Method and apparatus for coherent burst ranging

Patent · Tue Apr 28 00:00:00 EDT 1998

OSTI ID:871514

Wachter, Eric A ^[1]; Fisher, Walter G ^[2]

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1. 138 Bay Path Dr., Oak Ridge, TN 37830
2. 8514 Carl Valentine, Knoxville, TN 37931

A high resolution ranging method is described utilizing a novel modulated waveform, hereafter referred to as coherent burst modulation. In the coherent burst method, high frequency modulation of an acoustic or electromagnetic transmitter, such as a laser, is performed at a modulation frequency. This modulation frequency is transmitted quasi-continuously in the form of interrupted bursts of radiation. Energy from the transmitter is directed onto a target, interacts with the target, and the returning energy is collected. The encoded burst pattern contained in the collected return signal is detected coherently by a receiver that is tuned so as to be principally sensitive to the modulation frequency. The receiver signal is processed to determine target range using both time-of-flight of the burst envelope and phase shift of the high frequency modulation. This approach effectively decouples the maximum unambiguous range and range resolution relationship of earlier methods, thereby allowing high precision ranging to be conducted at arbitrarily long distances using at least one burst of encoded energy. The use of a receiver tuned to the high frequency modulation contained within the coherent burst vastly improves both sensitivity in the detection of the target return signal and rejection of background interferences, such as ambient acoustic or electromagnetic noise. Simultaneous transmission at several energies (or wavelengths) is possible by encoding each energy with a separate modulation frequency or pattern; electronic demodulation at the receiver allows the return pattern for each energy to be monitored independently. Radial velocity of a target can also be determined by monitoring change in phase shift of the return signal as a function of time.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• DOE Contract Number: AC05-84OR21400
• Assignee: Wachter, Eric A. (138 Bay Path Dr., Oak Ridge, TN 37830);Fisher, Walter G. (8514 Carl Valentine, Knoxville, TN 37931)
• Patent Number(s): US 5745437
• OSTI ID: 871514
• Country of Publication: United States
• Language: English

Related Subjects

method
apparatus
coherent
burst
ranging
resolution
described
utilizing
novel
modulated
waveform
hereafter
referred
modulation
frequency
acoustic
electromagnetic
transmitter
laser
performed
transmitted
quasi-continuously
form
interrupted
bursts
radiation
energy
directed
target
interacts
returning
collected
encoded
pattern
contained
return
signal
detected
coherently
receiver
tuned
principally
sensitive
processed
determine
range
time-of-flight
envelope
phase
shift
approach
effectively
decouples
maximum
unambiguous
relationship
earlier
methods
allowing
precision
conducted
arbitrarily
distances
vastly
improves
sensitivity
detection
rejection
background
interferences
ambient
noise
simultaneous
transmission
energies
wavelengths
encoding
separate
electronic
demodulation
allows
monitored
independently
radial
velocity
determined
monitoring
change
function
time
return signal
modulation frequency
earlier methods
phase shift
frequency modulation
receiver signal
range resolution
simultaneous transmission
coherent burst
resolution ranging
magnetic noise
vastly improves
burst envelope
background interference
described utilizing
/367/342/