Wave transmission lines and networks – Coupling networks – Balanced to unbalanced circuits
Patent
1987-08-27
1989-01-24
LaRoche, Eugene R.
Wave transmission lines and networks
Coupling networks
Balanced to unbalanced circuits
333 32, H03H 742
Patent
active
048003441
ABSTRACT:
The present invention comprises a balun for intercoupling an at least partially unbalanced line and a substantially balanced line having similar line impedances which is capable of passing differential signals over a wide bandwidth while substantially attenuating any common mode signals. The balun comprises a pair of transformers with bifilar windings, each connected as a choke. Each conductor of the unbalanced line is coupled to a different one of two substantially identical inductances of the first transformer and the other side of each inductance is coupled through the second transformer to a different one of the two conductors of the balanced line. Each of the connections between the two transformers is coupled to ground with a substantially identical capacitance. The capacitance in conjunction with the inductance acts to filter out the common mode signals while allowing the differential mode signals to pass through the balun. The capacitance is coupled to each transmission line by a transformer with sufficient inductance to prevent differential signals in either direction from being shunted to ground. Preferably, a resistor is added in parallel to each of the capacitances to provide for common mode attenuation at the resonant frequency of the system capacitance and inductances.
REFERENCES:
patent: 3195076 (1965-07-01), Morrison
patent: 3778759 (1973-12-01), Carroll
Sekhri, S. J., "Power Line Filter", IBM Technical Disclosure Bulletin, vol. 17, No. 7; Dec. 1974, p. 1998.
And Yet, Inc.
LaRoche Eugene R.
Lee Benny
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