Capacitive sensor with reduced noise
A method includes actuating a drive electrode to couple a majority of charge to a first sense electrode, a dielectric panel overlying the drive electrode, the first sense electrode, and a second sense electrode. The sense electrodes are separated by coupling gaps, the second sense electrode shielded from the drive electrode by the first sense electrode. The first sense electrode and at least one of the drive electrode and the second sense electrode each include at least two electrode elements, which are arranged interleaved on the dielectric panel in the sequence: drive electrode element, first sense electrode element, second sense electrode element, first sense electrode element, drive electrode element. The method includes sampling the first and second sense electrodes to collect respective first and second signal samples, subtracting the second signal sample from the first signal sample to obtain a final signal, and outputting the final signal.
1. A method of capacitive touch sensing comprising:
actuating a drive electrode to couple a majority of charge from the drive electrode to a first sense electrode, a capacitive touch sensor comprising a dielectric panel overlying the drive electrode, the first sense electrode, and a second sense electrode, the first and second sense electrodes being separated by coupling gaps, the second sense electrode being positioned to be shielded from the drive electrode by the first sense electrode, wherein the first sense electrode and at least one of the drive electrode and the second sense electrode each comprise at least two electrode elements, and the electrode elements are arranged interleaved on the dielectric panel in at least one repeat of the sequence: drive electrode element, first sense electrode element, second sense electrode element, first sense electrode element, drive electrode element;
sampling the first sense electrode to collect a first signal sample;
sampling the second sense electrode to collect a second signal sample;
subtracting the second signal sample from the first signal sample to obtain a final signal; and
outputting the final signal.
2. The method of claim 1 , wherein said sampling steps are carried out simultaneously.
3. The method of claim 1 , comprising subtracting the second signal sample from the first signal sample on a sample-by-sample basis.
4. The method of claim 1 , comprising subtracting the second signal sample from the first signal sample after summing a plurality of samples from each of the first and second sense electrodes separately and performing the subtraction on the summed samples from each of the first and second sense electrodes.
5. A method of capacitive touch sensing comprising:
sampling a measurement electrode of a plurality of measurement electrodes to collect a first signal sample, a capacitive touch sensor comprising a dielectric panel overlying the plurality of measurement electrodes and a continuous noise electrode distributed over an area common to the plurality of measurement electrodes, the measurement electrode and the continuous noise electrode separated by a gap, the plurality of measurement electrodes located at one or more input areas and the continuous noise electrode positioned adjacent to the plurality of measurement electrodes, so that in use one or more of the plurality of measurement electrodes receive a majority of charge coupled from an object and the continuous noise electrode primarily registers noise;
sampling the continuous noise electrode to collect a second signal sample;
subtracting the second signal sample from the first signal sample to obtain a final signal; and
outputting the final signal.
6. The method of claim 5 , wherein said sampling steps are carried out simultaneously.
7. The method of claim 5 , comprising subtracting the second signal sample from the first signal sample on a sample-by-sample basis.
8. The method of claim 5 , comprising subtracting the second signal sample from the first signal sample after summing a plurality of samples from each of the measurement electrode and the continuous noise electrode separately and performing the subtraction on the summed samples from each of the measurement electrode and the continuous noise electrode.
9. The method of claim 5 , wherein one or more of the measurement electrode and the continuous noise electrode comprises at least two electrode elements.
10. The method of claim 9 , wherein the at least two electrode elements are arranged interleaved on the dielectric panel.
11. A method of capacitive touch sensing comprising:
actuating a drive electrode to couple a majority of charge from the drive electrode to a first sense electrode, a capacitive touch sensor comprising a dielectric panel overlying the drive electrode, the first sense electrode and a second sense electrode, the electrodes being separated by coupling gaps, wherein the second sense electrode is positioned to be shielded from the drive electrode by the first sense electrode;
sampling the first sense electrode to collect a first signal sample via a first detector channel;
Sampling the second sense electrode to collect a second signal sample via a second detector channel;
subtracting the second signal sample from the first signal sample to obtain a final signal;
outputting the final signal.
12. The method of claim 11 , wherein in use the first sense electrode receives the majority of charge coupled from the drive electrode and the second sense electrode primarily registers noise.
13. The method of claim 11 , wherein
sampling the first sense electrode to collect the first signal sample and
sampling the second sense electrode to collect the second signal sample are carried out simultaneously.
14. The method of claim 11 ,
wherein subtracting the second signal sample from the first signal sample comprises subtracting the second signal sample from the first signal sample on a sample-by-sample basis.
15. The method of claim 11 , wherein:
the second signal sample is subtracted from the first signal sample after summing a plurality of samples from each of the first and second sense electrodes separately; and
the subtraction on the summed samples is performed from each of the first and second electrodes.