RF switch with bypass topology
An RF signal switch circuit that allows connection of any of N radio frequency (RF) input terminals to a switch output port, either in an in-circuit mode or in a bypass mode. Embodiments of the invention allow for both a single switch in the series input path while still having the ability to isolate the bypass path from an input matching network. In both modes, the circuit simultaneously exhibits low input insertion loss (and thus a low noise factor) and high bypass mode isolation.
1. A radio frequency (RF) signal switch, including:
(a) at least one RF input port, each RF input port having a shunt switch coupled between the RF input port and circuit ground and configured to selectively shunt the RF input port to ground, a bypass switch coupled between the RF input port and a switch output port, and at least one set of in-path connector switches coupled to the RF input port and the shunt switch;
(b) at least one in-circuit path each coupled to a corresponding isolation shunt switch and coupled to a corresponding one set of in-path connector switches, each in-circuit path being configured to be coupled to an input of a corresponding target circuit;
(c) at least one switch return path configured to be coupled to an output of a corresponding target circuit, and being coupled to a corresponding output connector shunt; and
(d) at least one output connector switch coupled to a corresponding one switch return path and to the switch output port.
2. The radio frequency (RF) signal switch of claim 1 , wherein the RF signal switch is configured in an in-circuit mode for a selected RF input port and a selected target circuit such that a signal applied to the selected RF input port passes through only one of the corresponding in-path connector switches for the selected RF input port and through no other switch.
3. The radio frequency (RF) signal switch of claim 1 , wherein the RF signal switch is configured in a bypass mode for a selected RF input port such that a signal applied to the selected RF input port passes to the switch output port through the corresponding bypass switch for the selected RF input port, and the input of each target circuit is isolated from the switch output port.
4. The radio frequency (RF) signal switch of claim 1 , wherein the RF signal switch is configured in an in-circuit mode for a selected RF input port and a selected target circuit in which:
(a) the shunt switch and bypass switch for the selected RF input port are open, at least one set of the in-path connector switches corresponding to one in-circuit path for the selected RF input port is closed, the isolation shunt switch corresponding to such one in-circuit path is open, the output connector shunt switch corresponding to the switch return path for the selected target circuit is open, and the output connector switch corresponding to the switch return path for the selected target circuit is closed; and
(b) for each other RF input port, the respective in-path connector switches and bypass switch are open, and the respective shunt switch is closed.
5. The radio frequency (RF) signal switch of claim 4 , further including isolating each non-selected target circuit from each at least one RF input port and from the switch output.
6. The radio frequency (RF) signal switch of claim 1 , wherein the RF signal switch is configured in a bypass mode for a selected RF input port in which:
(a) the shunt switch and each set of in-path connector switches for the selected RF input port are open, the bypass switch for the selected RF input port is closed, each isolation shunt switch and each output connector shunt switch is closed, and each output connector switch is open; and
(b) for each other RF input port, the respective in-path connector switch and bypass switch is open, and the respective shunt switch is closed.
7. The radio frequency (RF) signal switch of claim 1 , wherein each bypass switch comprises a “T” type series/shunt/series bypass switch circuit.
8. The radio frequency (RF) signal switch of claim 7 , wherein the “T” type series/shunt/series circuit includes a first series switch coupled at a junction to a second series switch, and a shunt switch coupled to the junction and to circuit ground, wherein (a) for an active RF input port in a bypass mode, the first series switch and second series switch are closed and the shunt switch is open; and (b) for an active RF input port in an in-circuit mode and for inactive RF input ports in either the in-circuit mode or the bypass mode, the first series switch and the second series switch are open and the shunt switch is closed.
9. The radio frequency (RF) signal switch of claim 1 , wherein each switch is a field effect transistor.
10. A radio frequency (RF) signal switch, including:
(a) at least one RF input port, each RF input port having a shunt switch coupled between the RF input port and circuit ground and configured to selectively shunt the associated RF input port to ground, a bypass switch coupled between the RF input port and a switch output port, and an in-path connector switch coupled to the RF input port and the shunt switch;
(b) an in-circuit path coupled to a corresponding isolation shunt switch and coupled to the in-path connector switches, the in-circuit path being configured to be coupled to an input of a target circuit;
(c) a switch return path configured to be coupled to an output of the target circuit, and being coupled to an output connector shunt; and
(d) an output connector switch coupled to the switch return path and to the switch output port.
11. The radio frequency (RF) signal switch of claim 10 , wherein the RF signal switch is configurable to be in (1) an in-circuit mode for a selected RF input port and a selected target circuit such that a signal applied to the selected RF input port passes through only one of the corresponding in-path connector switches for the selected RF input port and through no other switch, or (2) a bypass mode for a selected RF input port such that a signal applied to the selected RF input port passes to the switch output port through the corresponding bypass switch for the selected RF input port, and the input of each target circuit is isolated from the switch output port.
12. The radio frequency (RF) signal switch of claim 10 , wherein the RF signal switch is configured in an in-circuit mode for a selected RF input port in which:
(a) the shunt switch and bypass switch for the selected RF input port are open, the in-path connector switch for the selected RF input port is closed, the isolation shunt switch and the output connector shunt switch are open, and the output connector switch is closed; and
(b) for each other RF input port, the respective in-path connector switches and bypass switch are open, and the respective shunt switch is closed.
13. The radio frequency (RF) signal switch of claim 10 , wherein the RF signal switch is configured in a bypass mode for a selected RF input port in which:
(a) the shunt switch and the in-path connector switch for the selected RF input port are open, the bypass switch for the selected RF input port is closed, the isolation shunt switch and the output connector shunt switch are closed, and the output connector switch is open; and
(b) for each other RF input port, the respective in-path connector switch and bypass switch is open, and the respective shunt switch is closed.
14. The radio frequency (RF) signal switch of claim 10 , wherein each bypass switch comprises a “T” type series/shunt/series bypass switch circuit.
15. The radio frequency (RF) signal switch of claim 10 , wherein each switch is a field effect transistor.
16. A method for switching radio frequency (RF) signals, including:
(a) providing at least one RF input port, each RF input port having an associated shunt switch, an associated bypass switch, and an associated in-path connector switch;
(b) for at least one RF input port, coupling the associated in-path connector switch to a corresponding in-circuit path, the corresponding in-circuit path being configured to be coupled to an input of a corresponding target circuit;
(c) for the at least one RF input port, coupling the associated bypass switch between such RF input port and a switch output port;
(d) for the at least one RF input port, coupling the associated shunt switch to circuit ground and configuring the associated shunt switch to selectively shunt such RF input port to ground;
(e) for each in-circuit path, coupling an associated isolation shunt switch to the corresponding in-circuit path;
(f) providing a switch return path, the switch return path being configured to be coupled to an output of the target circuit;
(g) coupling an output connector shunt switch to the switch return path; and
(h) coupling an output connector switch to the switch return path and to the switch output port.
17. The method of claim 16 , further including configuring an in-circuit mode for a selected RF input port by:
(a) opening the associated shunt switch and associated bypass switch for the selected RF input port, closing the associated in-path connector switch for the selected RF input port, opening the associated isolation shunt switch for the corresponding in-circuit path, opening the output connector shunt switch, and closing the output connector switch; and
(b) for each other RF input port, opening the associated in-path connector switch and the associated bypass switch, and closing the associated shunt switch.
18. The method of claim 16 , further including configuring a bypass mode for a selected RF input port by:
(a) opening the associated shunt switch and the associated in-path connector switch for the selected RF input port, closing the associated bypass switch for the selected RF input port, closing the associated isolation shunt switch for the corresponding in-circuit path, closing the output connector shunt switch, and opening the output connector switch; and
(b) for each other RF input port, opening the associated in-path connector switch and the associated bypass switch, and closing the associated shunt switch.
19. The method of claim 16 , wherein each associated bypass switch comprises a “T” type series/shunt/series circuit.
20. The method of claim 16 , wherein each switch is a field effect transistor.