Radio frequency switching circuit with distributed switches
An RF switching device having distributed shunt switches distributed along transmission lines to improve RF bandwidth as well as the signal isolation of the device. The shunt switches may be physically positioned on both sides of the transmission lines to keep an integrated circuit (IC) design essentially symmetrical so as to provide predictable and reliable operational characteristics. Some embodiments include stacked FET shunt switches and series switches to tolerate high voltages. In some embodiments, the gate resistor for each FET shunt switch is divided into two or more portions.
1. A radio frequency switching device including:
(a) at least one common port;
(b) at least one field effect transistor (FET) series switch, each coupled to at least one common port;
(c) at least one terminal port;
(d) at least one transmission line, the ends of each transmission line being series coupled between a respective one of the at least one FET series switch and a respective one of the at least one terminal port; and
(e) for at least one such transmission line, at least two FET shunt switch units coupled between circuit ground and such transmission line in a tuning network configuration, wherein each FET of the at least two FET shunt switch units includes a primary resistor coupled to a gate of such FET in close proximity to such gate, and further including at least one secondary resistor each series coupled to the primary resistor of two or more of such FETs but located farther away from the gate of each such FET than the primary resistor coupled to each such gate.
2. The invention of claim 1 , wherein each transmission line is arrayed on an integrated circuit so as to define a first side and a second side of such transmission line and at least two FET shunt switch units are positioned with respect to at least one arrayed transmission line such that at least one such FET shunt switch unit is positioned adjacent the first side of such arrayed transmission line and at least one other FET shunt switch unit is positioned adjacent the second side of such arrayed transmission line.
3. The invention of claim 1 , wherein at least one transmission line is arrayed on an integrated circuit layout in a substantially symmetrical manner.
4. The invention of claim 1 , wherein at least one FET shunt unit includes a series-coupled stack of FET switches.
5. The invention of claim 1 , wherein at least one FET series switch includes a series-coupled stack of FET switches.
6. The invention of claim 1 , wherein at least one transmission line further includes at least one coupled supplemental inductive tuning component.
7. The invention of claim 1 , wherein each FET shunt switch unit has an OFF state capacitance, and the tuning network configuration compensates for the OFF state capacitance.
8. The invention of claim 1 , further including at least one secondary isolation FET series switch, each coupled between a respective one of the at least one transmission line and a respective one of the at least one terminal port.
9. The invention of claim 1 , wherein the radio frequency switching device is embodied on a silicon-on-insulator integrated circuit substrate.
10. A radio frequency switching device including:
(a) at least one common port;
(b) at least one field effect transistor (FET) series switch, each coupled to at least one common port;
(c) at least one terminal port;
(d) at least one transmission line, the ends of each transmission line being series coupled between a respective one of the at least one FET series switch and a respective one of the at least one terminal port, each transmission line including one or more compensating inductance elements; and
(e) for each transmission line, at least two FET shunt switch units coupled between circuit ground and such one or more compensating inductance elements in a tuning network configuration, wherein each FET shunt switch unit has an OFF state capacitance and the tuning network configuration compensates for such OFF state capacitance, and wherein each FET of the at least two FET shunt switch units includes a primary resistor coupled to a gate of such FET in close proximity to such gate, and further including at least one secondary resistors each series coupled to the primary resistor of two or more of such FETs but located farther away from the gate of each such FET than the primary resistor coupled to each such gate.
11. A method for configuring a radio frequency switching device, including the steps of:
(a) providing at least one common port;
(b) coupling at least one field effect transistor (FET) series switch to at least one common port;
(c) coupling a first end of at least one transmission line to a respective one of the at least one FET series switch, each transmission line including at least one series-coupled inductive tuning component;
(d) coupling at least one terminal port to a second end of a respective one of the at least one transmission line; and
(e) coupling at least two FET shunt switch units between circuit ground and a corresponding one of the at least one transmission line in a tuning network configuration, wherein each FET of the at least two FET shunt switch units includes a primary resistor coupled to a gate of such FET in close proximity to such gate; and
(f) coupling at least one secondary resistor in series to the primary resistor of two or more FETs, wherein each secondary resistor is located farther away from the gate of each such coupled FET than the primary resistor coupled to each such gate.
12. The method of claim 11 , further including:
(a) arraying each transmission line on an integrated circuit so as to define a first side and a second side of such transmission line;
(b) for at least one arrayed transmission line, positioning at least two FET shunt switch units such that at least one such FET shunt switch unit is positioned adjacent the first side of such arrayed transmission line and at least one other FET shunt switch unit is positioned adjacent the second side of such arrayed transmission line.
13. The method of claim 11 , further including arraying at least one transmission line on an integrated circuit layout in a substantially symmetrical manner.
14. The method of claim 11 , wherein at least one FET shunt unit includes a series-coupled stack of FET switches.
15. The method of claim 11 , wherein at least one FET series switch includes a series-coupled stack of FET switches.
16. The method of claim 11 , further including coupling at least one supplemental inductive tuning component to at least one transmission line.
17. The method of claim 11 , wherein each FET shunt switch unit has an OFF state capacitance, and the tuning network configuration compensates for the OFF state capacitance.
18. The method of claim 11 , further including coupling at least one secondary isolation FET series switch between a respective one of the at least one transmission line and a respective one of the at least one terminal port.
19. The method of claim 11 , further including embodying the radio frequency switching device on a silicon-on-insulator integrated circuit substrate.
20. A method for configuring a radio frequency switching device, including the steps of:
(a) providing at least one common port;
(b) coupling at least one field effect transistor (FET) series switch to at least one common port;
(c) coupling a first end of at least one transmission line to a respective one of the at least one FET series switch, each transmission line including one or more compensating inductance elements;
(d) coupling at least one terminal port to a second end of a respective one of the at least one transmission line;
(e) coupling at least two FET shunt switch units to a corresponding one of the at least one transmission line, wherein each FET shunt switch unit is coupled between circuit ground and such one or more compensating inductance elements of such at least one transmission line in a tuning network configuration, wherein each FET shunt switch unit has an OFF state capacitance and the tuning network configuration compensates for such OFF state capacitance, and wherein each FET switch of the at least two FET shunt switch units includes a primary resistor coupled to a gate of such FET switch in close proximity to such gate and
(f) coupling at least one secondary resistor in series to the primary resistor of two or more FET switches, wherein each secondary resistor is located farther away from the gate of each such coupled FET switch than the primary resistor coupled to each such gate.