Aperture-Level Simultaneous Transmit and Receive (STAR) with Digital Phased Arrays

In the signal processing community, it has long been assumed that transmitting and receiving useful signals at the same time in the same frequency band at the same physical location was impossible. A number of insights in antenna design, analog hardware, and digital signal processing have allowed researchers to achieve simultaneous transmit and receive (STAR) capability, sometimes also referred to as in-band full-duplex (IBFD). All STAR systems must mitigate the interference in the receive channel caused by the signals emitted by the system. This poses a significant challenge because of the immense disparity in the power of the transmitted and received signals. As an analogy, imagine a person that wanted to be able to hear a whisper from across the room while screaming at the top of their lungs. The sound of their own voice would completely drown out the whisper. Approaches to increasing the isolation between the transmit and receive channels of a system attempt to successively reduce the magnitude of the transmitted interference at various points in the received signal processing chain. Many researchers believe that STAR cannot be achieved practically without some combination of modified antennas, analog self-interference cancellation hardware, digital adaptive beamforming, and digital self-interference cancellation. The aperture-level simultaneous transmit and receive (ALSTAR) paradigm confronts that assumption by creating isolation between transmit and receive subarrays in a phased array using only digital adaptive transmit and receive beamforming and digital self-interference cancellation. This dissertation explores the boundaries of performance for the ALSTAR architecture both in terms of isolation and in terms of spatial imaging resolution. It also makes significant strides towards practical ALSTAR implementation by determining the performance capabilities and computational costs of an adaptive beamforming and self-interference cancellation implementation inspired by the mathematical structure of the isolation performance limits and designed for real-time operation

Bayesian Estimation of Transient Engine Exhaust Composition from Fourier Transform Infrared Spectroscopy Measurements

Mobile sources comprise a substantial portion of anthropogenic volatile organic compound (VOC) emissions worldwide. Many research efforts have sought to elucidate the relationships between VOC emissions and engine operating conditions, which are largely transient in real-world scenarios. However, the literature remains dominated by steady-state data and batch measurements of total emissions over entire driving cycles. Fourier transform infrared (FTIR) spectroscopy is a promising technique for obtaining instantaneous, time-resolved VOC measurements. However, FTIR measurements of chemically evolving samples are biased due to sample recirculation and signal non-stationarity. To extract accurate emissions profiles from biased FTIR measurements of transient emissions, an Unscented Kalman filter (UKF) is developed. The UKF is a model-based algorithm which incorporates sample mixing dynamics, a measurement model of non-stationarity effects, and noise statistics to infer instantaneous exhaust composition in a statistically optimal manner. The sample mixing model is developed and validated using computational fluid dynamics and mixing network simulations. Non-stationarity effects – which produce FTIR measurements that are unevenly weighted by spectral IR powers at/near the centerburst position of the modulating mirror – are mathematically and experimentally proven to emerge due to alternating scan directions. A numerical method is developed to estimate the degree of centerburst weighting on measurements of unique VOCs, which is mathematically shown to scale with spectral absorbance broadening. The UKF is experimentally validated by flowing transient, trace quantities of acetylene and propylene through a FTIR gas cell and filtering the resulting measurements. Average improvements of 58% and 51% are achieved for estimations of acetylene and propylene composition, respectively, compared to unfiltered FTIR measurements. The UKF is employed to investigate transient effects on emissions of various fuel component VOCs (cyclohexane, ethanol and pentane) and intermediates (1,3 butadiene, acetylene, ethylene, formaldehyde and methane) from a spark-ignited, port fuel-injected gasoline engine under various load ramps. Deterministic transient effects are evident, as emissions deviate from quasi-steady predictions by statistically significant quantities in 14 of the 21 species/load profile combinations explored. For the intermediate species, greater quasi-steady prediction errors correspond to faster ramp rates, while greater errors occur during moderate load ramps for fuel component species

Survey of FPGA applications in the period 2000 – 2015 (Technical Report)

Romoth J, Porrmann M, Rückert U. Survey of FPGA applications in the period 2000 – 2015 (Technical Report).; 2017.Since their introduction, FPGAs can be seen in more and more different fields of applications. The key advantage is the combination of software-like flexibility with the performance otherwise common to hardware. Nevertheless, every application field introduces special requirements to the used computational architecture. This paper provides an overview of the different topics FPGAs have been used for in the last 15 years of research and why they have been chosen over other processing units like e.g. CPUs

Mobile Robots Navigation

Mobile robots navigation includes different interrelated activities: (i) perception, as obtaining and interpreting sensory information; (ii) exploration, as the strategy that guides the robot to select the next direction to go; (iii) mapping, involving the construction of a spatial representation by using the sensory information perceived; (iv) localization, as the strategy to estimate the robot position within the spatial map; (v) path planning, as the strategy to find a path towards a goal location being optimal or not; and (vi) path execution, where motor actions are determined and adapted to environmental changes. The book addresses those activities by integrating results from the research work of several authors all over the world. Research cases are documented in 32 chapters organized within 7 categories next described

Flight Mechanics/Estimation Theory Symposium, 1991

Twenty-six papers and abstracts are presented. A wide range of issues related to orbit attitude prediction, orbit determination, and orbit control are examined including attitude sensor calibration, attitude dynamics, and orbit decay and maneuver strategy. Government, industry, and the academic community participated in the preparation and presentation of these papers

MIMO OFDM Radar-Communication System with Mutual Interference Cancellation

This work describes the OFDM-based MIMO Radar-Communication System, intended for operation in a multiple-user network, especially the automotive sector in the vehicle-to vehicle/infrastructure network. The OFDM signals however are weak towards frequency offsets causing subcarrier misalignment and corrupts the radar estimation and the demodulation of the communication signal. A simple yet effective interference cancellation algorithm is detailed here with real time measurement verification

Coordinated Transit Response Planning and Operations Support Tools for Mitigating Impacts of All-Hazard Emergency Events

This report summarizes current computer simulation capabilities and the availability of near-real-time data sources allowing for a novel approach of analyzing and determining optimized responses during disruptions of complex multi-agency transit system. The authors integrated a number of technologies and data sources to detect disruptive transit system performance issues, analyze the impact on overall system-wide performance, and statistically apply the likely traveler choices and responses. The analysis of unaffected transit resources and the provision of temporary resources are then analyzed and optimized to minimize overall impact of the initiating event

Publications of the Jet Propulsion Laboratory, 1977

This bibliography cites 900 externally distributed technical reports released during calendar year 1977, that resulted from scientific and engineering work performed, or managed, by the Jet Propulsion Laboratory. Report topics cover 81 subject areas related in some way to the various NASA programs. The publications are indexed by: (1) author, (2) subject, and (3) publication type and number. A descriptive entry appears under the name of each author of each publication; an abstract is included with the entry for the primary (first-listed) author