Cavity ringdown spectroscopy (CRDS) measures the decay time, of a resonant optical cavity containing a measurand, as a function of optical frequency. The measurand is identified and quantified by the cavity decay time...
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ISBN:
(纸本)9780819486066
Cavity ringdown spectroscopy (CRDS) measures the decay time, of a resonant optical cavity containing a measurand, as a function of optical frequency. The measurand is identified and quantified by the cavity decay time, which is modified by the measurand within. As coupling light into a high-finesse optical cavity is difficult, the throughput of the cavity is small. A recent variant, swept-cavity heterodyne CRDS, interferes backward escaping cavity light, with light reflected from the cavity input mirror, providing better signal sensitivity due to the heterodyne advantage. The measured interference signal is demodulated and log-amplified to produce a signal whose slope is representative of the cavity decay time. This paper, for the first time, examines the conditions required for high-fidelity measurements of the cavity decay time using swept-cavity heterodyne CRDS and log-amplification technique. We demonstrate that, due to the very large bandwidth and dynamic range of the log-amplifier, for realistic measurement conditions, the log-amplifier does not impose any significant restrictions on the measurement accuracy. We also demonstrate, however, the measurement accuracy is limited by two factors, the detector bandwidth, and segment of acquired data used to measure the slope.
In this paper, the performance of three-dimensional (3-D) image obtained by processing single-pass multi-azimuth-angle (SP-MAA) synthetic aperture radar (SAR) data is analyzed and the result shows that it is unsuitabl...
ISBN:
(数字)9781728123455
ISBN:
(纸本)9781728123462
In this paper, the performance of three-dimensional (3-D) image obtained by processing single-pass multi-azimuth-angle (SP-MAA) synthetic aperture radar (SAR) data is analyzed and the result shows that it is unsuitable for 3-D imaging using SP-MAA SAR data. Firstly, the imaging geometry and signal model of the SP-MAA SAR are built. Then, the 3-D imaging algorithm is used to process the SP-MAA SAR data, and the 3-D image is obtained. Thirdly, the performance of the 3-D image is analyzed, and there are many ghost targets caused by azimuth sidelobes of the true targets in the 3-D image, which means it is unsuitable to obtain 3-D image using the SP-MAA SAR data. Finally, the simulation results verify the analysis results.
Recent advances in knowledge-aided space-time adaptive processing (KA-STAP) have resulted in significant performance improvements for ground moving target indication (GMTI) radar systems. In particular, the use of pri...
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Recent advances in knowledge-aided space-time adaptive processing (KA-STAP) have resulted in significant performance improvements for ground moving target indication (GMTI) radar systems. In particular, the use of prior knowledge including terrain, clutter discretes, and previously detected targets has been shown to be effective for mitigating the poor performance often encountered when operating in heterogeneous clutter environments. This paper provides an evaluation of KA-STAP techniques based on extensive processing of experimental data. Two major performance issues are addressed: high false alarm rates due to under-nulled clutter discretes and target cancellation due to corruption of the STAP training data by other targets in the scene. Each of these problems is demonstrated using experimental multi-channel X-band radar data. Methods for using prior knowledge to improve performance are presented and processing results using the experimental data are provided that show how KA-STAP can lead to significantly improved detection performance relative to conventional STAP processing.
A vectorized belief propagation polar code decoder is desirable because of the potentially high throughput and the ability of integration in processors that perform vectorized processing and access wide memory words. ...
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ISBN:
(纸本)9781450375047
A vectorized belief propagation polar code decoder is desirable because of the potentially high throughput and the ability of integration in processors that perform vectorized processing and access wide memory words. However, current state-of-the-art belief propagation polar code decoder algorithms do not perform vector processing and store intermediate results in non consecutive memory locations. Also the current state-of-the-art belief propagation polar code decoders require separate memories to store left and right bound intermediate results. In this paper we propose a vectorized in-order in-place belief propagation polar code decoder algorithm where all stages access vectorized data from memory. This results in a high throughput because vectors of elements can be fetched from and stored in memory in each clock cycle. Our algorithm also accommodates for per stage in-place computations which halves the required internal memory. Furthermore, the algorithm has a regular memory addresses access pattern. Conflict free vectorized memory access is achieved by making use of transpose operations on small groups of intermediate results. The use of the transpose operations also results in that both input and output results are placed on subsequent locations in memory.
In this paper, we consider the problem of radar detector threshold optimization for maneuvering targets in clutter. In the earlier works, the problem was studied in the context of the probabilistic data association fi...
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In this paper, we consider the problem of radar detector threshold optimization for maneuvering targets in clutter. In the earlier works, the problem was studied in the context of the probabilistic data association filter (PDAF) for non-maneuvering targets. In this study, we have extended the ideas, which were applied to the PDAF, to the interacting multiple model PDAF (IMM-PDAF) for maneuvering targets. The proposed optimization problem and its solution show better results over the traditional approaches in terms of track loss percentage and RMS position error criteria.
This paper studies the unmanned aerial vehicle (UAV)-enabled integrated sensing and communication (ISAC), in which UAVs are dispatched as aerial dual-functional access points (APs) that can exploit the UAV maneuver co...
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ISBN:
(数字)9781538683477
ISBN:
(纸本)9781538683477
This paper studies the unmanned aerial vehicle (UAV)-enabled integrated sensing and communication (ISAC), in which UAVs are dispatched as aerial dual-functional access points (APs) that can exploit the UAV maneuver control and strong line-of-sight (LoS) aerial-to-ground (A2G) links for efficient ISAC. Particularly, we consider a scenario with one UAV-AP equipped with a vertically placed uniform linear array (ULA), which sends combined information and sensing signals to communicate with multiple users and at the same time sense potential targets on the ground. Our objective is to jointly design the UAV trajectory and transmit beamforming to maximize the average weighted sum-rate throughput of communication users over the whole period, subject to the sensing beampattern gain requirements and transmit power constraints over different time slots, as well as practical flight constraints. While the above problem is challenging to solve, we propose an efficient algorithm by adopting the alternating optimization together with the successive convex approximation (SCA) and semidefinite relaxation (SDR). Numerical results are provided to validate the superiority of our proposed designs as compared to various benchmark schemes with heuristic trajectory designs.
In both military and civilian contexts, accurate detection of radar attitude deviations using ISAR is crucial but challenging due to the incomplete target edges and missing electromagnetic scattering components. Avail...
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ISBN:
(数字)9798331541460
ISBN:
(纸本)9798331541477
In both military and civilian contexts, accurate detection of radar attitude deviations using ISAR is crucial but challenging due to the incomplete target edges and missing electromagnetic scattering components. Available dynamic detection of space targets transforms detection into binary classification, which faces an imbalanced dataset and an incomplete repre-sentation of all anomalous samples. In this paper, we propose an abnormal dynamic detection method with small amounts of anomalies. An LSTM architecture is first constructed for the geometrical feature flow regression for stabilized space targets. Then, a small number of anomalies and normal samples are used to calculate the value of the mean absolute error (MAE) threshold to distinguish anomalies from normal samples using a statistical histogram. In this way, abnormal dynamic detection can be accomplished by comparing MAE to the threshold. Experiments validate the effectiveness of the proposal with limited anomalies.
Time-lenses in general proved to be useful for many applications and specifically when utilizing them for temporal imaging schemes where they can image ultrafast signals that cannot be detected by any electronic based...
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ISBN:
(纸本)9781510632714;9781510632721
Time-lenses in general proved to be useful for many applications and specifically when utilizing them for temporal imaging schemes where they can image ultrafast signals that cannot be detected by any electronic based device. Over the last few years, we demonstrated that when joining together several time-lenses into a single time-lens array, it is possible to gain more information on the input signal. Such as measuring temporal depth imaging, the state of polarization of the input signal as a function of time, and retrieving the phase dynamics. However, when designing an array of time-lenses, there is a trade-off between joining large number of small time-lenses, so each signal will interact with many time-lenses but each one has low resolution, and joining small number of large time-lenses, so each has better temporal resolution but on the expanse of interacting with smaller number of time-lenses in the array. We showed that one way to overcome this drawback is to overlap adjacent time-lenses. Thus it is possible to both have large number of time-lenses without compromising on the size of each time-lens and obtaining high temporal resolution. In this proceeding, we overlap two time-lenses and measure the spectrum of the idler. We compare the numerical simulations of the frequency domain of the idler to the measured spectrum of the idler.
The problem of target tracking from distributed sensors in a cluttered environment is addressed. The author and P. Forster have introduced a new and original approach in target tracking and target motion analysis. Two...
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The problem of target tracking from distributed sensors in a cluttered environment is addressed. The author and P. Forster have introduced a new and original approach in target tracking and target motion analysis. Two variants of this method have been developed, one using the Bayesian probabilities theory, and one using the theory of evidence. These variants and their specificities with regard to classic tracking methods are recalled, with some extensions to the previous work. Special attention is given to the comparison of these two variants, and to difficult cases such as multiple maneuvering targets or crossing targets.< >
This paper presents a novel technique for data sharing through neural network training target manipulation. It uses correlations between output values of a network to create a set of non-zero targets for each training...
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This paper presents a novel technique for data sharing through neural network training target manipulation. It uses correlations between output values of a network to create a set of non-zero targets for each training pattern. Experimental results show that more than 20% error reduction is achieved on a speaker-independent continuous digit string recognition task.
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