Antenna swapping without blanking symbols
Apparatus and methods for sounding reference signal (SRS) switching are provided. In certain embodiments, a controller internal to the power amplifier module initiates a sequence of instructions, in response to a single command from UE. The instructions cause a reduction in RF signal amplitude at the power amplifier output and then cause the antenna switch to actuate. Thus ensuring a single command transition and preventing over-power on the power amplifier and antenna switch. The teachings herein can be used to facilitate reduction in gap times between transitions on different antennas and avoid the use of a blank symbol before and after each SRS symbol.
1. A front end system comprising:
a power amplifier configured to amplify a radio frequency signal to provide an amplified radio frequency signal on an amplifier output;
an antenna switch coupled to the amplifier output and configured to switch between providing the amplifier output to a first antenna terminal and providing the amplifier output to a second antenna terminal; and
a controller configured to receive a trigger command that initiates an ordered list of commands that cause in the following order: a reduction in a gain of the power amplifier to protect the power amplifier, an actuation of the antenna switch to switch between providing the amplifier output to the first antenna terminal to providing the amplifier output the second antenna terminal, and an increase in the gain of the power amplifier prior to transmission of a sounding reference symbol to the second antenna terminal with the power amplifier and without blank symbols.
2. The front end system of claim 1 wherein the controller is a sequence register.
3. The front end system of claim 1 wherein causing reduction of the gain of the power amplifier includes causing reduced bias of one or more stages of the power amplifier.
4. A mobile device comprising:
a baseband system configured to generate a sequence of symbols for transmission and a command for initiating sounding reference signal switching; and
a power amplifier module including a power amplifier and a switch configured to switch between a first antenna and a second antenna, the power amplifier module, in response to receiving the command, is configured in the following order to: reduce gain of the power amplifier to protect the power amplifier, switch between providing an output of the power amplifier to the first antenna to providing the output of the power amplifier to the second antenna, and increase the gain of the power amplifier prior to transmission of a sounding reference symbol on the second antenna without blank symbols inserted into the sequence of symbols for transmission during switching.
5. The mobile device of claim 4 wherein reducing the gain of the power amplifier includes shunting one or more amplifier stages of the power amplifier.
6. The mobile device of claim 4 wherein reducing the gain of the power amplifier includes placing the power amplifier in an off mode.
7. The mobile device of claim 4 wherein the power amplifier module further includes a mobile industry processor interface, a bias controller and a switch controller.
8. The mobile device of claim 7 wherein the mobile industry processor interface is configured to receive the command and control the bias controller and the switch controller.
9. The mobile device of claim 8 wherein the bias controller is configured to control the gain of one or more stages of the power amplifier in response to a signal from the mobile industry processor interface.
10. The mobile device of claim 8 wherein the switch controller is configured to control actuation of the switch in response to a signal from the mobile industry processor interface.
11. A method of sounding reference signal switching in a mobile device, the method comprising:
transmitting a sequence of symbols through a power amplifier;
receiving a command that causes in the following order to: reduce gain of the power amplifier to protect the power amplifier, actuate an antenna switch to switch between providing an output of the power amplifier to a first antenna to providing the output of the power amplifier to a second antenna, and increase the gain of the power amplifier; and
transmitting a sounding reference symbol on the second antenna without blank symbols inserted into the sequence of symbols.
12. The method of claim 11 wherein reducing the gain of the power amplifier includes reducing a bias of one or more stages of the power amplifier.
13. The method of claim 11 wherein reducing the gain of the power amplifier includes placing the power amplifier in a low power mode.
14. The method of claim 11 further comprising implementing a delay in response to receiving the command.
15. The method of claim 14 wherein the antenna switch actuation occurs after the delay.
16. The method of claim 11 wherein the antenna switch actuation occurs between the symbols.
17. The method of claim 11 wherein the command is a single command that initiates a self-sequenced mode within the power amplifier.
18. The method of claim 11 further comprising receiving a signal from the antenna switch indicating completion of the switch actuation.
19. The method of claim 11 further comprising diverting an output of the power amplifier to a load while waiting for the antenna switch to settle after actuation.