Processing for mode S signals suffering multipath distortion

[54] PROCESSING FOR MODE S SIGNALS SUFFERING MULTIPATH DISTORTION

[75] Inventor: Carl E. Schwab, Huntington Station, N.Y.

[73] Assignee: Cardion, Inc., Woodbury, N.Y.

[21] Appl. No.: 414,675

[22] Filed: Mar. 31, 1995

[51] Int. CI.6 G01S 13/93

[52] U.S. CI 342/37; 342/30; 342/32;

342/39

[58] Field of Search 342/29, 30, 32,

342/36, 37, 39, 40, 46, 50

[56] References Cited

U.S. PATENT DOCUMENTS

4,688,046 8/1987 Schwab 342/456

4,870,425 9/1989 Gunny 342/455

5,077,673 12/1991 Brodegard et al 364/461

5,089,822 2/1992 Abaunza et al 342/30

5,107,268 4/1992 Sturm et al 342/36

5,122,804 6/1992 Shulenberger 342/37

5,144,315 9/1992 Schwab 342/49

5,157,615 10/1992 Brodegard et al 364/461

5,182,563 1/1993 Blinchikoff et al 342/32

5,196,855 3/1993 Kuroda 342/37

5,208,591 5/1993 Ybarra et al 340/961

5,400,031 3/1995 Fitts 342/36

5,448,243 9/1995 Bethke et al .'. 342/59

OTHER PUBLICATIONS

Article entitled "Propogation of Mode-S Beacon Signals on the Airport Surface," by M. L. Wood, 1989 pp. 397-410. Sales brochure of Cardion, Inc., entitled "CAPTS Cooperative Area Precision Tracking System," 1993.

USDOT/FAA Specification, "Mode-S Beacon System (Mode S) Sensor, FAA-E-2716 & Amendment 2", Mar. 24, 1983 pp. 121-125 & 139-154.

Primary Examiner—John B. Sotomayor
Attorney, Agent, or Firm—Lawrence C. Edelman

[57] ABSTRACT

A communication system for receiving aircraft reply squits (transmissions) normally used in a radar beacon system for surveilling aircraft in a given geographic area. The communication system includes a plurality of omnidirectional receivers, each receiver having a function of omnidirectionally receiving the aircraft squits and developing therefrom two types of information strings, namely a data string, indicative of a message in the aircraft squit, and a corresponding confidence string indicative of the reliability of the developed data string. A data communication link transmits the data and confidence strings between the plurality of omnidirectional receivers and the master data processor. The master data processor processes the data strings and corresponding confidence strings developed by each of the plurality of omnidirectional receivers by performing a bit-by-bit comparison of the received data strings and corresponding confidence strings, so as to develop by the comparison a corrected data string which minimizes the use of data bits from the data strings received over the data communication link that are indicated by the corresponding confidence strings as having a low reliability.

19 Claims, 4 Drawing Sheets