Method to compensate for the frequency dependence of sense signal preprocessing

• US 8,363,021 B2
• Filed: 09/11/2009
• Issued: 01/29/2013
• Est. Priority Date: 09/11/2009
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Krah, Christoph Horst, Hori, Yutaka
• Primary Examiner(s): MERCEDES, DISMERY E
• Application Number:
  US12/558,397
• Publication Number:
  US 20110063229A1
• Time in Patent Office: 1,236 Days
• Field of Search: None
• US Class Current: 345/173
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• 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

Compensating for the frequency dependence of sense signal preprocessing in preprocessing channel circuitry is provided. The frequency dependence of the preprocessing channels can be modified to change a frequency dependent channel into a frequency independent channel, to change a frequency independent channel into a frequency dependent channel, or to change the frequency dependency characteristics of a frequency dependent channel. Modification of frequency dependency may be accomplished, for example, by modifying certain parameters of a preprocessing channel'"'"'s components, which can include components for amplifying, filtering, phase adjusting, demodulating, decrypting, for example. A pipelined process may be used to modify the frequency dependency of multiple channels. Compensating for frequency dependencies can have multiple advantages, such as reduction of memory requirements and DIE size.

Claims

1. A method of modifying a frequency dependency of a sense signal preprocessing channel of a sensing system, the method comprising:

linearly scaling a parameter of a first transfer function of a component of the preprocessing channel based on a frequency of the sense signal to obtain a scaled parameter value;

nonlinearly scaling the scaled parameter value based on a second transfer function of an adjustment process of the component to obtain an adjustment value; and

adjusting a parameter value of the component the parameter value of the component based on the scaled parameter value by performing the adjustment process based on the adjustment value.

2. The method of claim 1, wherein the parameter of the first transfer function includes an internal parameter of the component.

3. The method of claim 2, wherein the component is a preamplifier and the internal parameter includes a feedback resistance of the preamplifier.

4. The method of claim 2, wherein the component is a bandpass filter and the internal parameter includes a center frequency of the bandpass filter.

5. The method of claim 2, wherein the component is a DCL (Digital Control Logic) circuit element and the internal parameter includes a DCL parameter.

6. The method of claim 1, wherein the linear scaling is performed for a plurality of sense signal preprocessing channels, the first transfer function of each channel being based on one or more signal path lengths corresponding to one or more stimulation signals on which a sense signal of the channel is based.

7. The method of claim 6, wherein the first transfer function of each channel is stored in one or more look-up tables, and the linear scaling includes performing one of linear and nonlinear interpolation based on the one or more look-up tables.

8. The method of claim 1, wherein the linear scaling and the nonlinear scaling are performed by interpolation of a single look-up table.

9. The method of claim 1, wherein the parameter of the first transfer function includes a parameter of an external device.

10. The method of claim 1, wherein the parameter is linearly scaled such that the first transfer function of the component is substantially independent of a frequency of the sense signal.

11. The method of claim 1, wherein the parameter is linearly scaled such that the first transfer function of the component substantially compensates for a frequency dependence of another component of the preprocessing channel.

12. The method of claim 1, further comprising:

performing the linearly scaling, the nonlinearly scaling, and the adjusting the parameter for each of a plurality of preprocessing channels in a pipeline process.

13. An apparatus for modifying a frequency dependency of a circuit component of a sense signal preprocessing channel of a touch sensing system, the apparatus comprising:

a first memory that stores a linear scaling factor representing a predetermined frequency characteristic of a first transfer function of the component based on a first frequency;

an operator that scales a parameter of the first transfer function with the linear scaling factor to obtain a first scaled value;

a second memory includes a plurality of entries representing a second transfer function of a parameter adjustment process of the component that has been calibrated to the first frequency, such that selecting an entry corresponding to the first scaled value returns a second scaled value; and

an adjuster that applies the second scaled value to the adjustment process of the component, such that the frequency dependency of the component is modified according to the predetermined frequency characteristic.

14. The apparatus of claim 13, wherein the parameter of the first transfer function includes an internal parameter of the component.

15. The apparatus of claim 14, wherein the component is a preamplifier and the internal parameter includes a feedback resistance of the preamplifier.

16. The apparatus of claim 14, wherein the component is a bandpass filter and the internal parameter includes a center frequency of the bandpass filter.

17. The apparatus of claim 13, wherein the parameter of the first transfer function includes a parameter of an external device.

18. The apparatus of claim 13, wherein the parameter is linearly scaled such that the first transfer function of the component is substantially independent of a frequency of the sense signal.

19. The apparatus of claim 13, wherein the parameter is linearly scaled such that the first transfer function of the component substantially compensates for a frequency dependence of another component of the preprocessing channel.

20. The apparatus of claim 13, further comprising a pipeline system comprising:

a sequencer that controls a pipeline process wherein the operator scales a plurality of parameters, each parameter corresponding to one of a plurality of preprocessing channels to obtain a plurality of the first scaled values, which are each applied to the second memory to obtain a plurality of second scaled values, which are each applied to the adjustment process of the component in the preprocessing channel of the corresponding parameter.

21. A touch sensing system comprising:

the apparatus for modifying a frequency dependency of a circuit component of a sense signal preprocessing channel of the touch sensing system of claim 13; and

a touch screen.

22. A non-transitory computer-readable storage medium storing computer-executable instructions that are executable to perform a method of modifying a frequency dependency of a sense signal preprocessing channel in a sensing system, the method comprising:

linearly scaling a parameter of a first transfer function of a component of the preprocessing channel based on a frequency of the sense signal to obtain a scaled parameter value;

nonlinearly scaling the scaled parameter value based on a second transfer function of an adjustment process of the component to obtain an adjustment value; and

adjusting the parameter of the first transfer function based on the scaled parameter value by performing the adjustment process based on the adjustment value.

23. The non-transitory computer-readable storage medium of claim 22, wherein the parameter of the first transfer function includes an internal parameter of the component.

24. The non-transitory computer-readable storage medium of claim 23, wherein the component is a preamplifier and the internal parameter includes a feedback resistance of the preamplifier.

25. The non-transitory computer-readable storage medium of claim 23, wherein the component is a bandpass filter and the internal parameter includes a center frequency of the bandpass filter.