Multiphase fingerprint sensor layout and construction

Patent metadata

Field	Value
Publication number	US-10013593-B2
Application number	US-201514964562-A
Country	US
Kind code	B2
Filing date	Dec 9, 2015
Priority date	Sep 9, 2015
Publication date	Jul 3, 2018
Grant date	Jul 3, 2018

Abstract

A capacitive fingerprint sensor includes a set of capacitive sensor electrodes in a sensing area. The set of capacitive sensor electrodes includes a set of transmit (Tx) sensor electrodes, a set of receive (Rx) sensor electrodes, and a set of compensation electrodes. The fingerprint sensor also includes a multiphase capacitance sensor that is configured to perform a sensing scan of the capacitive sensor electrodes by applying a first Tx signal to a first subset of the Tx sensor electrodes while simultaneously applying a second Tx signal to a second subset of the set of Tx sensor electrodes, and based on a compensation signal received at the set of compensation electrodes, reduce a component of the Rx signal originating from a source other than a contact at the sensing area.

First claim

What is claimed is:

1. A capacitive fingerprint sensor, comprising:
a set of capacitive sensor electrodes in a sensing area, wherein the set of capacitive sensor electrodes includes a set of one or more transmit (Tx) sensor electrodes and a set of one or more receive (Rx) sensor electrodes;
a set of one or more compensation electrodes, the set of one or more compensation electrodes comprising a Tx baseline electrode capacitively coupled to an Rx baseline electrode outside the sensing area, the Tx baseline electrode and the Rx baseline electrode disposed outside of the sensing area;
a multiphase capacitance sensor coupled with the set of capacitive sensor electrodes and with the set of compensation electrodes, wherein the multiphase capacitance sensor is configured to:
perform a sensing scan of the set of capacitive sensor electrodes to generate an Rx signal at the set of one or more Rx sensor electrodes by applying a first Tx signal to a first subset of the set of one or more Tx sensor electrodes while simultaneously applying a second Tx signal to a second subset of the set of one or more Tx sensor electrodes; and
based on a first compensation signal of the set of one or more compensation electrodes, reduce a component of the Rx signal originating from a source other than a contact at the sensing area, wherein the first compensation signal comprises a baseline compensation current received from the Rx baseline electrode and generated by applying the first Tx signal to the Tx baseline electrode that is capacitively coupled to the Rx baseline electrode.

2. The capacitive fingerprint sensor of claim 1 , wherein the second Tx signal is a phase-altered form of the first Tx signal, wherein the set of one or more compensation electrodes includes a plurality of Rx baseline electrodes, wherein the first compensation signal comprises the baseline compensation current generated by applying the first Tx signal to the Tx baseline electrode that is capacitively coupled to the plurality of Rx baseline electrodes, wherein the Tx baseline electrode and the plurality of Rx baseline electrodes are capacitively isolated from the sensing area, and wherein the baseline compensation current reduces a baseline current generated by the sensing scan.

3. The capacitive fingerprint sensor of claim 2 , wherein the set of Tx sensor electrodes is formed from a first layer of conductive material overlying the set of Rx sensor electrodes, and wherein the set of Rx sensor electrodes is formed from a second layer of conductive material overlying the Tx baseline electrode and the one or more Rx baseline electrodes.

4. The capacitive fingerprint sensor of claim 2 , further comprising a grounded shield interposed between the set of capacitive sensor electrodes and Tx and Rx baseline electrodes.

5. The capacitive fingerprint sensor of claim 1 , wherein the set of compensation electrodes comprises multiple Tx baseline electrodes and a single Rx baseline electrode that is capacitively coupled with each of the multiple Tx baseline electrodes.

6. The capacitive fingerprint sensor of claim 1 , wherein the set of compensation electrodes comprises multiple Rx baseline electrodes each capacitively coupled with the Tx baseline electrode.

7. The capacitive fingerprint sensor of claim 6 , further comprising, for each Rx baseline electrode of the multiple Rx baseline electrodes, a switch configured to selectively connect the Rx baseline electrode to an analog input of the multiphase capacitance sensor based on a multiphase sensing mode for performing the sensing scan.

8. The capacitive fingerprint sensor of claim 1 , wherein the set of compensation electrodes comprises:
a noise listener electrode coupled with the multiphase capacitance sensor, wherein the Tx and Rx baseline electrodes are capacitively isolated from the sensing area, and wherein the noise listener electrode is located in the sensing area and has a surface area substantially equal to a surface area of one of the Rx sensor electrodes.

9. The capacitive fingerprint sensor of claim 8 , wherein the multiphase capacitance sensor is further configured to measure noise by generating a second compensation signal at the noise listener electrode contemporaneously with the sensing scan.

10. A method of imaging a contact, the method comprising:
providing a set of capacitive sensor electrodes in a sensing area, wherein the set of capacitive sensor electrodes includes a set of transmit (Tx) sensor electrodes and a set of receive (Rx) sensor electrodes;
providing a set of one or more compensation electrodes capacitively isolated from the sensing area, wherein the set of one or more compensation electrodes comprise an RX baseline electrode disposed outside of the sensing area;
performing a sensing scan of a set of capacitive sensor electrodes to generate an Rx signal at the set of Rx sensor electrodes by applying a first Tx signal to a first subset of the set of Tx sensor electrodes while simultaneously applying a second Tx signal to a second subset of the set of Tx sensor electrodes; and
based on a compensation signal received at the set of one or more compensation electrodes, reducing a component of the Rx signal originating from a source other than the contact at the sensing area, wherein the compensation signal comprises a baseline compensation current received from the Rx baseline electrode and generated by applying the first Tx signal to the Rx baseline electrode.

11. The method of claim 10 , further comprising shielding a set of one or more baseline electrodes from the set of capacitive sensor electrodes with a grounded shield interposed between the set of capacitive sensor electrodes and the set of baseline electrodes, wherein the one or more compensation electrodes comprises the set of baseline electrodes, the set of baseline electrodes comprising Tx baseline electrode.

12. The method of claim 10 , further comprising transmitting the first Tx signal from each of multiple Tx baseline electrodes to a single Rx baseline electrode that is capacitively coupled with each of the multiple Tx baseline electrodes, wherein the one or more compensation electrodes comprises the multiple Tx baseline electrodes and the single Rx baseline electrode, and wherein the second Tx signal is a phase-altered form of the first Tx signal.

13. The method of claim 10 , further comprising transmitting the first Tx signal via a single Tx baseline electrode to each of multiple Rx baseline electrodes, wherein each of the multiple Rx baseline electrodes is capacitively coupled with the single Tx electrode, and wherein the set of compensation electrodes comprises the single Tx baseline electrode and the multiple Rx baseline electrodes.

14. The method of claim 10 , further comprising, for each Rx baseline electrode of multiple Rx baseline electrodes, operating a switch to selectively connect the Rx baseline electrode to an analog input of a multiphase capacitance sensor based on a multiphase sensing mode for performing the sensing scan, wherein each of the multiple Rx baseline electrodes is capacitively coupled with at least one of a set of Tx baseline electrodes, and wherein the set of compensation electrodes comprises the multiple Rx baseline electrodes and the set of Tx baseline electrodes.

15. The method of claim 10 , further comprising measuring noise received through a noise listener electrode contemporaneously with the sensing scan, wherein the noise listener electrode is located in the sensing area and has a surface area substantially equal to a surface area of one of the Rx sensor electrodes, and wherein the set of compensation electrodes co

Assignees

• Cypress Semiconductor Corp

Inventors

• Kravets Igor
• Hoshtanar Oleksandr
• Klein Hans
• Karpin Oleksandr

Classifications

• G06F3/044

  by capacitive means · CPC title

• G06F3/0418

  for error correction or compensation, e.g. based on parallax, calibration or alignment · CPC title

• G06K9/0002 Primary

  Physics · mapped topic

• G06F3/0445 Primary

  using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer · CPC title

• G06V40/1306 Primary

  non-optical, e.g. ultrasonic or capacitive sensing · CPC title