Sensor pattern with signal-spreading electrodes
A capacitive sensor array may include a plurality of row sensor electrodes and a column sensor electrode capacitively coupled with each of the plurality of row sensor electrodes to form a plurality of unit cells. For each row sensor electrode, a unit cell that is associated with the column sensor electrode and the row sensor electrode comprises an area where a capacitance between the column sensor electrode and the row sensor electrode is greater than any other capacitance between the column sensor electrode and a different row sensor electrode. The capacitive sensor array further includes a first plurality of dummy electrodes, where each of the first plurality of dummy electrodes is capacitively coupled with the column sensor electrode and two adjacent row sensor electrodes of the plurality of row sensor electrodes.
1. A capacitive sensor array, comprising:
a plurality of row sensor electrodes;
a column sensor electrode capacitively coupled with each row sensor electrode of the plurality of row sensor electrodes to form a plurality of unit cells, wherein for each row sensor electrode of the plurality of row sensor electrodes, each point within a unit cell of the plurality of unit cells that is associated with the column sensor electrode and the row sensor electrode is nearer to a location of a shortest distance between the row electrode and the column electrode than to a location of a shortest distance between any other row electrode and the column electrode; and
a first plurality of dummy electrodes, wherein each of the first plurality of dummy electrodes is floating and is capacitively coupled with the column sensor electrode and two adjacent row sensor electrodes of the plurality of row sensor electrodes, and wherein each of the first plurality of dummy electrodes has a total area smaller than at least one of the plurality of unit cells.
2. The capacitive sensor array of claim 1 , wherein the column sensor electrode further comprises a plurality of subtraces.
3. The capacitive sensor array of claim 2 , wherein a first subtrace of the plurality of subtraces having a width that is less than a width of a second subtrace of the plurality of subtraces is nearer than the second subtrace to a central axis of the column electrode.
4. The capacitive sensor array of claim 2 , wherein each of the first plurality of dummy electrodes is located between the plurality of subtraces of the column electrode, and wherein for each dummy electrode of the first plurality of dummy electrodes, the dummy electrode has a length that is at least half the length, along a longitudinal axis of the column sensor electrode, of a unit cell including at least a portion of the dummy electrode.
5. The capacitive sensor array of claim 1 , wherein for each dummy electrode of the first plurality of dummy electrodes, the dummy electrode overlaps at least two adjacent unit cells of the plurality of unit cells.
6. The capacitive sensor array of claim 1 , wherein the plurality of row sensor electrodes is formed from a first layer of conductive material, wherein the column sensor electrode is one of a plurality of column sensor electrodes formed from a second layer of conductive material, wherein the first plurality of dummy electrodes is formed from the second layer of conductive material, and wherein for each dummy electrode of the first plurality of dummy electrodes, the dummy electrode overlaps each of the two adjacent row sensor electrodes to which the dummy electrode is capacitively coupled.
7. The capacitive sensor array of claim 1 , wherein each dummy electrode of the first plurality of dummy electrodes comprises a first portion and a second portion coupled together by a connecting trace that is narrower than either of the first portion and the second portion and that overlaps a gap between the two adjacent row sensor electrodes to which the dummy electrode is capacitively coupled.
8. The capacitive sensor array of claim 7 , wherein a length of the connecting trace along a longitudinal axis of the column sensor electrode is at least 0.5 millimeters.
9. The capacitive sensor array of claim 1 , further comprising a plurality of optical dummy electrodes, wherein each optical dummy electrode of the plurality of optical dummy electrodes is formed from a same layer of conductive material as the column sensor electrode and is located between subtraces of the column sensor electrode.
10. A capacitive sensor array, comprising:
a plurality of row sensor electrodes;
a column sensor electrode capacitively coupled with each row sensor electrode of the plurality of row sensor electrodes to form a plurality of unit cells, wherein for each row sensor electrode of the plurality of row sensor electrodes, each point within a unit cell of the plurality of unit cells that is associated with the column sensor electrode and the row sensor electrode is nearer to a location of a shortest distance between the row electrode and the column electrode than to a location of a shortest distance between any other row electrode and the column electrode; and
a first plurality of dummy electrodes, wherein for each dummy electrode of the first plurality of dummy electrodes, the dummy electrode is floating and overlaps at least two adjacent unit cells of the plurality of unit cells and has a total area smaller than at least one of the plurality of unit cells.
11. The capacitive sensor array of claim 10 , wherein the column sensor electrode further comprises a plurality of subtraces.
12. The capacitive sensor array of claim 11 , wherein a first subtrace of the plurality of subtraces having a width that is less than a width of a second subtrace of the plurality of subtraces is nearer than the second subtrace to a central axis of the column electrode.
13. The capacitive sensor array of claim 11 , wherein each of the first plurality of dummy electrodes is located between the plurality of subtraces of the column electrode, and wherein for each dummy electrode of the first plurality of dummy electrodes, the dummy electrode has a length that is at least half the length, along a longitudinal axis of the column sensor electrode, of a unit cell including at least a portion of the dummy electrode.
14. The capacitive sensor array of claim 10 , wherein the plurality of row sensor electrodes is formed from a first layer of conductive material, wherein the column sensor electrode is one of a plurality of column sensor electrodes formed from a second layer of conductive material, wherein the first plurality of dummy electrodes is formed from the second layer of conductive material, and wherein for each dummy electrode of the first plurality of dummy electrodes, the dummy electrode overlaps each of two adjacent row sensor electrodes to which the dummy electrode is capacitively coupled.
15. The capacitive sensor array of claim 10 , wherein each dummy electrode of the first plurality of dummy electrodes comprises a first portion and a second portion coupled together by a connecting trace that is narrower than either of the first portion and the second portion and that overlaps a boundary between the two adjacent unit cells, wherein a length of the connecting trace along a longitudinal axis of the column sensor electrode is at least 0.5 millimeters.
16. A capacitance sensing system, comprising:
a capacitance sensor;
a capacitive sensor array coupled with the capacitance sensor, wherein the capacitive sensor array comprises:
a plurality of row sensor electrodes;
a column sensor electrode capacitively coupled with each row sensor electrode of the plurality of row sensor electrodes to form a plurality of unit cells, wherein for each row sensor electrode of the plurality of row sensor electrodes, each point within a unit cell of the plurality of unit cells that is associated with the column sensor electrode and the row sensor electrode is nearer to a location of a shortest distance between the row electrode and the column electrode than to a location of a shortest distance between any other row electrode and the column electrode; and
a first plurality of dummy electrodes, wherein each dummy electrode is floating and is capacitively coupled with the column sensor electrode and two adjacent row sensor electrodes of the plurality of row sensor electrodes, and wherein each of the first plurality of dummy electrodes has a total area smaller than at least one of the plurality of unit cells.
17. The capacitance sensing system of claim 16 , further comprising a lookup table (LUT) coupled with the capacitance sensor, wherein the LUT is configured to store a plurality of correction vectors each corresponding to a different location on the capacitive sensor array.
18. The capacitance sensing system of claim 16 , wherein the capacitance sensor is configured to apply a transmit (TX) signal to each of the plurality of row sensor electrodes, and to measure a resulting receive (RX) signal at each of the plurality of column sensor electrodes.
19. The capacitance sensing system of claim 16 , wherein the column sensor electrode further comprises a plurality of subtraces, wherein a first subtrace of the plurality of subtraces having a width that is less than a width of a second subtrace of the plurality of subtraces is nearer than the second subtrace to a central axis of the column electrode.
20. The capacitance sensing system of claim 16 , wherein the plurality of row sensor electrodes is formed from a first layer of conductive material, wherein the column sensor electrode is one of a plurality of column sensor electrodes formed from a second layer of conductive material, wherein the first plurality of dummy electrodes is formed from the second layer of conductive material and overlaps, wherein for each dummy electrode of the first plurality of dummy electrodes, the dummy electrode overlaps each of the two adjacent row sensor electrodes to which the dummy electrode is capacitively coupled, and wherein each dummy electrode of the first plurality of dummy electrodes comprises a first portion and a second portion coupled together by a connecting trace thinner than either of the first portion and the second portion and overlapping a gap between the two adjacent row sensor electrodes to which the dummy electrode is capacitively coupled.