SLIM sensor design with minimum tail effect
Techniques for designs of single-layer touch sensors are described herein. In an example embodiment, a device comprises a sensor array. The sensor array comprises first plurality of electrodes and second plurality of electrodes that are interleaved without intersecting each other within a touch-sensing area in a single layer on a substrate of the sensor array. A first electrode (of the first or second plurality) comprises at least two shaped portions. The two shaped portions may be disposed across at least a portion of a given second electrode from each other, or may be disposed between two or more portions of the given second electrode. The two shaped portions of the first electrode are routed in different directions on the substrate and are coupled to each other outside of the touch-sensing area of the sensor array.
1. A sensor array comprising:
a substrate;
a first plurality of receive (RX) electrodes and a second plurality of transmit (TX) electrodes, wherein the first plurality of RX electrodes and the second plurality of TX electrodes are interleaved without intersecting each other within a central area in a single layer on the substrate;
wherein a first shaped portion of a first RX electrode, of the first plurality of RX electrodes, is connected to a first primary trace of the first RX electrode and a second shaped portion of the first RX electrode is connected to a second primary trace of the first RX electrode;
wherein the first shaped portion and the second shaped portion of the first RX electrode are interleaved with a second TX electrode of the second plurality of TX electrodes, thereby forming a single sensor element of the sensor array;
wherein the first primary trace of the first RX electrode is routed in a first direction on the substrate through the central area to a first edge of the central area and the second primary trace of the first RX electrode is routed in a second different direction on the substrate through the central area to a second opposite edge of the central area; and
wherein the first primary trace of the first RX electrode is coupled to the second primary trace of the first RX electrode outside of the central area.
2. The sensor array of claim 1 , wherein:
a first secondary trace of the first RX electrode is electrically connected to the first primary trace of the first RX electrode in a first portion of the outer area corresponding to the first direction;
a second secondary trace of the first RX electrode is electrically connected to the second primary trace of the first RX electrode in a second portion of the outer area corresponding to the second direction; and
the first secondary trace and the second secondary trace are coupled to each other in the outer area.
3. The sensor array of claim 1 , wherein each of the first plurality of RX electrodes comprises multiple pairs of shaped portions, the shaped portions in a pair being positioned across one of the second plurality of TX electrodes and each of the shaped portions in the pair being connected to a corresponding primary trace extending in one of the first direction or the second direction.
4. The sensor array of claim 1 , wherein the first plurality of RX electrodes is disposed on the substrate in one of an X-pattern, an I-pattern, and an H-pattern.
5. The sensor array of claim 1 , wherein the first shaped portion of the first RX electrode comprises at least two bars disposed in an H-pattern such that one of the at least two bars has a different width than another one of the at least two bars.
6. The sensor array of claim 1 , further comprising a ground electrode disposed between the first primary trace of the first RX electrode and one or more second primary traces of one or more of the first plurality of RX electrodes different from the first RX electrode.
7. The sensor array of claim 1 , wherein the first plurality of RX electrodes is disposed in multiple rows on the substrate and the second plurality of TX electrodes is disposed in multiple columns on the substrate.
8. The sensor array of claim 7 , wherein the shaped portions, of a first subset of the first plurality of RX electrodes in a first row, have different widths or heights than the shaped portions of a second subset of the first plurality of RX electrodes in a second row.
9. A device comprising:
a sensor array comprising receive (RX) electrodes and transmit (TX) electrodes, wherein the RX electrodes and the TX electrodes are interleaved without intersecting each other within a central area in a single layer on a substrate of the sensor array;
wherein a first shaped portion of an RX electrode is connected to a first primary trace of the RX electrode and a second shaped portion of the RX electrode is connected to a second primary trace of the RX electrode, wherein the first shaped portion and the second shaped portion of the RX electrode are interleaved with a TX electrode, thereby forming a single sensor element of the sensor array, and wherein the first primary trace of the RX electrode is routed in a first direction on the substrate through the central area to a first edge of the central area and the second primary trace of the RX electrode is routed in a second different direction on the substrate through the central area to a second opposite edge of the central area; and
wherein the first primary trace of the RX electrode is coupled to the second primary trace of the RX electrode outside of the central area of the sensor array.
10. The device of claim 9 , wherein the sensor element represents an area of the sensor array from which a distinct measurement, that represents a mutual capacitance between the RX electrode and the TX electrode, can be measured.
11. The device of claim 9 , wherein, as disposed on the substrate, the first shaped portion and the second shaped portion of the RX electrode create a shield from primary traces or shaped portions of other RX electrodes.
12. The device of claim 9 , wherein the sensor array is disposed in a stack-up that includes an overlay, wherein an adhesive layer attaches the overlay to one side of the substrate.
13. The device of claim 9 , wherein in a particular scan operation the RX electrodes are configured to transmit scan signals and the TX electrodes are configured to measure signals that represent mutual capacitances formed between the RX electrodes and the TX electrodes.
14. The device of claim 9 , further comprising a processing logic configured to perform a common mode filter operation that corrects both a common mode noise and a tail effect caused by contact from a conductive object that affects the first shaped portion of the RX electrode but does not affect one or more shaped portions of one or more RX electrodes, along the TX electrode, that are different from the RX electrode.
15. The device of claim 14 , wherein the tail effect comprises a parasitic signal increase or a parasitic signal decrease that is caused by parasitic coupling between the TX electrode and one or more primary traces of the one or more RX electrodes that are different from the RX electrode.
16. A system comprising:
a capacitive sensor array comprising first receive (RX) electrodes and second transmit (TX) electrodes, wherein the first RX electrodes and the second TX electrodes are interleaved without intersecting each other within a central area in a single layer on a substrate of the capacitive sensor array;
wherein a first shaped portion of a first RX electrode is connected to a first primary trace of the first RX electrode and a second shaped portion of the first RX electrode is connected to a second primary trace of the first RX electrode, wherein the first shaped portion and the second shaped portion of the first RX electrode are interleaved with a second TX electrode, thereby forming a single sensor element of the capacitive sensor array, wherein the first primary trace of the first RX electrode is routed in a first direction on the substrate through the central area to a first edge of the central area and the second primary trace of the first RX electrode is routed in a second different direction on the substrate through the central area to a second opposite edge of the central area, and wherein the first primary trace of the first RX electrode is coupled to the second primary trace of the first RX electrode outside of the central area of the sensor array; and
a capacitance sensor coupled to the capacitive sensor array, wherein the capacitance sensor is configured to measure a plurality of measurements from the first RX electrodes, the plurality of measurements being representative of a conductive object that is in contact with the capacitive sensor array.
17. The system of claim 16 , further comprising a display disposed under the capacitive sensor array, wherein the capacitance sensor is configured to perform a common mode filter operation that corrects both a tail effect caused by the contact and a noise signal caused by the display.
18. The system of claim 17 , wherein:
a set of diff signals is generated based on the plurality of measurements;
the set of diff signals is corrected by the common mode filter operation; and
the set of diff signals is used to determine location coordinates of the contact.