USAGE OF WEIGHTING MATRICES IN MULTI-PHASE SCANNING MODES

• US 20130021294A1
• Filed: 09/27/2012
• Published: 01/24/2013
• Est. Priority Date: 04/19/2011
• Status: Active Grant

• Current Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Maharyta, Andriy, Bihday, Volodyrmyr
• Granted Patent: US 8,729,911 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

Apparatuses and methods of driving different transmit (TX) phase sequences of a TX signal on TX electrodes in different sensing stages according to a weighting matrix as the excitation matrix. One method drives the TX signals according to the weighting matrix and measures receive (RX) signals on the RX electrodes to determine if an object is proximate to the electrodes.

Claims

1. A method comprising:

driving different transmit (TX) phase sequences of a transmit (TX) signal in different sensing stages on a plurality of TX electrodes of a capacitance sense array, wherein the different TX phase sequences are defined by an excitation matrix, wherein the excitation matrix is a weighting matrix;

measuring receive (RX) signals on a plurality of RX electrodes of the capacitance sense array; and

determining if an object is proximate to the capacitance sense array based on the measured RX signals.

2. The method of claim 1, wherein the weighting matrix (W) is an n×

n matrix with each element of the weighting matrix being at least one of −

1, +1, or 0.

3. The method of claim 1, wherein the pseudo-weighting matrix (pW) is an n×

m matrix with each element of the weighting matrix being at least one of −

1, +1, or 0, wherein n and m are different integer values.

4. The method of claim 2, wherein the weighting matrix (W) is denoted by a W(n,w), where n is the order and w is the weight of the weighting matrix, and wherein the weighting matrix is a conference matrix, and wherein the conference matrix is denoted as W(n,n−

1).

5. The method of claim 2, wherein the weighting matrix (W) is denoted by a W(n,w), where n is the order and w is the weight of the weighting matrix, and wherein the weighting matrix is a Hadamard matrix, and wherein the Hadamard matrix is denoted as W(n,n).

6. The method of claim 1, wherein each element of the weighting matrix comprises at least one of three states, a one state, a negative one state, or a zero state, wherein the one state and negative one state indicate an excitation of the TX electrodes by the TX signal with the same amplitude, frequency, and form, but with a phase shifted by 180°

for the negative one state, and wherein the zero state indicates that the amplitude of the TX signal is zero.

7. The method of claim 1, wherein the weighting matrix is a Hadamard matrix (H-matrix) that is a square matrix whose elements are either +1 or −

1 and whose rows are mutually orthogonal.

8. The method of claim 1, wherein the weighting matrix is a conference matrix (C-matrix) whose elements are zero on a diagonal and either +1 or −

1 off of the diagonal.

9. The method of claim 8, wherein the C-matrix comprise an order of eight and a weight of seven as represented below:

10. The method of claim 1, wherein the weighting matrix comprises an order of eight and a weight of six as represented below:

11. The method of claim 1, wherein the weighting matrix is a pseudo-weighting (pW) matrix comprising n×

m elements, where m is greater than n.

12. The method of claim 11, wherein the pW matrix comprises an order of seven and a weight of eight as represented below:

13. The method of claim 1, wherein the weighting matrix is an extended weighting matrix comprising n×

m elements, where m is greater than n.

14. The method of claim 1, wherein the plurality of TX electrodes comprises eight TX electrodes and wherein the driving different TX phase sequence of the TX signal comprises driving the different TX phase sequences on four of the eight TX electrodes, wherein the weighting matrix is a distributed weighting matrix as represented below:

15. A capacitance sensing system, comprising:

a memory device; and

a controller coupled to the memory device, wherein the controller is configured to;

drive different transmit (TX) phase sequences of a transmit (TX) signal in different sensing stages on a plurality of TX electrodes of a capacitance sense array to be coupled to the controller, wherein the different TX phase sequences are defined by an excitation matrix, wherein the excitation matrix is a weighting matrix;

measure receive (RX) signals on a plurality of RX electrodes of the capacitance sense array; and

determine if an object is proximate to the capacitance sense array based on the measured RX signals.

16. The capacitance sensing system of claim 15, wherein the weighting matrix is at least one of a conference matrix, a Hadamard matrix, a pseudo-weighting matrix, or an extended weighting matrix.

17. The capacitance sensing system of claim 15, wherein each element of the weighting matrix comprises at least one of three states, a one state, a negative one state, or a zero state, wherein the one state and negative one state indicate an excitation of the TX electrodes by the TX signal with the same amplitude, frequency, and form, but with a phase shifted by 180°

for the negative one state, and wherein the zero state indicates that the amplitude of the TX signal is zero.

18. A host device, comprising:

a display;

a capacitance sensing array disposed in connection with the display, the capacitance sensing array comprises a plurality of transmit (TX) electrodes and a plurality of receive (RX) electrodes;

a touchscreen controller coupled to the capacitance sensing array, wherein the touch screen controller is configured to;

drive different transmit (TX) phase sequences of a transmit (TX) signal in different sensing stages on a plurality of TX electrodes of a capacitance sense array to be coupled to the controller, wherein the different TX phase sequences are defined by an excitation matrix, wherein the excitation matrix is a weighting matrix;

measure receive (RX) signals on a plurality of RX electrodes of the capacitance sense array; and

determine if an object is proximate to the capacitance sense array based on the measured RX signals

19. The host device of claim 18, wherein the excitation matrix is at least one of a weighing matrix, a pseudo-weighting matrix, or an extended weighting matrix.

20. The host device of claim 18, wherein each element of the weighting matrix comprises at least one of three states, a one state, a negative one state or a zero state, wherein the one state and negative one state indicate an excitation of the TX electrodes by the TX signal with the same amplitude, frequency, and form, but with a phase shifted by 180°

for the negative one state, and wherein the zero state indicates that the amplitude of the TX signal is zero.