US Patent 7961063 Balun signal transformer and method of forming

A balanced-unbalanced (balun) signal transformer includes an unbalanced port, a balanced port coupled to the unbalanced port, the balanced port comprising a first terminal and a second terminal, a first capacitor coupled to the first terminal, a first inductor coupled to ground and the first capacitor, a second capacitor coupled to the second terminal, and a second inductor coupled to ground and the second capacitor. The transformer may also include a third capacitor coupled to a terminal of the unbalanced port; and a third inductor coupled to the third capacitor and the third terminal.