# US 2018/0025197 A1 · Sensing element and fingerprint sensor comprising the sensing elements > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0025197 A1 - Document ID: US20180025197A1 - Status: Published application - Kind: A1 - Application number: 15/214,924 - Filed: 2016-07-20 - Published: 2018-01-25 - Earliest claimed: 2016-07-20 - Assignees: Image Match Design Inc. - Applicants: Image Match Design Inc. - Inventors: YEN-KUO LO; CHIA-HUA YEH - Web page: https://patentgrep.com/patent/US20180025197A1 ## CPC - G06V 40/1306: {non-optical, e.g. ultrasonic or capacitive sensing} - G06F 3/0416: {Control or interface arrangements specially adapted for digitisers} - G06F 3/0443: {using a single layer of sensing electrodes} - G06F 2203/04107: Shielding in digitiser, i.e. guard or shielding arrangements, mostly for capacitive touchscreens, e.g. driven shields, driven grounds - G06V: IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) ## Abstract A fingerprint sensor comprises a substrate, a first sensing electrode over the substrate, a second sensing electrode spaced apart from the first sensing electrode over the substrate, a first conductive plate and a second conductive plate. The first sensing electrode is configured to detect a capacitance in response to a touch event on the fingerprint sensor, and to receive an input signal from a signal source. The second sensing electrode is configured to detect a capacitance in response to the touch event. The first conductive plate is configured to shield at least a portion of each of the first sensing electrode and the second sensing electrode from the substrate. The second conductive plate is disposed between the substrate and the second sensing electrode. The sensitivity of the fingerprint sensor is inversely proportional to the capacitance between the second sensing electrode and the second conductive plate. ## Claims ### Claim 1 A fingerprint sensor, comprising: a substrate; a first sensing electrode over the substrate, configured to detect a capacitance in response to a touch event on the fingerprint sensor, and to receive an input signal from a signal source; a second sensing electrode spaced apart from the first sensing electrode over the substrate, configured to detect a capacitance in response to the touch event; a first conductive plate to shield at least a portion of each of the first sensing electrode and the second sensing electrode from the substrate; and a second conductive plate between the substrate and the second sensing electrode, wherein sensitivity of the fingerprint sensor is inversely proportional to the capacitance between the second sensing electrode and the second conductive plate. ### Claim 2 (depends on 1) The fingerprint sensor of claim 1 further comprising an amplifier, the amplifier including: an inverting terminal coupled to the second sensing electrode; and an output coupled to the second conductive plate and, via a switch, to the second sensing electrode. ### Claim 3 (depends on 2) The fingerprint sensor of claim 2, wherein a parasitic capacitance between the first sensing electrode and the second sensing electrode, and a capacitance between the first conductive plate and each of the first sensing electrode and the second sensing electrode form a capacitor network between the signal source and the inverting terminal of the amplifier. ### Claim 4 (depends on 3) The fingerprint sensor of claim 3, wherein the sensitivity of the fingerprint sensor is independent of the parasitic capacitance. ### Claim 5 (depends on 3) The fingerprint sensor of claim 3, wherein the sensitivity of the fingerprint sensor is independent of the capacitance between the first conductive plate and each of the first sensing electrode and the second sensing electrode. ### Claim 6 (depends on 3) The fingerprint sensor of claim 3, wherein the amplifier includes a non-inverting terminal configured to receive a reference voltage, and the sensitivity of the fingerprint sensor is independent of the reference voltage. ### Claim 7 (depends on 3) The fingerprint sensor of claim 3, wherein the capacitor network further includes capacitances detected by the first sensing electrode and the second sensing electrode. ### Claim 8 (depends on 1) The fingerprint sensor of claim 1, wherein the sensitivity (ΔVout) of the fingerprint sensor is defined by the following equation: Δ   Vout = ( CF 2 ) c   2 × Vin where Vin represents the input signal, CF represents the capacitance in response to the touch event, and C2 represents the capacitance between the second sensing electrode and the second conductive plate. ### Claim 9 (depends on 1) The fingerprint sensor of claim 1 further comprising a low-k insulating layer between the second sensing electrode and the second conductive plate. ### Claim 10 A sensing element in a fingerprint sensor, the sensing element comprising: a first sensing electrode configured to receive an input signal from a signal source; a second sensing electrode spaced apart from the first sensing electrode, the second sensing electrode and the first sensing electrode configured to detect a capacitance in response to a touch event on the fingerprint sensor; a first conductive plate configured to overlap at least a portion of each of the first sensing electrode and the second sensing electrode; a second conductive plate configured to define a capacitance with respect to the second sensing electrode; and an amplifier including an input terminal coupled to the second sensing electrode, and an output coupled to the second conductive plate and, via a switch, to the second sensing electrode. ### Claim 11 (depends on 10) The sensing element of claim 10, wherein sensitivity of the fingerprint sensor is inversely proportional to the capacitance between the second sensing electrode and the second conductive plate. ### Claim 12 (depends on 10) The sensing element of claim 10, wherein sensitivity of the fingerprint sensor is independent of a parasitic capacitance between the first sensing electrode and the second sensing electrode. ### Claim 13 (depends on 10) The sensing element of claim 10, wherein sensitivity of the fingerprint sensor is independent of a capacitance between the first conductive plate and each of the first sensing electrode and the second sensing electrode. ### Claim 14 (depends on 11) The sensing element of claim 11, wherein sensitivity (ΔVout) of the fingerprint sensor is defined by the following equation: Δ   Vout = ( CF 2 ) c   2 × Vin where Vin represents the input signal, CF represents the capacitance in response to the touch event, and C2 represents the capacitance between the second sensing electrode and the second conductive plate.