SEMI-CLOSE LOOP DC OFFSET COMPENSATION TECHNIQUE
Systems and methods for calibrating DC offset of wireless device are disclosed. The calibration process includes determining the DC offset based on the step size determined for each particular wireless chipset or wireless device, which may be determined in the factory or in the field. The DAC compensation corresponding to the DC offset may then be applied to the baseband of the receive chain of the chipset.
1 . A wireless device comprising:
a receiver to receive a receive signal from one or more other wireless devices;
an antenna coupled to the receiver;
a processor configured to determine a DC offset compensation of the wireless device based on a calculation of step size of the wireless device and apply the DC offset compensation to the wireless device; and
memory to store the step size and DC offset compensation.
2 . The wireless device of claim 1 , wherein the step size is calculated by determining the DC offset between two values which are four steps apart and dividing the DC offset by four.
3 . The wireless device of claim 1 , wherein the receiver comprises an RF block and baseband, and wherein the DC offset compensation is applied to the baseband.
4 . The wireless device of claim 1 , wherein the receiver further comprises an analog to digital converter (ADC) and a digital to analog converter (DAC).
5 . The wireless device of claim 1 , wherein the DC offset compensation is determined by dividing the negative value at the ADC when the DAC is at 0 by the step size.
6 . A method comprising:
applying a first DAC value at the baseband of a wireless device;
measuring a first ADC value at the ADC of the wireless device;
applying a second DAC value at the baseband of a wireless device, wherein the second DAC value differs from the first DAC value by a plurality of steps;
measuring a second ADC value at the ADC of the wireless device;
determining a DAC step size, wherein determining the DAC step size comprises calculating the difference between the first ADC value and the second ADC value, and dividing the difference by the plurality of steps;
determining a DC offset compensation value for the wireless device based on the DAC step size; and
applying the DC offset compensation value at the DAC of the wireless device.
7 . The method of claim 6 , wherein the plurality of steps comprises +4.
8 . The method of claim 6 , wherein the plurality of steps comprises −4.
9 . The method of claim 6 , wherein the DAC value is a value between −500 mV and 500 mV.
10 . The method of claim 6 , wherein the first DAC value is 0.
11 . The method of claim 6 , wherein when the DC offset compensation value is applied to the DAC, the value at the ADC is 0.
12 . The method of claim 10 , wherein the second DAC value is −4, and wherein the plurality of steps is 4.
13 . The method of claim 6 , wherein the determining the DAC compensation comprises dividing the first ADC value by the determined DAC step size.
14 . A method comprising:
determining a DC offset compensation of a specific wireless device based on a step size of the specific wireless device; and
applying the DC offset compensation to the specific wireless device.
15 . The method of claim 14 , wherein the DC offset compensation is applied to baseband of the specific wireless device.
16 . The method of claim 14 , wherein the step size is calculated by determining the DC offset between two values which are four steps apart and dividing the DC offset by four.
17 . The method of claim 16 , wherein the step size is calculated by measuring a first ADC value at a DAC value of 0, measuring a second ADC value at a DAC value of +/−4 steps, and dividing the difference between the first ADC value and the second ADC value by four.
18 . The method of claim 14 , wherein the step size is calculated by measuring a first ADC value at a first DAC value, measuring a second ADC value at a second DAC value separated by a number of steps, and dividing the difference between the first ADC value and the second ADC value by the number of steps.
19 . The method of claim 14 , wherein the number of steps is at least four steps.
20 . The method of claim 14 , wherein the DC offset compensation is determined by dividing the negative value at the ADC when the DAC is at 0 by the step size.