Universal network interface module

Details Universal network interface module Universal network interface module

1998-03-09

2001-01-02

Pham, Chi H. (Department: 2731)

Pulse or digital communications

Transmitters

Angle modulation

C375S223000, C375S295000, C332S100000

Utility Patent

active

06169767

ABSTRACT:

The present invention relates to digital information communications equipment, and, more particularly, to a universal network interface module used in subscriber equipment of a digital information communication system.
BACKGROUND OF THE INVENTION
Digital information communications network utilization has shown phenomenal growth as represented by the growth in cellular telephones, cable and satellite television, the INTERNET, and the like. However, to fulfill the ever-growing need for communications systems, communications systems manufacturers utilize various network interfaces and, as a result, networks and their interfaces are as diverse as the applications which they support. Presently there are no universal network interface modules that allow a variety of application hardware types to interface with a plurality of bi-directional communications networks.
Therefore, it is seen to be desirable to provide a universal network interface module that directly interfaces with a transport network to transmit and receive data therefrom and pass the data to/from various types of application hardware.
SUMMARY OF THE INVENTION
The disadvantages heretofore associated with the prior art are overcome by the present invention of a universal network interface module that is connected between a digital information communications network and application hardware. The universal network interface module contains a forward channel receiver that is capable of demodulating forward channel information (e.g., video). The universal network interface module also contains a back channel transmitter for transmitting control information from the application hardware to the network. The back channel transmitter contains a variable rate modulator and digital-to-analog converter, a low pass filter and a power amplifier. The variable rate modulator is “universal” in that it generates a binary phase shift key (BPSK), quadrature-phase shift key (QPSK) or 16-level quadrature amplitude modulated (16QAM) signals. The modulated type is software selectable. This variable rate modulator uses a novel clock synchronization scheme as well as a polyphase FIR filter to perform both image rejection filtering and pulse shape filtering simultaneously.
Specifically, an apparatus according to the invention for selectively encoding a variable rate data stream according to one of a plurality of modulation formats, comprises: a timing control circuit, coupled to receive a data clock associated with the variable rate data stream and a fixed frequency master clock, for phase locking the data clock to the master clock to produce a locked data clock; an encoder, coupled to the timing control circuit and receiving the variable rate data stream at a rate determined by the locked data clock, for encoding, in response to a format selection signal, the variable rate data stream according to one of a plurality of encoding formats; and a polyphase filter, coupled to the encoder and the timing control circuit, for adapting a pulse shape characteristic and a baud rate characteristic of the encoded variable rate data stream to produce a modulated baseband signal.


REFERENCES:
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