Application of random time and frequency multiplexing to a data collection satellite.
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Clarke, S. P.↗
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Results for “time multiplexing”
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A comparison of time division and Walsh multiplexing for a multiuser communication satellite link
Multiuser satellite communications system transmission capacity, comparing time division with Walsh multiplexing
Bayless, J. W.↗
SAPT units turn-on in an interference-dominant environment
A stand alone pressure transducer (SAPT) is a credit-card-sized smart pressure sensor inserted between the tile and the aluminum skin of a space shuttle. Reliably initiating the SAPT units via RF signals in a prelaunch environment is a challenging problem. Multiple-source interference may exist if more than one GSE (ground support equipment) antenna is turned on at the same time to meet the simultaneity requirement of 10 ms. A polygon model for orbiter, external tank, solid rocket booster, and tail service masts is used to simulate the prelaunch environment. Geometric optics is then applied to identify the coverage areas and the areas which are vulnerable to multipath and/or multiple-source interference. Simulation results show that the underside areas of an orbiter have incidence angles exceeding 80 deg. For multipath interference, both sides of the cargo bay areas are found to be vulnerable to a worst-case multipath loss exceeding 20 dB. Multiple-source interference areas are also identified. Mitigation methods for the coverage and interference problem are described. It is shown that multiple-source interference can be eliminated (or controlled) using the time-division-multiplexing method or the time-stamp approach.
Peng, W.-C.↗
Electro-optic architecture (EOA) for sensors and actuators in aircraft propulsion systems
Results of a study to design an optimal architecture for electro-optical sensing and control in advanced aircraft and space systems are described. The propulsion full authority digital Electronic Engine Control (EEC) was the focus for the study. The recommended architecture is an on-engine EEC which contains electro-optic interface circuits for fiber-optic sensors on the engine. Size and weight are reduced by multiplexing arrays of functionally similar sensors on a pair of optical fibers to common electro-optical interfaces. The architecture contains common, multiplex interfaces to seven sensor groups: (1) self luminous sensors; (2) high temperatures; (3) low temperatures; (4) speeds and flows; (5) vibration; (6) pressures; and (7) mechanical positions. Nine distinct fiber-optic sensor types were found to provide these sensing functions: (1) continuous wave (CW) intensity modulators; (2) time division multiplexing (TDM) digital optic codeplates; (3) time division multiplexing (TDM) analog self-referenced sensors; (4) wavelength division multiplexing (WDM) digital optic code plates; (5) wavelength division multiplexing (WDM) analog self-referenced intensity modulators; (6) analog optical spectral shifters; (7) self-luminous bodies; (8) coherent optical interferometers; and (9) remote electrical sensors. The report includes the results of a trade study including engine sensor requirements, environment, the basic sensor types, and relevant evaluation criteria. These figures of merit for the candidate interface types were calculated from the data supplied by leading manufacturers of fiber-optic sensors.
Glomb, W. L., Jr.↗
A pseudo random-access synchronous meteorological satellite system
Communications satellite system uses pseudo-random time frequency multiplexing technique for extracting real-time meteorological data from great number of isolated weather stations /data collection platforms/ situated randomly throughout the world.
Darcey, R. J.↗
Conceptual design of the modular detector and readout system for the CMB-S4 survey experiment
We present the conceptual design of the modular detector and readout system for the Cosmic Microwave Background – Stage four (CMB-S4) ground-based survey experiment. CMB-S4 will map the cosmic microwave background (CMB) and the millimeter-wave sky to unprecedented sensitivity, using 500,000 superconducting detectors observing from Chile and Antarctica to map over 60% of the sky. The fundamental building block of the detector and readout system is a detector module package operated at 100 mK, which is connected to a readout and amplification chain that carries signals out to room temperature. It uses arrays of feedhorn-coupled orthomode transducers (OMT) that collect optical power from the sky onto dc-voltage-biased transition-edge sensor (TES) bolometers. The resulting current signal in the TESs is then amplified by a two-stage cryogenic Superconducting Quantum Interference Device (SQUID) system with a time-division multiplexer to reduce wire count, and matching room-temperature electronics to condition and transmit signals to the data acquisition system. Sensitivity and systematics requirements are being developed for the detector and readout system over wide range of observing bands (20 to 300 GHz) and optical powers to accomplish CMB-S4’s science goals. While the design incorporates the successes of previous generations of CMB instruments, CMB-S4 requires an order of magnitude more detectors than any prior experiment. This requires fabrication of complex superconducting circuits on over 10 m2 of silicon, as well as significant amounts of precision wiring, assembly and cryogenic testing
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
A dynamic packet-switching system for satellite broadcast channels
A new satellite multi-access scheme for packet-switching computer communications combines a dynamic allocation technique with conventional time-division multiplexing to minimize delays and maximize traffic thruput. The scheme is designed to give the shortest delays to short-duration interactive or priority traffic, at the expense of longer delays for large data transfers. Simulation results show markedly improved delay-thruput characteristics over conventional time-division multiplexing for a wide range of traffic mixes, with especially significant performance gains as the traffic imbalance among the nodes increases.
Binder, R.↗
Monopulse receiver
A time division multiplexing and a quadraphase combining dual channel system were analyzed, designed, and tested. Analyses performed include the following: (1) boresight error as a function of the error channel bandwidth; (2) error channel interference with the sum channel functions; (3) threshold performance; and (4) error channel crosstalk, linearity, and drift as a function of signal level, Doppler, and environment. Test results indicate that the time division multiplexing system meets the design goals of the program. However, careful selection and alignment of all gain controlled amplifiers are required along with temperature compensation of the angle channel gain. The quadraphase system crosstalk performance is comparatively poor (-15 dB) with respect to the -30 dB requirements and this consequently affects gain tracking performance. Gain tracking was found to be + or - 20 percent rather than the + or - 5 percent specification. Data for the two systems is compared and recommendations are presented.
Source record↗
Tetrad bubble domain chip arrangement for multiplexing
Rotating magnetic field of bubble domain memory is used to obtain time-division multiplexing of bubble domain circuits into quadrants. Memory bits are assigned on bit-per-chip rather than bit-per-module basis; power is reduced by circulating only portion of bubbles at a time.
Almasi, G. S.↗
Method Development for Multiplex, In-Situ, and Real-Time Detection of Herpesvirus Reactivation in Spaceflight Crews using Nanopore Sequencing
Reactivation of latent herpesviruses in crews onboard the International Space Station (ISS) is a well-established spaceflight-associated phenomenon and has been linked to overall immune stress. Beyond an indicator of an altered immune state, this stress-induced reactivation of viruses such as herpesvirus simplex virus 1 (HSV-1), Epstein-Barr virus (EBV), and Varicella-Zoster virus (VZV) may cause clinical symptoms in crew. There is currently no established protocol for in-flight monitoring, and samples are analyzed post-flight using ground-based assays. A real-time, in-flight method for herpesvirus detection followed by stress-mitigation strategies would be a significant advance. In this study, we developed a real-time assay for the multiplex detection of HSV-1, EBV, and VZV from saliva that could be implemented for in-situ monitoring of ISS crew. This method builds on previously validated spaceflight-compatible portable molecular protocols and platforms, such as the miniPCR thermal cycler and the MinION sequencer. Since a metagenomic approach is not currently permitted for crew samples (NASA policy), we employed multiplexing-ready primers directed toward targeted regions within the HSV-1, EBV, and VZV genomes. We also used primers for the human gene, Statherin (STATH), as an internal control. These primers were validated using spiked-in, positive control HSV-1, EBV, and VZV from virus-negative saliva extracted using the Zymo-Research Quick-DNA/RNA Viral MagBead Kit. The PCR Barcoding Kit was used to prepare DNA libraries that were then sequenced on the MK1C and analyzed against known reference genomes using minimap2. Following validation of this method with spiked saliva samples, suspected herpesvirus-positive clinical saliva samples were successfully tested. Prior to use onboard the ISS, this method will be deployed to an analog environment during overwintering at Palmer Station, Antarctica in 2023. This work represents the successful application of molecular technologies currently onboard the ISS for the real-time monitoring of latent herpesvirus reactivation from saliva samples. This assay, in combination with stress-reduction strategies, holds the potential to manage herpesvirus reactivation in ISS crew, thereby improving health outcomes and overall immunity.
Patrick M. Rydzak↗
Multiplexing technique for computer communications via satellite channels
Multiplexing scheme combines technique of dynamic allocation with conventional time-division multiplexing. Scheme is designed to expedite short-duration interactive or priority traffic and to delay large data transfers; as result, each node has effective capacity of almost total channel capacity when other nodes have light traffic loads.
Binder, R.↗
Parallel Information Processing (Image Transmission Via Fiber Bundle and Multimode Fiber
Growing demand for visual, user-friendly representation of information inspires search for the new methods of image transmission. Currently used in-series (sequential) methods of information processing are inherently slow and are designed mainly for transmission of one or two dimensional arrays of data. Conventional transmission of data by fibers requires many fibers with array of laser diodes and photodetectors. In practice, fiber bundles are also used for transmission of images. Image is formed on the fiber-optic bundle entrance surface and each fiber transmits the incident image to the exit surface. Since the fibers do not preserve phase, only 2D intensity distribution can be transmitted in this way. Each single mode fiber transmit only one pixel of an image. Multimode fibers may be also used, so that each mode represent different pixel element. Direct transmission of image through multimode fiber is hindered by the mode scrambling and phase randomization. To overcome these obstacles wavelength and time-division multiplexing have been used, with each pixel transmitted on a separate wavelength or time interval. Phase-conjugate techniques also was tested in, but only in the unpractical scheme when reconstructed image return back to the fiber input end. Another method of three-dimensional imaging over single mode fibers was demonstrated in, using laser light of reduced spatial coherence. Coherence encoding, needed for a transmission of images by this methods, was realized with grating interferometer or with the help of an acousto-optic deflector. We suggest simple practical holographic method of image transmission over single multimode fiber or over fiber bundle with coherent light using filtering by holographic optical elements. Originally this method was successfully tested for the single multimode fiber. In this research we have modified holographic method for transmission of laser illuminated images over commercially available fiber bundle (fiber endoscope, or fiberscope).
Kukhtarev, Nicholai↗
Multiplexing Technology for Acoustic Emission Monitoring of Aerospace Vehicles
The initiation and propagation of damage mechanisms such as cracks and delaminations generate acoustic waves, which propagate through a structure. These waves can be detected and analyzed to provide the location and severity of damage as part of a structural health monitoring (SHM) system. This methodology of damage detection is commonly known as acoustic emission (AE) monitoring, and is widely used on a variety of applications on civil structures. AE has been widely considered for SHM of aerospace vehicles. Numerous successful ground and flight test demonstrations have been performed, which show the viability of the technology for damage monitoring in aerospace structures. However, one significant current limitation for application of AE techniques on aerospace vehicles is the large size, mass, and power requirements for the necessary monitoring instrumentation. To address this issue, a prototype multiplexing approach has been developed and demonstrated in this study, which reduces the amount of AE monitoring instrumentation required. Typical time division multiplexing techniques that are commonly used to monitor strain, pressure and temperature sensors are not applicable to AE monitoring because of the asynchronous and widely varying rates of AE signal occurrence. Thus, an event based multiplexing technique was developed. In the initial prototype circuit, inputs from eight sensors in a linear array were multiplexed into two data acquisition channels. The multiplexer rapidly switches, in less than one microsecond, allowing the signals from two sensors to be acquired by a digitizer. The two acquired signals are from the sensors on either side of the trigger sensor. This enables the capture of the first arrival of the waves, which cannot be accomplished with the signal from the trigger sensor. The propagation delay to the slightly more distant neighboring sensors makes this possible. The arrival time from this first arrival provides a more accurate source location determination. The multiplexer also identifies which channels are acquired by encoding TTL logic pulses onto the latter portion of the signals. This prototype system was demonstrated using pencil lead break (Hsu-Neilsen) sources on an aluminum plate. It performed as designed providing rapid low noise trigger based switching with encoded channel identification. this multiplexing approach is not limited to linear arrays, but can be easily extended to monitor sensors in planar ot three dimensional arrays. A 32 channel multiplexing system is under development that will allow arbitrary sensor placement. Another benefit of this multiplexing system is the reduction in the expense of data acquisition hardware. In addition, the reduced weight and power requirements are of extreme importance for proposed AE systems on aerospace vehicles.
Prosser, William↗
End-to-End Modeling of the TDM Readout System for CMB-S4
The CMB-S4 experiment is developing next-generation ground-based microwave telescopes to observe the cosmic microwave background with unprecedented sensitivity. This will require an order of magnitude increase in the 100-mK detector count, which, in turn, increases the demands on the readout system. The CMB-S4 readout will use time-division multiplexing (TDM), taking advantage of faster switches and amplifiers in order to achieve an increased multiplexing factor. To facilitate the design of the new readout system, we have developed a model that predicts the bandwidth and noise performance of this circuitry and its interconnections. This is then used to set requirements on individual components in order to meet the performance necessary for the full system. Here, we present an overview of this model and compare the model results to the performance of both legacy and prototype readout hardware.
47 OTHER INSTRUMENTATION↗
Improved Frequency-Domain Steady-State Modeling of the Dual-Active-Bridge Converter Considering Finite ZVS Transition Time Effects
This article presents an improved analytical modeling (IAM) approach for the dual-active-bridge (DAB) converter in the frequency-domain. Specifically, finite transition times are incorporated into the improved modeling that are significant in DAB converters operated at high frequency. The IAM approach is first motivated by comparing traditional frequency-domain modeling against realistic simulation results in LTspice. Next, the IAM approach is mathematically developed in an iterative fashion, where the conventional frequency-domain approach is used as the initialization of the operational behavior of the converter. Subsequent iterations of the IAM algorithm incorporate finite rise- and falltimes of device output capacitances based on detailed switching behavior analyses, which may considerably perturb the desired modulation parameters (i.e., phase shift and zero states). While the initially proposed IAM approach demonstrates advantages over ideal modeling, it is still shown to exhibit errors when applied to device transitions with significant nonlinearity in parasitic output capacitance. To account for this, a three-slope approximation to the switching transition is then motivated and developed, which enables significantly improved steady-state prediction accuracy. Simulation and experimental results confirm unacceptable inaccuracies associated with the conventional frequency-domain modeling across a wide range of operating conditions, alongside enhanced accuracy provided by the proposed modeling approach.
14 SOLAR ENERGY↗
BICEP Array: 150 GHz Detector Module Development
The Background Imaging of Cosmic Extragalactic Polarization (BICEP)/Keck (BK) collaboration is currently leading the quest for the highest-sensitivity measurements of the polarized cosmic microwave background (CMB) anisotropies on a degree scale with a series of cryogenic telescopes, of which BICEP Array (BA) is the latest Stage-3 upgrade with a total of ~ 32,000 detectors. The instrument comprises 4 receivers spanning 30–270 GHz, with the low-frequency 30/40 GHz deployed to the South Pole Station in late 2019. The full complement of receivers is forecast to set the most stringent constraints on the tensor-to-scalar ratio r. Building on these advances, the overarching small-aperture telescope concept is already being used as the reference for further Stage-4 experiment design. This paper describes the development of the BICEP Array 150 GHz detector module and its fabrication requirements, with highlights on the high-density time division multiplexing (TDM) design of the cryogenic circuit boards. The low-impedance wiring required between the detectors and the frst stage of superconducting quantum interference device amplifers is crucial to maintaining a stable bias current on the detectors. Here, a novel multilayer FR4 Printed Circuit Board with superconducting traces, capable of reading out up to 648 detectors, is detailed along with its validation tests. An ultra-high-density TDM detector module concept we developed for a CMB-S4-like experiment that allows up to 1920 detectors to be read out is also presented. TDM has been chosen as the detector readout technology for the Cosmic Microwave Background Stage-4 (CMB-S4) experiment based on its proven low-noise performance, predictable costs, and overall maturity of the architecture. The heritage for TDM is rooted in mm- and sub-mm-wave experiments dating back 20 years and has since evolved to support a multiplexing factor of 64x in Stage-3 experiments.
79 ASTRONOMY AND ASTROPHYSICS↗
Multi-Wavelength Mode-Locked Laser Arrays for WDM Applications
Multi-wavelength arrays of colliding pulse mode-locked (CPM) lasers have been demonstrated for wavelength division multiplexing (WDM) applications. The need for increased bandwidth is driving the development of both increased speed in time division multiplexing (TDM) and more channels in WDM for fiber optic communication systems.
division↗
Design, modeling, and analysis of multi-channel demultiplexer/demodulator
Traditionally, satellites have performed the function of a simple repeater. Newer data distribution satellite architectures, however, require demodulation of many frequency division multiplexed uplink channels by a single demultiplexer/demodulator unit, baseband processing and routing of individual voice/data circuits, and remodulation into time division multiplexed (TDM) downlink carriers. The TRW MCDD (Multichannel Demultiplexer/Multirate Demodulator) operates on a 37.4 MHz composite input signal. Individual channel data rates are either 64 Kbps or 2.048 Mbps. The wideband demultiplexer divides the input signal into 1.44 MHz segments containing either a single 2.048 Mbps channel or thirty two 64 Kbps channels. In the latter case, the narrowband demultiplexer further divides the single 1.44 MHz wideband channel into thirty two 45 KHz narrowband channels. With this approach the time domain Fast Fourier Transformation (FFT) channelizer processing capacity is matched well to the bandwidth and number of channels to be demultiplexed. By using a multirate demodulator fewer demodulators are required while achieving greater flexibility. Each demodulator can process a wideband channel or thirty two narrowband channels. Either all wideband channels, a mixture of wideband and narrowband channels, or all narrowband channels can be demodulated. The multirate demodulator approach also has lower nonrecurring costs since only one design and development effort is needed. TRW has developed a proof of concept (POC) model which fully demonstrates the signal processing fuctions of MCDD. It is capable of processing either three 2.048 Mbps channels or two 2.048 Mbps channels and thirty two 64 Kbps channels. An overview of important MCDD system engineering issues is presented as well as discussion on some of the Block Oriented System Simulation analyses performed for design verification and selection of operational parameters of the POC model. Systems engineering analysis of the POC model confirmed that the MCDD concepts are not only achievable but also balance the joint goals of minimizing on-board complexity and cost of ground equipment, while retaining the flexibility needed to meet a wide range of system requirements.
Lee, David D.↗