초록 ▼

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 m

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.

대표청구항 ▼

In combination: means for generating an electromagnetic beam of continuous wave energy with a predetermined beamwidth; means for frequency modulating said continuous wave energy; means for scanning said modulated beam of continuous wave energy through a predetermined region; wherein the frequency mo

In combination: means for generating an electromagnetic beam of continuous wave energy with a predetermined beamwidth; means for frequency modulating said continuous wave energy; means for scanning said modulated beam of continuous wave energy through a predetermined region; wherein the frequency modulating means modulates the frequency of the continuous wave energy in a modulation period greater than the time said frequency modulated beam is scanned through portion of the predetermined region equal to said beamwidth; means for receiving portions of said frequency modulated beam of continuous wave energy reflected by a target; and means for determining the range of the target, said target range determining means comprising means for mixing said received, target-reflected portions with an instantaneous portion of said frequency modulated beam of continuous wave energy to produce a beat signal having a frequency representative of the range of the target.