification of photonic device life test and packaging durability. The document focuses on pre-qualification activity at the optical component level to achieve TRL 6. The recommended tests in this document are intended to excite typical failure mechanisms encountered with photonic devices in an aerospace operating environment, and to build confidence that a technology is qualifiable during a programā€™s engineering and manufacturing development phase. This recommended practice is targeting components to support electrical-to-optical, optical-to-electrical, or optical-to-optical functionality. Passive optical waveguide, fiber optic cable, and connector components that are integral to a photonic package are included. Component and photonic
AS-3 Fiber Optics and Applied Photonics Committee
Integrating Optical Components into Existing Chip DesignsTBMG-290566/1/2018
Moving from electrical communication to optical communication is attractive to chip manufacturers because it could significantly increase chipsā€™ speed and reduce power consumption, an advantage that will grow in importance as chipsā€™ transistor count continues to rise.
A Nondestructive Evaluation and Structural Health Monitoring Framework for X-COR Sandwich CompositesF-0074-2018-128865/14/2018
ABSTRACT A combination of nondestructive evaluation (NDE) and structural health monitoring technique has been used to detect and localize in situ damage in X-COR sandwich composites. The NDE techniques, flash thermography and ultrasonic C-Scan, were used, and the inspection results showed promising capabilities as well as their inherent limitations. Subsequently, a guided wave based active interrogation technique was used to enable real-time damage detection and localization capabilities. Macro fiber composite and piezoelectric wafers were used for actuation and sensing, and the interaction of guided waves with the primary damage modes, delaminations and foam core separations, were studied. The results showed that delaminations lead to the guided wave mode conversion phenomenon within the material discontinuity area. A multidimensional signal processing technique, which was developed with a real-time and reference-free perspective, was used to analyze the converted wave modes in the
Li, Guoyi, Huff, Daniel, Neerukatti, Rajesh, Rajadas, Abhishek, Chattopadhyay, Aditi
High Temperature Graphene-Peek AdhesiveTBMG-2795312/1/2017
Joining of composites can be a challenging issue. If adhesives are used, the joints are permanent and cannot be undone. If they need to be undone, inserts are often used and these inserts increase cost and weight. Additionally, fibers can be cut in the process leading to a part with weakened mechanical properties.
High Temperature Graphene-Peek Adhesive17AERP12_0912/1/2017
Compounding graphene into polymers has the potential to improve various material properties, even at very low concentrations. Armament Research, Development and Engineering Center, Watervliet, New York Joining of composites can be a challenging issue. If adhesives are used, the joints are permanent and cannot be undone. If they need to be undone, inserts are often used and these inserts increase cost and weight. Additionally, fibers can be cut in the process leading to a part with weakened mechanical properties. Even with these drawbacks, most components that need to be joined are threaded together, allowing for removal of the parts at a later time. However, threaded connections are costly to design and manufacture, and are often the location of fatigue failures due to their inherent stress concentrations. From an environmental and cost standpoint, there is a large waste associated with the removal of material to form the threads, even more so in sectored threads, where up to half of
Lens-Coupled Dielectric WaveguidesTBMG-251678/1/2016
NASAā€™s Jet Propulsion Laboratory has developed a low-loss dielectric waveguide that provides a simple, versatile, and flexible transmission medium. Dielectric waveguides ā€” long, solid pieces of dielectric that confine electromagnetic waves ā€” offer high bandwidth and low transmission loss compared to conventional metallic waveguides. Despite these advantages, practical use of these waveguides has been limited because a large fraction of signal power is lost at the state-of-the-art interconnects joining conventional metallic waveguides and dielectric waveguides. JPLā€™s interconnect solution uses lens coupling to reduce these losses by a factor of 10 or more, yielding a reliable, cost-effective alternative to conventional waveguides.
Advanced Laser Welding Technology Meets the Challenges of Medical Device ManufacturingTBMG-243764/1/2016
The medical industry continues to develop new devices that are smaller in size and more sophisticated in functionality. From in vitro diagnostics and treatment of chronic disease to completely taking over bodily functions, todayā€™s medical devices are performing tasks that were hardly even imagined just a decade ago. In every case, their design requires perfection in form and function, and new assembly technologies are needed to meet these challenging requirements.
Quantitative Diagnostics of Multilayered Composite Structures with Ultrasonic Guided WavesTBMG-2350312/1/2015
Aging infrastructure has a major impact on safety, increasing the need to assess damage severity. Machinery, systems, and components such as airplanes, cars, pumps, and pipes in the oil and chemical industry are subject to varying cyclic service loading and environmental influences. Sometimes multilayered coatings are used, requiring a high-resolution inspection to confirm the presence of a defect such as a delamination, and accurately locate and quantify its size. Highly attenuating materials may significantly increase the inspection time while limiting defect observability. Guided waves have been recognized as having excellent potential for nondestructive inspection. However, the presence of viscoelastic coatings used for corrosion protection is one of the major obstacles for guided wave inspection.
Automatic-Alignment Fiber Optic Coupling System for Optimal Signal TransmissionTBMG-203458/1/2014
Using the current method of characterizing waveguides manufactured for research in optical communications, it can take up to 8 hours to characterize the waveguides on a single silicon wafer. Using the automatic computer automation system developed, the characterization process has been reduced to less than an hour. After the silicon wafer containing the waveguides is manufactured, the waveguides must be evaluated to determine the optical characteristics of the various waveguides on the silicon wafer.
Oil Pipeline Fault Detection System Determines Material Permittivity at Microwave FrequenciesTBMG-1752710/1/2013
Researching fault location techniques for the oil industry requires data on the complex permittivity of the polyamide Rilsan at microwave frequencies. Rilsan is a vital material used in oil pipe construction. Currently there is no published data for the complex permittivity of Rilsan. The task for this project was to develop an accurate method to measure the complex permittivity of Rilsan to gain an understanding of the dielectric relaxations that occur within it. A fast, accurate method was developed using a vector network analyzer (VNA) and rectangular waveguide.
Using Polyimide In 3D Thin Film Multilayer CircuitryTBMG-1751910/1/2013
Today, the cost and complexity of all platforms and systems in military and defense technologies are being challenged by the need for high functionality in smaller but less expensive architecture, especially in light of current national budget challenges. In the area of RF and microwave electronics it is becoming evident that a move from two dimensional (2D) planar circuitry architecture to three dimensional (3D) thin film multilayer technology can result in dramatic reduction of chip size, increase of operation speed, and lower total module costs.
High-Power, High-Speed Electro-Optic Pockels Cell ModulatorTBMG-172029/1/2013
Electro-optic modulators rely on a change in the index of refraction for the optical wave as a function of an applied voltage. The corresponding change in index acts to delay the wavefront in the waveguide. The goal of this work was to develop a high-speed, highpower waveguide-based modulator (phase and amplitude) and investigate its use as a pulse slicer. The key innovation in this effort is the use of potassium titanyl phosphate (KTP) waveguides, making the high-power, polarization- based waveguide amplitude modulator possible. Furthermore, because it is fabricated in KTP, the waveguide component will withstand high optical power and have a significantly higher RF modulation figure of merit (FOM) relative to lithium niobate. KTP waveguides support highpower TE and TM modes ā€” a necessary requirement for polarization-based modulation as with a Pockels cell.
On-Chip Power-Combining for High-Power Schottky Diode- Based Frequency MultipliersTBMG-154671/1/2013
A 1.6-THz power-combined Schottky frequency tripler was designed to handle approximately 30 mW input power. The design of Schottky-based triplers at this frequency range is mainly constrained by the shrinkage of the waveguide dimensions with frequency and the minimum diode mesa sizes, which limits the maximum number of diodes that can be placed on the chip to no more than two. Hence, multiple-chip power-combined schemes become necessary to increase the power-handling capabilities of high-frequency multipliers. However, the traditional powercombining topologies that are used below 1 THz present some inconvenience beyond 1 THz. The use of Y-junctions or hybrid couplers to divide/combine the input/output power at these frequency bands increases unnecessarily the electrical path of the signal in the range of frequencies where waveguide losses are considerable. Also, guaranteeing a perfect alignment of the very small chips during assembly, in order to preserve the balanced nature of the
Adjusting Permittivity by Blending Varying Ratios of SWNTsTBMG-1508511/1/2012
A new composite material of singlewalled carbon nanotubes (SWNTs) displays radio frequency (0 to 1 GHz) permittivity properties that can be adjusted based upon the nanotube composition. When varying ratios of raw to functionalized SWNTs are blended into the silicone elastomer matrix at a total loading of 0.5 percent by weight, a target real permittivity value can be obtained between 70 and 3. This has particular use for designing materials for microwave lenses, microstrips, filters, resonators, high-strength/low-weight electromagnetic interference (EMI) shielding, antennas, waveguides, and low-loss magneto-dielectric products for applications like radome construction.
Theory of a Traveling Wave Feed for a Planar Slot Array AntennaTBMG-1486910/1/2012
Planar arrays of waveguide-fed slots have been employed in many radar and remote sensing applications. Such arrays are designed in the standing wave configuration because of high efficiency. Traveling wave arrays can produce greater bandwidth at the expense of efficiency due to power loss in the load or loads. Traveling wave planar slot arrays may be designed with a long feed waveguide consisting of centered-inclined coupling slots. The feed waveguide is terminated in a matched load, and the element spacing in the feed waveguide is chosen to produce a beam squinted from the broadside.
On-Wafer Measurement of a Multi-Stage MMIC Amplifier With 10 dB of Gain at 475 GHzTBMG-135485/1/2012
JPL has measured and calibrated a WR2.2 waveguide wafer probe from GGB Industries in order to allow for measurement of circuits in the 325ā€“500 GHz range. Circuits were measured, and one of the circuits exhibited 10 dB of gain at 475 GHz.
Mid- and Long-IR Broadband Quantum Well PhotodetectorTBMG-135805/1/2012
A single-stack broadband quantum well infrared photodetector (QWIP) has been developed that consists of stacked layers of GaAs/AlGaAs quantum wells with absorption peaks centered at various wavelengths spanning across the 9-to-11-Ī¼m spectral regions. The correct design of broadband QWIPs was a critical step in this task because the earlier implementation of broadband QWIPs suffered from a tuning of spectral response curve with an applied bias. Here, a new QWIP design has been developed to overcome the spectral tuning with voltage that results from nonuniformity and bias variation of the electrical field across the detector stacks with different absorption wavelengths.
Integrated Optics Achromatic Nuller for Stellar InterferometryTBMG-126861/1/2012
This innovation will replace a beam combiner, a phase shifter, and a mode conditioner, thus simplifying the system design and alignment, and saving weight and space in future missions. This nuller is a dielectric-waveguidebased, four-port asymmetric coupler. Its nulling performance is based on the mode-sorting property of adiabatic asymmetric couplers that are intrinsically achromatic. This nuller has been designed, and its performance modeled, in the 6.5-micrometer to 9.25-micrometer spectral interval (36% bandwidth). The calculated suppression of starlight for this 15-cm-long device is 10ā€“5 or better through the whole bandwidth. This is enough to satisfy requirements of a flagship exoplanet-characterization mission.
Analysis of Microwave RadiationTBMG-109099/1/2011
Microwave heating is an important process for many commercial, industrial, and household applications. Industrial microwave ovens are widely used for chemical processing, agri-food, medical products, and consumer products applications. Resonant cavities are often used to speed up chemical reactions, and have the advantages of being small and producing efficient distributions of microwave energy. These multimode cavities can be considered as batch ovens where products can be treated; alternatively, microwave tunnels with multiple waveguides can be used to provide continuous production.
Excitation of a Parallel Plate Waveguide by an Array of Rectangular WaveguidesTBMG-108299/1/2011
This work addresses the problem of excitation of a parallel plate waveguide by an array of rectangular waveguides that arises in applications such as the continuous transverse stub (CTS) antenna and dual-polarized parabolic cylindrical reflector antennas excited by a scanning line source. In order to design the junction region between the parallel plate waveguide and the linear array of rectangular waveguides, waveguide sizes have to be chosen so that the input match is adequate for the range of scan angles for both polarizations.
Ridge Waveguide Structures in Magnesium-Doped Lithium NiobateTBMG-101416/1/2011
This work proposes to establish the feasibility of fabricating isolated ridge waveguides in 5% MgO:LN. Ridge waveguides in MgO:LN will significantly improve power handling and conversion efficiency, increase photonic component integration, and be well suited to space-based applications. The key innovation in this effort is to combine recently available large, high-photorefractive-damage-threshold, z-cut 5% MgO:LN with novel ridge fabrication techniques to achieve high-optical power, low-cost, high-volume manufacturing of frequency conversion structures. The proposed ridge waveguide structure should maintain the characteristics of the periodically poled bulk substrate, allowing for the efficient frequency conversion typical of waveguides and the high optical damage threshold and long lifetimes typical of the 5% doped bulk substrate. The low cost and large area of 5% MgO:LN wafers, and the improved performance of the proposed ridge waveguide structure, will enhance existing measurement
Ridge Waveguide Structures in Magnesium-Doped Lithium NiobateTBMG-TB-0101416/1/2011
This work proposes to establish the feasibility of fabricating isolated ridge waveguides in 5% MgO:LN. Ridge waveguides in MgO:LN will significantly improve power handling and conversion efficiency, increase photonic component integration, and be well suited to space-based applications. The key innovation in this effort is to combine recently available large, high-photorefractive-damage-threshold, z-cut 5% MgO:LN with novel ridge fabrication techniques to achieve high-optical power, low-cost, high-volume manufacturing of frequency conversion structures. The proposed ridge waveguide structure should maintain the characteristics of the periodically poled bulk substrate, allowing for the efficient frequency conversion typical of waveguides and the high optical damage threshold and long lifetimes typical of the 5% doped bulk substrate. The low cost and large area of 5% MgO:LN wafers, and the improved performance of the proposed ridge waveguide structure, will enhance existing measurement
Dielectric Covered Planar Antennas at Submillimeter Wavelengths for Terahertz ImagingTBMG-98885/1/2011
Most optical systems require antennas with directive patterns. This means that the physical area of the antenna will be large in terms of the wavelength. When non-cooled systems are used, the losses of microstrip or coplanar waveguide lines impede the use of standard patch or slot antennas for a large number of elements in a phased array format.
Higher Order Mode Coupling in Feed Waveguide of a Planar Slot Array AntennaTBMG-96114/1/2011
A simple technique was developed to account for the higher order mode coupling between adjacent coupling slots in the feed waveguide of a planar slot array. The method uses an equation relating the slot impedance to the slot voltage and a reaction integral involving the equivalent magnetic current of the slot aperture and the magnetic field coupled from an adjacent slot.
In Situ Guided Wave Structural Health Monitoring SystemTBMG-90171/1/2011
Aircraft engine rotating equipment operates at high temperatures and stresses. Noninvasive inspection of microcracks in those components poses a challenge for nondestructive evaluation. A low-cost, low-profile, high-temperature ultrasonic guided wave sensor was developed that detects cracks in situ. The transducer design provides nondestructive evaluation of structures and materials.
Update on Waveguide-Embedded Differential MMIC AmplifiersTBMG-889012/1/2010
There is an update on the subject matter of ā€œDifferential InP HEMT MMIC Amplifiers Embedded in Waveguidesā€ (NPO-42857) NASA Tech Briefs, Vol. 33, No. 9 (September 2009), page 35. To recapitulate: Monolithic microwave integrated-circuit (MMIC) amplifiers of a type now being developed for operation at frequencies of hundreds of gigahertz contain InP high-electron-mobility transistors (HEMTs) in a differential configuration. The MMICs are designed integrally with, and embedded in, waveguide packages. The instant work does not mention InP HEMTs but otherwise reiterates part of the subject matter of the cited prior article, with emphasis on the following salient points:
Multiple Differential-Amplifier MMICs Embedded in WaveguidesTBMG-888812/1/2010
Compact amplifier assemblies of a type now being developed for operation at frequencies of hundreds of gigahertz comprise multiple amplifier units in parallel arrangements to increase power and/or cascade arrangements to increase gains. Each amplifier unit is a monolithic microwave integrated circuit (MMIC) implementation of a pair of amplifiers in differential (in contradistinction to single-ended) configuration.
Demonstration of a Submillimeter-Wave HEMT Oscillator Module at 330 GHzTBMG-80576/1/2010
In this work, radial transitions have been successfully mated with a HEMT-based MMIC (high-electron-mobility-transistor-based monolithic microwave integrated circuit) oscillator circuit. The chip has been assembled into a WR2.2 waveguide module for the basic implementation with radial E-plane probe transitions to convert the waveguide mode to the MMIC coplanar waveguide mode. The E-plane transitions have been directly integrated onto the InP substrate to couple the submillimeter-wave energy directly to the waveguides, thus avoiding wirebonds in the RF path. The oscillator demonstrates a measured 1.7 percent DC-RF efficiency at the module level.
MMIC Amplifiers and Wafer Probes for 350 to 500 GHzTBMG-80596/1/2010
Several different experimental monolithic microwave integrated circuit (MMIC) amplifiers have been designed to operate in frequency bands ranging from 350 to 500 GHz and were undergoing fabrication at the time of reporting the information for this article. Probes for on-wafer measurement of electrical parameters [principally, the standard scattering parameters (ā€œSā€ parameters)] of these amplifiers have been built and tested as essential components of systems to be used in quantifying the performances of the amplifiers. These accomplishments are intermediate products of a continuing effort to develop solid-state electronic amplifiers capable of producing gain at ever-higher frequencies, now envisioned to range up to 800 GHz. Such amplifiers are needed for further development of compact, portable imaging systems and scientific instruments for a variety of potential applications that include detection of hidden weapons, measuring winds, and measuring atmospheric concentrations of certain
Novel Microstrip-to-Waveguide Feed Employing a Double-Y JunctionTBMG-79365/1/2010
Previous microstrip-to-waveguide transitions either required a hermetically sealed waveguide configuration, or a balun that needed to be tuned according to the frequency band of interest. In this design, the balun is realized using a double-Y junction to transition from microstrip to coplanar strip feeding a quasi-Yagi dipole array (see figure). The length of the feed (Lf) extending into the waveguide is 15.54 mm. The length of the ground plane below the ULTRALAM substrate is 7.75 mm. The lengths L1, L2, and L3 are 8.50 mm, 4.38 mm, and 2.14 mm, respectively. These lengths were computed via a preliminary optimization aimed at improving the return loss at the band edges.
Improved Model of Spectral Response of an HEB MixerTBMG-TB-0074772/12/2010
Fringing fields and the inductance of the HEB microbridge are taken into account. An improved mathematical model enables the somewhat more accurate prediction of the spectral response of a mixer circuit (see figure) that comprises a twin-slot antenna coupled via coplanar waveguides to a hot-electron bolometer (HEB). The development of the improved model is part of a continuing effort to understand and overcome the limitations of circuit models in order to enhance capabilities for designing and analyzing heterodyne mixers to operate at frequencies in the terahertz range.
Quad-Chip Double-Balanced Frequency TriplerTBMG-71632/1/2010
Solid-state frequency multipliers are used to produce tunable broadband sources at millimeter and submillimeter wavelengths. The maximum power produced by a single chip is limited by the electrical breakdown of the semiconductor and by the thermal management properties of the chip. The solution is to split the drive power to a frequency tripler using waveguides to divide the power among four chips, then recombine the output power from the four chips back into a single waveguide.
Optical Tapers as White-Light WGM ResonatorsTBMG-TB-00663112/23/2009
Such resonators could be attractive for broad-band optical processing applications. A theoretical analysis has revealed that tapered optical waveguides could be useful as white-light whispering-gallerymode (WGM) optical resonators. The compactness and the fixed-narrow-frequency- band nature of the resonances of prior microdisk and microsphere WGM resonators are advantageous in low-power, fixed-narrow-frequency-band applications. However for optical-processing applications in which there are requirements for power levels higher and/or spectral responses broader than those of prior microdisk and microsphere WGM resonators, white-light WGM resonators in the form of optical tapers would be preferable.
Inventions Utilizing Microfluidics and Colloidal ParticlesTBMG-637012/1/2009
Several related inventions pertain to families of devices that utilize microfluidics and/or colloidal particles to obtain useful physical effects. The families of devices can be summarized as follows:
Differential InP HEMT MMIC Amplifiers Embedded in WaveguidesTBMG-56239/1/2009
Monolithic microwave integrated-circuit (MMIC) amplifiers of a type now being developed for operation at frequencies of hundreds of gigahertz contain InP high- electron-mobility transistors (HEMTs) in a differential configuration. The differential configuration makes it possible to obtain gains greater than those of amplifiers having the single-ended configuration. To reduce losses associated with packaging, the MMIC chips are designed integrally with, and embedded in, waveguide packages, with the additional benefit that the packages are compact enough to fit into phased transmitting and/or receiving antenna arrays.
Dual-Polarization, Sideband-Separating, Balanced Receiver for 1.5 THzTBMG-55058/1/2009
A proposed heterodyne receiver would be capable of detecting electromagnetic radiation in both of two orthogonal linear polarizations, separating sidebands, and providing balanced outputs in a frequency band centered at 1.5 THz with a fractional bandwidth >40 percent. Dual-polarization, sideband-separating, and balanced-output receivers are well- known and have been used extensively at frequencies up to about 100 GHz; and there was an earlier proposal for such a receiver for frequencies up to 900 GHz. However, the present proposal represents the first realistic design concept for such a receiver capable of operating above 1 THz. The proposed receiver is intended to be a prototype of mass-producible receiver units, operating at frequencies up to 6 THz, that would be incorporated into highly sensitive heterodyne array instruments to be used in astronomical spectroscopic and imaging studies.
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