Method and system for adjusting transmission power

Abstract

A system and method for measuring transmission power distortion in a wireless communication device are disclosed. In one embodiment, the method comprises reading an operating temperature of the wireless communication device and enabling a loopback path between a transmission circuit and a receiver circuit of the wireless communication device. Using the loopback path, the wireless communication device can calibrate the transmission power output by storing data for compensating the distortion of the transmission power. The data can be stored in a calibration look up table for use by the wireless communication device.

What is claimed is: 
     
         1 . A wireless communication device to maintain a constant transmission output power across temperature variations, comprising:
 a transmitter circuit, including an output coupled to a transmission antenna, to transmit signals generated by a core logic;   a compensation table to store a plurality of power correction values, wherein each of the power correction values is to adjust a gain level of an amplifier within the transmitter circuit in response to a corresponding operating temperature;   a receiver circuit to receive signals from another wireless communication device via a reception antenna;   a switching circuit to selectively connect an input of the receiver circuit to either the reception antenna or to the output of the transmitter circuit in response to a mode select signal indicating whether the device is in a normal operational mode or in a calibration mode; and   a test circuit, coupled to the receiver circuit and to the core logic, to dynamically derive the power correction values for various operating temperatures in response to a test signal generated by the core logic.   
     
     
         2 . The device of  claim 1 , wherein:
 during the normal operational mode, the switching circuit is to route signals received from the reception antenna to the receiver circuit; and   during the calibration mode, the switching circuit is to route the test signal from the transmitter circuit to the test circuit via the receiver circuit.   
     
     
         3 . The device of  claim 2 , wherein the device is to automatically enter the calibration mode upon detection of a transmission downtime. 
     
     
         4 . The device of  claim 3 , wherein the transmission downtime comprises a predetermined time period during which the transmitter circuit is not providing signals to the transmission antenna. 
     
     
         5 . The device of  claim 1 , wherein the test circuit is to derive the power correction values by measuring a distortion product of the test signal. 
     
     
         6 . The device of  claim 1 , wherein the test circuit comprises:
 a temperature detector to measure the current operating temperature;   a memory to store a plurality of reference power values, each corresponding to a different temperature; and   a processor, coupled to the temperature detector and the memory, to measure a power level of the test signal and to compare the measured power level with the reference power value corresponding with the measured current operating temperature to derive the power correction value.   
     
     
         7 . The device of  claim 6 , wherein the processor comprises:
 a digital rotator to measure the power level of a third-order harmonic of the test signal;   a filter to filter unwanted frequencies from the test signal; and   an energy calculator to measure energy remaining in the filtered test signal.   
     
     
         8 . The device of  claim 1 , wherein the test circuit is to measure the distortion product by:
 measuring a difference between a first transmission power at a first gain level and a second transmission power at a second gain level; and   selecting one of the first and second gain levels for calibration in response to the measured difference between the first transmission power and the second transmission power.