Dual multipoint data transmission system modem

• US 4,335,464 A
• Filed: 01/24/1980
• Issued: 06/15/1982
• Est. Priority Date: 01/24/1980
• Status: Expired due to Term

• Current Assignee: Paradyne Corporation (Dasan Networks Incorporated)
• Original Assignee: Paradyne Corporation (Dasan Networks Incorporated)
• Inventors: Bremer, Gordon, Armstrong, Thomas R., Betts, William
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US06/115,118
• Time in Patent Office: 873 Days
• Field of Search: 179/2 DP, 179/84, 179/1 GS, 332/45, 370/37, 370/45, 370/69, 370/71, 370/72, 375/38, 375/43, 375/61, 375/79, 455/46, 455/47, 455/59
• US Class Current: 375/270
• CPC Class Codes: H04J 1/08 Arrangements for combining channels branching filters H01P1/213, H03H7/46

Abstract

A modem is provided which allows two independent sets of multipoint users to share a common communication media such as a telephone channel. At each site there is provided a modem which transmits and receives two independent frequency division multiplexed data streams simultaneously over a common telephone channel. Each data stream is encoded into an eight phase PSK or QAM signal. One data stream signal is transmitted in a low frequency range and the second is transmitted in a high frequency range. Means are provided at each site to combine the data streams for transmission over a single communication line and to separate the received combined signal from the communication line.

Claims

1. A data communication system comprising at least two independent multipoint networks sharing common user site locations and a common communications link connecting said common user site locations, said system comprising:

a first network terminal at each of said common site locations;

a second network terminal at each of said common site locations;

and a modem at each of said common site locations, each of said modems including;

a transmitter having a first modulator connected to said first network terminal and a second modulator connected to said second network terminal;

first high pass filter means connected to the output of one of said modulators and first low pass filter means connected to the output of the other of said modulators;

means for combining the outputs of said first high pass and first low pass filters and feeding the combined output to said common communications link;

a receiver having a first demodulator connected to said first network terminal and a second demodulator connected to said second network terminal; and

,

second high pass filter means interposted between said communications link and said first demodulator and second low pass filter means interposed between said communications link and said second demodulator whereby each of said modems receives and transmits data over said common communications link within a high frequency spectrum defined by said first and second high pass filter means for said first network and within a low frequency spectrum defined by said first and second low pass filter means for said second network.

2. The invention in accordance with claim 1 wherein said first and second high pass filters have the same frequency range, said first and second low pass filters have the same frequency range, and a guard band is provided between said high pass frequency range and said low pass frequency range.