Patent
FM-CW laser radar system
Albert V. Jelalian,Wayne H. Keene,Charles M. Sonnenschein,Clarke E. Harris,Clifford E. Morrow +4 more
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TLDR
In this article, a scanning laser radar system utilizing a frequency modulated (fm)-continuous wave (cw) beam to coherently detect echo signal returns from an object in a predetermined region is presented.Abstract:
A scanning laser radar system utilizing a frequency modulated (fm)-continuous wave (cw) beam to coherently detect echo signal returns from an object in a predetermined region. The frequency of the beam is repeatedly changed as a function of time to produce a symmetrical triangular-shaped frequency modulated waveform. The echo signals received are frequency shifted, as a function of range and Doppler shift, from the signal being transmitted at that time. The frequency shift is detected by homodyning a portion of the instantaneous transmitted signal with the received echo signal to produce an output signal having a frequency which is substantially constant during a portion of the frequency modulation period. The constant frequency portion of the output signal is related to the range and Doppler speed of the target. Target information such as range, Doppler speed, intensity and angle information are derived by processing the output signal. The signal to noise ratio of the output signal is improved by using a frequency modulation period greater than the scanning time across an arc of a size equal to a predetermined multiple of the beamwidth because with such relationship the time duration of the constant amplitude portion of the output signal is increased. Further, with such arrangement, because of the relatively long modulation period, the ambiguity in detection of the range to the target is reduced. The system is particularly useful in terrain following or obstacle avoidance applications.read more
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References
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Book
Introduction to Radar Systems
TL;DR: This chapter discusses Radar Equation, MTI and Pulse Doppler Radar, and Information from Radar Signals, as well as Radar Antenna, Radar Transmitters and Radar Receiver.
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