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, 1989
Filed:
Mar. 30, 1988
Adriaan Kamerman, Ta Nieuwegein, NL;
Johannes P Haagh, Eindhoven, NL;
NCR Corporation, Dayton, OH (US);
Abstract
A data modem communication system includes a data modem transmitter adapted to transmit data on a main channel at a relatively high bit rate and to transmit data at a relatively low bit rate on a secondary channel. At the receiver, a single analog-to-digital converter (54) supplies digital signals via a notch filter (58) to the main channel receiver (60) and to the secondary channel receiver (62) wherein a single IIR low-pass digital filter (110) is utilized for processing at three different sample rates to eliminate the main channel signal with frequency conversion taking place between processing at the first and second sample rates. The invention enables the provision of a reliable secondary channel while using a minimum amount of circuitry for complex-valued digital signal processing.