High frequency test balun
AssigneeBH Electronics, Inc.
InventorsJohn E. DeCramer, Nathan Doose
Life of this patent
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Abstract
A passive, highly efficient, low noise adapter device includes a balun and noise reduction circuitry uniquely configured to converting an unbalanced signal line on a 50 ohm signal line to a balanced signal on a 100 ohm transmission line or vice versa. The device facilitates the use of commercially available and accepted test equipment for accurate transmission measurements on balanced twisted pairs of cables and connectors. A typical utilization includes an adapter device connected between the 100 ohm twisted pair cable and suitable test equipment such as a network analyzer and/or a signal generator for determining losses in the telephone wire and connectors.
Claims11
An adapter device for connection between test equipment having unbalanced signal lines with a first characteristic impedance and balanced signal lines to be tested having a second characteristic impedance, the device comprising:
- a) an impedance matching transformer comprised of a pair of input conductors, a pair of output conductors, and a core, the input conductors electrically connectable to the unbalanced signal lines, the impedance matching transformer matching the first characteristic impedance to the second characteristic impedance and for providing a balanced signal at the output conductors,
- b) a capacitor extending across the input conductors,
- c) a common mode choke comprised of a core, a pair of windings having a pair of input ends and a pair of output ends, the input ends of the windings electrically connected to balun output conductors, the pair of output ends electrically connectable to the pair of balanced signal lines by a pair of output signal conductors;
- and
- d) a common mode shunt extending across the pair of output signal conductors, the common mode shunt having a center tap connectable to an unbalanced signal line.
An adapter device for connection between a first pair of unbalanced signal lines having a first characteristic impedance and a second pair of balanced signal lines having a second characteristic impedance, the device comprising:
- a) an impedance matching transformer comprised of a pair of input conductors, a pair of output conductors, the input conductors electrically connectable to the unbalanced signal line, the impedance matching transformer matching the first characteristic impedance to the second characteristic impedance and for providing a balanced signal at the output conductors, the impedance matching transformer having a first winding connecting to the input conductors and a second winding connecting to the output conductors,
- b) a capacitor connected across at least one of the input conductors and the output conductors,
- c) a common mode choke having a pair of input ends and a pair of output ends, the input ends of the windings electrically connected to output conductors, the pair of output ends electrically connectable to the pair of balanced signal lines by a pair of output signal conductors, and
- d) a common mode shunt extending across the pair of output signal conductors.
An adapter for use with a multi-frequency signal generator with an output impedance of substantially 50 ohms and a signal analyzer with an input impedance of approximately 50 ohms for testing the electrical balance of a specimen with a characteristic impedance of approximately 100 ohms, the adapter comprising:
- a) a first unbalanced input port with a signal conductor and a shielded conductor connected to ground;
- b) a capacitor connected across the signal conductor to ground;
- c) a balanced output port with a first conductor and a second conductor,
- d) an impedance matching transformer comprising:
- a core;
- a first input lead connecting to the signal conductor of the input port;
- a second input lead connecting to the shielded conductor;
- a first output lead;
- a second output lead;
- a first winding wound on the core with a first end connecting to the signal conductor of the first unbalanced input port, and a second end connecting to the first output lead;
- a second winding wound on the core with a first end connecting to the first output lead, and a second end connecting to ground;
- a third winding wound on the core with a first end connecting to ground and a second end connecting to the second output lead;
- the first, second, and third windings configured to provide an input impedance of substantially 50 ohms and an output impedance of substantially 100 ohms;
- and
- e) a longitudinal common mode choke with a pair of input leads connecting to the impedance matching transformer output leads and a pair of output leads connecting to the first and second conductors of the output port.
Dependencies are inferred from the claim text.