Balun circuit with a cancellation element in each coupled line
AssigneeNippon Telegraph and Telephone Corporation
InventorsKenjiro Nishikawa, Ichihiko Toyoda, Tsuneo Tokumitsu
Life of this patent
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Abstract
A Marchand balun cirucit having a pair of coupled lines of quarter wavelength for dividing and/or combining signals with the same amplitude and opposite phase with each other is improved by inserting a cancellation element between said pair of coupled lines. Said cancellation element may be a transmission line, a capacitor, or an inductor which improves amplitude difference error and phase difference error of a pair of outputs by controlling phase velocity for an even mode so that phase velocity for an even mode becomes equal to that for an odd mode. Thus, a balun circuit with wide operation band, and less error of amplitude difference and phase difference is obtained.
Claims5
A balun circuit having an input port and a pair of output ports which provide output signals having the same amplitude and opposite phase to each other relating to an input signal input into said input port, comprising:
- a first coupled line and a second coupled line each equal to or shorter than a quarter wavelength, and each having an input port, a through port, a coupled port and an isolation port, each defined in accordance with a reference port;
- a reference port of the first coupled line and a reference port of the second coupled line being coupled, an isolation port of the first coupled line being grounded, and an isolation port of the second coupled line being grounded;
- a through port of the second coupled line being open;
- a through port of the first coupled line being an input port of the balun circuit;
- coupling ports of the first and second coupled lines respectively being output ports of the balun circuit;
- a cancellation element being coupled with each coupled line for compensating amplitude difference and phase difference error of output signals on said output ports;
- wherein said cancellation element comprises a transmission line inserted in one of the lines of each coupled line between ground and an output port.
A balun circuit having an input port and a pair of output ports which provide output signals having the same amplitude and opposite phase to each other relating to an input signal input into said input port, comprising:
- a first coupled line and a second coupled line each equal to or shorter than a quarter wavelength, and each having an input port, a through port, a coupled port and an isolation port, each defined in accordance with a reference port;
- a reference port of the first coupled line and a reference port of the second coupled line being coupled, an isolation port of the first coupled line being grounded, and an isolation port of the second coupled line being grounded;
- a through port of the second coupled line being open;
- a through port of the first coupled line being an input port of the balun circuit;
- coupling ports of the first and the second coupled lines respectively being output ports of the balun circuit;
- a cancellation element being coupled with each coupled line for compensating amplitude difference and phase difference error of output signals on said output ports;
- wherein said cancellation element comprises an inductor inserted in one of the lines of each coupled line between ground and an output port in each coupled line.
Dependencies are inferred from the claim text.