Patent ID: 11881715
Assignee: APPLE INC.
Field: Basic communication processes (Electrical engineering)
Classification: CPC H | IPC H

Claim 17:
18. A method of operating an electronic device having a signal path with a transformer that includes a first coil, a second coil, a third coil, a fourth coil, a first adjustable capacitor coupled to the third coil, and a second adjustable capacitor coupled to the fourth coil, the method comprising:
forming a first open circuit in the third coil and a second open circuit in the fourth coil, the first open circuit in the third coil and the second open circuit in the fourth coil configuring the transformer to pass radio-frequency signals in a first frequency band and a second frequency band higher than the first frequency band; and
forming the second open circuit in the fourth coil and controlling the first adjustable capacitor to form a non-open circuit capacitance in the third coil, the second open circuit in the fourth coil and the non-open circuit capacitance in the third coil configuring the transformer to pass the radio-frequency signals in the second frequency band while filtering out the first frequency band.