Radio-frequency switch having improved linearity
Radio-frequency switch having improved linearity. In some embodiments, a radio-frequency switch circuit can include first and second switch arms, with each switch arm including a plurality of transistors arranged in series to form a stack between a first node and a second node. The first node of the first switch arm can be coupled to the first node of the second switch arm. The radio-frequency switch circuit can further include an amplitude-phase cancelling block implemented across one or more transistors of each switch arm, and configured such that a third harmonic resulting from an ON state of the first switch arm is substantially canceled by a third harmonic resulting from an OFF state of the second switch arm.
1. A radio-frequency switch circuit comprising:
first and second switch arms, each switch arm including a plurality of transistors arranged in series to form a stack between a first node and a second node, the first node of the first switch arm coupled to the first node of the second switch arm; and
an amplitude-phase cancelling block implemented across one or more transistors of each switch arm, and configured such that a third harmonic resulting from an ON state of the first switch arm is substantially canceled by a third harmonic resulting from an OFF state of the second switch arm.
2. The radio-frequency switch circuit of claim 1 wherein the amplitude-phase cancelling block includes a first combination arranged in series with a second combination, each of the first and second combinations including a series combination of a diode and a capacitance in a parallel arrangement with a resistance, the diode of the first combination implemented in an anti-parallel manner relative to the diode of the second combination.
3. The radio-frequency switch circuit of claim 2 wherein the diodes of the first and second combinations are configured to generate harmonics by voltage distributed by a voltage divider formed by the resistances of the first and second combinations.
4. The radio-frequency switch circuit of claim 3 wherein the capacitances of the first and second combinations are configured to provide respective phase shifts of the harmonics.
5. The radio-frequency switch circuit of claim 4 wherein the anti-parallel configuration of the diodes of the first and second combinations results in the amplitude-phase cancelling block generating substantially nil amount of a second harmonic.
6. The radio-frequency switch circuit of claim 4 wherein the amplitude-phase cancelling blocks associated with the first and second switch arms are selected so that a third harmonic associated with the first switch arm is substantially canceled by a third harmonic associated with the second switch arm.
7. The radio-frequency switch circuit of claim 4 wherein each diode of the amplitude-phase cancelling block is implemented as a field-effect transistor configured as a diode, where source and drain of the field-effect transistor are coupled.
8. The radio-frequency switch circuit of claim 7 wherein bodies of the field-effect transistors are coupled.
9. The radio-frequency switch circuit of claim 7 wherein a gate-drain capacitance or a gate-source capacitance of each field-effect transistor is configured to provide the respective phase shifts of the harmonics.
10. The radio-frequency switch circuit of claim 1 wherein the amplitude-phase cancelling block is implemented with the respective switch arm in a symmetric manner.
11. The radio-frequency switch circuit of claim 10 wherein the number of transistors between the phase cancelling block and the first node is the same as the number of transistors between the phase cancelling block and the second node.
12. The radio-frequency switch circuit of claim 10 wherein each switch arm is configured to be operated with the first node as an input node, or with the second node as an input node.
13. The radio-frequency switch circuit of claim 1 wherein the amplitude-phase cancelling block is implemented with the respective switch arm in an asymmetric manner.
14. The radio-frequency switch circuit of claim 13 wherein each switch arm is configured to be operated with one of the first and second nodes as an input node, and the other node as an output node.
15. The radio-frequency switch circuit of claim 1 wherein at least the plurality of transistors are implemented as field-effect transistors.
16. The radio-frequency switch circuit of claim 15 wherein the field-effect transistors are implemented as silicon-on-insulator devices.
17. The radio-frequency switch circuit of claim 15 wherein at least some of the amplitude-phase cancelling blocks are implemented as field-effect transistor like devices.