Carrier detector

Details Carrier detector Carrier detector

1976-11-10

1978-05-09

Safourek, Benedict V.

Telegraphy

Code transmitters

Rotary contact

325324, H04L 1524

Patent

active

040888339

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.

REFERENCES:
patent: 3646446 (1972-02-01), Rittenbach
patent: 3696203 (1972-10-01), Leonard
patent: 3949206 (1976-04-01), Edwards

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