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Results for “MULTICHANNEL RECEIVER”

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NASA NTRS2004

Multiplex coherent raman spectroscopy detector and method

A multiplex coherent Raman spectrometer (10) and spectroscopy method rapidly detects and identifies individual components of a chemical mixture separated by a separation technique, such as gas chromatography. The spectrometer (10) and method accurately identify a variety of compounds because they produce the entire gas phase vibrational Raman spectrum of the unknown gas. This is accomplished by tilting a Raman cell (20) to produce a high-intensity, backward-stimulated, coherent Raman beam of 683 nm, which drives a degenerate optical parametric oscillator (28) to produce a broadband beam of 1100-1700 nm covering a range of more than 3000 wavenumber. This broadband beam is combined with a narrowband beam of 532 nm having a bandwidth of 0.003 wavenumbers and focused into a heated windowless cell (38) that receives gases separated by a gas chromatograph (40). The Raman radiation scattered from these gases is filtered and sent to a monochromator (50) with multichannel detection.

Chen, Peter↗

NASA NTRS1965

Results of tests at Goonhilly using the experimental communication satellites Telstar I and Telstar II

The first active communication satellite-Telstar I-was launched from Cape Canaveral by the National Aeronautics and Space Administration (NASA) on 10th July, 1962, and was later followed by Relay and Telstar II. Since the 10th July, 1962, many tests and demonstrations of television, multichannel telephony and telegraphy, facsimile and data transmission have been made via these experimental satellites. In addition, much data has been accumulated on microwave propagation, earth-station receiving system noise temperatures and satellite tracking accuracy. Such tests and data will be of considerable value for the planning and design of future operational communication-satellite systems.

GROUND STATION↗

NASA NTRS1980

Multichannel coincidence circuit

Digital circuit detects coincident pulses in two or more channels, and records time between primary pulses that are coincident with secondary pulses. Circuit has three major blocks: interval time subcircuit, measurement control subcircuit, and time sequence generator. Timer can be used in laser velocimeter or other instruments receiving data at irregular rates from two or more sources.

Clemmons, J. I., Jr.↗

NASA NTRS1974

Device for recording the 20 Hz - 200 KHz sound frequency spectrum using teletransmission

The device described consists of two distinct parts: (1) The sound pickup system consisting of the wide-frequency band condenser microphone which contains in the same assembly the frequency-modulated oscillator and the output stage. Being transistorized and small, this system can be easily moved, so that sounds can be picked up even in places that are difficult to reach with larger devices. (2) The receiving and recording part is separate and can be at a great distance from the sound pickup system. This part contains a 72 MHz input stage, a frequency changer that gives an intermediate frequency of 30 MHz and a multichannel analyzer coupled to an oscilloscope and a recorder.

Baciu, I.↗

NASA NTRS1979

On the design of a postprocessor for a search for extraterrestrial intelligence /SETI/ system

The design of an on-line postprocessor for a search for extraterrestrial intelligence (SETI) system is described. Signal processing tasks of the postprocessor include: (1) analysis of power level, phase coherence, and state of polarization of single-channel signals in a search for significant signals; (2) grouping or aggregation of adjacent channel data, time averaging of data; and (3) the detection of drifting and modulated signals. Control functions include multichannel spectrum analyzer frequency and clock control, system calibration and selfdiagnostic, control of data flow to and from short-term and long-term (archival) memories, and operation of detection subsystems, such as a visual display and a tunable receiver.

Healy, T. J.↗

NASA NTRS2006

NASA Tech Briefs, July 2006

Topics covered include: Airport Remote Tower Sensor Systems; Implantable Wireless MEMS Sensors for Medical Uses; Embedded Sensors for Measuring Surface Regression; Coordinating an Autonomous Earth-Observing Sensorweb; Range-Measuring Video Sensors; Stability Enhancement of Polymeric Sensing Films Using Fillers; Sensors for Using Times of Flight to Measure Flow Velocities; Receiver Would Control Phasing of a Phased-Array Antenna; Modern Design of Resonant Edge-Slot Array Antennas; Carbon-Nanotube Schottky Diodes; Simplified Optics and Controls for Laser Communications; Coherent Detection of High-Rate Optical PPM Signals; Multichannel Phase and Power Detector; Using Satellite Data in Weather Forecasting: I; Using Dissimilarity Metrics to Identify Interesting Designs; X-Windows PVT Widget Class; Shuttle Data Center File-Processing Tool in Java; Statistical Evaluation of Utilization of the ISS; Nanotube Dispersions Made With Charged Surfactant; Aerogels for Thermal Insulation of Thermoelectric Devices; Low-Density, Creep-Resistant Single-Crystal Superalloys; Excitations for Rapidly Estimating Flight-Control Parameters; Estimation of Stability and Control Derivatives of an F-15; Tool for Coupling a Torque Wrench to a Round Cable Connector; Ultrasonically Actuated Tools for Abrading Rock Surfaces; Active Struts With Variable Spring Stiffness and Damping; Multiaxis, Lightweight, Computer-Controlled Exercise System; Dehydrating and Sterilizing Wastes Using Supercritical CO2; Alpha-Voltaic Sources Using Liquid Ga as Conversion Medium; Ice-Borehole Probe; Alpha-Voltaic Sources Using Diamond as Conversion Medium; White-Light Whispering-Gallery-Mode Optical Resonators; Controlling Attitude of a Solar-Sail Spacecraft Using Vanes; and Wire-Mesh-Based Sorber for Removing Contaminants from Air.

Source record↗

NASA NTRS1974

Miniature multichannel biotelemeter system

A miniature multichannel biotelemeter system is described. The system includes a transmitter where signals from different sources are sampled to produce a wavetrain of pulses. The transmitter also separates signals by sync pulses. The pulses amplitude modulate a radio frequency carrier which is received at a receiver unit. There the sync pulses are detected by a demultiplexer which routes the pulses from each different source to a separate output channel where the pulses are used to reconstruct the signals from the particular source.

Carraway, J. B.↗

NASA NTRS1973

Multichannel telemetry system

A two-channel telemetry system is described in which one channel is used for high-rate data and the other channel for low-rate data communication. In the transmitter a signal, which subsequently phase modulates a carrier, is produced which is a function of at least the high-rate data, the low-rate data and the frequency of the subcarrier of the low-rate channel. In the receiver which includes a phase-locked loop, the high-rate data is detected off the receiver inphase channel output and the low-rate off the quadrature channel output.

Butman, S.↗

NASA NTRS1973

Laser communication system for controlling several functions at a location remote to the laser

A multichannel laser remote control system is described. The system is used in areas where radio frequency, acoustic, and hardware control systems are unsatisfactory or prohibited and where line of sight is unobstructed. A modulated continuous wave helium-neon laser is used as the transmitter and a 360 degree light collector serves as the antenna at the receiver.

Burcher, E. E.↗

NASA NTRS1986

Mesoscale and synoptic scale features of North Pacific weather systems observed with the scanning multichannel microwave radiometer on Nimbus 7

Employing data on integrated atmospheric water vapor, total cloud liquid water and rain rate obtainable from the Nimbus 7 Scanning Multichannel Microwave Radiometer (SMMR), the frontal structure of several mid-latitude cyclones over the North Pacific Ocean as they approach the West Coast of North America in the winter of 1979. The fronts, analyzed with all available independent data, are consistently located at the leading edge of the strongest gradient in integrated water vapor. The cloud liquid water content, which unfortunately has received very little in situ verification, has patterns which are consistent with the structure seen in visible and infrared imagery. The rain distribution is also a good indicator of frontal location and rain amounts are generally within a factor of two of what is observed with rain gauges on the coast. Furthermore, the onset of rain on the coast can often be accurately forecast by simple advection of the SMMR observed rain areas.

Katsaros, K. B.↗

NASA NTRS1977

Technology advances in active and passive microwave sensing through 1985

The capabilities of passive and active microwave sensors are discussed. The Nimbus-G and Seasat-A scanning multichannel microwave spectrometer, the Seasat-A radar altimeter, scatterometer and synthetic aperture radar represent the first systematic attempt at exploring a wide variety of applications utilizing microwave sensing techniques and are indicators of the directions in which the pertinent technology is likely to evolve. The trend is toward high resolution multi-frequency imagers spanning wide frequency ranges and wide swaths requiring sophisticated receivers, real-time data processors and most importantly, complex antennas.

Barath, F. T.↗

NASA NTRS1977

Technology advances in active and passive microwave sensing through 1985

As a result of a growing awareness by the remote sensing community of the unique capabilities of passive and active microwave sensors, these instruments are expected to grow in the next decade in numbers, versatility and complexity. The Nimbus-G and Seasat-A Scanning Multichannel Microwave Spectrometer (SMMR), the Seasat-A radar altimeter, scatterometer and synthetic aperture radar represent the first systematic attempt at exploring a wide variety of applications utilizing microwave sensing techniques and are indicators of the directions in which the pertinent technology is likely to evolve. The trend is toward high resolution multi-frequency imagers spanning wide frequency ranges and wide swaths requiring sophisticated receivers, real-time data processors and most importantly, complex antennas.

Barath, F. T.↗

NASA NTRS1984

Observing atmospheric water in storms with the Nimbus 7 scanning multichannel microwave radiometer

Employing data on integrated atmospheric water vapor, total cloud liquid water and rain rate obtainable from the Nimbus 7 Scanning Multichannel Microwave Radiometer (SMMR), we study the frontal structure of several mid-latitude cyclones over the North Pacific Ocean as they approach the West Coast of North America in the winter of 1979. The fronts, analyzed with all available independent data, are consistently located at the leading edge of the strongest gradient in integrated water vapor. The cloud liquid water content, which unfortunately has received very little in situ verification, has patterns which are consistent with the structure seen in visible and infrared imagery. The rain distribution is also a good indicator of frontal location and rain amounts are generally within a factor of two of what is observed with rain gauges on the coast. Furthermore, the onset of rain on the coast can often be accurately forecast by simple advection of the SMMR observed rain areas.

Katsaros, K. B.↗

NASA NTRS2019

Adaptive Antenna Pattern Notching of Interference in Synthetic Aperture Radar Data Using Digital Beamforming

Radio Frequency Interference (RFI) is a growing problem in Synthetic Aperture Radar (SAR)systems as scientific motivations push the radars to lower frequencies and as more wireless services share the frequency spectrum. New, advanced SAR instruments, such as NASA's EcoSAR, DBSAR and DLR's Tandem-L mission, employ a multichannel architecture capable of Digital Beamforming (DBF). Radars with DBF are capable of notching the antenna pattern in specific directions, which can be utilized to suppress RFI on board or in post-processing. A well-researched beamformer for this purpose is the Minimum Variance Distortionless Response (MVDR) Beamformer. However, the number of interferers that can be removed through notching is limited by the number of receive channels. It is therefore essential to adaptively change the antenna pattern notching throughout the image in time and frequency for the best results with a given number of receive channels. In this paper, we present several methods to achieve this notching by making use of the spatial SAR signal distribution in range time, range frequency, azimuth time and azimuth Doppler that is inherent to the SAR imaging geometry. Because this distribution is time-variable and yet predictable, it can be used to improve the angle of arrival estimation of the RFI and the adaptive notching. The presented methods can be applied to a Digital Beamforming (DBF) SAR signal with multiple channels in elevation and/or in azimuth. Simulations show that the proposed methods increase the ability to notch out-of-swath interference from multiple directions and lessen the impact on in-swath interference. The improvement of the interferometric coherence for a single-pass interferogram acquired by NASA's EcoSAR system (capable of DBF in elevation) is demonstrated. The removal of periodic RFI artifacts is achieved.

RFI↗

NASA NTRS2017

NISAR L-SAR Digital Electronics Subsystem - A Multichannel Distributed Processing System with Synchronous Timing Control for Digital Beam Forming and Multiple Echo Tracking

The NASA-ISRO Synthetic Aperture Radar (NISAR) L-band SAR instrument employs multiple digital channels to optimize resolution while keeping a large swath on a single pass. High-speed digitization with fine synchronization and digital beam forming are necessary in order to facilitate this new technique called SweepSAR. An architecture employing multiple FPGA based digital signal processors has been conceived to facilitate digital calibration on an individual channel basis as well as digital signal processing to optimize the receive signal. On-board processing and data compression has been implemented to reduce the volume of data in order to satisfy the operational requirements of near global coverage for the desired science targets. A novel command and timing architecture was developed to manage this complex system while providing detailed control of individual channel receive window timing required for digital beam forming. The NISAR L-band Digital Electronics Subsystem is the combination of the hardware, firmware and software components architected and implemented to operate this radar and return the desired quantity and quality of data for the science community.

Chuang, Chung-Lun↗

NASA NTRS1992

Temperature/pressure and water vapor sounding with microwave spectroscopy

Two intense microwave spectra lines exist in the martian atmosphere that allow unique sounding capabilities: water vapor at 183 GHz and the (2-1) rotational line of CO at 230 GHz. Microwave spectra line sounding is a well-developed technique for the Earth's atmosphere for sounding from above from spacecraft and airplanes, and from below from fixed surface sites. Two simple instruments for temperature sounding on Mars (the CO line) and water vapor measurements are described. The surface sounder proposed for the MESUR sites is designed to study the boundary layer water vapor distribution and the temperature/pressure profiles with vertical resolution of 0.25 km up to 1 km with reduced resolution above approaching a scale height. The water channel will be sensitive to a few tenths of a micrometer of water and the temperature profile will be retrieved to an accuracy between 1 and 2 K. The latter is routinely done on the Earth using oxygen lines near 60 GHz. The measurements are done with a single-channel heterodyne receiver looking into a 10-cm mirror that is canned through a range of elevation angles plus a target load. The frequency of the receiver is sweep across the water and CO lines generating the two spectra at about 1-hr intervals throughout the mission. The mass and power for the proposed instrument are 2 kg and 5-8 W continuously. The measurements are completely immune to the atmospheric dust and ice particle loads. It was felt that these measurements are the ultimate ones to properly study the martian boundary layer from the surface to a few kilometers. Sounding from above requires an orbiting spacecraft with multichannel microwave spectrometers such as the instrument proposed for MO by a subset of the authors, a putative MESUR orbiter, and a proposed Discovery mission called MOES. Such an instrument can be built with less than 10 kg and use less than 15 W. The obvious advantage of this approach is that the entire atmosphere can be sounded for temperature and water vapor in a few hours with somewhat better than a scale height resolution. If a bigger mirror is used (greater than 30 cm) limb sounding geometry can be employed and half scale height resolution achieved to altitudes up to at least 60 km. Again, the measurements are immune to dust and ice loads. Water vapor sensitivity of 0.1 micrometer can be achieved (even with a nadir instrument) and temperature profiles retrieved to an accuracy of better than 2 K from the surface to about 60 km. Winds can be measured from the doppler shifts of CO lines in the limb sounding mode.

Muhleman, D. O.↗

NASA NTRS1991

High altitude airborne remote sensing mission using the advanced microwave precipitation radiometer (AMPR)

The advanced microwave precipitation radiometer (AMPR) is an airborne multichannel imaging radiometer used to better understand how the earth's climate structure works. Airborne data results from the October 1990 Florida thunderstorm mission in Jacksonville, FL, are described. AMPR data on atmospheric precipitation in mesoscale storms were retrieved at 10.7, 19.35, 37.1, and 85.5 GHz onboard the ER-2 aircraft at an altitude of 20 km. AMPR's three higher-frequency data channels were selected to operate at the same frequencies as the spaceborne special sensor microwave/imager (SSM/I) presently in orbit. AMPR uses two antennas to receive the four frequencies: the lowest frequency channel uses a 9.7-in aperture lens antennas, while the three higher-frequency channels share a separate 5.3-in aperture lens antenna. The radiometer's temperature resolution performance is summarized.

Galliano, J.↗

NASA NTRS1980

A bimodal search strategy for SETI

A SETI plan has been developed jointly by the NASA Ames Research Center and the Jet Propulsion Laboratory with the objective of both observing all potential sites to some limiting equivalent isotropic radiated power and surveying with greater sensitivity a set of especially promising sites. The bimodal search strategy assumes that existing radio telescopes with state-of-the-art receivers and data processing devices will have the sensitivity to explore the vicinity of nearby stars for similar transmitters and the entire galaxy for more powerful signals. The discrete source observational mode is designed to observe 773 F, G and K-type stars within 25 pc of the sun at frequencies from 1.2 to 3 GHz and spot bands between 3 and 25 GHz with sensitivities from 10 to the -25th to 10 to the -27th W/sq m. The sky survey is intended to search the entire celestial sphere between 1.2 and 10 GHz and spot bands between 10 and 25 GHz at a sensitivity limit of approximately 10 to the -23rd times the square root of the frequency. Instrumentation for the surveys includes a large multichannel spectrum analyzer. Immediate goals of the program are the investigation of the RF background at high resolution and the development of signal detection algorithms, with operation to begin in 1984.

Gulkis, S.↗