Patent ID: 8412121

Claim:
A radio frequency transceiver circuit comprising: a planar antenna having a resonant frequency that is adjustable, wherein the planar antenna includes a conductive ground plane having a T-shaped slot in the conductive ground plane, and switching elements connected between opposite edges of the ground plane on a horizontal section of the T-shaped slot in the conductive ground plane, the switching elements being configured to adjust the resonance frequency of the antenna; a bidirectional coupler configured to couple power to and from the antenna, the bidirectional coupler including a primary line and a secondary line, the secondary line providing a first signal representative of transmitted power and a second signal representative of reflected power on the primary line; a first detection circuit configured to detect the first signal representative of transmitted power; a second detection circuit configured to detect the second signal representative of reflected power; and a control circuit configured to adjust the resonance frequency of the antenna, based on a ratio of the detected transmitted power to the detected reflected power, by controlling the switching elements of the planar antenna.