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Full-Text Articles in Engineering
A Simplified Accuracy Enhancement To The Saleh Am/Am Modeling And Linearization Of Solid-State Rf Power Amplifiers, Haider Al-Kanan, Fu Li
A Simplified Accuracy Enhancement To The Saleh Am/Am Modeling And Linearization Of Solid-State Rf Power Amplifiers, Haider Al-Kanan, Fu Li
Electrical and Computer Engineering Faculty Publications and Presentations
The Saleh behavioral model exhibits high prediction accuracy for nonlinearity of traveling-wave tube power amplifiers (TWT-PAs). However, the accuracy of the Saleh model degrades when modeling solid-state power amplifiers (SSPAs) technology. In addition, the polynomial expansion of the Saleh model consists of only odd-order terms as analyzed in this work. This paper proposes a novel model accuracy enhancement for the Saleh amplitude-to-amplitude (AM/AM) model when applied to radio frequency (RF) SSPAs. The proposed model enhancement accounts for the second-order intermodulation distortion, which is an important nonlinearity challenge in wideband wireless communications. The proposed static AM/AM model is a three-parameter rational …
Inversion Of Head Waves In Ocean Acoustic Ambient Noise, Jie Li, Peter Gerstoft, Martin Siderius, Jun Fan
Inversion Of Head Waves In Ocean Acoustic Ambient Noise, Jie Li, Peter Gerstoft, Martin Siderius, Jun Fan
Electrical and Computer Engineering Faculty Publications and Presentations
The virtual head wave is produced through cross-correlation processing of signals containing the real, acoustic head wave. The virtual head wave has the same phase speed as the head wave, but the travel time is offset, thus the term virtual. The virtual head wave, like the real head wave, propagates in a direction corresponding to the seabed critical angle. The virtual head wave travel time varies with array depth and water column depth. However, in a refracting environment, the travel time is also dependent on the depth-dependent sound speed profile. Previously, the virtual head wave was shown as observable from …
Head Waves In Ocean Acoustic Ambient Noise: Measurements And Modeling, Martin Siderius, Jie Li, Peter Gerstoft
Head Waves In Ocean Acoustic Ambient Noise: Measurements And Modeling, Martin Siderius, Jie Li, Peter Gerstoft
Electrical and Computer Engineering Faculty Publications and Presentations
Seismic interferometry recovers the Green’s function between two receivers by cross-correlating the field measured from sources that surround the receivers. In the seismic literature, it has been widely reported that this processing can produce artifacts in the Green’s function estimate called “spurious multiples” or the “virtual refracted wave.” The spurious multiples are attributed to the head wave and its multiples and travels in the seabed. The head wave phenomenon is shown to be observable from both controlled active sources and from ocean ambient noise and for both vertical and horizontal arrays. The processing used is a generalization of the passive …
Exploitation Of Frequency Information In Continuous Active Sonar, Lisa Zurk, Daniel Rouseff, Scott Schecklman
Exploitation Of Frequency Information In Continuous Active Sonar, Lisa Zurk, Daniel Rouseff, Scott Schecklman
Electrical and Computer Engineering Faculty Publications and Presentations
In pulsed active sonar, short duration coded waveforms insonify the area of interest. The low duty cycle limits detection opportunities and decreases average energy. A recent concept is continuous active sonar (CAS), which has continuous source transmission over a broad frequency band. The low duty cycle limits detection opportunities and decreases average energy. A recent concept is continuous active sonar (CAS), which has continuous source transmission over a broad frequency band. Previous work by the authors has investigated the utility of extracting the propagation-induced frequency structure in pulsed sonar. The broadband, continuous CAS waveforms particularly lend themselves to this approach. …
Aspect-Dependent Radiated Noise Analysis Of An Underway Autonomous Underwater Vehicle, John Gebbie, Martin Siderius, John S. Allen Iii
Aspect-Dependent Radiated Noise Analysis Of An Underway Autonomous Underwater Vehicle, John Gebbie, Martin Siderius, John S. Allen Iii
Electrical and Computer Engineering Faculty Publications and Presentations
This paper presents an analysis of the acoustic emissions emitted by an underway REMUS-100 autonomous underwater vehicle(AUV) that were obtained near Honolulu Harbor, HI using a fixed, bottom-mounted horizontal line array (HLA). Spectral analysis,beamforming, and cross-correlation facilitate identification of independent sources of noise originating from the AUV. Fusion of navigational records from the AUV with acoustic data from the HLA allows for an aspect-dependent presentation of calculated source levels of the strongest propulsion tone.
Striation-Based Beamforming For Estimating The Waveguide Invariant With Passive Sonar, Lisa M. Zurk, Daniel Rouseff
Striation-Based Beamforming For Estimating The Waveguide Invariant With Passive Sonar, Lisa M. Zurk, Daniel Rouseff
Electrical and Computer Engineering Faculty Publications and Presentations
The waveguide invariant summarizes the pattern of constructive and destructive interference between acoustic modes propagating in the ocean waveguide. For many sonar signal-processing schemes, it is essential to know the correct numerical value for the waveguide invariant. While conventional beamforming can estimate the ratio between the waveguide invariant and the range to the source, it cannot unambiguously separate the two terms. In the present work, striationbased beamforming is developed. It is shown that the striation-based beamformer can be used to produce an estimate for the waveguide invariant that is independent of the range. Simulation results are presented.
The Dsp Of Money, Thad B. Welch, Cameron H. G. Wright, Michael G. Morrow
The Dsp Of Money, Thad B. Welch, Cameron H. G. Wright, Michael G. Morrow
Electrical and Computer Engineering Faculty Publications and Presentations
This paper discusses a simple framework that can be used to connect a significant number of the tools and techniques developed in a first course in either discrete-time signals and systems or digital signal processing. While this framework is not revolutionary, it allows for the rapid placement of new material into the course’s context. Additionally, a simple model of an unstable financial system allows for a rapid introduction and overview of the course while observably increasing student interest and motivation. In these challenging economic times, it is somewhat reassuring to know that some unstable financial accounts are actually a good …
Depth-Shifting Of Shallow Water Guide Source Observations, Lisa M. Zurk, Brian H. Tracey
Depth-Shifting Of Shallow Water Guide Source Observations, Lisa M. Zurk, Brian H. Tracey
Electrical and Computer Engineering Faculty Publications and Presentations
In theory, matched field processing offers the significant benefit of higher signal gains and increased localization capability. However, this has not been robustly observed in practice because of inherent uncertainties about details of the shallow water propagation environments which limit the prediction of the channel response. The use of guide sources to directly measure the transfer function between source and receiver arrays has been proposed as a means for reducing mismatch. However, the guide source measurement only provides a measured transfer function at the guide source location. In this paper a method of depth-shifting guide source observations is proposed, making …
Source Motion Mitigation For Adaptive Matched Field Processing, Lisa M. Zurk, Nigel Lee, James Ward
Source Motion Mitigation For Adaptive Matched Field Processing, Lisa M. Zurk, Nigel Lee, James Ward
Electrical and Computer Engineering Faculty Publications and Presentations
Application of adaptive matched field processing to the problem of detecting quiet targets in shallow water is complicated by source motion, both the motion of the target and the motion of discrete interferers. Target motion causes spreading of the target peak, thereby reducing output signal power. Interferer motion increases the dimensionality of the interference subspace, reducing adaptive interference suppression. This paper presents three techniques that mitigate source motion problems in adaptive matched field processing. The first involves rank reduction, which enables adaptive weight computation over short observation intervals where motion effects are less pronounced. The other two techniques specifically compensate …