Digital Data Link Research Articles

Four-Level Micro-Via Technology (4LµV) for ASIC Integration in Active Flexible Sensor Arrays.

Systems-in-foil with multi-sensor arrays require extensive wiring with large numbers of data lines. This prevents scalability of the arrays and thus limits the applications. To enable multiplexing and thus reducing the external connections down to few digital data links and a power supply, active circuits in the form of ASICs must be integrated into the foils. However, this requires reliable multilayer wiring of the sensors and contacts for chip integration. As an elegant solution to this, a new manufacturing process for multilayer wiring in polyimide-based sensor foils has been developed that also allows ASIC chips to be soldered. The electrical four-level micro-via connections and the contact pads are generated by galvanic copper deposition after all other process steps, including stacking and curing of polyimide layers, are completed. Compared to layer by layer via technology, the processing time is considerably reduced. Because copper plating of vias and solderable copper contact pads happens as the final step, the risk of copper oxidation during polyimide curing is completely eliminated. The entire fabrication process is demonstrated for six strain sensor nodes connected to a surface-mounted ASIC as a detecting unit for sensing spatially resolved bending states. Each sensor node is a full-bridge configuration consisting of four strain gauges distributed across interconnected layers. The sensor foil allows bending of +/−120° without damage. This technology can be used in future for all kinds of complex flexible systems-in-foil, in particular for large arrays of sensors.

Interference of Spread-Spectrum EMI and Digital Data Links under Narrowband Resonant Coupling

In this paper, the effects of electromagnetic interference (EMI) coupled to a radio-frequency (RF) communication channel by resonant mechanisms are investigated and described in the framework of Shannon information theory in terms of an equivalent channel capacity loss so that to analyze and compare the effects of non-modulated and random Spread Spectrum (SS) modulated EMI. The analysis reveals a higher EMI-induced capacity loss for SS-modulated compared to non modulated EMI under practical values of the quality factor Q, while a modest improvement in the worst case capacity loss is observed only for impractical values of Q. Simulations on a 4-quadrature amplitude modulation (4-QAM) digital link featuring Turbo coding under EMI resonant coupling reveal that SS-modulated EMI gives rise to higher bit error rate (BER) at lower EMI power compared non-modulated EMI in the presence of resonant coupling for practical values of Q, thus suggesting a worse interfering potential of SS-modulated EMI.

Research on the security of communication addressing and reporting system of civil aircraft

ACARS is a digital data link system that transmits short messages by radio or satellite between aircraft and ground stations. ACARS control centre is connected with each ACARS ground station and each airline information centre through the ground communication network. Exchange data and information with airlines in both directions through code addressing. However, because ACARS messages use plaintext transmission, anyone can monitor and decode ACARS messages with a low-cost receiver and obtain details such as aircraft type, location, planned route, passenger status and aircraft operation state, etc., thus posing a major threat to flight safety. The following security problems exist in the current ACARS system.

Power-Optimized Temperature-Distributed Digital Data Link

Interfacing superconducting rapid single flux quantum logic with room temperature electronics requires the development of low-power semiconductor circuitry capable of operating at tens of Gb/s while maintaining sufficient signal to noise to achieve acceptable bit-error-rates. Such data-links must operate with sufficiently low power consumption to permit tens to hundreds of parallel channels to coexist in a single cryostat. This requires a careful trade-off between the power and noise performance of the cryogenically cooled digital amplifiers. Previously demonstrated ultra low-power cryogenic-to-room temperature digital data links have been limited to data rates on the order of a few Gb/s. In this paper we demonstrate a temperature distributed amplifier chain optimized for 30 Gb/s data transmission and consuming just 140 microwatts at 4 K.

Low-Power High-Speed Hybrid Temperature Heterogeneous Technology Digital Data Link

High-speed digital data links from 4-K superconductor electronics to room temperature are challenging due to the fact that energy/bit for single flux quantum logic is many (six) orders of magnitude lower than that of standard room-temperature logic. Our approach of building an energy-efficient high-speed data link involves a joint electrical-thermal design of a temperature-distributed architecture using different electronic technologies. This differential digital data link design involves superconductor, multiple cryogenic semiconductor and additional room-temperature semiconductor circuitry. The current design involves three cryogenic semiconductor ICs for integration with a multistage cryocooled digital system. The first cryogenic semiconductor IC is designed to operate at 4 K with a power consumption of 0.3 mW and interface directly with the superconductor differential single flux quantum/dc drivers. For testing it, a superconductor carrier chip containing an analog-to-digital converter has been designed for the HYPRES dual- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$J_{c}$</tex></formula> (4.5 and 20 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{kA/cm}^{2}$</tex></formula> ) fabrication process.

High-Speed Hybrid Superconductor-to-Semiconductor Interface Circuit With Ultra-Low Power Consumption

Superconductor electronics for high-performance computing and high-speed analog-to-digital converters requires multi-channel digital data links. Most difficult is the amplification of the weak signals from the superconductor circuit to the volt level of semiconductor electronics. We developed a hybrid digital interface based on a Josephson latching driver, the so-called Suzuki stack, and a clocked CMOS comparator. The input can be directly triggered by a single flux quantum pulse and the output provides a 1 V CMOS-level signal. In contrast to existing systems, our interface is optimized for ultra-low-power consumption to enable its application for parallel multi-bit data interfaces. We provide evaluation of various types of Suzuki stacks and various CMOS comparators. We present experimental data on the delay of the overall hybrid interface and the total power consumption. The bit-error rate has been measured to be below 10-12. We will discuss the trade-off among circuit robustness, speed, and power consumption.

A Multichannel Electrophysiology Workbench for Single Ion Channel Screening

Ion channels are involved into a large amount of processes of the cell life, regulating ion exchange between intra and extra cellular environment. Several diseases are affected by unregulated protein behavior and the possibility to test target drugs with single ion channels will open new approaches for the drug discovery and screening. This could be accomplished by testing single ion channels into artificial lipid membranes arrays.Currently, it is possible to monitor ionic current flowing through ion channels embedded into BLMs, cells or giant lipid vesicles, by characterizing the electrical transmembrane protein behaviour using laboratory techniques and low noise equipment for signal acquisition. State-of-the-art equipments offer high precision recording amplifiers that are able to sense single ion channels. However, these techniques require sophisticated manual skills. On the other hand, High Throughput Screening systems require high data volumes implemented with automatic procedures. At the moment, they are available only for patch-clamp techniques.We present a multichannel electrophysiology system for single ion channel recording, based on a modular system embedded into a hybrid architecture that is able to record single ion channels on an arbitrary number of spots. The system is composed of:• an array of disposable microfluidic chambers with embedded Silver/SilverChloride electrodes, for manual or automatic formation of BLMs to host single ion channel experiments, tightly interfaced with low noise electronics front-end;• an array of low noise integrated microelectronic interfaces for signal amplification and analog to digital conversion;• digital data elaboration and link to PC;• a graphical user interface for data display and storage.The flexibility of the proposed architecture allows different configurations, ranging from a limited number of data channels to be monitored, suitable for manual experiments, to thousands of data channels, coping with automatic HTS requirements.

The Development of On-Chip Serial Link Transmitter for MAPS

Most applications of future CMOS Monolithic Active Pixel Sensors (MAPS) require high-speed digital serial data link for data transmission. Commercial monolithic serial transmitters can be found that meet the bandwidth requirements of the MAPS. However, there is no available space for additional chips on the MAPS layers in the detector. To address this issue, a serial transmitter prototype, containing a phase-locked loop (PLL) clock generator, an 8B/10B encoder, a serializer and a low-voltage differential signaling (LVDS) driver was developed. Since the clock is embedded into the data by using serial transmission, the detector material budget due to data transmission is minimized. The serial transmitter prototype is integrated in a sensor chip, MIMOSA26, developed in IPHC (Institut Pluridisciplinaire Hubert-Curien, France). It has been implemented in a 0.35 ?m CMOS technology. This first serial transmitter prototype was designed aiming to transmit data at 160 Mbit/s. Measurements proved our design is fully functional.

Field Evaluation of the Tailored Arrivals Concept for Datalink-Enabled Continuous Descent Approach

Allowing aircraft to descend uninterrupted at low engine power, continuous descent operations promise to maximize fuel efficiency while minimizing environmental impact. Tailored arrivals is a concept for enabling continuous descents under constrained airspace conditions by integrating advanced air and ground automation through digital datalink. Operational trials were completed in January 2007 involving transpacific flights into San Francisco during early morning hours. Leveraging newly deployed Federal Aviation Administration automation in the oceanic environment, trajectory-based clearances were transmitted by datalink to Boeing 777 aircraft equipped with future air navigation system avionics. NASA's prototype ground-based automation for high-density arrival management tailored trajectory clearances to accommodate artificially imposed metering constraints. Upon sharing wind and descent-speed-intent data, ground-based and airborne automation were found to predict meter-fix arrival times to within a mean accuracy of 3 s over a 25 min prediction horizon. Corresponding mean altitude and along-track prediction errors of ground-based automation were -500 ft and -1.3 n mile, respectively, in comparison with surveillance truth. A benefits analysis suggests Boeing 777 fuel savings of between 200 and 3000 1b per flight (depending highly upon baseline traffic conditions) together with a corresponding reduction in CO 2 emissions of between 700 and 10,000 1b per flight.

Superconducting Switching Amplifiers for High Speed Digital Data Links

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In a superconductor digital-RF transmitter, the power amplifier chain can be implemented in hybrid temperature, hybrid technology environment, where the superconductor switching amplifier forms the first stage of the amplification chain. We have designed several flavors of SQUID based switching amplifiers, each targeted for different power output and speed. One of the amplifiers is a differential amplifier featuring dynamic equalization. To minimize the intersymbol interference, the amplifier employs a pre-emphasis technique, thereby compensating for the bandwidth limitations of the channel. The differential output voltage of this amplifier is 16 mV at low speed (200 Mbps), which rolls off to 2 mV at 16 Gbps data rate, for an “1100” pattern (no consecutive transitions on the input data sequence). For high speed operation of the SQUID amplifiers, simultaneous switching of SQUIDs is desired to reduce the output rise and fall times. Hence, in another amplifier design, called the Differential H-Tree Amplifier, the SQUIDs are arranged in an “H-tree” structure, to equalize the propagation delay of the control signal to each SQUID. The amplifier's differential output voltage is 8 mV at low speed (200 Mbps), and rolls off to 2 mV at 10 Gbps data rate. A third type of amplifier is a differential SFQ-to-DC amplifier; it consists of a pair of synchronously driven SFQ-to-DC converters that produce complementary positive and negative voltage waveforms respectively. The differential output voltage of this amplifier is 0.8 mV, and it can be operated at very high speeds. Moreover, the complexity of this amplifier enables it to be yielded in higher critical current density process. Both, the speed and the output voltage scale as the square root of the process critical current density. </para>

VDL mode E receiver performance measurments

VDL Mode E is a digital communications system proposed as a worldwide standard for replacement of the existing analog AM voice system used for VHF aeronautical communications. It provides a needed increase in voice channel capacity as well as offering a digital data link for CPDLC with the high integrity and low latency needed for time-critical ATC messages. This report summarizes results of measurements of proposed minimum requirements for an aeronautical receiver for VDL Mode E. A software defined radio (SDR) currently used in Commercial Air Transport communications was used for the tests.

Using Airport Layout Information to Improve Automatic Speech Recognition for Digitizing Taxi Instructions

During taxiing, an Electronic Flight Bag (EFB) showing airport and route-data can support pilots. In the present study, the possibility of using a Voice Recognition System (VRS) to enable pilots to enter route instructions, for usage in situations where digital data link is not available, was investigated. The potential of techniques that utilize information on airport layout to detect and correct voice recognition errors was explored. Experiment I investigated the accuracy rates that can be achieved with the basic VRS. Although high, the resulting accuracy was insufficient, for safety reasons as well as user-acceptance of the system. A configurable system that interprets user utterances based on possible taxi routes on the airport, was designed and implemented. Experiment II explored the potential improvement of the different configuration options on error detection and correction performance. With one of the configurations, an increase of 42% in overall recognition rates was achieved.

Connectivity of Ad Hoc Networks for Advanced Air Traffic Management

This paper presents the concept and studies connectivities of wireless ad hoc networks among aircraft for enhanced situational awareness. Under this multi-hop broadcast concept, an aircraft would periodically broadcast not only its own state information, but also relay state information received from neighboring aircraft. In this paper, a basic architecture of such an airborne ad hoc network is established. The relationship between network connectivity and information reachability, which accounts for information latency and depends on transmission protocols, is discussed. Two general performance criteria are introduced that measure the connectivity performance of an airborne network subject to a specified maximum number of hops in the network. The first metric is the ratio of the total coverage area of a network cluster over that of a single aircraft. The second metric is the number of aircraft each individual aircraft can connect to within the network cluster. Three representative types of traffic scenarios are considered: a one-dimensional flight stream, two streams merging into one, and randomly distributed traffic over a horizontal region. In all cases, aircraft positions are checked against their conflict-free requirements. For the onedimensional traffic and merging traffic scenarios, the best, the worst, and the average values of the connectivity performance criteria are obtained via numerical simulations. For the two-dimensional random traffic scenario, random simulations are repeated, and both average connectivity performances and their standard deviations are calculated. Simulation results indicate that the connectivity of the proposed airborne ad hoc network is always better than that of the non-relay scheme. Overall, the proposed concept offers great flexibilities through the use of different transmission protocols and maximizes the benefits of a given digital data link.

Single-event upset studies of a high-speed digital optical data link

The results from a series of neutron and photon irradiation tests of a high-speed digital optical data link based on a commercial serialiser and a vertical cavity surface emitting laser are described. The link was developed as a candidate for the front-end readout of the ATLAS electromagnetic calorimeter. The components at the emitting end of the link were unaffected by neutron and photon irradiation levels exceeding those expected during 10 years of LHC running. However, the link suffered from Single-Event Upsets (SEUs) when irradiated with energetic neutrons. A very general method based on the Burst Generation Rate (BGR) model has been developed and is used to extrapolate the error rate observed during tests to that expected at the LHC. A model-independent extrapolation was used to check the BGR approach and the results were consistent once systematic errors were taken into account.

Demonstration of a monolithic multichannel module for multi-Gb/s intra-MCM optical interconnects

In this letter, we report on the demonstration of a 2.48-Gb/s multichannel optical data-link for intramultichip module interconnects. The optical module was fabricated in polymethylmethacrylate (PMMA) by deep proton lithography and monolithically integrates micromirrors and cylindrical lenses. With the same technology, we have also fabricated a single-channel optical bridge and used this component to demonstrate a proof-of-principle optical intrachip interconnect by establishing a digital data-link between optoelectronic transceivers integrated on the same chip.

Radiation testing of fiber optic systems

Tests have been performed to examine the effects of radiation exposure on opto-electronic components that can be used in digital fiber optic data links. The response of fiber waveguides to ionizing radiation has been studied. Measurements of the growth and decay of the radiation-induced loss at 850 and 1300 nm have revealed that fibers are very sensitive to low γ-doses (2000 rad). The linear dependence of a short circuit current on a γ-dose rate, up to 380 rad/s for the photodiode has been shown. At very high dose levels permanent damage is noticed in the diode characteristics and its current decreases where a value of 1600 μA, measured at light intensity level of 8000 1x, was reduced to 1200, 950, 820, 700, 600 and 550 μA after γ-exposure up to 2.0, 16, 38, 70, 105 and 140 M rad respectively. The forward current gain factor of a phototransistor, measured as a function of operating collector current, shows a severe decrease due to γ-exposure. The minimum damage effects, usually correspond to the lower and higher ends of the operating collector current range of a device. Proposals using photodiodes for γ-dose and dose rate-dosimetry are given, tested and proved to be satisfactory.

Smuggling interdiction using an adaptation of the AN/APG-76 multimode radar

The AN/APG-76 multimode radar was designed and developed for a multimode attack fighter application requiring rapid search, detection, identification, and precision location of both airborne and surface targets from long standoff ranges under adverse weather conditions. Unique is the radar's ability to generate SAR images of a selected area while simultaneously detecting and tracking all-speed moving objects located within that imaged region. Northrop Grumman Norden Systems has recently upgraded and adapted this radar to smuggling interdiction and related law enforcement missions. These adaptations have added an integrated GPS/INS subsystem for enhanced self-navigation and target location accuracy, a long range wide-band digital data link and ground station for mission control and data dissemination, a 3-D interferometric SAR imaging capability for detailed high resolution topographic mapping, and 1 meter and 0.3 meter resolution SAR modes for positive target identification. Additionally, the radar has been installed into wing-mounted pods and adapted for side-looking and 360 degree coverage applications. Automatic target detection and enhanced-range sea-surveillance and air-targeting modes are also now available through the use of open architecture commercial processors and non-proprietary transportable programming languages.

Optical receiver systems for high speed parallel digital data links

This paper presents an analysis as well as experimental results on developing receiver arrays for parallel digital datalinks for 10-100 m in the Gb/s range. Interchannel crosstalk can be a dominant limiting factor on the bit-error-rate in such parallel arrays. We present a novel analysis of the physical origins of crosstalk arising from the power-supply distribution, as well as an efficient circuit simulation technique for the effect of crosstalk on digital signal transmission in multichannel systems. It is shown that while differential receivers exhibit a far lower crosstalk than single-ended ones, it is possible to obtain low crosstalk values in the latter case by means of suitable power supply decoupling. Experimental results in the form of two low crosstalk multichannel receiver arrays are presented to corroborate the theory. >

Design and Evaluation of an ATC-Display in Modern Glass Cockpit

To accommodate the future anticipated increase in air traffic, the Air Traffic Control (ATC) systems have to provide increased capacity by using enhanced technology. Future digital air-ground data link will enable the transmissions of automatically generated ATC messages into the cockpit. The feasibility of the visual presentation of such information is studied, using an Airbus A340 full flight training and research simulator. The study addresses in particular the development and integration of a display into the A340 cockpit, which presents tactical ATC messages and its evaluation. To specify the mental workload of the pilots, a secondary task technique, the NASA Task Load Index, a recall test, interviews and eye movement measurements are used.

A Simulator Study of the Effect of Information Load and Datalink on Crew Error

This study investigated the effects of air traffic control (ATC) induced information load and ATC communication modality on crew error in a fixed-base Boeing 747-400 flight deck simulator. To accomplish this, data from an experiment conducted by Boeing (Logan, et al., 1992) were re-analyzed. In this experiment, flightcrews engaged in two high-fidelity, full-mission scenarios. For this re-analysis, the variability in the amount of information ATC transmitted to the crew in the scheduled clearances was examined as an independent variable. To quantify this measure of information load, each scheduled ATC clearance was decomposed into mutually exclusive informational units called propositions. Each proposition consisted of one discrete “chunk” of information. On average, ATC clearances in the high information load condition contained more than two and a half times as many propositions as clearances in the low information load condition. Flightcrews made significantly more errors, and more errors per proposition, in the high information load condition than in the low information load condition. This indicates that it was the density of the information, or how many propositions were packed into each clearance, and not just the quantity of information which affected crew performance. Another manipulated variable was ATC communication modality. Each flightcrew participated in one scenario using a standard voice communications modality exclusively and in the other scenario using a combination of voice and digital DataLink. Though flightcrew error was significantly lower in the DataLink condition than the voice condition, this tendency was moderated by information load. In the low information load condition, flightcrews committed approximately the same number of errors in the voice and DataLink conditions, but in the high information load condition, flightcrews committed many more errors in the voice condition than the DataLink condition.