One example discloses a wireless device, including: a first near-field device, including a near-field transmitter or receiver and a controller, configured to be coupled to a near-field antenna having a first conductive surface and a set of feed-points; wherein the controller is configured to receive a transmitter output voltage from the set of feed-points; wherein the controller is configured to generate a correction signal based on a difference between the transmitter output voltage and a target transmitter output voltage; wherein the correction signal varies in response to a change in a distance between the first surface and a second conductive surface; and wherein the controller is configured to calculate the distance, between the first conductive surface and the second conductive surface, based on the correction signal.