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A Novel Modified Omega-K Algorithm for Synthetic Aperture Imaging Lidar through the Atmosphere

View Article: PubMed Central

ABSTRACT

The spatial resolution of a conventional imaging lidar system is constrained by the diffraction limit of the telescope's aperture. The combination of the lidar and synthetic aperture (SA) processing techniques may overcome the diffraction limit and pave the way for a higher resolution air borne or space borne remote sensor. Regarding the lidar transmitting frequency modulation continuous-wave (FMCW) signal, the motion during the transmission of a sweep and the reception of the corresponding echo were expected to be one of the major problems. The given modified Omega-K algorithm takes the continuous motion into account, which can compensate for the Doppler shift induced by the continuous motion efficiently and azimuth ambiguity for the low pulse recurrence frequency limited by the tunable laser. And then, simulation of Phase Screen (PS) distorted by atmospheric turbulence following the von Karman spectrum by using Fourier Transform is implemented in order to simulate turbulence. Finally, the computer simulation shows the validity of the modified algorithm and if in the turbulence the synthetic aperture length does not exceed the similar coherence length of the atmosphere for SAIL, we can ignore the effect of the turbulence.

No MeSH data available.


FMCW signal in frequency-time domain.
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f1-sensors-08-03056: FMCW signal in frequency-time domain.

Mentions: Figure 1 shows the frequency versus time characteristics of the transmitted signal (solid line) and the received signal (dashed line).The received signal is a delayed version of the transmitted one. The lidar continuously transmits linear FM chirps with duration Tp equal to the pulse repetition interval PRI and the reciprocal of PRF. The transmitted signal is expressed as(1)sT=A·rect[t^Tp]exp(j2π(fc+12γt^2))where −Tp /2 ≤ t̂ < Tp /2, the chirp rate γ= B/ PRI, where B is the transmitted bandwidth and fc is the center frequency. The envelope of the transmitted pulse and the antenna diagram are included in the parameter A with a constant phase but a varying amplitude.


A Novel Modified Omega-K Algorithm for Synthetic Aperture Imaging Lidar through the Atmosphere
FMCW signal in frequency-time domain.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3675531&req=5

f1-sensors-08-03056: FMCW signal in frequency-time domain.
Mentions: Figure 1 shows the frequency versus time characteristics of the transmitted signal (solid line) and the received signal (dashed line).The received signal is a delayed version of the transmitted one. The lidar continuously transmits linear FM chirps with duration Tp equal to the pulse repetition interval PRI and the reciprocal of PRF. The transmitted signal is expressed as(1)sT=A·rect[t^Tp]exp(j2π(fc+12γt^2))where −Tp /2 ≤ t̂ < Tp /2, the chirp rate γ= B/ PRI, where B is the transmitted bandwidth and fc is the center frequency. The envelope of the transmitted pulse and the antenna diagram are included in the parameter A with a constant phase but a varying amplitude.

View Article: PubMed Central

ABSTRACT

The spatial resolution of a conventional imaging lidar system is constrained by the diffraction limit of the telescope's aperture. The combination of the lidar and synthetic aperture (SA) processing techniques may overcome the diffraction limit and pave the way for a higher resolution air borne or space borne remote sensor. Regarding the lidar transmitting frequency modulation continuous-wave (FMCW) signal, the motion during the transmission of a sweep and the reception of the corresponding echo were expected to be one of the major problems. The given modified Omega-K algorithm takes the continuous motion into account, which can compensate for the Doppler shift induced by the continuous motion efficiently and azimuth ambiguity for the low pulse recurrence frequency limited by the tunable laser. And then, simulation of Phase Screen (PS) distorted by atmospheric turbulence following the von Karman spectrum by using Fourier Transform is implemented in order to simulate turbulence. Finally, the computer simulation shows the validity of the modified algorithm and if in the turbulence the synthetic aperture length does not exceed the similar coherence length of the atmosphere for SAIL, we can ignore the effect of the turbulence.

No MeSH data available.