Matched filter for a first order sigma delta capacitance measurement system and a method to determine the same
First Claim
1. A processing system for generating filtered digital touch capacitance data, the processing system comprising:
- a sigma-delta converter configured to;
receive a first resulting signal with a first capacitive sensing electrode of a plurality of capacitive sensing electrodes, andapply sigma-delta conversion to the first resulting signal to generate a first sigma-delta quantized signal; and
a filter logic unit configured to apply a first matched filter to the first sigma-delta quantized signal to generate a first filtered sigma-delta quantized signal, wherein the first matched filter is based on a discrete time cumulative sum signal.
2 Assignments
0 Petitions
Accused Products
Abstract
A processing system that includes a sigma-delta converter and a filter unit that applies a matched filter to the output of the sigma-delta converter. The processing system drives sensor electrodes for capacitive sensing and receives resulting signals with the sensor electrodes in response. The processing system applies these resulting signals to sigma-delta converters. The matched filter boosts the signal-to-noise ratio of the signal received from the sigma-delta converter, thereby improving the ability to sense presence of an input object. The filter unit may apply different, customized matched filters for different capacitive pixels to improve the signal-to-noise ratio of each capacitive pixel in a customized manner.
23 Citations
25 Claims
-
1. A processing system for generating filtered digital touch capacitance data, the processing system comprising:
-
a sigma-delta converter configured to; receive a first resulting signal with a first capacitive sensing electrode of a plurality of capacitive sensing electrodes, and apply sigma-delta conversion to the first resulting signal to generate a first sigma-delta quantized signal; and a filter logic unit configured to apply a first matched filter to the first sigma-delta quantized signal to generate a first filtered sigma-delta quantized signal, wherein the first matched filter is based on a discrete time cumulative sum signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
-
-
9. A method for generating filtered digital touch capacitance data, the method comprising:
-
receiving a first resulting signal with a first capacitive sensing electrode of a plurality of capacitive sensing electrodes; applying sigma-delta conversion to the first resulting signal to generate a first sigma-delta quantized signal; and applying a first matched filter to the first sigma-delta quantized signal to generate a first filtered sigma-delta quantized signal, wherein the first matched filter is based on a discrete time cumulative sum signal. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
-
-
17. An input device, comprising:
-
a plurality of capacitive sensing electrodes; and a processing system coupled to the plurality of capacitive sensing electrodes, the processing system comprising; a sigma-delta converter configured to; receive a first resulting signal with a first capacitive sensing electrode of a plurality of capacitive sensing electrodes, and apply sigma-delta conversion to the first resulting signal to generate a first sigma-delta quantized signal; and a filter logic unit configured to apply a first matched filter to the first sigma-delta quantized signal to generate a first filtered sigma-delta quantized signal, wherein the first matched filter is based on a discrete time cumulative sum signal. - View Dependent Claims (18)
-
-
19. A processing system for generating filtered digital touch capacitance data, the processing system comprising:
-
a sigma-delta converter configured to; receive a first resulting signal with a first capacitive sensing electrode of a plurality of capacitive sensing electrodes, and apply sigma-delta conversion to the first resulting signal to generate a first sigma-delta quantized signal; and a filter logic unit configured to apply a first matched filter to the first sigma-delta quantized signal to generate a first filtered sigma-delta quantized signal; wherein the sigma-delta converter is further configured to; receive a second resulting signal with a second capacitive sensing electrode of the plurality of capacitive sensing electrodes, and apply sigma-delta conversion to the second resulting signal to generate a second sigma-delta quantized signal; and wherein the filter logic unit is further configured to; apply a second matched filter to the second sigma-delta quantized signal to generate a second filtered sigma-delta quantized signal, the second matched filter differing from the first matched filter in a manner that is based on differences in impedance characteristics between the first capacitive sensing electrode and the second capacitive sensing electrode.
-
-
20. A processing system for generating filtered digital touch capacitance data, the processing system comprising:
-
a sigma-delta converter configured to; receive a first resulting signal with a first capacitive sensing electrode of a plurality of capacitive sensing electrodes, and apply sigma-delta conversion to the first resulting signal to generate a first sigma-delta quantized signal; a filter logic unit configured to apply a first matched filter to the first sigma-delta quantized signal to generate a first filtered sigma-delta quantized signal; and wherein the first matched filter is periodic, and the filter logic unit is further configured to store the first matched filter as a plurality of constants in a phase-indexed lookup table.
-
-
21. A processing system for generating filtered digital touch capacitance data, the processing system comprising:
-
a sigma-delta converter configured to; receive a first resulting signal with a first capacitive sensing electrode of a plurality of capacitive sensing electrodes, and apply sigma-delta conversion to the first resulting signal to generate a first sigma-delta quantized signal; a filter logic unit configured to apply a first matched filter to the first sigma-delta quantized signal to generate a first filtered sigma-delta quantized signal; and wherein the filter logic unit is further configured to; apply a second matched filter that is phase-shifted with respect to the first matched filter by approximately 90 degrees to the first sigma-delta quantized signal to generate a quadrature-phase filtered sigma-delta quantized signal.
-
-
22. A method for generating filtered digital touch capacitance data, the method comprising:
-
receiving a first resulting signal with a first capacitive sensing electrode of a plurality of capacitive sensing electrodes; applying sigma-delta conversion to the first resulting signal to generate a first sigma-delta quantized signal; applying a first matched filter to the first sigma-delta quantized signal to generate a first filtered sigma-delta quantized signal; receiving a second resulting signal with a second capacitive sensing electrode of the plurality of capacitive sensing electrodes, applying sigma-delta conversion to the second resulting signal to generate a second sigma-delta quantized signal; and applying a second matched filter to the second sigma-delta quantized signal to generate a second filtered sigma-delta quantized signal, the second matched filter differing from the first matched filter in a manner that is based on differences in impedance characteristics between the first capacitive sensing electrode and the second capacitive sensing electrode.
-
-
23. A method for generating filtered digital touch capacitance data, the method comprising:
-
receiving a first resulting signal with a first capacitive sensing electrode of a plurality of capacitive sensing electrodes; applying sigma-delta conversion to the first resulting signal to generate a first sigma-delta quantized signal; applying a first matched filter to the first sigma-delta quantized signal to generate a first filtered sigma-delta quantized signal, wherein the first matched filter is periodic; and
;storing the first matched filter as a plurality of constants in a phase-indexed lookup table.
-
-
24. An input device comprising:
-
a plurality of capacitive sensing electrodes; and a processing system coupled to the plurality of capacitive sensing electrodes, the processing system comprising; a sigma-delta converter configured to; receive a first resulting signal with a first capacitive sensing electrode of a plurality of capacitive sensing electrodes, and apply sigma-delta conversion to the first resulting signal to generate a first sigma-delta quantized signal; and a filter logic unit configured to apply a first matched filter to the first sigma-delta quantized signal to generate a first filtered sigma-delta quantized signal; and wherein the sigma-delta converter is further configured to; receive a second resulting signal with a second capacitive sensing electrode of the plurality of capacitive sensing electrodes, and apply sigma-delta conversion to the second resulting signal to generate a second sigma-delta quantized signal; and wherein the filter logic unit is further configured to; apply a second matched filter to the second sigma-delta quantized signal to generate a second filtered sigma-delta quantized signal, the second matched filter differing from the first matched filter in a manner that is based on differences in impedance characteristics between the first capacitive sensing electrode and the second capacitive sensing electrode.
-
-
25. An input device comprising:
-
a plurality of capacitive sensing electrodes; and a processing system coupled to the plurality of capacitive sensing electrodes, the processing system comprising; a sigma-delta converter configured to; receive a first resulting signal with a first capacitive sensing electrode of a plurality of capacitive sensing electrodes, and apply sigma-delta conversion to the first resulting signal to generate a first sigma-delta quantized signal; a filter logic unit configured to apply a first matched filter to the first sigma-delta quantized signal to generate a first filtered sigma-delta quantized signal; and wherein the first matched filter is periodic, and the filter logic unit is further configured to store the first matched filter as a plurality of constants in a phase-indexed lookup table.
-
Specification