Switch circuit and method of switching radio frequency signals
A novel RF switch circuit and method for switching RF signals is described. The RF switch circuit is fabricated in a silicon-on-insulator (SOI) technology. The RF switch includes pairs of switching and shunting transistor groupings used to alternatively couple RF input signals to a common RF node. The switching and shunting transistor grouping pairs are controlled by a switching control voltage (SW) and its inverse (SW_). The switching and shunting transistor groupings comprise one or more MOSFET transistors connected together in a “stacked” or serial configuration. The stacking of transistor grouping devices, and associated gate resistors, increase the breakdown voltage across the series connected switch transistors and operate to improve RF switch compression. A fully integrated RF switch is described including digital control logic and a negative voltage generator integrated together with the RF switch elements. In one embodiment, the fully integrated RF switch includes a built-in oscillator, a charge pump circuit, CMOS logic circuitry, level-shifting and voltage divider circuits, and an RF buffer circuit. Several embodiments of the charge pump, level shifting, voltage divider, and RF buffer circuits are described. The inventive RF switch provides improvements in insertion loss, switch isolation, and switch compression.
1. A method of switching an RF signal comprising:
generating a voltage substantially negative with respect to ground using a negative voltage generator circuit comprising a charge pump;
generating one or more control signals using an integrated digital logic circuit;
controlling, using the generated one or more control signals, a switch transistor grouping to a switch ON state or a switch OFF state and a shunt transistor grouping to a shunt ON state or a shunt OFF state, wherein the controlling the shunt transistor grouping to the shunt OFF state and the controlling the switch transistor grouping to the switch OFF state is controlled, at least in part, with the substantially negative voltage;
passing the RF signal between a first RF node and a second RF node using the switch transistor grouping comprising stacked switch N-type metal oxide semiconductor field effect transistors (NMOSFETs) in the switch ON state, the stacked switch NMOSFET transistors coupling the RF nodes; and
not shunting the first RF node to ground using the shunt transistor grouping comprising stacked shunt NMOSFET transistors in the shunt OFF state, the stacked shunt NMOSFET transistors coupling the first RF node and ground;
wherein the generatings, the controlling, the passing and the not shunting take place in a single integrated circuit chip.
2. The method of claim 1 , wherein the passing and the not shunting take place at least partially concurrently.
3. The method of claim 1 , wherein the switching the RF signal comprises switching the RF signal in an RF module.
4. The method of claim 3 , wherein the switching the RF signal in the RF module comprises switching the RF signal in the RF module of a communication device.
5. The method of claim 1 , wherein the controlling the shunt transistor grouping to the OFF state comprises electrically biasing the shunt transistor grouping to the OFF state, at least in part, with the substantially negative voltage.
6. The method of claim 5 , wherein the electrically biasing comprises electrically biasing the stacked shunt NMOSFET transistors to withstand a voltage across the shunt transistor grouping with a voltage magnitude greater than a breakdown voltage of an individual shunt NMOSFET transistor in the transistor grouping.
7. The method of claim 1 , wherein the controlling the one or more respective transistor groupings comprises respectively electrically biasing the NMOSFET transistors thereof through at least one gate resistor coupled to at least one NMOSFET transistor of the NMOSFET transistors.
8. The method of claim 7 , wherein the respectively electrically biasing through the at least one gate resistor comprises respectively electrically biasing through at least one resistor having a resistance of at least 30 kohms.
9. The method of claim 1 , wherein the passing the RF signal comprises passing the RF signal between the first RF node and the second RF node in the single integrated circuit chip implemented in silicon on insulator (SOI) technology.
10. The method of claim 9 , wherein the passing the RF signal comprises passing the RF signal between the first RF node and the second RF node in a thin film silicon layer.
11. The method of claim 10 , wherein the passing the RF signal comprises passing the RF signal between the first RF node and the second RF node in the single integrated circuit chip implemented with at least the thin film silicon layer on an insulating layer in which sources and drains of the NMOSFET transistors extend through the entire thickness of the thin film silicon layer to the insulating layer.
12. The method of claim 9 , wherein the passing the RF signal comprises passing the RF signal between the first RF node and the second RF node with increased electrical isolation between the one or more transistor groupings and the negative voltage generator circuit in the single integrated circuit at least in part via the SOI technology comprising at least an insulating layer.
13. The method of claim 12 , wherein the passing the RF signal comprises passing the RF signal between the first RF node and the second RF node with increased electrical isolation at least so as to be capable to use the single integrated circuit chip in a cellular wireless communication system.
14. The method of claim 1 , wherein the not shunting the first RF node to ground comprises not shunting to ground a high power RF signal at the first RF node.
15. The method of claim 14 , wherein the not shunting to ground the high power RF signal comprises not shunting the high power RF signal in the single integrated circuit chip during use of the single integrated circuit chip in a cellular communications system.
16. A method of switching an RF signal comprising:
generating a voltage substantially negative with respect to ground using a negative voltage generator circuit comprising a charge pump;
generating one or more control signals using an integrated digital logic circuit;
controlling, using the generated one or more control signals, a switch transistor grouping to a switch ON state or a switch OFF state and a shunt transistor grouping to a shunt ON state or a shunt OFF state, wherein the controlling the shunt transistor grouping to the shunt OFF state and the controlling the switch transistor grouping to the switch OFF state is controlled, at least in part, with the substantially negative voltage;
not passing the RF signal between a first RF node and a second RF node using the switch transistor grouping comprising stacked switch N-type metal oxide semiconductor field effect transistors (NMOSFETs) in the switch OFF state, the stacked switch NMOSFET transistors coupling the RF nodes;
shunting the first RF node to ground using the shunt transistor grouping comprising stacked shunt NMOSFET transistors in the shunt ON state, the stacked shunt NMOSFET transistors coupling the first RF node and ground; and
wherein the generatings, the controlling, the not passing and the shunting take place in a single integrated chip.
17. The method of claim 16 , wherein the shunting and the not passing take place at least partially concurrently.
18. The method of claim 16 , wherein the switching the RF signal comprises switching the RF signal in an RF module.
19. The method of claim 18 , wherein the switching the RF signal in the RF module comprises switching the RF signal in the RF module of a communication device.
20. The method of claim 16 , wherein the controlling the switch transistor grouping to the OFF state comprises electrically biasing the switch transistor grouping to the OFF state, at least in part, with the substantially negative voltage.
21. The method of claim 20 , wherein the electrically biasing comprises electrically biasing the stacked switch NMOSFET transistors to withstand a voltage across the switch transistor grouping with a voltage magnitude greater than a breakdown voltage of an individual switch NMOSFET transistor in the transistor grouping.
22. The method of claim 16 , wherein the controlling one or more respective transistor groupings comprises respectively electrically biasing the NMOSFET transistors thereof through at least one gate resistor coupled to at least one NMOSFET transistor of the NMOSFET transistors.
23. The method of claim 22 , wherein the respectively electrically biasing through the at least one gate resistor comprises respectively electrically biasing through at least one resistor having a resistance of at least 30 kohms.
24. The method of claim 16 , wherein the shunting the first RF node comprises shunting the first RF node to ground in the single integrated circuit chip implemented in silicon on insulator (SOI) technology.
25. The method of claim 24 , wherein the shunting the first RF node comprises shunting the first RF node to ground in a thin film silicon layer.
26. The method of claim 25 , wherein the shunting the first RF node comprises shunting the first RF node to ground in the single integrated circuit chip implemented in the SOI technology with at least the thin film silicon layer on an insulating layer in which sources and drains of the NMOSFET transistors extend through the entire thickness of the thin film silicon layer to the insulating layer.
27. The method of claim 24 , wherein the shunting the first RF node comprises shunting the first RF node to ground with increased electrical isolation between the one or more transistor groupings and the negative voltage generator circuit in the single integrated circuit chip at least in part via the SOI technology comprising at least an insulating layer.
28. The method of claim 27 , wherein the shunting the first RF node comprises shunting the first RF node to ground with increased electrical isolation at least so as to be capable to use the single integrated circuit chip in a cellular wireless communication system.
29. The method of claim 16 , wherein the not passing the RF signal comprises not passing a high power RF signal between the first RF node and the second RF node.
30. The method of claim 29 , wherein the not passing the high power RF signal comprises not passing in the single integrated circuit chip during use of the single integrated circuit chip in a cellular communications system.