Advanced receive channel architecture

• US 8,659,556 B2
• Filed: 09/10/2008
• Issued: 02/25/2014
• Est. Priority Date: 09/10/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Wilson, Thomas James
• Primary Examiner(s): Liang, Regina
• Application Number:
  US12/208,303
• Publication Number:
  US 20100060589A1
• Time in Patent Office: 1,994 Days
• Field of Search: 345173-178, 178 1801- 1811
• US Class Current: 345/173
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• 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 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer

Abstract

This relates to an architecture of a receive channel circuit used during both a spectrum analysis phase and a touch panel detection phase. Various components of the receive channel can be used during both the spectrum analysis phase and the touch panel detection phase. For example, a plurality of digital signal mixers used in the receive channel circuit can be used to demodulate signals during both a spectrum analysis phase and a touch sensor panel detection phase. In addition, the number of digital mixers needed in the receive channel can be reduced by dividing groups of signals to be demodulated into multiple sets of signals and demodulating each set at different times.

Claims

1. A method of scanning a touch sensor panel, comprising:

demodulating a first plurality of signals received from a plurality of sense lines in a single scan of the touch sensor panel with a demodulation frequency using a plurality of mixers;

wherein the plurality of mixers demodulate different ones of the first plurality of signals received in the single scan at different times using the demodulation frequency; and

wherein a number of the plurality of mixers is less than a number of the first plurality of signals.

2. The method of claim 1, further comprising:

demodulating a summation of a second plurality of signals received from the plurality of sense lines of the touch sensor panel with a plurality of sample frequency signals using the plurality of mixers.

3. The method of claim 2, further comprising generating the plurality of sample frequency signals and the demodulation frequency using a single numerically controlled oscillator (NCO).

4. The method of claim 2, further comprising selecting one of the plurality of sample frequency signals as a low noise signal.

5. The method of claim 4, wherein the demodulation frequency has the same frequency as the selected low noise signal.

6. The method of claim 4, further comprising applying a stimulation signal to each of a plurality of drive lines of the touch sensor panel, the stimulation signal having the same frequency as the selected low noise signal.

7. The method of claim 2, wherein at least some of the plurality of sample frequency signals have different frequencies.

8. The method of claim 2, wherein the demodulation of the summation of the second plurality of signals with the plurality of sample frequency signals comprises:

demodulating the summation of the second plurality of signals with a first set of the plurality of sample frequency signals using the plurality of mixers during a first time period; and

demodulating the summation of the second plurality of signals with a second set of the plurality of sample frequency signals using the plurality of mixers during a second time period that is different from the first time period,

wherein a number of the plurality of mixers is equal to a number of sample frequency signals in each set of the plurality of sample frequency signals.

9. The method of claim 1, further comprising storing the first plurality of signals and outputting the different ones of the first plurality of signals for demodulation at the different times.

10. The method of claim 1, further comprising accumulating the demodulated first plurality of signals to generate a plurality of values representative of the accumulated demodulated signals for each sense line.

11. The method of claim 1, wherein the demodulation of the first plurality of signals comprises:

demodulating a first set of the first plurality of signals using the plurality of mixers during a first time period; and

demodulating a second set of the first plurality of signals using the plurality of mixers during a second time period that is different from the first time period,

wherein a number of the plurality of mixers is equal to a number of the first plurality of signals in each set of the first plurality of signals.

12. An apparatus for obtaining a plurality of values used to generate an image of touch from a touch sensor panel, comprising:

a plurality of analog-to-digital converters (ADCs), each ADC configured to receive an analog signal from a different sense line of the touch sensor panel and convert the signal into a digital signal;

a waveform generator circuit operable to generate a plurality of signals having different waveforms; and

a plurality of mixers,

wherein, during a first phase, the plurality of mixers are configured to mix different ones of the signals outputted from the plurality of ADCs in a single scan of the touch sensor panel at different times with at least one signal generated by the waveform generator circuit; and

wherein a number of signals received from the plurality of ADCs is equal to N, a number of the plurality of signals having different waveforms is equal to N, and a number of the plurality of mixers is less than N.

13. The apparatus of claim 12, further comprising:

a summation circuit couplable to the plurality of ADCs and operable to generate a sum representative of a summation of the digital signals from the plurality of ADCs; and

wherein during a second phase, the plurality of mixers are configured to mix each of a plurality of signals having different waveforms generated by the waveform generator with the sum.

14. The apparatus of claim 13, further comprising:

an amplitude window generator circuit; and

a further mixer operable to mix an output of the amplitude window generator with an input signal to generate a windowed representation of the signal,

wherein, during the second phase, the input signal is the signal representative of the summation of the ADC outputs, and, during the first phase, the input signal is the at least one signal generated by the waveform generator circuit.

15. The apparatus of claim 12, further comprising a multiplexer configured to output a first set of the plurality of signals having different waveforms to the plurality of mixers at a first time, and output a second set of the plurality of signals having different waveforms to the plurality of mixers at a second time that is different from the first time.

16. The apparatus of claim 15, wherein the first time corresponds to a first edge of a control clock signal and the second time corresponds to a second edge of a control clock signal.

17. The apparatus of claim 15, wherein the first set comprises half of the plurality of signals having different waveforms and the second set comprises the remaining half of the plurality of signals having different waveforms.

18. The apparatus of claim 15, wherein the plurality of signals having different waveforms comprise signals having different frequencies and phases.

19. The apparatus of claim 15, further comprising a multiplexer configured to output a first set of the plurality of signals outputted from the ADCs to the plurality of mixers at a third time, and output a second set of the plurality of signals outputted from the ADCs to the plurality of mixers at a fourth time that is different from the third time.

20. The apparatus of claim 12, further comprising an accumulator coupled to each of the plurality of mixers for generating a value representing an accumulated mixer output.

21. The apparatus of claim 12, wherein the waveform generator circuit comprises a numerically controlled oscillator (NCO).

22. A computing system comprising the apparatus of claim 12.

23. A mobile telephone comprising the computing system of claim 22.

24. A digital audio player comprising the computing system of claim 22.