A device includes an antenna, a parasitic element, and a telemetry control module. The parasitic element modifies a radiation pattern of the antenna. The parasitic element has an impedance value that is adjustable, and the radiation pattern of the antenna depends on the impedance value of the parasitic element. The telemetry control module is configured to transmit data to a medical device using the antenna, receive data from the medical device using the antenna, and detect communication errors using data that is received from the medical device. Additionally, the telemetry control module is configured to adjust the impedance value of the parasitic element in response to detection of communication errors.
