Publications
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The Lincoln Near-Earth Asteroid Research (LINEAR) Program
Summary
Summary
Lincoln Laboratory has been developing electro-optical space-surveillance technology to detect, characterize, and catalog satellites for more than forty years. Recent advances in highly sensitive, large-format charge-coupled devices (CCDs) allow this technology to be applied to detecting and cataloging asteroids, including near-Earth objects (NEOs). When equipped with a new Lincoln Laboratory...
AM-FM separation using auditory-motivated filters
Summary
Summary
An approach to the joint estimation of sine-wave amplitude modulation (AM) and frequency modulation (FM) is described based on the transduction of frequency modulation into amplitude modulation by linear filters, being motivated by the hypothesis that the auditory system uses a similar transduction mechanism in measuring sine-wave FM. An AM-FM...
Description of radar correlation and interpolation algorithms for the ASR-9 Processor Augmentation Card (9-PAC)
Summary
Summary
MIT Lincoln Laboratory, under sponsorship from the Federal Aviation Adminstration (FAA), is conducting a program to replace/upgrade the existing ASR-9 array signal processor (ASP) and associated algorithms to improve performance and future maintainability. The ASR-9 processor augmentation card (9-PAC) replaces the ASP four-board set with a single card containing three...
Digital signal processing applications in cochlear-implant research
Summary
Summary
We have developed a facility that enables scientists to investigate a wide range of sound-processing schemes for human subjects with cochlear implants. This digital signal processing (DSP) facility-named the Programmable Interactive System for Cochlear Implant Electrode Stimulation (PISCES)-was designed, built, and tested at Lincoln Laboratory and then installed at the...
Energy separation in signal modulations with application to speech analysis
Summary
Summary
Oscillatory signals that have both an amplitude-modulation (AM) and a frequency-modulation (FM) structure are encountered in almost all communication systems. We have also used these structures recently for modeling speech resonances, being motivated by previous work on investigating fluid dynamics phenomena during speech production that provide evidence for the existence...
Detection of transient signals using the energy operator
Summary
Summary
A function of the Teager-Kaiser energy operator is introduced as a method for detecting transient signals in the presence of amplitude-modulated and frequency-modulated tonal interference. This function has excellent time resolution and is robust in the presence of white noise. The output of the detection function is also independent of...
Two-talker pitch tracking for co-channel talker interference suppression
Summary
Summary
Almost all co-channel talker interference suppression systems use the difference in the pitches of the target and jammer speakers to suppress the jammer and enhance the target. While joint pitch estimators outputting two pitch estimates as a function of time have been proposed, the task of proper assignment of pitch...
Initialization for improved IIR filter performance
Summary
Summary
A new method for initializing the memory registers of IIR filters is introduced. In addition to providing improved performance as compared to other methods of initialization, this method is unique in that it makes no a priori assumptions regarding the input-signal content. Therefore, this method applies equally well to a...
Speech nonlinearities, modulations, and energy operators
Summary
Summary
In this paper, we investigate an AM-FM model for representing modulations in speech resonances. Specifically, we propose a frequency modulation (FM) model for the time-varying formants whose amplitude varies as the envelope of an amplitude-modulated (AM) signal. To detect the modulations we apply the energy operator (psi)(x) = (x)^2 -...
Short-time signal representation by nonlinear difference equations
Summary
Summary
The solution of a nonlinear difference equation can take on complicated deterministic behavior which appears to be random for certain values of the equation's coefficients. Due to the sensitivities to initial conditions of the output of such "chaotic" systems, it is difficult to duplicate the waveform structure by parameter analysis...