Air Force Avionics Laboratory Research Articles

History of the mera antenna

Texas Instruments began development of the molecular electronics for radar applications (MERA) solid-state X-band phased-array antenna for the U.S. Air Force Avionics Laboratory in 1964. Its development is very briefly mentioned.

The beginnings of stealth technology

The work led by the Air Force Avionics Laboratory from the early 1950s to 1970s is discussed. Emphasis is placed on radar echo, although all observables-infrared radiation, optical, acoustics, etc.-are important to stealth design. The current capability to minimize observables is traced from the first efforts to understand what determines radar echo through the development of materials and techniques to minimize it. Applications and demonstrations are reviewed. >

Comparing how atomicity mechanisms support replication

Most pessimistic mechanisms for implementing atomicity in distributed systems fall into three broad categories: two-phase locking schemes, timestamping schemes, and hybrid schemes employing both locking and timestamps. This paper proposes a new criterion for evaluating these mechanisms: the constraints they impose on the availability of replicated data.A replicated data item is a typed object that provides a set of operations to its clients. A quorum for an operation is any set of sites whose co-operation suffices to execute that operation, and a quorum assignment associates a set of quorums with each operation. Constraints on quorum assignment determine the range of availability properties realizable by a replication method.This paper compares the constraints on quorum assignment necessary to maximize concurrency under generalized locking, timestamping, and hybrid concurrency control mechanisms. This comparison shows that hybrid schemes impose weaker constraints on availability than timestamping schemes, and locking schemes impose constraints incomparable to those of the others. Because hybrid schemes permit more concurrency than locking schemes, these results suggest that hybrid schemes are preferable to the others for ensuring atomicity in highly available and highly concurrent distributed systems.This research was sponsored by the Defense Advanced Research Projects Agecy (DOD), ARPA Order No. 3597, monitored by the Air Force Avionics Laboratory Under Contract F33615-81-K-1539.The views and conclusions contained in this document are those of the authords and should not be interpreted as representing the official policies, either expressed or implied, of the Defense Advanced Research Projects Agency or the US Government.

Distributed transactions for reliable systems

Facilities that support distributed transactions on user-defined types can be implemented efficiently and can simplify the construction of reliable distributed programs. To demonstrate these points, this paper describes a prototype transaction facility, called TABS, that supports objects, transparent communication, synchronization, recovery, and transaction management. Various objects that use the facilities of TABS are exemplified and the performance of the system is discussed in detail. The paper concludes that the prototype provides useful facilities, and that it would be feasible to build a high performance implementation based on its ideas. This work was supported by IBM and the Defense Advanced Research Projects Agency, ARPA Order No. 3597, monitored by the Air Force Avionics Laboratory under Contract F33615-81-K-1539, and by graduate fellowships from the National Science Foundation and the Office of Naval Research. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of any of the sponsoring agencies or the US government. Accent is a trademark of Carnegie.Mellon University. Perq is a trademark of Perq Systems Corporation. TAB is a trademark of the Coca-Cola Company. Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Association for Computing Machinery. To copy otherwise, or to republish, requires a fee and/or specific permission. © 1985 A C M 0 8 9 7 9 l1 7 4 1 1 2 / 8 5 0 1 2 7 $ 0 0 . 7 5 1. In t roduct ion General purpose facilities that support distributed transactions are feasible to implement and useful in simplifying the construction of reliable distributed applications. To justify this assertion, this paper describes the design, implementation, use, and performance of TABS [Spector et al. 85], a prototype facility that supports transactions on user-defined abstract objects. We attempt to generalize from our experi6nces with the prototype, particularly in the sections on the usage and performance of TABS. We define a distributed transaction facility as a distributed collection of components that supports not only such standard abstractions as processes and inter-process communication, but also the execution of transactions and the implementation of objects on which operations can be performed. Although there is room for diversity in its exact functions, a distributed transaction facility must make it easy to initiate and commit transactions, to call operations on .objects from within transactions, and to implement abstract types that have correct synchronization and recovery properties. Transactions provide three properties that should make them useful in a variety of distributed applications [Lomet 77, Liskov 82, Spector and Schwarz 83]. Synchronization properties, such as serializability, guarantee that concurrent readers and writers of data do not interfere with each other. Failure atomicity simplifies the maintenance of invariants on data by ensuring that updates are not partially done. Permanence provides programmers the luxury of knowing that only catastrophic failures will corrupt or erase previously made updates. Certainly, these properties of transactions are useful in database applications [Gray 78, Date 83]. Database applications are typically characterized by the need for absolute data integrity, permanent updates, and careful synchronization between processes that access large quantities of shared data. When considering the application of transactions to other domains such as the construction of distributed operating systems and real time systems, there are questions pertaining to what transaction facilities should be provided, how they should

Knowledge-based expert systems

This research was sponsored by the Defense Advanced Research Projects Agency (DOD), ARPA Order No. 3597, monitored by the Air Force Avionics Laboratory Under Contract F33615-78-C-1551. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Defense Advanced Research Projects Agency or the US Government.

Determination of optical transfer functions by direct measurement

The success of using the Modulation Transfer Function (MTF) in characterizing image location and image quality for aerial mapping cameras is dependent upon the ability to successfully and accurately measure this quantity. This paper will present the results of such measurements, made by the Air Force Avionics Laboratory, on two cameras, A Wild RC-8 R-10 and a Zeiss RMK AR 15/23. MTF measurements were made on-axis and at 10°, 20°, 30°, 40° and 45° for both radial and tangential orientations. Through-focus runs at each field position were conducted. All measurements were made in filtered green light ( λ = 546.1 nm). The results are compared with those made at the “Physikalisch-Technische Bundesanstalt” in West Germany.

LASER COMMUNICATIONS IN SPACE: Nd:YAG TECHNOLOGY STATUS

Annals of the New York Academy of SciencesVolume 267, Issue 1 p. 342-358 LASER COMMUNICATIONS IN SPACE: Nd:YAG TECHNOLOGY STATUS Laser Communications in Space J. Dale Barry, J. Dale Barry Space Laser Communications, Program 405B Air Force Avionics Laboratory (AFAL/405B) Wright-Patterson Air Force Base Ohio 45433 SAMSO/DYC, Space Laser Communications, 405B, P.O. Box 92960, Worldway Postal Center, Los Angeles, Calif. 90009.Search for more papers by this author J. Dale Barry, J. Dale Barry Space Laser Communications, Program 405B Air Force Avionics Laboratory (AFAL/405B) Wright-Patterson Air Force Base Ohio 45433 SAMSO/DYC, Space Laser Communications, 405B, P.O. Box 92960, Worldway Postal Center, Los Angeles, Calif. 90009.Search for more papers by this author First published: January 1976 https://doi.org/10.1111/j.1749-6632.1976.tb41619.xCitations: 5 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume267, Issue1Third Conference on the LaserJanuary 1976Pages 342-358 RelatedInformation

Digital Phase Processing for Low-Cost Omega Receivers

Under a continuing program sponsored by the Air Force Avionics Laboratory, a variety of new phase-processing techniques have been developed at the Charles Stark Draper Laboratory [1, 2, 3, 4]. Recently, special types of digital-phase-locked loops [3, 4] have been developed and appear to offer special advantages when applied to radio-navigation receivers and timing receivers. One of these loops, which is referred to as a serial digital phase filter (SDPF), appears to be so simple in construction and useful in application as to be worth producing as a basic LSI building block. In this paper, the application of the SDPF to Omega receivers is explored. It is shown that the internal functions of an Omega receiver can be organized to take advantage of one or more SDPF's used in combination with an LSI microprocessor. The SDPF's can be used to reduce the load on the microprocessor by reducing the bandwidth of the phase data being presented to it. The SDPF's can also accomplish demodulation and analog-to-digital conversion, thereby eliminating the need for special circuitry to perform these functions. Because of the reduction in data bandwidth, there is an increase in efficiency and productivity of the microprocessor. The processing efficiency of the entire receiver is then more closely maximized with respect to hardware and software cost. The design approach is applicable to a bare-bones receiver, which would incorporate the most elementary and inexpensive microprocessor or no microprocessor at all, or to a high-performance airborne receiver where a variety of sophisticated functions must be performed automatically by the microprocessor. The paper is divided into five main sections. First, the organization of the receiver is described and the advantages of the recommended approach are pointed out. Then the SDPF is described in detail. Then the hardware developed for laboratory demonstration is described. The tracking performance of the receiver is discussed next, and theoretical and experimental data are provided for illustration. Finally, procedures for automatic synchronization are described and supported by experimental data. Some important areas, such as lane identification, propagation prediction, antenna design, etc., are treated only lightly as being more relevant to specific designs than to the problem of reducing cost by improving the efficiency of phase processing.

Transform Method of Fast Digital Synthesis of Unvoiced Speech Sounds

Digital speech synthesis is often carried out by direct convolution of a sequence of unit samples with a sampled impulse response. In the case of unvoiced sounds, this method can lead to the need for an excessively large number of additions per output sample of the synthesized waveform. This is because of the requirement that the synthesized output be essentially Gaussian and possess the correct spectral energy distribution in order to achieve natural-sounding unvoiced sounds. This paper describes a transform method based upon the Cramer-Kolmogarov representation for a stationary process that reduces the required number of additions per output sample by a factor of at least 10, and which has been found experimentally to produce high-quality synthetic speech. The performance of the method is demonstrated by playing a tape recording of the output of an all-digital vocoder that uses this method of synthesis. [Work supported by Air Force Avionics Laboratory, Wright-Patterson Air Force Base, Ohio.]

An Accumulator Chip

A large-scale integrated-circuit chip has been designed under the sponsorship of the Air Force Avionics Laboratory. The chip was developed as part of a logic synthesizer effort of the Design Automation group at Litton Systems, Inc., Guidance and Control Systems Division. It was designed as a type or category to be multiply used with one other gating type chip whose format is prescribed by the logic synthesizer. A major goal of this effort will be to design a complete digital system by design-automated techniques using only these two types of chips in a large-scale array.

Astronaut Maneuvering-Unit Voice Controller

An experimental voice controller to be used in conjunction with an astronaut maneuvering unit has been developed by RCA Advanced Technology under the sponsorship of the Air Force Aero Propulsion Laboratory and the Air Force Avionics Laboratory. The voice controller will permit the spaceman to move about freely outside his space capsule merely by speaking commands into his helmet microphone. The experimental unit recognizes 13 command words in continuous speech, in real time, including such combinations as “roll right” and “pitch up.” The command vocabulary was chosen so that no two words differ only by a single phoneme. This was done to ensure that confusion between command words would not occur and so that the equipment could be simplified to the point where it could be built small enough to be included in the backpack of the astronaut. The experimental model is about the size of a suitcase, weighs 25 lb, and consumes 46 W. However, the experimental unit incorporates design principles necessary to construct a space unit that is less than 100 in.3 in volume, weighs less than 5 lb, and consumes less than 10 W.

Speech Recognition, Using Analog Threshold Logic

A speech-analysis system using analog threshold logic (ATL) for feature abstraction is being developed to recognize consonants in utterances of CVC words by a number of talkers. The ATL element, originally modeled after the biological neuron, has an output that is linearly proportional to the net sum of excitatory and inhibitory inputs, provided that this net sum is greater than some adjustable threshold. The speech-analysis system abstracts relatively steady-state as well as transient features over almost 60 dB of dynamic range from the logarithmitized outputs of 19 low-Q filters. Feature abstraction takes place in real time, does not require segmentation, utilizes parallel processing, and provides information about both the presence and magnitude of the frequency-energy-temporal characteristics of speech sounds. Many features corresponding to results of speech-recognition experiments described in the literature have been automatically abstracted by ATL networks, which measure the slope of the spectral envelope in real time. Using the experimental system, recognition scores in the range of 82%–99% were obtained for 16 consonants. Results for the fricative consonants are discussed and some of their invariant features described. [Work supported by the U. S. Air Force Research and Technology Division, Air Force Avionics Laboratory.]