Pulse or digital communications – Repeaters – Testing
Patent
1981-04-03
1983-05-17
Safourek, Benedict V.
Pulse or digital communications
Repeaters
Testing
375 8, 179 2DP, H03H 738
Patent
active
043843565
ABSTRACT:
A method and apparatus are described for coupling a high-speed data communication modem to a communication line such as a coaxial cable with minimal transmission losses when the modem is not transmitting data. The transmitter coupling apparatus comprises a transformer, first and second transistors, biasing circuits for each of the transistors and a low-pass filter. The data signal to be transmitted is applied to the first transistor which is biased for linear amplification when data are being transmitted and for saturation when data are not being transmitted. The output of the first transistor is applied to the primary winding of the transformer where it is coupled to the secondary winding which is connected in series with the central conductors of the coaxial transmission line. When saturated, the first transistor grounds the winding terminal to which it is connected. The second transistor is biased so as to couple a power supply through the low-pass filter to the other terminal of the primary winding when data are being transmitted and to be non-conducting when data are not being transmitted. The low-pass filter and the first transistor provide a short circuit with respect to high frequency signals across the primary winding when data are not being transmitted. The receiver is likewise transformed coupled with its primary winding being in shunt across the transmission line. As a result of these connections, the output impedance of the transmitter can be made small enough so that the modem insertion loss is about 0.2 db.
REFERENCES:
patent: 3504118 (1970-03-01), Hans-Martin
patent: 3721958 (1973-03-01), Dixon
patent: 4110711 (1978-08-01), Gaetano et al.
patent: 4205360 (1980-05-01), Drucker
patent: 4254501 (1981-03-01), Griffith et al.
Britsol Babcock Inc.
Chin Stephen
Safourek Benedict V.
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