Electronic Device Antennas with Filter and Tuning Circuitry

摘要

An electronic device may have an antenna that includes conductive antenna structures forming an antenna resonating element and an antenna ground. A band-stop filter may be coupled between first and second portions of the conductive structures. The band-stop filter may be formed from multiple series-connected resonant circuits. The band-stop filter and an impedance matching circuit may be coupled in series between the antenna resonating element and the antenna ground. The band-stop filter may be characterized by a stop band. The antenna may be configured to operate in a first communications band that is outside of the stop band and a second communications band that is covered by the stop band. The impedance matching circuit may be an adjustable circuit that is used to tune the antenna. The adjustable circuit may be a switch-based adjustable capacitor that is adjusted to tune the response of the antenna in the first communications band.