Phase compensation for multi-stimulus controller

• US 8,791,920 B2
• Filed: 08/06/2012
• Issued: 07/29/2014
• Est. Priority Date: 09/10/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Krah, Christoph H.
• Primary Examiner(s): Nguyen, Kevin M
• Assistant Examiner(s): Lee, Jr., Kenneth B
• Application Number:
  US13/568,027
• Publication Number:
  US 20120299880A1
• Time in Patent Office: 722 Days
• Field of Search: 345173-182, 178/18.01
• US Class Current: 345/173
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• 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

Determining a compensated phase matrix for a multi-stimulus demodulation process is provided. A first drive line of a multi-stimulus sensing system is selected, and a stimulation signal is transmitted on the selected drive line. A channel gain resulting from the stimulation signal is measured from a received sense signal resulting from the stimulation signal. The measured channel gain is compared with a known channel gain to obtain an individual phase compensation for the selected drive line. A compensated phase matrix is formed of the individual phase compensation values for multiple drive lines.

Claims

1. A method comprising:

measuring individual phase characteristics of each drive line and sense line combination of a multi-stimulus sensing system, the multi-stimulus system capable of scanning, in a plurality of steps, a plurality of drive lines with stimulation signals of different phases, each step including simultaneously stimulating two or more of the plurality of drive lines with a plurality of drive signals, the phases of the drive signals corresponding to a plurality of predetermined different phases; and

calculating phase compensation values based on the individual phase characteristics;

wherein measuring individual phase characteristics includes stimulating a first drive line with a first stimulation signal, receiving, at a first sense channel, a sense signal generated on a first sense line by the first stimulation signal, and calculating the individual phase delay of the first drive line and sense line combination.

2. The method of claim 1, wherein measuring the individual phase characteristics comprises:

receiving, at a plurality of sense channels, a plurality of sense signals generated on a plurality of sense lines by the first stimulation signal; and

calculating the individual phase delay of each combination of the first drive line and corresponding sense line.

3. The method of claim 1, wherein calculating the individual phase delay of the first drive line and sense line combination comprises:

demodulating the first sense signal to obtain a measurement of the phase delay; and

adjusting an adjustable delay value such that the measurement of phase characteristic is maxzimized or minimized, wherein the individual phase delay is based on the value of the adjustable delay at the maximum or minimum measurement of phase delay.

4. The method of claim 2, wherein calculating the individual phase delay of each combination of the first drive line and corresponding sense line comprises:

demodulating the corresponding sense signal to obtain a measurement of phase delay;

adjusting an adjustable delay value such that the measurement of phase delay is maximized or minimized for a particular combination of the first drive line and corresponding sense line, wherein the individual phase delay for that particular combination is based on the value of the adjustable delay at the maximum or minimum measurement of phase delay; and

repeating the adjusting of the adjustable delay for the combinations of the first drive line and other corresponding sense lines to obtain corresponding individual phase delays.

5. An apparatus comprising:

drive logic configurable to scan, in a plurality of steps, a plurality of drive lines with stimulation signals of different phases, each step including simultaneously stimulating two or more of the plurality of drive lines with a plurality of drive signals, the phases of the drive signals corresponding to a plurality of predetermined different phases;

a plurality of sense channels to receive a plurality of sense signals generated on a plurality of sense lines by the two or more drive signals in each step, each sense signal including a superposition of component signals that correspond to the two or more of the plurality of drive lines paired with the corresponding sense channel receiving the sense signal; and

one or more processors capable of;

measuring an individual phase delay of each drive line and sense line pair; and

calculating a plurality of compensated phases based on the individual phase delays.

6. The apparatus of claim 5, the one or more processors further capable of applying a first drive signal to a first drive line, the first drive signal generating a first sense signal on at least a first sense line, and measuring the individual phase delay of the first drive line and first sense line pair.

7. The apparatus of claim 6, the one or more processors further capable of demodulating the first sense signal to obtain a measurement of phase delay and adjusting an adjustable delay value such that the measurement of phase delay is maximized or minimized, wherein the individual phase delay is calculated based on the value of the adjustable delay at the maximum or minimum measurement of phase delay.

8. The apparatus of claim 5, the one or more processors further capable of applying a first drive signal to a first drive line, the first drive signal generating a plurality of sense signals on the plurality of sense lines, and measuring the individual phase delay of each pair of first drive line and corresponding sense line.

9. The apparatus of claim 8, the one or more processors further capable of demodulating each of the plurality of sense signals to obtain a plurality of measurements of phase delay and adjusting a plurality of adjustable delay values such that each of the plurality of measurement of phase delay is maximized or minimized, wherein the individual phase delay of each pair of first drive line and corresponding sense line is calculated based on the value of the adjustable delay at the maximum or minimum measurement of phase delay for each pair of the first drive line and corresponding sense line.