Integrated switch-filter network
A radio-frequency module includes a switching device having first and second switch arms and a common pole node connected to both the first and second switch arms, a first shunt arm connected to the first switch arm, and a first transmission line disposed in the first switch arm between the common pole node and the first shunt arm, the first transmission line being configured to present a substantially open circuit looking into the first switch arm from the common pole node at a fundamental frequency of a signal transmitting on the second switch arm when the first switch arm is in an OFF-state and the first shunt arm is in an ON-state.
1. A switching device comprising:
a first switch arm configured to transmit a first signal having a first wavelength λ 1 ;
a second switch arm configured to transmit a second signal having a second wavelength λ 2 ;
a common pole node connected to both the first and second switch arms;
a first shunt arm connected to the first switch arm;
a second shunt arm connected to the second switch arm;
a first transmission line disposed in the first switch arm between the common pole node at a first end of the first transmission line and the first shunt arm at a second end of the first transmission line, the first transmission line having a length of ¾ λ 2 ; and
a second transmission line disposed in the second switch arm between the common pole node at a first end of the second transmission line and the second shunt arm at the second end of the second transmission line, the second transmission line having a length of ¼ λ 1 .
2. The switching device of claim 1 wherein the first transmission line is further configured to present a substantially short circuit looking into the first switch arm from the common pole node at at least one harmonic of a fundamental frequency of the second signal.
3. The switching device of claim 2 wherein the first shunt arm includes a switch in series with a tank circuit connected to ground, the tank circuit being configured to resonate at a third harmonic of the fundamental frequency of the second signal and present a substantially short circuit to ground at the fundamental frequency of the second signal.
4. The switching device of claim 3 wherein the tank circuit includes a capacitor in parallel with an inductor.
5. The switching device of claim 1 wherein the second transmission line is configured to present a substantially open circuit looking into the second switch arm from the common pole node at a fundamental frequency of the first signal when the second switch arm is in an OFF-state and the second shunt arm is in an ON-state.
6. The switching device of claim 1 wherein the first shunt arm is connected to a plurality of transmission paths, each of the plurality of transmission paths including a switch for transmitting a signal corresponding to a different frequency band.
7. The switching device of claim 1 wherein the first transmission line includes an inductor-capacitor network.
8. The switching device of claim 7 wherein the inductor-capacitor network includes a first shunt capacitor, a second shunt capacitor, and an inductor disposed between the first and second shunt capacitors.
9. A switching circuit comprising:
a first switch arm configured to transmit a first signal having a first wavelength λ 1 , the first switch arm including a first switch;
a second switch arm configured to transmit a second signal having a second wavelength λ 2 , the second switch arm including a second switch;
a common pole node connected to both the first switch arm and the second switch arm;
a first shunt arm connected to the first switch arm between the pole node and the first switch;
a second shunt arm connected to the second switch arm between the pole node and the second switch;
a first transmission line disposed in the first switch arm between the common pole node at a first end of the first transmission line and the first shunt arm at a second end of the first transmission line, the first transmission line having a length of ¾ λ 2 ; and
a second transmission line disposed in the second switch arm between the common pole node at a first end of the second transmission line and the second shunt arm at the second end of the second transmission line, the second transmission line having a length of ¼ λ 1 .
10. The switching circuit of claim 9 wherein the first transmission line is further configured to present a substantially short circuit looking into the first switch arm from the common pole node at at least one harmonic of a fundamental frequency of the second signal.
11. The switching circuit of claim 10 wherein the first shunt arm includes a switch in series with a tank circuit connected to ground, the tank circuit being configured to resonate at the at a third harmonic of the fundamental frequency of the second signal and present a substantially short circuit to ground at the fundamental frequency of the second signal.
12. The switching circuit of claim 11 wherein the tank circuit includes a capacitor in parallel with an inductor.
13. The switching circuit of claim 9 wherein the second transmission line is configured to present a substantially open circuit looking into the second switch arm from the common pole node at a fundamental frequency of the first signal when the second switch arm is in an OFF-state and the second shunt arm is in an ON-state.
14. The switching circuit of claim 13 wherein the first signal corresponds to band 8 of the LTE spectrum and the second signal corresponds to band 17 of the LTE spectrum.
15. A wireless device comprising:
an antenna configured to transmit a radio-frequency output signal;
a first switch arm coupled to the antenna via a pole node, the first switch arm being configured to transmit a first signal having a first wavelength λ 1 and including a first switch;
a second switch arm coupled to the antenna via the pole node, the second switch arm being configured to transmit a second signal having a second wavelength λ 2 and including a second switch;
a first shunt arm connected to the first switch arm between the pole node and the first switch;
a second shunt arm connected to the second switch arm between the pole node and the second switch;
a first transmission line disposed in the first switch arm between the pole node at a first end of the first transmission line and the first switch and the first shunt arm at a second end of the first transmission line, the first transmission line having a length of ¾ λ 2 ; and
a second transmission line disposed in the second switch arm between the pole node at a first end of the second transmission line and the second shunt arm at the second end of the second transmission line, the second transmission line having a length of ¼ λ 1 .