Radio frequency front end with tunable filters
Aspects of this disclosure relate to a radio frequency system with tunable notch filtering. The radio frequency system includes a first tunable filter and a second tunable filter. The first tunable filter is coupled between an output of a power amplifier and a radio frequency switch. The second tunable filter is coupled between an antenna switch and an antenna node. The second tunable filter has a notch at a lower frequency than a notch of the first tunable filter. Related methods and wireless communication devices are also disclosed.
1. A radio frequency system with tunable notch filtering,
the radio frequency system comprising:
a power amplifier having an output;
a multi-throw switch;
a first tunable filter coupled between the output of the power amplifier and the multi-throw switch, the first tunable filter having at least a first tunable notch;
an antenna switch coupled to the multi-throw switch by way of one or more radio frequency signal paths; and
a second tunable filter coupled between the antenna switch and an antenna node, the second tunable filter having at least a second tunable notch, the second tunable notch being at a lower frequency than the first tunable notch, the second tunable filter being an L network that includes a parallel inductor-capacitor circuit and a shunt series inductor-capacitor circuit, and the parallel inductor-capacitor circuit arranged in series between the antenna switch and the antenna node.
2. The radio frequency system of claim 1 wherein the second tunable notch corresponds to a higher order harmonic than the first tunable notch.
3. The radio frequency system of claim 1 wherein the first tunable filter has a plurality of tunable notches, the plurality of tunable notches including the first tunable notch.
4. The radio frequency system of claim 3 wherein the plurality of tunable notches each correspond to a higher respective frequency than the second tunable notch.
5. The radio frequency system of claim 3 wherein the second tunable filter has a single tunable notch, the single tunable notch being the second tunable notch.
6. The radio frequency system of claim 3 wherein the second tunable filter has a second plurality of tunable notches, the second plurality of tunable notches including the second tunable notch.
7. The radio frequency system of claim 1 wherein the parallel inductor-capacitor circuit includes a tunable capacitance circuit.
8. The radio frequency system of claim 7 wherein the shunt series inductor-capacitor circuit includes a second tunable capacitance circuit.
9. The radio frequency system of claim 1 wherein the one or more radio frequency signal paths includes a first radio frequency signal path, and the first radio frequency signal path includes a band pass filter.
10. A radio frequency system with tunable notch filtering, the radio frequency system comprising:
a power amplifier having an output;
a multi-throw switch;
a first tunable filter coupled between the output of the power amplifier and the multi-throw switch, the first tunable filter having at least a first tunable notch;
an antenna switch coupled to the multi-throw switch by way of one or more radio frequency signal paths; and
a second tunable filter coupled between the antenna switch and an antenna node, the second tunable filter having at least a second tunable notch, the second tunable notch being at a lower frequency than the first tunable notch, the second tunable filter including a first inductor, a second inductor mutually coupled to the first inductor, and a tunable capacitance circuit coupled to the first inductor.
11. The radio frequency system of claim 10 wherein the first tunable filter includes a third inductor, a fourth inductor mutually coupled to the third inductor, and a second tunable capacitance circuit coupled to the third inductor.
12. The radio frequency system of claim 10 wherein the second tunable filter is an L network.
13. The radio frequency system of claim 12 wherein the L network includes a parallel inductor-capacitor circuit and a shunt series inductor-capacitor circuit, the parallel inductor-capacitor circuit arranged in series between the antenna switch and the antenna node.
14. The radio frequency system of claim 10 further comprising a tunable shunt capacitance circuit coupled to a node between the first tunable filter and the multi-throw switch, the tunable shunt capacitance circuit being configured to tune a load line.
15. A radio frequency system with tunable notch filtering, the radio frequency system comprising:
a power amplifier having an output;
a multi-throw switch;
a first tunable filter coupled between the output of the power amplifier and the multi-throw switch, the first tunable filter having at least a first tunable notch, the first tunable filter including a first inductor, a second inductor mutually coupled to the first inductor, and a tunable capacitance circuit coupled to the first inductor;
an antenna switch coupled to the multi-throw switch by way of one or more radio frequency signal paths, and
a second tunable filter coupled between the antenna switch and an antenna node, the second tunable filter having at least a second tunable notch, the second tunable notch being at a lower frequency than the first tunable notch.
16. The radio frequency system of claim 15 further comprising a tunable shunt capacitance circuit coupled to a node between the first tunable filter and the multi-throw switch, the tunable shunt capacitance circuit being configured to tune a load line.
17. The radio frequency system of claim 15 wherein the second tunable filter is an L network that includes a parallel inductor-capacitor circuit and a shunt series inductor-capacitor circuit, the parallel inductor-capacitor circuit arranged in series between the antenna switch and the antenna node.
18. A radio frequency system with tunable notch filtering, the radio frequency system comprising:
a power amplifier having an output;
a multi-throw switch;
a first tunable filter coupled between the output of the power amplifier and the multi-throw switch, the first tunable filter having at least a first tunable notch;
a tunable shunt capacitance circuit coupled to a node between the first tunable filter and the multi-throw switch, the tunable shunt capacitance circuit being configured to tune a load line;
an antenna switch coupled to the multi-throw switch by way of one or more radio frequency signal paths; and
a second tunable filter coupled between the antenna switch and an antenna node, the second tunable filter having at least a second tunable notch, the second tunable notch being at a lower frequency than the first tunable notch.
19. The radio frequency system of claim 18 wherein the second tunable filter is an L network that includes a parallel inductor-capacitor circuit and a shunt series inductor-capacitor circuit, the parallel inductor-capacitor circuit arranged in series between the antenna switch and the antenna node.
20. The radio frequency system of claim 18 wherein the second tunable notch corresponds to a higher order harmonic than the first tunable notch.