Switch circuit and method of switching radio frequency signals
An RF switch circuit and method for switching RF signals that may be fabricated using common integrated circuit materials such as silicon, particularly using insulating substrate technologies. The RF switch includes switching and shunting transistor groupings to alternatively couple RF input signals to a common RF node, each controlled by a switching control voltage (SW) or its inverse (SW_), which are approximately symmetrical about ground. The transistor groupings each comprise one or more insulating gate FET transistors connected together in a “stacked” series channel configuration, which increases the breakdown voltage across the series connected transistors and improves RF switch compression. A fully integrated RF switch is described including control logic and a negative voltage generator with the RF switch elements. In one embodiment, the fully integrated RF switch includes an oscillator, a charge pump, CMOS logic circuitry, level-shifting and voltage divider circuits, and an RF buffer circuit.
1. An RF switching circuit comprising:
a switch transistor grouping,
a shunt transistor grouping coupled with the switch transistor grouping and including a node with a reference voltage;
control logic configured to output a first control signal and a second control signal; and
a voltage generator coupled with the control logic, the voltage generator comprising a charge pump and being configured to generate a voltage substantially more negative than the reference voltage;
wherein:
the switch transistor grouping is configured to receive the first control signal;
the shunt transistor grouping is configured to receive the second control signal; and
the switch transistor grouping and/or the shunt transistor grouping comprise a plurality of stacked transistors.
2. The RF switching circuit of claim 1 , wherein the first control signal and the second control signal are switchable between respective higher and lower voltages than the reference voltage.
3. The RF switching circuit of claim 1 , wherein the reference voltage is ground.
4. The RF switching circuit of claim 3 , wherein the switch transistor grouping or the shunt transistor grouping comprise a plurality of stacked field effect transitor (FETs) in which the respective FETs have a gate that is insulated from its channel.
5. The RF switching circuit of claim 3 , wherein the RF switching circuit includes a semiconductor-on-insulator (SOI) substrate.
6. The RF switching circuit of claim 3 , wherein the shunt transistor grouping and/or the switch transistor grouping respectively comprise a plurality of stacked FETs; and
further comprising:
a plurality of switch gate resistors; and
a plurality of shunt gate resistors;
wherein:
the resistance value of the gate resistors respectively is at least 30 k ohms.
7. The RF switching circuit of claim 6 , wherein the RF switching circuit is capable of passing and/or capable of not passing one or more high-power RF signals in connection with RF transmission of RF signals.
8. The RF switching circuit of claim 4 , wherein the RF switching circuit includes a semiconductor-on-insulator (SOI) substrate.
9. The RF switching circuit of claim 8 , wherein the SOI substrate comprises a thin-film semiconductor layer.
10. The RF switching circuit of claim 9 , wherein the SOI substrate comprises at least a thin-film semiconductor layer and an insulating layer, wherein respective sources and drains of the respective FETs of the plurality of stacked FETs extend through an entire thickness of the semiconductor layer to the insulating layer.
11. The RF switching circuit of claim 1 , further comprising:
an oscillator coupled with the charge pump, the charge pump being configured to receive clocking input signals from the oscillator;
a level shifting circuit coupled with the control logic; and
an RF buffer circuit isolating RF signal energy between the charge pump and the control logic.
12. An RF switching circuit comprising:
a switch transistor grouping comprising a plurality of stacked transistors;
a shunt transistor grouping, comprising another plurality of stacked transistors, coupled with the switch transistor grouping and including a grounded node;
control logic configured to output a first control signal and a second control signal; and
a voltage generator comprising a charge pump coupled with the control logic, the voltage generator being configured to generate a voltage substantially more negative than ground;
wherein:
the switch transistor grouping is configured to receive the first control signal;
the shunt transistor grouping is configured to receive the second control signal,
the RF switching circuit is implemented with semiconductor-on-insulator (SOI) technology; and
the RF switching circuit to pass and/or to not pass one or more high-power RF signals in connection with RF transmission of RF signals.
13. An on-chip method of switching RF signals, comprising:
inputting an RF signal to a switch transistor grouping comprised of a plurality of stacked transistors implemented with semiconductor-on-insulator (SOI) technology;
generating a first control signal and a second control signal;
in an ON state of the switch transistor grouping: enabling the switch transistor grouping using the first control signal and disabling a shunt transistor grouping, comprised of another plurality of stacked transistors implemented with SOI technology, using the second control signal, thereby passing the RF signal; and
in an OFF state of the switch transistor grouping: disabling the switch transistor grouping using the first control signal and enabling the shunt transistor grouping using the second control signal, thereby not passing the RF signal;
wherein the passing the RF signal comprises passing a high-power RF signal in connection with RF transmission of RF signals; and
wherein the not passing the RF signal comprises not passing a high-power RF signal in connection with RF transmission of RF signals.
14. The method of claim 13 , wherein the switch transistor grouping and the shunt transistor grouping comprise field effect transitor (FETs) and the FETs respectively are coupled to gate resistors of at least 30 K ohms.