Browse Topic: Amplifiers

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Going Beyond the Basics: Innovative Step Motor Designs Give Machine Designers More Options for Motion ControlTBMG-360022/1/2020
Machine and system designers now have greater options in choosing a motor to meet motion control requirements. While basic step motors with open-loop control schemes abound in the marketplace, different motor and drive designs offer interesting solutions for smarter, faster, quieter operations with more torque. Some incorporate smart drives for higher-level streaming commands or onboard motion control, while others add encoders for greater torque and accuracy. These options can offer better solutions as applications become more sophisticated and demanding, while companies address initiatives for greener operations. This article outlines different step motor options available on the market and considerations for their use.
Smartphone Test Spots Poisoned Water RiskTBMG-347317/1/2019
Researchers have developed a biosensor that attaches to a smartphone and uses bacteria to detect unsafe arsenic levels. The device generates easy-to-interpret patterns similar to volume-bars that display the level of contamination.
Hardware Design of a High Dynamic Range Radio Frequency (RF) Harmonic Measurement SystemTBMG-337622/1/2019
Radio frequency (RF) circuit elements that are traditionally considered to be linear frequently exhibit nonlinear properties that affect the intended operation of many other RF systems. Devices such as RF connectors, antennas, attenuators, resistors, and dissimilar metal junctions generate nonlinear distortion that degrades primary RF system performance. The communications industry is greatly affected by these unintended and unexpected nonlinear distortions. The high transmit power and tight channel spacing of the communication channel makes communications very susceptible to nonlinear distortion.
Gated Chopper Integrator (GCI)TBMG-3339212/1/2018
Microvolt-level signals require gains of at least a thousand. Offsets and noise in the amplifier chain will be amplified by the same amount, which can saturate the amplifier or swamp the signal so it is not resolvable. Other methods use chopping and/or autozero techniques to lower the offset and noise. The key disadvantages of these methods are they require filters before and/or after demodulation of the amplified signal and delay equalization to account for the delay through the amplifier(s) prior to the demodulator. The gain of these circuits is generally limited to fixed values determined by resistors. These methods are also susceptible to transient noise associated with the switching action of the modulator.
Acoustic Waves Offer Treatment for Kidney StonesTBMG-3324511/1/2018
Researchers are investigating the use of time reversal (TR) signal processing to focus waves sound with high amplitudes in a room. In biomedical applications, focused ultrasound can be used in lithotripsy procedures for treating kidney stones or to target brain tumors.
Simplifying Access to High Energy Sub-5-fs PulsesTBMG-3327611/1/2018
In order to make ultrafast pulses accessible to the broadest possible field of applications, Coherent has been implementing a comprehensive program of design methodologies, materials qualification and sourcing and HALT/HASS testing protocols that go under the name of the Industrial Revolution in Ultrafast Science. This approach emphasizes performance, operational simplicity, repeatability and reliability.
Soft, Pliable, 3D Stretchable ElectronicsTBMG-3312010/1/2018
By stacking and connecting layers of stretchable circuits on top of one another, soft, pliable 3D stretchable electronics were fabricated that can pack a lot of functions while staying thin and small in size.
Compact Power Amplifier Solution for Electronic WarfareTBMG-3302210/1/2018
Wolfspeed, a Cree company, provides field-tested silicon carbide (SiC) and gallium nitride (GaN) power and RF solutions. As a leader in wide-bandgap semiconductor technology, Wolfspeed partners with designers to build faster, smaller, lighter, and more powerful electronic systems.
High-Power Solid-State Power Amplifier SystemTBMG-287154/1/2018
NASA Marshall Space Flight Center (MSFC) has developed a High-Power Solid-State Power Amplifier System that combines 1-KW modules (16 amps total) to generate up to 16KW of radio frequency (RF) power from 230 MHz. The NASA device is a first step toward increasing the power of solid-state power amp devices so that they might replace the more cumbersome vacuum tube amps for some applications. Also, when vacuum tube amps fail, a total power failure occurs. Since the NASA device is a system of amplifiers, it enables graceful failure, meaning one or more stages can fail and the system will continue to operate, although at reduced power.
Using Air Gaging for Measurement of Orthopedic DevicesTBMG-287444/1/2018
For patients, high-quality orthopedic components mean that implants can be kept for as long as possible, reducing or even eliminating the need for further procedures down the road. In order to ensure the level of quality required, many orthopedic device manufacturers use high-precision air gaging during development and in production.
Remote Detection of Electronic DevicesTBMG-285593/1/2018
Non-Linear Junction Detection is a well-known technique for detecting electronics that utilize semiconductor (solid-state) junctions. The current state of the art for finding hidden electronics — such as electronic eavesdropping devices — using this technology has a maximum range of about 2 m, and more typically between 6 and 12”.
Shaper Design in CMOS for High Dynamic RangeTBMG-275519/1/2017
Front-end electronics for capacitive sensors typically include a preamplifier followed by a filter. The preamplifier provides low-noise amplification of the signals induced in the sensor electrodes. The filter, by properly limiting the signal bandwidth, maximizes the Signal-to-Noise (S/N) ratio. Additionally, the filter limits the duration of the output signal associated with the measured event and, for those sensors where the induced signal is relatively slow, it maximizes the signal amplitude.
Chip-Sized Terahertz Modulator for Faster Data TransmissionTBMG-270446/1/2017
Tufts University engineers have invented a chip-sized, high-speed modulator that operates at terahertz (THz) frequencies at room temperature and at low voltages without consuming DC power. The discovery could transmit data at significantly higher speeds than currently possible.
Wideband, GaN MMIC, Distributed Amplifier-Based Microwave Power ModuleTBMG-242624/1/2016
Historically, the term microwave power module (MPM) has been associated with a small, fully integrated, self-contained radio frequency (RF) amplifier that combines both solid-state and microwave vacuum electronics technologies. Typically, the output power of these MPMs is on the order of about 100 Watts CW over an octave bandwidth. The MPMs require both a solid-state amplifier at the front end and a microwave vacuum electronics amplifier at the back end. However, such MPMs cannot be utilized for communications because the MPMs are not optimized for linearity or efficiency. Also, the MPMs can be very expensive to manufacture, particularly when modules are produced in very small quantities for space applications. Also, a kilovolt (kV) class power supply is required to power the traveling-wave tube amplifier, which is a part of the microwave vacuum electronics.
Miller-Jogging for Synthesizer Lock Algorithm ExtensionTBMG-240923/1/2016
The University of California Los Angeles (UCLA) has developed a wide range of CMOS (complementary metal–oxide–semiconductor) phase lock loop (PLL) chips with self-healing/self-calibration capabilities, allowing them to adapt, on the fly, to changes in temperature and other environment parameters. All CMOS PLLs typically have three major settings that self-healing and calibration can adjust: VCO (voltage controlled oscillator) coarse tuning, divider tuning, and CML (current mode logic) tuning. Previous work done at UCLA uses these “knobs” or settings exclusively to self-lock a PLL. Locking criteria is established by monitoring the control voltage with an analog-to-digital converter (ADC) to see if the PLL loop is settled in the middle of the range (locked), or sitting at the ground or supply (unlocked).
Ultra-High-Power W-Band/F-Band Schottky Diode-Based Frequency MultipliersTBMG-236561/1/2016
All-solid-state, room-temperature, multipixel, sub milli meter-wave re ceiv ers are in demand for efficient spatial mapping of a planet’s atmosphere composition and wind velocities for future NASA missions to Venus, Jupiter, and its moons. Roomtemperature operation based on Schottky diode technology is a must in order to avoid cryogenic cooling and enable long-term missions. This technology is also being successfully applied for very-high-resolution imaging radars for standoff detection of concealed weapons. For submillimeter-wave radar imaging, the main issue is that, in order to reach video frame rates with high image pixel density, multi-pixel focal plane transceiver arrays are needed to illuminate targets with many radar beams simultaneously.
High-Power, Solid-State Power Amplifier SystemTBMG-2324411/1/2015
The purpose of the invention was to increase the operational power levels of solid-state power amplifiers using state-ofthe- art power amplifier design and combining methodology. Using 1-kW RF modules and proper RF combining techniques, a system was built that generated 16 kW of RF power for use in electric plasma propulsion. The 1-kW units were fault-protected against excessive power, excessive current, and high VSWR, since the RF power devices are extremely sensitive to variations in their operating conditions.
Unmanned Ground Vehicle Communications RelaysTBMG-226518/1/2015
The need for a high-bandwidth communication link to carry multiple video channels from a mobile robot (unmanned ground vehicle, or UGV) back to a control station requires using high-frequency RF communication links. These links are mostly line-of-sight, often limiting the flexibility of the robot’s movement. The Autonomous Mobile Communication Relays project demonstrated the capability of autonomous slave robots to provide communication-relaying capability for a lead robot exploring an unknown environment.
Electronic Warfare TechnologyTBMG-218814/1/2015
Military electronic warfare (EW) systems including navigation, radar guidance, terrain mapping and others, require lightweight compact components, with radio frequency (RF) output power levels to several kilowatts typically needed to meet system requirements. As GaN transistor technology advances in frequency and power output, solid state power amplifiers (SSPAs) have begun replacing traveling wave tubes (TWTs) at frequencies up to 6 GHz. The utilization of this technology results in a lower cost and greater efficiency over the life of a product.
Test Results of A Sensor-Less, Highly Nonlinear Electro-Mechanical Brake2014-01-25419/28/2014
The electro-mechanical brake (EMB) of Vienna Engineering (VE) uses a highly non-linear mechanism to create the high pressing force of the pad. The advantage is that the pad moves very fast when the pad pressing force is low and moves slower with increasing pressing force. The normal force in EMBs is often controlled by observing mechanical deformation to conclude to stress or force, commonly using strain gauges. It causes costs of the gauge itself and attaching them to e.g. the caliper and a sensitive amplifier. The full gauge equipment goes into the safety-related brake control system. The faintest damage (e.g. stone impacts, heat) gets the vehicle to the repair shop making expensive replacement necessary. To avoid the costs of the force measurement in the safety related system VE took the electrical motor measurements from the very beginning of the brake development for EMB control. These electrical values (position, rpm, current, voltage) are already present to operate the brushless DC motor and need no additional parts. In this paper a comparison is done between the effort to use force measurement and the sensor-less approach of VE. Safety concepts with gauges and without (using motor data) are discussed as well as long- and short term accuracy. With the constant torque of the non-linear VE EMB the motor current does not directly represent the force on the pad. In this paper it is discussed how normal force can be calculated in the non-linear brake. The theory is compared with test stand results. The potential of improved algorithm for calculation is discussed.
Putz, Michael Herbert, Wunsch, Christian, Schiffer, Markus, Peternel, Jure
Micromachined Thermopile Arrays with Novel Thermo-electric MaterialsTBMG-199086/1/2014
Future missions to outer planets will have stringent limits on payload mass. Thermal imaging instruments to map planetary surfaces will be part of those payloads, and, consequently, will have to be compact and low mass. For thermal instruments, another key requirement will be state-of-the-art, highly sensitive detectors. Thermopiles are prime candidates for high-resolution thermal mapping in the far-infrared (17- to 250-μm wavelength) spectral range. Thermopile detector arrays can be made to be very lightweight and compact. Furthermore, they require very few ancillary components (e.g., readout electronics, optics, amplifiers), which can add to instrument volume and mass. The implementation of thermopiles on these missions is likely because they (1) generate an output voltage that is proportional to the incoming radiation within the spectral range being mapped; (2) do not require an electrical bias or an optical chopper; (3) have negligible 1/f noise; (4) are radiation hard; and (5) have a reported specific detectivity of 1 × 109 cm·Hz1/2/W at room temperature.
RF FPGAs for Multi-Function SystemsTBMG-194174/1/2014
State-of-the-art RF integrated circuits (ICs) achieve high performance via custom circuit elements with dedicated signal paths for application-specific functions, but long design lead times and non-recurring fabrication costs increase time-to-market for new applications and limit reuse. The key to developing an RF FPGA (radio frequency field-programmable gate array) is to provide RF switching components with very low insertion loss and high isolation that can be integrated with high-performance RF circuits in silicon germanium (SiGe) and gallium nitride (GaN) technologies, and integrating these circuits in a reconfigurable topology to allow an RF FPGA to perform a wide variety of functions.
Submillimeter Planetary Atmospheric Chemistry Exploration SounderTBMG-167647/1/2013
A report describes the Submillimeter Planetary Atmospheric Chemistry Exploration Sounder (SPACES), a highsensitivity laboratory breadboard for a spectrometer targeted at orbital planetary atmospheric analysis. The frequency range is 520 to 590 GHz, with a target noise temperature sensitivity of 2,500 K for detecting water, sulfur compounds, carbon compounds, and other atmospheric constituents. SPACES is a prototype for a powerful tool for the exploration of the chemistry and dynamics of any planetary atmosphere. It is fundamentally a single-pixel receiver for spectral signals emitted by the relevant constituents, intended to be fed by a fixed or movable telescope/antenna. Its front-end sensor translates the received signal down to the 100-MHz range where it can be digitized and the data transferred to a spectrum analyzer for processing, spectrum generation, and accumulation.
Feedback Augmented Sub-Ranging (FASR) QuantizerTBMG-1524912/1/2012
This innovation is intended to reduce the size, power, and complexity of pipeline analog-to-digital converters (ADCs) that require high resolution and speed along with low power. Digitizers are important components in any application where analog signals (such as light, sound, temperature, etc.) need to be digitally processed. The innovation implements amplification of a sampled residual voltage in a switched capacitor amplifier stage that does not depend on charge redistribution. The result is less sensitive to capacitor mismatches that cause gain errors, which are the main limitation of such amplifiers in pipeline ADCs. The residual errors due to mismatch are reduced by at least a factor of 16, which is equivalent to at least 4 bits of improvement. The settling time is also faster because of a higher feedback factor.
670-GHz Down- and Up-Converting HEMT-Based MixersTBMG-1525012/1/2012
A large category of scientific investigation takes advantage of the interactions of signals in the frequency range from 300 to 1,000 GHz and higher. This includes astronomy and atmospheric science, where spectral observations in this frequency range give information about molecular abundances, pressures, and temperatures of small-sized molecules such as water. Additionally, there is a minimum in the atmospheric absorption at around 670 GHz that makes this frequency useful for terrestrial imaging, radar, and possibly communications purposes. This is because 670 GHz is a good compromise for imaging and radar applications between spatial resolution (for a given antenna size) that favors higher frequencies, and atmospheric losses that favor lower frequencies. A similar trade-off applies to communications link budgets: higher frequencies allow smaller antennas, but incur a higher loss.
Amplifier Module for 260-GHz Band Using Quartz Waveguide TransitionsTBMG-1506811/1/2012
Packaging of MMIC LNA (monolithic microwave integrated circuit low-noise amplifier) chips at frequencies over 200 GHz has always been problematic due to the high loss in the transition between the MMIC chip and the waveguide medium in which the chip will typically be used. In addition, above 200 GHz, wirebond inductance between the LNA and the waveguide can severely limit the RF matching and bandwidth of the final waveguide amplifier module.
Ka-Band Waveguide Three-Way Serial Combiner for MMIC AmplifiersTBMG-1485510/1/2012
In this innovation, the three-way combiner consists internally of two branchline hybrids that are connected in series by a short length of waveguide. Each branch-line hybrid is designed to combine input signals that are in phase with an amplitude ratio of two. The combiner is constructed in an E-plane splitblock arrangement and is precision machined from blocks of aluminum with standard WR-28 waveguide ports. The port impedances of the combiner are matched to that of a standard WR-28 waveguide. The component parts include the power combiner and the MMIC (monolithic microwave integrated circuit) power amplifiers (PAs). The three-way series power combiner is a sixport device. For basic operation, power that enters ports 3, 5, and 6 is combined in phase and appears at port 1. Ports 2 and 4 are isolated ports. The application of the three-way combiner for combining three PAs with unequal output powers was demonstrated.
Ultra-Compact Motor ControllerTBMG-1492410/1/2012
This invention is an electronically commutated brushless motor controller that incorporates Hall-array sensing in a small, 42-gram package that provides 4096 absolute counts per motor revolution position sensing. The unit is the size of a miniature hockey puck, and is a 44-pin male connector that provides many I/O channels, including CANbus, RS-232 communications, general-purpose analog and digital I/O (GPIO), analog and digital Hall inputs, DC power input (18–90 VDC, 0–l0 A), three-phase motor outputs, and a strain gauge amplifier.
670-GHz Schottky Diode-Based Subharmonic Mixer With CPW Circuits and 70-GHz IFTBMG-142278/1/2012
GaAs-based, sub-harmonically pumped Schottky diode mixers offer a number of advantages for array implementation in a heterodyne receiver system. Since the radio frequency (RF) and local oscillator (LO) signals are far apart, system design becomes much simpler.
Self-Nulling Lock-in Detection Electronics for Capacitance Probe ElectrometerTBMG-142318/1/2012
A multi-channel electrometer voltmeter that employs self-nulling lock-in detection electronics in conjunction with a mechanical resonator with non-contact voltage sensing electrodes has been developed for space-based measurement of an Internal Electrostatic Discharge Monitor (IESDM). The IESDM is new sensor technology targeted for integration into a Space Environmental Monitor (SEM) subsystem used for the characterization and monitoring of deep dielectric charging on spacecraft.
885-nm Pumped Ceramic Nd:YAG Master Oscillator Power Amplifier Laser SystemTBMG-141317/1/2012
The performance of a traditional diode pumped solid-state laser that is typically pumped with 808-nm laser diode array (LDA) and crystalline Nd:YAG was improved by using 885-nm LDAs and ceramic Nd:YAG. The advantage is lower quantum defect, which will improve the thermal loading on laser gain medium, resulting in a higher-performance laser. The use of ceramic Nd:YAG allows a higher Nd dopant level that will make up the lower absorption at the 885-nm wavelength on Nd:YAG.
High-Speed Scanning Interferometer Using CMOS Image Sensor and FPGA Based on Multifrequency Phase- Tracking DetectionTBMG-140567/1/2012
A sub-aperture stitching optical interferometer can provide a cost-effective solution for an in situ metrology tool for large optics; however, the currently available technologies are not suitable for high-speed and real-time continuous scan. NanoWave’s SPPE (Scanning Probe Position Encoder) has been proven to exhibit excellent stability and sub-nanometer precision with a large dynamic range. This same technology can transform many optical interferometers into real-time subnanometer precision tools with only minor modification. The proposed field-programmable gate array (FPGA) signal processing concept, coupled with a new-generation, highspeed, mega-pixel CMOS (complementary metal-oxide semiconductor) image sensor, enables high speed (>1 m/s) and real-time continuous surface profiling that is insensitive to variation of pixel sensitivity and/or optical trans mission/ reflection. This is especially useful for large optics surface profiling.
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 325–500 GHz range. Circuits were measured, and one of the circuits exhibited 10 dB of gain at 475 GHz.
Design and Performance of a Wideband Radio TelescopeTBMG-132744/1/2012
The Goldstone Apple Valley Radio Telescope (GAVRT) is an outreach project, a partnership involving NASA’s Jet Propulsion Laboratory (JPL ), the Lewis Center for Educational Research (LCER), and the Apple Valley Unified School District near the NASA Goldstone deep space communication complex. This educational program currently use s a 34 -meter antenna, DSS12, at Goldstone for classroom radio astronomy observations via the Internet. The current program utilizes DSS12 in two narrow frequency bands around S-band (2.3 GHz) and X-band (8.45 GHz), and is used by a training program involving a large number of secondary school teachers and their classrooms. To expand the program, a joint JPL/LCER project was started in mid-2006 to retrofit an additional existing 34-meter be am-waveguide antenna, D S S28, with wideband feeds and receivers to cove r the 0.5-to-14-GHz frequency bands.
Low-Noise, Large-Area Quad Photoreceivers Based on Low-Capacitance Quad PhotodiodesTBMG-130773/1/2012
The Laser Interferometry Space Antenna’s (LISAs) scientific mission to detect gravity waves demands stringent noise limits on the system components, especially the large-area quad photoreceiver front end, for ultra-high-precision (≈10 pm/Hz1/2) distance measurements. The optical LO (local oscillator) power on LISA is limited to 100 μW to keep power dissipation and thermal fluctuation low on the optical bench. Consequently, a large-area quad photoreceiver having an equivalent input current noise of the order of 1 pm/Hz1/2 is needed. Additionally, the quad photoreceiver must demonstrate low crosstalk between individual quadrants to allow accurate direction sensing of the incoming optical beam. This performance must be achieved over a bandwidth of 2 to 20 MHz to meet LISA’s requirements. Commercially available quad photodetectors do not have the combination of large area, low capacitance (and therefore low noise), and low crosstalk, which is critical for LISA’s scientific objectives.
Frequency to Voltage Converter Analog Front-End PrototypeTBMG-127842/1/2012
The frequency to voltage converter analog front end evaluation prototype (F2V AFE) is an evaluation board designed for comparison of different methods of accurately extracting the frequency of a sinusoidal input signal. A configurable input stage is routed to one or several of five separate, configurable filtering circuits, and then to a configurable output stage. Amplifier selection and gain, filter corner frequencies, and comparator hysteresis and voltage reference are all easily configurable through the use of jumpers and potentiometers.
Technique for Radiometer and Antenna Array Calibration — TRAACTBMG-126241/1/2012
detect minute amounts of emitted electromagnetic energy. Calibration of these receivers is vital to the accuracy of the measurements. Traditional calibration techniques depend on calibration reference internal to the receivers as reference for the calibration of the observed electromagnetic energy. Such methods can only calibrate errors in measurement introduced by the receiver only. The disadvantage of these existing methods is that they cannot account for errors introduced by devices, such as antennas, used for capturing electromagnetic radiation. This severely limits the types of antennas that can be used to make measurements with a high degree of accuracy. Complex antenna systems, such as electronically steerable antennas (also known as phased arrays), while offering potentially significant advantages, suffer from a lack of a reliable and accurate calibration technique.
Spectrally Compliant Waveforms for Wideband RadarTBMG-1228912/1/2011
Modern radars often require the use of wideband waveforms to perform high-resolution target imaging. In microwave systems, the bandwidth can be on the order of 1.5 GHz, while in UHF systems that typically operate between 200 and 500 MHz, the waveform bandwidth might exceed 200 MHz. A major issue in the operation of such systems is that they often overlap the spectrum used by other radars, and even the spectrum allocated for other types of systems such as communications and navigation devices.
Digital Interface Board to Control Phase and Amplitude of Four ChannelsTBMG-1222312/1/2011
An increasing number of parts are designed with digital control interfaces, including phase shifters and variable attenuators. When designing an antenna array in which each antenna has independent amplitude and phase control, the number of digital control lines that must be set simultaneously can grow very large. Use of a parallel interface would require separate line drivers, more parts, and thus additional failure points. A convenient form of control where single-phase shifters or attenuators could be set or the whole set could be programmed with an update rate of 100 Hz is needed to solve this problem.
Cryogenic 160-GHz MMIC Heterodyne Receiver ModuleTBMG-1221512/1/2011
A cryogenic 160-GHz MMIC heterodyne receiver module has demonstrated a system noise temperature of 100 K or less at 166 GHz. This module builds upon work previously described in “Development of a 150-GHz MMIC Module Prototype for Large-Scale CMB Radiation” (NPO-47664), NASA Tech Briefs, Vol. 35, No. 8 (August 2011), p. 27. In the original module, the local oscillator signal was saturating the MMIC low-noise amplifiers (LNAs) with power. In order to suppress the local oscillator signal from reaching the MMIC LNAs, the W-band (75–110 GHz) signal had to be filtered out before reaching 140–170 GHz. A bandpass filter was developed to cover 120–170 GHz, using microstrip parallelcoupled lines to achieve the desired filter bandwidth, and ensure that the unwanted W-band local oscillator signal would be sufficiently suppressed.
All-Solid-State 2.45-to-2.78-THz SourceTBMG-1222112/1/2011
Sources in the THz range are required in order for NASA to implement heterodyne instruments in this frequency range. The source that has been demonstrated here will be used for an instrument on the SOFIA platform as well as for upcoming astrophysics missions. There are currently no electronic sources in the 2–3-THz frequency range. An electronically tunable compact source in this frequency range is needed for lab spectroscopy as well as for compact space-deployable heterodyne receivers. This solution for obtaining useful power levels in the 2–3-THz range is based on utilizing power-combined multiplier stages. Utilizing power combining, the input power can be distributed between different multiplier chips and then recombined after the frequency multiplication.
Ka-Band, Multi- Gigabit-Per-Second TransceiverTBMG-1221912/1/2011
A document discusses a multi-Gigabitper- second, Ka-band transceiver with a software-defined modem (SDM) capable of digitally encoding/decoding data and compensating for linear and nonlinear distortions in the end-to-end system, including the traveling-wave tube amplifier (TWTA). This innovation can increase data rates of space-to-ground communication links, and has potential application to NASA’s future spacebased Earth observation system.
Aeroacoustics of Duct Branches-With Application to Silencers2011-24-02189/11/2011
The inclusion of flow-acoustic interaction effects in linear acoustic multiport models has been studied. It is shown, using a T-junction as illustration example, that as long the acoustic system is linear the required information is included in a scattering matrix obtained by experimental or numerical studies. Assuming small Mach numbers and low frequencies-as in most automotive silencer applications-the scattering matrix for the T-junction can be approximated using quasi-steady models. Models are derived that holds for all possible configurations of grazing and bias flow in the T-junctions. The derived models are then used to predict the performance of a novel silencer concept, where a resonator is formed by acoustically short-circuiting the inlet and outlet ducts of a flow reversal chamber. The agreement between experiments and simulations is excellent, justifying the use of the quasi-steady modeling approach.
Karlsson, Mikael, Abom, Mats, Glav, Ragnar
Control Program and Optical Improvements of Fresnel MicrospectrometerTBMG-110129/1/2011
This innovation is suitable for optical fiber communications and medical applications where multiple optical fibers are used.
Improvements in Speed and Functionality of a 670-GHz Imaging RadarTBMG-107228/1/2011
Significant improvements have been made in the instrument originally described in a prior NASA Tech Briefs article: “Improved Speed and Functionality of a 580-GHz Imaging Radar” (NPO-45156), Vol. 34, No. 7 (July 2010), p. 51. First, the wideband YIG oscillator has been replaced with a JPL-designed and built phase-locked, low-noise chirp source. Second, further refinements to the data acquisition and signal processing software have been performed by moving critical code sections to C code, and compiling those sections to Windows DLLs, which are then invoked from the main LabVIEW executive.
Development of a 150-GHz MMIC Module Prototype for Large-Scale CMB RadiationTBMG-107268/1/2011
HEMT-based receiver arrays with excellent noise and scalability are already starting to be manufactured at 100 GHz, but the advances in technology should make it possible to develop receiver modules with even greater operation frequency up to 200 GHz. A prototype heterodyne amplifier module has been developed for operation from 140 to 170 GHz using monolithic millimeter-wave integrated circuit (MMIC) low-noise InP high electron mobility transistor (HEMT) amplifiers.
A Note on the Interpretation of Acoustic Impedance in Confined Flows2011-01-15155/17/2011
The use of acoustic impedance to interpret the aeroacoustic behavior of flow ducts is discussed. The test case is a T-junction subjected to various combinations of grazing and bias mean flow. This geometry is not only prone to whistling but its aeroacoustic response varies with the incidence of the acoustic excitation, making it difficult to define a representative impedance. The acoustic impedance should, if correctly defined, have a real part that represents the exchange of energy between the hydrodynamic and acoustic fields and an imaginary part that can be interpreted as the inertia of the orifice. The appropriate definitions of the acoustic impedance and state variables are discussed and compared with experimental data.
Karlsson, Mikael K.
On-Wafer S-Parameter Measurements in the 325-508-GHz BandTBMG-98685/1/2011
New circuits have been designed and fabricated with operating frequencies over 325 GHz. In order to measure S-parameters of these circuits, an extensive process of wafer dicing and packaging, and waveguide transition design, fabrication, and packaging would be required. This is a costly and time-consuming process before the circuit can be tested in waveguide. The new probes and calibration procedures will simplify the testing process.
Monitoring Digital Closed-Loop Feedback SystemsTBMG-95504/1/2011
A technique of monitoring digital closed-loop feedback systems has been conceived. The basic idea is to obtain information on the performances of closed-loop feedback circuits in such systems to aid in the determination of the functionality and integrity of the circuits and of performance margins.
Visible Imager Technology for Euclid’s Dark Energy MissionTBMG-97064/1/2011
The European Space Agency is funding e2v’s development of an image sensor for the visible instrument in the Euclid space telescope. Euclid is a candidate mission for one of two launch opportunities in 2018. If selected, the mission aims to map the dark universe with two complementary methods: a galaxy red-shift survey and weak gravitational lensing using near infrared and visible instruments.
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