Robust coherent laser radar design and signal processing for vibrometry

Millnert, Mille; Carlsson, Christina; Karlsson, Christer J.; Letalick, Dietmar; Renhorn, Ingmar

doi:10.1117/12.243545

Cited by 4 publications

(10 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The price of this time-frequency resolution is interference effects which, are reduced by window functions listed below. The Choi-Williams JTFT has been studied in particular [3][4][5]9 for laser radar applications. JTFT extrapolation from analog to digital signals, as in a computer, however, is not as straightforward 15 as one might think.…”

Section: Joint Time-frequency Transform Processingmentioning

confidence: 99%

See 1 more Smart Citation

Joint time-frequency transform processing for linear and sinusoidal FM coherent ladars

Youmans

2003

SPIE Proceedings

View full text Add to dashboard Cite

We examine the signal processing of both linear and sinusoidal frequency modulation (FM) coherent ladar returns from resolved and unresolved targets, which are spread in Doppler. The Doppler spread may be due to target spin, tumbling, or vibration as well as to the applied linear or sinusoidal-FM on the transmitted E-field. Monte Carlo realizations of the target surface random phasor reflector elements interact with the incident E-field producing laser speckle, and the speckled returns are analyzed in this study. The speckle signals are processed (1) using several spectrum (periodogram based) estimators, (2) the conventional "spectrogram" approach, and (3) ten joint time-frequency transforms (JTFT). We show that the Born-Jordan JTFT is superior to the other spectral estimators tested here in suppressing local oscillator laser noise and accurately estimating the target's spectrum for signal processing under speckle target return conditions pertaining to coherent laser radar. A new algorithm which sums particular pixels of the JTFT image is introduced and is shown to be much more robust in low CNR conditions than the JTFT maxima or JTFT centroid processing when utilizing the applied linear or sinusoidal-FM modulation waveform.

show abstract

Section: Joint Time-frequency Transform Processingmentioning

confidence: 99%

“…Target vibration sensing by CW coherent ladar at distances greater than ~1 km have been investigated previously [1][2][3][4][5][6][7][8][9] . In those studies the spectrogram (discussed in Sect.…”

Section: Introductionmentioning

confidence: 99%

Joint time-frequency transform processing for linear and sinusoidal FM coherent ladars

Youmans

2003

SPIE Proceedings

View full text Add to dashboard Cite

show abstract

“…Target vibration sensing by CW or long-pulse quasi-CW coherent ladar at distances greater than ~1 km has been investigated and reported in previous research work [1][2][3][4][5][6][7][8][9] . The target's vibration spectrum is determined by the target's piston produced phase-shift: and its harmonics.…”

Section: Resolved Target Vibrating Surface Spectramentioning

confidence: 99%

Spectral estimation of Doppler spread vibrating targets using coherent ladar

Youmans

2004

SPIE Proceedings

View full text Add to dashboard Cite

Coherent laser radars observing a resolved (larger than the incident laser mode) target vibrating surface can estimate the target's piston-mode displacement motion from the target's Doppler produced frequency spectrum. We review recent work showing that a newly developed joint time-frequency transform algorithm is superior to older joint time-frequency transforms, the common short-time-Fourier transform (spectrogram) algorithm, and other elementary spectral estimation algorithms for resolving the target's spectra. In this paper we extend these approaches when the ladar is observing an unresolved (smaller than the incident laser mode) piston-mode vibrating object situated on the ground. Because the target is smaller than the laser spot, the surrounding ground produces a narrow-band constant frequency "clutter" signal at the baseband frequency. We show that a recently developed "sech-window" joint time-frequency transform is superior to other algorithms for separating the frequency modulated target piston motion signal from the narrow-band ground return. The analysis in this case includes a "signal-to-clutter ratio" (SCR) parameter variation as well as a "carrier-to-noise ratio" (CNR), or target signal strength to LO-laser noise strength, parameter variation.

show abstract

“…By including , as seen in Fig. 3, the gain at lower frequencies and up to the passband can be expressed as (6) When deriving (6) we have assumed infinite open loop OP-amp gain. From now on, this assumption is always made when deriving transfer functions.…”

Section: Solutionmentioning

confidence: 99%

Single-stage photodiode op-amp solution suited for a self-mixing fmcw system

Nordin¹,

Hyyppä²

2003

IEEE Trans. Instrum. Meas.

View full text Add to dashboard Cite

Abstract-The current delivered by the photodiode in a self-mixing frequency modulated continuous wave or optical frequency domain reflectometry system consists of a dc-current resulting from the local oscillator, the reflected signal, dark current in the photodiode, and current generated from background light. The current also contains the useful harmonic signal with a beat frequency corresponding to the range and radial velocity of a target. To avoid saturation and clipping due to the dc current generated in the photodiode, it is desirable to minimize the gain at dc while maintaining a high gain in the beat frequency region. We have investigated some different solutions and present a modified current-to-voltage converter using bootstrapping and added voltage gain, which addresses this problem using only one OP-amp and no dc shorting inductors.Index Terms-Frequency modulated continuous wave (FMCW), operation amplifier, optical frequency domain reflectometry (OFDR), photodiode, transimpedance amplifier.

show abstract

Robust coherent laser radar design and signal processing for vibrometry

Cited by 4 publications

References 4 publications

Joint time-frequency transform processing for linear and sinusoidal FM coherent ladars

Joint time-frequency transform processing for linear and sinusoidal FM coherent ladars

Spectral estimation of Doppler spread vibrating targets using coherent ladar

Single-stage photodiode op-amp solution suited for a self-mixing fmcw system

Contact Info

Product

Resources

About