Patent ID: 7239853

Claim:
A switching circuit for use at the antenna of a multiband mobile cellular handset, the circuit comprising: an antenna port, a transmit (TX) low band port, a TX high band port, at least one receiver (RX) port, the circuit further comprising a single pole, triple throw (SP3T) solid state voltage-controlled switch which includes a plurality of single pole, single throw (SP1T) solid state switching devices to selectively connect any one of the TX low band port, TX high band port and RX port to the antenna port the antenna port is connected to the TX low band port via a first SP1T device, to the TX high band port via a second SP1T device, and to the RX port via first and second frequency-dependent phase shifting elements connected in series, the switching circuit further including a first tuned circuit connected to the junction of the first and second frequency-dependent phase shifting elements via a third SP1T device and a second tuned circuit connected to an end of the second frequency-dependent phase shifting element via a fourth SP1T device, the first tuned circuit being tuned to resonate substantially at a center of a TX high band frequency range, the second tuned circuit being tuned to resonate substantially at a center of a TX low band frequency range, the first frequency-dependent phase shifting element corresponding to a quarter wavelength at frequencies in the TX high band frequency range, and the first and second frequency-dependent impedances in combination corresponding to a quarter wavelength at frequencies in the TX low band frequency range, wherein the first SP1T device includes an anode connected to the antenna port and a cathode connected to the TX low band port, wherein the second SP1T device includes an anode connected to the antenna port and a cathode connected to the TX high band port, wherein the third SP1T device includes an anode connected to the junction of the first and second frequency-dependent impedances and a cathode connected to the first tuned circuit, and wherein the fourth SP1T device includes an anode connected to the end of the second frequency-dependent impedance and a cathode connected to the second tuned circuit, the tuning circuit further including a first voltage input terminal connected to the anode of the first SP1T device and the cathode of the third SP1T device and a second voltage input terminal connected to the anode of the second SP1T device and the cathode of the fourth SP1T device.