5 research outputs found
An Efficient Polyphase Filter Based Resampling Method for Unifying the PRFs in SAR Data
Variable and higher pulse repetition frequencies (PRFs) are increasingly
being used to meet the stricter requirements and complexities of current
airborne and spaceborne synthetic aperture radar (SAR) systems associated with
higher resolution and wider area products. POLYPHASE, the proposed resampling
scheme, downsamples and unifies variable PRFs within a single look complex
(SLC) SAR acquisition and across a repeat pass sequence of acquisitions down to
an effective lower PRF. A sparsity condition of the received SAR data ensures
that the uniformly resampled data approximates the spectral properties of a
decimated densely sampled version of the received SAR data. While experiments
conducted with both synthetically generated and real airborne SAR data show
that POLYPHASE retains comparable performance to the state-of-the-art BLUI
scheme in image quality, a polyphase filter-based implementation of POLYPHASE
offers significant computational savings for arbitrary (not necessarily
periodic) input PRF variations, thus allowing fully on-board, in-place, and
real-time implementation
Efficient Approaches for Voice Change and Voice Conversion Systems
In this thesis, the study and design of Voice Change and Voice Conversion systems are
presented. Particularly, a voice change system manipulates a speaker’s voice to be perceived
as it is not spoken by this speaker; and voice conversion system modifies a speaker’s voice,
such that it is perceived as being spoken by a target speaker.
This thesis mainly includes two sub-parts. The first part is to develop a low latency and low
complexity voice change system (i.e. includes frequency/pitch scale modification and formant
scale modification algorithms), which can be executed on the smartphones in 2012 with very
limited computational capability. Although some low-complexity voice change algorithms
have been proposed and studied, the real-time implementations are very rare. According to the
experimental results, the proposed voice change system achieves the same quality as the
baseline approach but requires much less computational complexity and satisfies the
requirement of real-time. Moreover, the proposed system has been implemented in C
language and was released as a commercial software application. The second part of this
thesis is to investigate a novel low-complexity voice conversion system (i.e. from a source
speaker A to a target speaker B) that improves the perceptual quality and identity without
introducing large processing latencies. The proposed scheme directly manipulates the
spectrum using an effective and physically motivated method – Continuous Frequency
Warping and Magnitude Scaling (CFWMS) to guarantee high perceptual naturalness and
quality. In addition, a trajectory limitation strategy is proposed to prevent the frame-by-frame
discontinuity to further enhance the speech quality. The experimental results show that the
proposed method outperforms the conventional baseline solutions in terms of either objective
tests or subjective tests
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An Efficient Polyphase Filter Based Resampling Method for Unifying the PRFs in SAR Data
Variable and higher pulse repetition frequencies (PRFs) are increasinglybeing used to meet the stricter requirements and complexities of currentairborne and spaceborne synthetic aperture radar (SAR) systems associated withhigher resolution and wider area products. POLYPHASE, the proposed resamplingscheme, downsamples and unifies variable PRFs within a single look complex(SLC) SAR acquisition and across a repeat pass sequence of acquisitions down toan effective lower PRF. A sparsity condition of the received SAR data ensuresthat the uniformly resampled data approximates the spectral properties of adecimated densely sampled version of the received SAR data. While experimentsconducted with both synthetically generated and real airborne SAR data showthat POLYPHASE retains comparable performance to the state-of-the-art BLUIscheme in image quality, a polyphase filter-based implementation of POLYPHASEoffers significant computational savings for arbitrary (not necessarilyperiodic) input PRF variations, thus allowing fully on-board, in-place, andreal-time implementation
Abstracts on Radio Direction Finding (1899 - 1995)
The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography).
Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM.
The contents of these files are:
1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format];
2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format];
3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion