Patent ID: 8886137

Claim:
A frequency tunable transmit/receive (Tx/Rx) antenna switch, comprising: an antenna port; a receive port; a transmit port; a tuned PIN diode RF switch that alternately connects the receive and transmit ports to the antenna port, said switch including at least a first quarter-wavelength (λ c /4) transmission line to increase isolation between the transmit port and the antenna port, said switch exhibiting an initial transmission passband centered about an initial center frequency f c with an initial bandwidth set by said quarter-wavelength transmission line; a first tuning port on said RF switch; as first electronically tunable solid-state LC tank circuit, said LC tank circuit comprising a parallel structure of a series-connected fixed inductor and voltage-controlled capacitor and an electronic controller that applies a voltage to the voltage-controlled capacitor to set a capacitance value and adjust a circuit impedance of the LC tank circuit; and a coupling structure that couples the LC tank circuit and its circuit impedance to the first tuning port, said LC tank circuit adding capacitance to the switch to shift center frequency f c of a tuned transmission passband to a lower tuned frequency f tx and narrower tuned bandwidth.