Integrated circuit modem with a memory storage device for generating a

Abstract

An apparatus capable of transmitting digital data at high data rates over a communication link is disclosed. A carrier signal is modulated by serial groups of digital data signals to be transmitted during a plurality of successively appearing modulation periods. The data-modulated carrier is represented by a unique group of digital signals stored in a memory. The memory upon command, reads out a predetermined sequence of digital signals with each predetermined sequence representing the signal shape of a digital data modulated carrier signal which appears as though it has been passed through a narrow band limited linear phase network. The memory stores a predetermined number of such sequences of digital signals. The number of sequences is four in one preferred embodiment of this invention. In that preferred embodiment, each sequence occupies a spectrum frame which extends in time over four successive modulation periods. Timing at the transmitter insures that the starting time of each frame is successively offset by one modulation period relative to the start of the preceding frame. A summing circuit connected between the memory storage device and an input to the communication link adds the sequences of digital signals as they are read from the memory in a predetermined order. The summing operation generates a composite data modulated signal for application to a communication link.