Patent ID: 7129803

Claim:
A tuned transformer balun circuit comprises: a transformer balun having a single-ended winding and a differential winding, wherein the single-ended winding includes a first node and a second node and the differential winding includes a first node, a center node, and a second node; a first tuning capacitor having a first plate and a second plate, wherein the first plate of the first tuning capacitor is coupled to the first node of the differential winding and the second plate of the first tuning capacitor is connected directly to a circuit ground; a second tuning capacitor having a first plate and a second plate, wherein the first plate of the tuning capacitor is coupled to the second node of the differential winding and the second plate of the second tuning capacitor is connected directly to a circuit ground; a third tuning capacitor having a first plate and a second plate, wherein the first plate of the third tuning capacitor is coupled to the first node of the single-end winding and the second plate of the third tuning capacitor is coupled to transceiver radio frequency signals, wherein based on loading of the single-ended winding and the differential winding, the first, second, and third tuning capacitors resonate with the transformer balun; and a decoupling capacitor having a first plate and a second plate, wherein the first plate of the decoupling capacitor is coupled to the second node of the single-ended winding and to the center node of the differential winding and the second plate of the decoupling capacitor is coupled to the circuit ground to provide a low impedance AC ground connection over a range of frequencies.