United States Patent m
Kelly et al.
[54] ADAPTIVE FIXED-THRESHOLD PULSE TIME-OF-ARRIVAL DETECTION APPARATUS FOR PRECISION DISTANCE MEASURING EQUIPMENT APPLICATIONS
[75] Inventors: Robert J. Kelly, Baltimore; Michael G. Biggs, Catonsville; Howard H. Ireland, Abingdon; Gary A. Drutch, Ellicott City; Janice A. Winter, Sparks, all of Md.
[73] Assignee: Allied-Signal Inc., Morris Township, Morris County, N.J.
[21] Appl. No.: 739,074
[22] Filed: Aug. 1,1991
[51] Int. CI.* G01S 13/08
[52] U.S. CI 342/47; 364/569;
307/518
[58] Field of Search 364/569, 514, 517, 450;
342/47, 33, 35, 36, 118, 125, 134; 307/361, 228, 246, 518; 328/132, 147
[56] References Cited
U.S. PATENT DOCUMENTS
3,754,252 8/1973 Sanders 343/6.5
3,997,898 12/1976 LeGrand 343/6.5 R
4,010,465 3/1977 Dodington et al 343/5 LS
4,492,961 1/1985 Roller etal 342/47
4,568,942 2/1986 Letocquart 343/408
4,635,064 1/1987 Chisholm 342/408
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US005266953A
[li] Patent Number: 5,266,953 [45] Date of Patent: Nov. 30, 1993
4,646,097 2/1987 King 342/134 X
4,648,101 3/1987 Hamzaoui et al 375/99
4,670,756 6/1987 Lopez 342/372
4,677,442 6/1987 Enein 342/410
4,680,722 7/1987 Tomasi 364/569
4,723,126 2/1988 Chisholm 342/408
4,757,320 7/1988 Letoquart et al 342/410
4,890,110 12/1989 Kuwahara 342/35
4,912,479 3/1990 Nishimura et al 342/408
4,916,451 4/1990 Ishita 342/35
4,990,921 2/1991 Chisholm 342/35
5,032,840' 7/1991 Hethuin 342/35
5,121,413 6/1992 Voegtly et al 307/518 X
Primary Examiner—Mark Hellner
Attorney, Agent, or Firm—Howard G. Massung
[57] ABSTRACT
An apparatus to be employed within a precision distance measuring system for estimating pulse time-ofarrival. The apparatus facilitates the use of an Adaptive Fixed Threshold method for such estimation. The invention compensates for pulse time detection errors induced by variations in incident pulse amplitude and shape by adjusting the estimated time-of-arrival. This adjustment is performed as a function of the measured pulse slope between two low-amplitude threshold levels through the use of a predetermined reference table of error adjustment times.
3 Claims, 9 Drawing Sheets
