Rain sensor with sigma-delta modulation and/or footprinting comparison(s)
First Claim
1. A rain sensor comprising:
- a sensing circuit comprising at least one sensing capacitor that is sensitive to moisture on an external surface of a window;
an adder receiving, directly or indirectly, an analog output signal from the sensing circuit and determining a difference between the analog output signal from the sensing circuit and a feedback signal;
a quantizer including a comparator downstream of the adder that outputs a bitstream based at least on whether a received signal level is higher or lower than a predetermined threshold;
a lowpass digital filter downstream of the quantizer for lowpass filtering the bitstream so as to output a filtered digital signal; and
a correlation engine that performs correlation on the filtered digital signal in order to determine whether rain is present on the external surface of the window.
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Accused Products
Abstract
A system and/or method for sensing the presence of moisture (e.g., rain) and/or other material(s) on a window such as a vehicle window (e.g., vehicle windshield, sunroof or backlite). In certain example embodiments of the invention, at least one sensing capacitor is supported by a window such as a vehicle windshield, the capacitor(s) having a field that is affected by moisture (e.g., rain) on a surface of the window. A sensing circuit outputs an analog signal that is based on and/or related to the capacitance(s) of the sensing capacitor(s). The analog output of the circuit may be converted to a digital signal via sigma-delta modulation, and subjected to processing (e.g., correlation) for determining whether moisture (e.g., rain, dew, fog, etc.) or the like is present on the surface of the window.
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Citations
14 Claims
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1. A rain sensor comprising:
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a sensing circuit comprising at least one sensing capacitor that is sensitive to moisture on an external surface of a window; an adder receiving, directly or indirectly, an analog output signal from the sensing circuit and determining a difference between the analog output signal from the sensing circuit and a feedback signal; a quantizer including a comparator downstream of the adder that outputs a bitstream based at least on whether a received signal level is higher or lower than a predetermined threshold; a lowpass digital filter downstream of the quantizer for lowpass filtering the bitstream so as to output a filtered digital signal; and a correlation engine that performs correlation on the filtered digital signal in order to determine whether rain is present on the external surface of the window. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification