Parallel processing of multiple channels with very narrow bandpass digital filtering

1. A method comprises:

converting, by n analog to digital converter (ADC) circuits of an analog to digital conversion circuit, n analog signals into n first digital signals having a first data rate frequency, wherein an analog signal of the n analog signals includes an oscillation frequency and a set of pure tone components, and wherein n is an integer greater than 1;

converting, by n digital decimation filtering circuits of the analog to digital conversion circuit, the n first digital signals into n second digital signals having a second data rate frequency; and

converting, by n digital bandpass filter (BPF) circuits of the analog to digital conversion circuit, the n second digital signals into a plurality of outbound digital signals having a third data rate frequency, wherein a digital BPF circuit of the n digital BPF circuits includes a plurality of taps having a plurality of coefficients, wherein the plurality of coefficients for the plurality of taps is set to produce a bandpass region approximately centered at the oscillation frequency of the analog signal and having a bandwidth tuned for filtering a pure tone component of the set of pure tone components, wherein the first data rate frequency is a first integer multiple of the third data rate frequency, wherein the second data rate frequency is a second integer multiple of the third data rate frequency, and wherein the first data rate frequency is greater than the second data rate frequency.

2. The method of claim 1 , wherein the first data rate frequency is a third integer multiple of the second data rate frequency.

3. The method of claim 1 , wherein an ADC circuit of the n ADC circuits includes a digital decimation filtering circuit of the n digital decimation filtering circuits.

4. The method of claim 1 , wherein a first digital signal of then first digital signals is a 1-bit digital data stream at the first data rate frequency.

5. The method of claim 1 further comprises:

converting, by a first digital BPF circuit of the digital BPF circuit, a second digital signal of the n second digital signals into a first outbound digital signal of the plurality of outbound digital signals, wherein the first digital BPF circuit includes a first plurality of taps having a first plurality of coefficients, wherein the first plurality of coefficients for the first plurality of taps is set to produce a first bandpass region approximately centered at the oscillation frequency of the analog signal and having a first bandwidth tuned for filtering a first pure tone component of the set of pure tone components; and

converting, by a second digital BPF circuit of the digital BPF circuit, the second digital signal of the n second digital signals into a second outbound digital signal of the plurality of outbound digital signals, wherein the second digital BPF circuit includes a second plurality of taps having a second plurality of coefficients, wherein the second plurality of coefficients for the second plurality of taps is set to produce a second bandpass region approximately centered at the oscillation frequency of the analog signal and having a second bandwidth tuned for filtering a second pure tone component of the set of pure tone components.

6. The method of claim 5 further comprises:

selecting, by a processing module of the analog to digital conversion circuit, the first and second pure tone components; and

computing, by a coefficient processer of the digital BPF circuit, the first and second plurality of coefficients based on the selected first and second pure tone components.

7. The method of claim 1 further comprises:

the first data rate frequency is 2 17 times the third data rate frequency; and

the second data rate frequency is 2 12 times the third data rate frequency.

8. The method of claim 1 further comprises:

the first data rate frequency includes a first bit rate per interval;

the second data rate frequency includes a second bit rate per interval; and

the third data rate frequency includes a third bit rate per interval.

9. The method of claim 1 further comprises:

determining, by a processing module of the analog to digital conversion circuit a plurality of impedance values from the plurality of outbound digital signals, wherein a first outbound digital signal of the plurality of outbound digital signals is a vector having real and imaginary components.

10. The method of claim 1 , wherein the bandwidth tuned for filtering the pure tone component is less than 0.05 of channel spacing, and wherein the channel spacing is the bandwidth between two pure tone components of the set of pure tone components.

11. A method comprises:

converting, by n analog to digital converter (ADC) circuits of a touch screen display, n analog signals into n first digital signals having a first data rate frequency, wherein an analog signal of the n analog signals includes an oscillation frequency and a set of pure tone components, wherein n is an integer greater than 1, and wherein the touch screen display includes n electrodes;

converting, by n digital decimation filtering circuits of the touch screen display, the n first digital signals into n second digital signals having a second data rate frequency;

converting, by n digital bandpass filter (BPF) circuits of the touch screen display, the n second digital signals into a plurality of outbound digital signals having a third data rate frequency, wherein a digital BPF circuit of the n digital BPF circuits includes a plurality of taps having a plurality of coefficients, wherein the plurality of coefficients for the plurality of taps is set to produce a bandpass region approximately centered at the oscillation frequency of the analog signal and having a bandwidth tuned for filtering a pure tone component of the set of pure tone components, wherein the first data rate frequency is a first integer multiple of the third data rate frequency, wherein the second data rate frequency is a second integer multiple of the third data rate frequency, and wherein the first data rate frequency is greater than the second data rate frequency;

determining, by a processing module of the touch screen display, a plurality of impedance values from the plurality of outbound digital signals, wherein a first outbound digital signal of the plurality of outbound digital signals is a vector having real and imaginary components; and

interpreting, by the processing module, the plurality of impedance values as touch data of the touch screen display.

12. The method of claim 11 , wherein the first data rate frequency is a third integer multiple of the second data rate frequency.

13. The method of claim 11 , wherein a first digital signal of the n first digital signals is a 1-bit digital data stream at the first data rate frequency.

14. The method of claim 11 further comprises:

converting, by a first digital BPF circuit of the digital BPF circuit, a second digital signal of the n second digital signals into a first outbound digital signal of the plurality of outbound digital signals, wherein the first digital BPF circuit includes a first plurality of taps having a first plurality of coefficients, wherein the first plurality of coefficients for the first plurality of taps is set to produce a first bandpass region approximately centered at the oscillation frequency of the analog signal and having a first bandwidth tuned for filtering a first pure tone component of the set of pure tone components; and

converting, by a second digital BPF circuit of the digital BPF circuit, the second digital signal of then second digital signals into a second outbound digital signal of the plurality of outbound digital signals, wherein the second digital BPF circuit includes a second plurality of taps having a second plurality of coefficients, wherein the second plurality of coefficients for the second plurality of taps is set to produce a second bandpass region approximately centered at the oscillation frequency of the analog signal and having a second bandwidth tuned for filtering a second pure tone component of the set of pure tone components.

15. The method of claim 14 further comprises:

selecting, by the processing module, the first and second pure tone components; and

computing, by a coefficient processer of the digital BPF circuit, the first and second plurality of coefficients based on the selected first and second pure tone components.

16. The method of claim 15 further comprises:

selecting, by the processing module, the first pure tone component based on a known frequency; and

selecting, by the processing module, the second pure tone component based on a region of interest of the touch screen display.

17. The method of claim 11 , wherein the pure tone component corresponds to one of:

a self capacitance of an electrode of then electrodes;

a pen capacitance of the electrode; and

a mutual capacitance of the electrode.

18. The method of claim 11 further comprises:

the first data rate frequency is 2 17 times the third data rate frequency; and

the second data rate frequency is 2 12 times the third data rate frequency.

19. The method of claim 11 further comprises:

the first data rate frequency includes a first bit rate per interval;

the second data rate frequency includes a second bit rate per interval; and

the third data rate frequency includes a third bit rate per interval.

20. The method of claim 11 , wherein the bandwidth tuned for filtering the pure tone is less than 0.05 of channel spacing, wherein the channel spacing is the bandwidth between two pure tone components of the set of pure tone components.