The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 22, 1978
Filed:
Sep. 02, 1977
Edwin H Wrench, Jr, San Diego, CA (US);
Jay C Hicks, San Diego, CA (US);
Joseph F McCartney, Solana Beach, CA (US);
The United States of America as represented by the Secretary of the Navy, Washington, DC (US);
Abstract
An apparatus is capable of recovering signals from N sites, N.gtoreq.2, distributed along a single coaxial cable. This multiplexing technique allows the separation of signals from many transducers on one line. Time domain reflectometry (TDR) is used, with variable resistive elements distributed along the cable. TDR is used to detect discontinuities in the impedance of the cable as well as their specific location along the cable. The magnitude of these discontinuities is modulated by an impedance that is proportional to the applied signal. An excellent way of obtaining this kind of variable impendance along the line is to bias a field effect transistor (FET) so that it functions as a variable resistor. For a large number of signals to be multiplexed onto a coaxial cable, an FET is placed at each of the N signal sources. The coaxial cable has a characteristic impedance of Z.sub.o and the FET's are evenly spaced at a distance l. Each of the FET's produces a discontinuity on the cable that can be detected by using time domain reflectometry. Microphones may also be used instead of the FET's.