Phase compensation for multi-stimulus controller

• US 9,086,750 B2
• Filed: 06/25/2014
• Issued: 07/21/2015
• 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
• Assistant Examiner(s): Lee, Jr., Kenneth B
• Application Number:
  US14/315,162
• Publication Number:
  US 20140306913A1
• Time in Patent Office: 391 Days
• US Class Current: 1/1
• 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 phase characteristics of a plurality of transmit channels and sense channels of a multi-stimulus sensing system;

calculating a phase delay to apply to composite sense signals received by a sense channel based on the measured phase characteristics; and

calculating phase compensation values to apply to component signals of the composite sense signals received by the sense channel based on the phase characteristics and the phase delay.

2. The method of claim 1, wherein measuring the phase characteristics of the plurality of transmit channels and sense channels includes:

receiving a sense signal at one of the plurality of sense channels generated by a stimulation signal from one of the plurality of transmit channels;

demodulating the sense signal to obtain sense values;

adjusting an adjustable delay value; and

determining the phase characteristic of the one of the plurality of transmit channels and the one of the plurality of sense channels based on the adjustable delay value corresponding to a maximum or minimum sense value.

3. The method of claim 1, wherein measuring the phase characteristics of the plurality of transmit channels and sense channels includes:

receiving sense signals at the plurality sense channels generated by a stimulation signal from one of the plurality of transmit channels;

demodulating the sense signals to obtain a plurality of sense values;

adjusting an adjustable delay value for each sense channel; and

determining phase characteristics for the one of the plurality of transmit channels and corresponding sense channels based on the adjustable delay value corresponding to a maximum or minimum sense value for the corresponding sense channel.

4. The method of claim 1, wherein calculating the phase delay to apply to the composite sense signals of the sense channel includes:

averaging the phase characteristics of the plurality of transmit channels and sense channels associated with the sense channel.

5. The method of claim 4, wherein calculating the phase compensation values to apply to component signals includes:

calculating the difference between the phase characteristics of the plurality of transmit channels and sense channels associated with the sense channel and the phase delay to apply to the composite sense signals received by the sense channel.

6. The method of claim 1, further comprising:

storing the calculated phase delay and phase compensation values in a memory for use in demodulating sense signals received at the sense channel.

7. The method of claim 1, wherein the phase characteristics of the plurality of transmit channels and sense channels are measured at one or more frequencies corresponding to one or more stimulation frequencies, and the phase delay and phase compensation values are calculated for each of the one or more stimulation frequencies.

8. An apparatus comprising:

a plurality of transmit channels configured to transmit drive signals simultaneously to stimulate a multi-touch sensor panel;

a plurality of sense channels configured to receive sense signals generated by stimulation of the multi-touch sensor panel; and

a demodulation section capable of;

measuring phase characteristics of the plurality of transmit channels and sense channels;

calculating a phase delay to apply to composite sense signals received by a sense channel based on the measured phase characteristics; and

calculating phase compensation values to apply to component signals of the composite sense signals received by the sense channel based on the phase characteristics and the phase delay.

9. The apparatus of claim 8, wherein measuring the phase characteristics of the plurality of transmit channels and sense channels includes:

receiving a sense signal at one of the plurality of sense channels generated by a stimulation signal from one of the plurality of transmit channels;

demodulating the sense signal to obtain sense values;

adjusting an adjustable delay value; and

determining the phase characteristic of the one of the plurality of transmit channels and the one of the plurality of sense channels based on the adjustable delay value corresponding to a maximum or minimum sense value.

10. The apparatus of claim 8, wherein measuring the phase characteristics of the plurality of transmit channels and sense channels includes:

receiving sense signals at the plurality sense channels generated by a stimulation signal from one of the plurality of transmit channels;

demodulating the sense signals to obtain a plurality of sense values;

adjusting an adjustable delay value for each sense channel; and

determining phase characteristics for the one of the plurality of transmit channels and corresponding sense channels based on the adjustable delay value corresponding to a maximum or minimum sense value for the corresponding sense channel.

11. The apparatus of claim 8, wherein calculating the phase delay to apply to the composite sense signals of the sense channel includes:

averaging the phase characteristics of the plurality of transmit channels and sense channels associated with the sense channel.

12. The apparatus of claim 11, wherein calculating the phase compensation values to apply to component signals includes:

calculating the difference between the phase characteristics of the plurality of transmit channels and sense channels associated with the sense channel and the phase delay to apply to the composite sense signals received by the sense channel.

13. The apparatus of claim 8, further comprising:

a memory to store the calculated phase delay and phase compensation values for use in demodulating sense signals received at the sense channel.

14. The apparatus of claim 8, wherein the phase characteristics of the plurality of transmit channels and sense channels are measured at one or more frequencies corresponding to one or more stimulation frequencies, and the phase delay and phase compensation values are calculated for each of the one or more stimulation frequencies.