An exemplary tunable circuit includes an inductor coupled to a node and a first capacitor coupled to the node. The tunable circuit also includes a variable capacitor coupled to the node, such that a total capacitance of the tunable circuit depends on a fixed capacitance of the first capacitor and a variable capacitance of the variable capacitor. In an example, the inductor and the first capacitor are both included in a passive device and the variable capacitor is in a semiconductor device. The variable capacitor allows the total capacitance to be modified for the purpose of, for example, calibrating the capacitance to account for manufacturing variations, and/or adjusting to a frequency range of operation used by wireless devices in a region of the world. The first capacitor may be a higher quality capacitor providing a larger portion of the total capacitance than the variable capacitor.

An exemplary tunable circuit includes an inductor coupled to a node and a first capacitor coupled to the node. The tunable circuit also includes a variable capacitor coupled to the node, such that a total capacitance of the tunable circuit depends on a fixed capacitance of the first capacitor and a variable capacitance of the variable capacitor. In an example, the inductor and the first capacitor are both included in a passive device and the variable capacitor is in a semiconductor device. The variable capacitor allows the total capacitance to be modified for the purpose of, for example, calibrating the capacitance to account for manufacturing variations, and/or adjusting to a frequency range of operation used by wireless devices in a region of the world. The first capacitor may be a higher quality capacitor providing a larger portion of the total capacitance than the variable capacitor.

The invention relates to a method for automatically adjusting one or more tunable passive antennas and a single-input-port and single-output-port tuning unit. The invention also relates to an apparatus for radio communication using this method, for instance a radio transceiver. An apparatus for radio communication of the invention comprises: a tunable passive antenna; a feeder; a single-input-port and single-output-port tuning unit having an input port and an output port; a sensing unit; a transmission and signal processing unit which applies an excitation to the input port, which delivers one or more antenna adjustment instructions, and which delivers one or more tuning unit adjustment instructions; and a control unit which delivers one or more antenna control signals to the tunable passive antenna, and one or more tuning control signals to the single-input-port and single-output-port tuning unit.