Noise compensation using a spatial noise model

1. A computing device comprising:

a display;

a touch sensor comprising an array of sensor antennas spatially distributed across the touch sensor;

a logic machine; and

a storage machine comprising a spatial noise model comprising a plurality of noise compensation ratios, each noise compensation ratio comprises a characterized noise level of one sensor antenna compared to a characterized noise level of another sensor antenna, and instructions executable by the logic machine to determine a stylus location by,

for a frame of touch sensor data, select a reference antenna from the array of sensor antennas, and

compensate for noise in the frame of touch sensor data to form a reduced-noise frame of touch sensor data by, for each sensor antenna of a set of sensor antennas of the array of sensor antennas, applying a noise compensation ratio, from the spatial noise model, representing a characterized noise level of the sensor antenna to a characterized noise level of the reference antenna.

2. The computing device of claim 1 , wherein the instructions executable to select the reference antenna comprise instructions executable to determine an untouched antenna.

3. The computing device of claim 1 , wherein the instructions executable to select the reference antenna comprise instructions executable to determine a probable untouched antenna.

4. The computing device of claim 3 , wherein the instructions are executable to determine the probable untouched antenna by selecting a sensor antenna determined to have a low likelihood of containing a stylus signal or injected noise.

5. The computing device of claim 3 , wherein the instructions are executable to determine the probable untouched antenna by determining a sensor antenna outside of a probable stylus location.

6. The computing device of claim 1 , wherein

the instructions are further executable to, for the frame of touch sensor data, select a second reference antenna from the array of sensor antennas, and

wherein the instructions executable to compensate for the noise in the frame of touch sensor data are further executable to compensate for the noise in the frame of touch sensor data by, for each sensor antenna of the set of sensor antennas of the array of sensor antennas, applying a second noise compensation ratio, from the noise model, representing the characterized noise level of the sensor antenna to a characterized noise level of the second reference antenna.

7. The computing device of claim 1 , wherein the instructions are further executable to determine the stylus location in the reduced-noise frame of touch sensor data.

8. The computing device of claim 7 , further comprising instructions executable to

for a subset of sensor antennas of the array of sensor antennas, further compensate for the noise based at least on a noise level of a first sensor antenna of the subset of sensor antennas and a noise level of a second sensor antenna of the subset of sensor antennas, the subset of sensor antennas of the array of sensor antennas located within a range of the stylus location.

9. The computing device of claim 8 , further comprising instructions executable to adjust the stylus location based at least on reduced noise in the subset of sensor antennas.

10. The computing device of claim 1 , wherein the touch sensor comprises a touch on encapsulation (TOE) touch sensor.

11. A computing device comprising:

a display;

a touch sensor comprising an array of sensor antennas spatially distributed across the touch sensor;

a logic machine; and

a storage machine comprising a spatial noise model comprising a plurality of noise compensation ratios, each noise compensation ratio comprises a characterized noise level of one sensor antenna compared to a characterized noise level of another sensor antenna, and instructions executable by the logic machine to

for a frame of touch sensor data, select a reference antenna from the array of sensor antennas,

compensate for noise in the frame of touch sensor data to form a reduced-noise frame of touch sensor data by, for each sensor antenna of a set of sensor antennas of the array of sensor antennas, applying a noise compensation ratio, from the spatial noise model, representing a characterized noise level of the sensor antenna compared to a characterized noise level of the reference antenna,

determine a stylus location in the reduced-noise frame of touch sensor data,

for a subset of sensor antennas of the array of sensor antennas, further reduce the noise in the reduced-noise frame of touch sensor data by compensating for the noise based at least on a noise level of a first sensor antenna of the subset of sensor antennas and a noise level of a second sensor antenna of the subset of sensor antennas, the subset of sensor antennas of the array of sensor antennas located within a range of the stylus location, and

adjust the stylus location determined based at least on the noise reduced in the subset of sensor antennas.

12. The computing device of claim 11 , wherein within the range of the stylus location comprises a distance of two to five antennas from the stylus location.

13. The computing device of claim 11 , wherein the instructions executable to, for the subset of sensor antennas of the array of sensor antennas, further reduce the noise in the reduced-noise frame of touch sensor data by compensating for the noise comprise instructions executable to compensate for the noise based at least on an interpolation of the noise level of the first sensor antenna of the subset of sensor antennas and the noise level of the second sensor antenna of the subset of sensor antennas.

14. The computing device of claim 11 , wherein the instructions executable to determine the stylus location comprise instructions executable to determine the stylus location based at least on a Fourier transform of touch signals from the touch sensor.

15. The computing device of claim 11 , wherein the touch sensor comprises a touch on encapsulation (TOE) touch sensor.