Fast antenna swapping

1. A method of sounding reference signal switching in a mobile device, the method comprising:

with a packaged front end module of the mobile device, transmitting a sequence of symbols using a transmit path through a power amplifier and antenna switch to a first antenna;

receiving a command at an interface of the packaged front end module, the command generated at a baseband system;

in response to receiving the command at the interface of the packaged front end module, with circuitry of the packaged front end module, and without external control, causing: reduced gain of the power amplifier, initiation of a switching delay in response to the reduced gain of the power amplifier, and actuation of the antenna switch to switch to a second antenna after the switching delay; and

subsequent to actuation of the antenna switch, transmitting a sounding reference signal symbol using the transmit path through the power amplifier and the antenna switch to the second antenna.

2. The method of claim 1 wherein the sequence of symbols includes a sounding reference signal.

3. The method of claim 1 wherein the command initiates sounding reference signal switching.

4. The method of claim 1 wherein the antenna switch is open for a portion of the actuation of the antenna switch.

5. The method of claim 1 wherein the antenna switch makes connection with the second antenna before breaking a connection with the first antenna during the actuation of the antenna switch.

6. A mobile device comprising:

a baseband system configured to generate a sequence of symbols for transmission to a first antenna and a command to initiate sounding reference signal switching; and

a front end module including a module package, a power amplifier within the module package, and a switch within the module package configured to switch between the first antenna and a second antenna, the front end module configured to, in response to receiving the command at an interface of the front end module, and without external control, reduce gain of the power amplifier, initiate a switching delay, after the switching delay, switch the switch from the first antenna to the second antenna, and transmit a sounding reference signal symbol on the second antenna through the power amplifier and the switch.

7. The mobile device of claim 6 wherein the command is received at a mobile industry processor interface within the front end module.

8. The mobile device of claim 6 wherein switching of switch occurs during a cycle prefix associated with the sounding reference signal symbol.

9. The mobile device of claim 6 wherein receipt of the command initiates a sequence stored in a register internal to the front end module.

10. The mobile device of claim 6 wherein the front end module further includes a power amplifier module that includes the power amplifier and a first controller, the front end module further including a switch module that includes the switch and a second controller.

11. The mobile device of claim 10 wherein the first controller is configured to reduce the gain of the power amplifier in response to receiving the command.

12. The mobile device of claim 10 wherein the second controller is configured to initiate the delay and switch the switch in response to receiving the command.

13. The mobile device of claim 6 wherein the front end module further includes a controller that is configured to receive the command and initiate an ordered set of actions in response to receiving the command.

14. The mobile device of claim 6 wherein transmission of the sounding reference signal symbol occurs without transmitting a blank symbol before and after the sounding reference signal symbol.

15. The mobile device of claim 6 wherein the switching of the switch occurs during a cycle prefix associated with the sounding reference signal symbol.

16. The mobile device of claim 6 wherein the baseband system notifies a base station in a communication network that the sounding reference signal symbols are transmitted without preceding and following blank symbols.

17. A front end system comprising:

a module package;

a power amplifier within the module package configured to provide an amplified radio frequency signal at a switch input for transmission to a first antenna terminal;

an antenna switch within the module package configured to receive the amplified radio frequency signal at the switch input and switch between the first antenna terminal and a second antenna terminal; and

a controller within the module package configured, in response to a trigger word received at an interface of the front end module and, and without external control, reduce gain of the power amplifier, initiate a switching delay, and cause, after the switching delay, actuation of the antenna switch, such that following actuation, the switch input of the switch is in communication with the second antenna terminal, the controller further configured to cause transmission of a sounding reference signal symbol through the power amplifier and the antenna switch to the second antenna terminal.

18. The front end system of claim 17 wherein reducing the gain of the power amplifier includes lowering a bias of the power amplifier.

19. The front end system of claim 18 wherein lowering the bias of the power amplifier includes lowering the bias of one or more amplifying stages of the power amplifier.

20. The front end system of claim 17 wherein the controller includes a sequence register.