Switch circuit and method of switching radio frequency signals
View Patent ↗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 switch circuit for switching RF signals, comprising:
a) a first RF port capable of outputting or receiving a first RF signal;
b) a second RF port capable of outputting or receiving a second RF signal;
c) a switch transistor grouping having a first node coupled to the first RF port and a second node coupled to the second RF port, wherein the switch transistor grouping is controlled by a first switch control signal (SW); and
d) a shunt transistor grouping having a first node coupled to the first RF port and a second node coupled to ground, wherein the shunt transistor grouping is controlled by a second switch control signal (SW);
wherein the RF switch circuit is fabricated in a fully integrated device, wherein the fully integrated device includes a negative voltage generator coupled to the RF switch circuit wherein the negative voltage generator generates a negative power supply voltage, and wherein the negative voltage generator comprises a charge pump circuit;
and wherein when the first switch control signal SW is enabled, the switch transistor grouping is enabled and the shunt transistor grouping is disabled thereby electrically coupling the first RF port to the second RF port, and wherein when the second switch control signal SW is enabled, the shunt transistor grouping is enabled while the switch transistor grouping is disabled thereby shunting the first RF port to ground.
2. The RF switch of claim 1 , wherein the switch transistor grouping comprises a single MOSFET, and wherein the shunt transistor grouping comprises a single MOSFET.
3. The RF switch of claim 1 , wherein the switch transistor grouping comprises a plurality of MOSFETs arranged in a stacked configuration, and wherein the shunt transistor grouping comprises a plurality of MOSFETs arranged in a stacked configuration.
4. The RF switch of claim 1 , wherein the switch transistor grouping comprises a first number of MOSFETs arranged in a stacked configuration, and wherein the shunt transistor grouping comprises a second number of MOSFETs arranged in a stacked configuration, and wherein the first number and the second number differ from one another.
5. An RF switch circuit for switching RF signals, comprising:
(a) a first RF port capable of receiving or outputting a first RF signal (RF 1 );
(b) a second RF port capable receiving or outputting a second RF signal (RF 2 );
(c) an RF common port;
(d) a first switch transistor grouping having a first node coupled to the first RF port and a second node coupled to the RF common port, wherein the first switch transistor grouping is controlled by a first switch control signal;
(e) a second switch transistor grouping having a first node coupled to the second RF port and a second node coupled to the RF common port, wherein the second switch transistor grouping is controlled by a second switch control signal;
(f) a first shunt transistor grouping having a first node coupled to the second RF port and a second node coupled to ground, wherein the first shunt transistor grouping is controlled by the first switch control signal; and
(g) a second shunt transistor grouping having a first node coupled to the first RF port and a second node coupled to ground, wherein the second shunt transistor grouping is controlled by the second switch control signal;
wherein the RF switch circuit is fabricated in a fully integrated device, wherein the fully integrated device includes a negative voltage generator coupled to the RF switch circuit wherein the negative voltage generator generates a negative power supply voltage, and wherein the negative voltage generator comprises a charge pump circuit, and wherein, when the first switch control signal is enabled, the first switch and first shunt transistor groupings are enabled while the second switch and shunt transistor groupings are disabled, thereby electrically coupling the first RF port with the RF common port and shunting the second RF port to ground, and wherein when the first switch control signal is disabled and the second switch control signal is enabled, the second switch and shunt transistor groupings are enabled while the first switch and shunt transistor groupings are disabled, thereby electrically coupling the second RF port with the RF common port and shunting the first RF port to ground.
6. The RF switch circuit of claim 5 , wherein the RF switch comprises a single-pole, multi-throw switch.
7. The RF switch circuit of claim 5 , wherein the RF switch comprises a multi-pole, single-throw switch.
8. The RF switch of claim 5 , wherein the RF switch comprises a multi-pole, multi-throw switch.