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:
May. 09, 1978
Filed:
Nov. 10, 1976
Dominique N Godard, Le Rouret, FR;
Andrzej T Milewski, Saint-Jeannet, FR;
International Business Machines Corporation, Armonk, NY (US);
Abstract
The invention provides a carrier detector for use in a multipoint communication system. In these systems a common communication link interconnects a master modem to a plurality of remote slave modems and a slave modem has to initialize itself without disturbing transmission of data between the master modem and another slave modem. Initialization is to be performed on such data, and the slave modem must be provided with a detector capable of detecting when data is being transmitted. The invention describes such a detector which is independent of the received signal power. The input signal is sampled at rate 6/T, T being the baud rate, and passed into two narrow band filters F1 and F2, centered at Nyquist frequencies f.sub.1 and f.sub.2, respectively. The sum of the outputs from filters F1 and F2 is sampled at a rate of 1/T for each of six different phases of the sampling rate 1/T. The energy of the six samples so obtained is measured. If only noise is received, the six measured energies must be theoretically equal; in practice, they will be of the same order of magnitude. When data is received, the six energies are very different. The indication 'data is being transmitted' is given if the largest energy E.sub.max is greater than a fixed multiple of the smallest one E.sub.min.