Phase shifters for gallium nitride amplifiers and related methods

Abstract

Circuits for protecting devices, such as gallium nitride (GaN) devices, and operating methods thereof are described. Such circuits may include a temperature sensor configured to sense the temperature of at least a portion of a device, and a phase shifter configured to shift the phase of the signal output by the device, when the sensed temperature is outside a safe temperature range, e.g., above a predefined temperature threshold. The phase may be shifted discretely or continuously. These circuits safeguard devices from damaging operating conditions to prolong the operating life of the protected devices.

What is claimed is: 
     
         1 . An apparatus comprising:
 a gallium nitride (GaN) radio-frequency (RF) amplifier comprising an output terminal and configured to output an RF signal through the output terminal;   a temperature sensor thermally coupled to the GaN RF amplifier and configured to sense a temperature of the GaN RF amplifier;   a phase shifter electrically coupled to the output terminal of the GaN RF amplifier; and   control circuitry coupled to the temperature sensor and the phase shifter and configured to:
 receive, from the temperature sensor, data representing the temperature of the GaN RF amplifier; and 
 cause, based at least in part on the data representing the temperature of the GaN RF amplifier, the phase shifter to shift the phase of the RF signal by a phase amount until the temperature of the GaN RF amplifier is within a safe temperature range. 
   
     
     
         2 . The apparatus of  claim 1 , wherein the control circuitry is configured to cause the phase shifter to shift the phase of the RF signal when it determines that the data representing the temperature of the GaN RF amplifier is greater than a threshold value. 
     
     
         3 . The apparatus of  claim 1 , wherein the phase amount is selected from a discrete set of selectable phase amounts. 
     
     
         4 . The apparatus of  claim 3 , wherein the discrete set of selectable phase amounts comprises approximately zero and approximately π. 
     
     
         5 . The apparatus of  claim 1 , wherein the phase amount is selected from a continuous set of selectable phase amounts. 
     
     
         6 . The apparatus of  claim 1 , wherein the phase shifter comprises a microstrip phase shifter. 
     
     
         7 . The apparatus of  claim 1 , wherein the phase shifter comprises a pin diode hybrid phase shifter. 
     
     
         8 . The apparatus of  claim 1 , wherein the GaN RF amplifier, the temperature sensor, the phase shifter and the control circuitry are disposed on a common substrate. 
     
     
         9 . The apparatus of  claim 1 , wherein the temperature sensor comprises one selected from the group consisting of a thermistor, a thermocouple, and a silicon bandgap temperature sensor. 
     
     
         10 . The apparatus of  claim 1 , wherein the phase amount is adjustable. 
     
     
         11 . A method comprising:
 outputting a radio-frequency (RF) signal using a gallium nitride (GaN) RF amplifier;   sensing a temperature of the GaN RF amplifier using a temperature sensor;   determining whether the temperature of the GaN RF amplifier is within a safe temperature range; and   shifting a phase of the RF signal until the sensed temperature of the GaN RF amplifier is within the safe temperature range responsive to determining that the temperature of the GaN amplifier is outside the safe temperature range.   
     
     
         12 . The method of  claim 11 , wherein shifting the phase of the RF signal until the sensed temperature of the GaN RF amplifier is within the safe temperature range comprises shifting the phase of the RF signal until the sensed temperature of the GaN RF amplifier is less than a threshold value. 
     
     
         13 . The method of  claim 11 , wherein shifting the phase of the RF signal comprises shifting the phase of the RF signal by a predefined phase amount. 
     
     
         14 . The method of  claim 13 , wherein the predefined phase amount is selected from among a discrete set of selectable phase amounts. 
     
     
         15 . The method of  claim 14 , wherein the discrete set of selectable phase amounts comprises approximately zero and approximately π. 
     
     
         16 . The method of  claim 13 , wherein the predefined phase amount is selected from among a continuous set of selectable phase amounts. 
     
     
         17 . A system for providing an RF signal to a load, the system comprising:
 a gallium nitride (GaN) radio-frequency (RF) amplifier comprising an output terminal and configured to output the RF signal through the output terminal;   a temperature sensor disposed in proximity to the GaN RF amplifier and configured to sense a temperature of the GaN RF amplifier;   a phase shifter electrically coupled to the output terminal of the GaN RF amplifier; and   control circuitry coupled to the temperature sensor and the phase shifter and configured to:
 receive, from the temperature sensor, data representing the temperature of the GaN RF amplifier; 
 determine whether the temperature of the GaN RF amplifier is above a threshold; and 
 cause the phase shifter to shift the phase of the RF signal such that the temperature of the GaN RF amplifier is reduced responsive to the temperature of the GaN RF amplifier being above the threshold. 
   
     
     
         18 . The system of  claim 17 , wherein the control circuitry is configured to cause the phase shifter to shift the phase of the RF signal by a predefined phase amount. 
     
     
         19 . The system of  claim 18 , wherein the predefined amount is adjustable. 
     
     
         20 . The system of  claim 18 , wherein the predefined amount is selectable from among a discrete set of selectable phase amounts.