Coupled-line balun with common-mode nulling

A method of signal transformation with common-mode compensation, the method comprising:

• providing signal transformation using a coupled-line balun that includes a first transmission line configured to transfer energy to a second transmission line through an electromagnetic field, including handling an unbalanced signal using a first terminal of the coupled-line balun, handling a first component of a balanced signal using a second terminal of the coupled-line balun, and handling a second component of the balanced signal using a third terminal of the coupled-line balun;
• receiving a reference voltage for the unbalanced signal at a fourth terminal of the coupled-line balun;
• and
• controlling a common-mode response of the coupled-line balun using a series resistor-inductor (RL) network connected between the second terminal and the fourth terminal.

A coupled-line balun with common-mode compensation, the coupled-line balun comprising:

• a first terminal configured to carry an unbalanced signal;
• a second terminal configured to carry a first component of a balanced signal;
• a third terminal configured to carry a second component of the balanced signal;
• a fourth terminal configured to receive a reference voltage for the unbalanced signal;
• and
• a series resistor-inductor (RL) network electrically connected between the second terminal and the fourth terminal, wherein the second terminal is coupled through the series RL network to ground, and wherein the first terminal is coupled through the second terminal to the series RL network.