Dr. Hector A. Ochoa Profile

Dr. Hector A. Ochoa

Assistant Professor at Stephen F Austin State Univ

SPIE Involvement:

Author

Proceedings Article | 21 May 2015 Paper

The implementation of compressive sensing on an FPGA for chaotic radars

Hector Ochoa, David Hoe, Dinesh Veeramachaneni

Proceedings Volume 9461, 946110 (2015) https://doi.org/10.1117/12.2177369

KEYWORDS: Compressed sensing, Field programmable gate arrays, Radar, MATLAB, Matrices, Imaging systems, Image processing, Data processing, Optimization (mathematics), Linear algebra

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Proceedings Article | 31 May 2013 Paper

A compressive radar system with chaotic-based FM signals using the Bernoulli map

Hector Ochoa, Charan Teja Enugula

Proceedings Volume 8714, 871404 (2013) https://doi.org/10.1117/12.2016012

KEYWORDS: Radar, Compressed sensing, Frequency modulation, Fermium, Doppler effect, Signal generators, Chaos, Electronic filtering, Reflectivity, Time-frequency analysis

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Proceedings Article | 27 April 2010 Paper

Effects of using a first-order approximation to compensate the Doppler on large time-bandwidth product signals

Hector Ochoa, Pavan Vutukur

Proceedings Volume 7669, 76690U (2010) https://doi.org/10.1117/12.850458

KEYWORDS: Doppler effect, Electronic filtering, Radar, Analytical research, Fermium, Frequency modulation, Digital filtering, Convolution, Signal analyzers, Mathematical modeling

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Current generation radars employ a first order approximation to compensate the frequency shift due to target's velocity. This approach is inadequate when high velocity targets are considered; however, real targets do not possess such high velocities. For that reason, this research analyzes how the increment of the Time-Bandwidth (TBW) product and the target velocity would impact the analysis of radar signals when a first order approximation is implemented to compensate the Doppler shift. The common approach to improved resolution and performance of radar system is to increase the time-bandwidth product of the transmitted signal. The problem of using the first order approximation to compensate the Doppler is that it is limited only to the first two terms of a power series expansion of a full Doppler compensation. As a consequence, an increment on the target's velocity or the time-bandwidth product of the transmitted signal will result in a significant error at the output of the matched filter. On this research a Linear FM (chirp) signal with a large TBW is considered as the transmitted signal. First, to observe the effects of increasing the time-bandwidth product and target velocity the received signal is modeled using a full Doppler compensation and a first order approximation. Second, each signal is applied to the input of one matched filter in which the transmitted signal is used as a reference. Finally, the outputs from both matched filters are analyzed in order to observe the effects of using the first order approximation to model the Doppler induced on the reflected signal. This analysis was performed assuming that the target was moving at a constant velocity. By increasing the time-bandwidth product of the transmitted signal the output of both matched filters are compared and analyzed to observe the differences between modeling the reflected signal using the first order compensation and the full Doppler compensation. The simulation results showed that, by increasing the time-bandwidth product of the transmitted signal the output of the matched filter using the first order approximation deviates significantly with respect to the matched filter that contains the signal modeled using the full Doppler compensation. From these results it is concluded that a dramatic increase in time-bandwidth product of the received signal, results in a significant error at the output of the matched filter if the first order approximation is used to model the reflected signal instead of the Full Doppler compensation.

Proceedings Article | 8 May 2006 Paper

Doppler correction for high-velocity targets using a relativistic approach

Hector Ochoa, Benjamin Flores

Proceedings Volume 6210, 62100F (2006) https://doi.org/10.1117/12.666299

KEYWORDS: Fermium, Frequency modulation, Doppler effect, Stochastic processes, Radar, Phase compensation, Receivers, Electroluminescence, Reflection, Radar sensor technology

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Proceedings Article | 12 August 2004 Paper

Resolution issues in the analysis of radar signals via Fourier approaches

Benjamin Flores, Hector Ochoa, Gabriel Thomas

Proceedings Volume 5410, (2004) https://doi.org/10.1117/12.537368

KEYWORDS: Radar, Doppler effect, Signal analyzers, Spectral resolution, Destructive interference, Signal processing, Electroluminescence, Optical resolution, Computer simulations, Image resolution

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Classical work in the field of high-resolution radar often assumes that an echo signal is made of a number of components that can be decomposed via Fourier analysis. Adjacent components are said to be resolved in the frequency domain if the intensity between them drops at least 3 decibels. This working definition is an extension of Lord Rayleigh's criterion for optical resolution. The problem with this approach is that whereas Rayleigh's criterion assumes signal incoherence, thus allowing for the addition of power components, a high-resolution radar signal is often the coherent sum of sinusoids, which implies voltage addition. The purpose of this paper is to discuss the consequences of using Rayleigh's criterion in the analysis of radar signals. Specifically, computer simulations using a complex signal are analyzed via the periodogram as the relative phase between the two components of the signal is allowed to change. The net effect introduced by this phase variation is to reduce or increase the spacing and intensity between two adjacent spectral peaks. These changes are due to constructive or destructive interference of spectral cross terms that cannot be ignored when attempting to resolve frequency components from one another. For instance, the simulations show that when using the averaged periodogram, the intensity in-between two adjacent components is above the -3 decibel threshold for a phase range of 1.2π radians, although the standard resolution criterion of c/2β is satisfied. Similar results are obtained when using a number of windows that are known to control sidelobe levels. Thus, the use of Rayleigh's criterion to define the resolution of a high-resolution radar system is technically inconsistent and undermines our ability to perform quantitative comparisons of target profiles, Doppler profiles and range-Doppler images. In this light, the authors promote the adoption of alternative criteria for judging resolution gains based on the norm of the signal in the (spatial) frequency domain.

Conference Committee Involvement (11)

Radar Sensor Technology XXV

12 April 2021 | Online Only, Florida, United States

Radar Sensor Technology XXIV

27 April 2020 | Online Only, California, United States

Radar Sensor Technology XXIII

15 April 2019 | Baltimore, MD, United States

Radar Sensor Technology XXII

16 April 2018 | Orlando, FL, United States

Radar Sensor Technology XXI

10 April 2017 | Anaheim, CA, United States

Showing 5 of 11 Conference Committees

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