Method and system for processing fingerprint sensing signals and fingerprint identification terminal

• US 9,940,501 B2
• Filed: 10/09/2014
• Issued: 04/10/2018
• Est. Priority Date: 08/15/2014
• Status: Active Grant

• Current Assignee: Shenzhen Goodix Technology Co., Ltd.
• Original Assignee: Shenzhen Goodix Technology Co., Ltd.
• Inventors: Yang, Meng-Ta, Sung, Ming-ju
• Primary Examiner(s): Chu, Randolph I
• Application Number:
  US15/104,495
• Publication Number:
  US 20170147860A1
• Time in Patent Office: 1,279 Days
• Field of Search: None
• CPC Class Codes: G06F 18/00 Pattern recognition
• CPC Class Codes: G06V 10/30 Noise filtering
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing
• CPC Class Codes: G06V 40/1347 Preprocessing; Feature extraction

Abstract

The present invention relates to the field of fingerprint identification technologies, and provides a method and a system for processing fingerprint sensing signals, and a fingerprint identification terminal. The method includes a frequency mixing step by mixing a collected high frequency fingerprint sensing signal with a first high frequency signal to obtain a low frequency signal; and an amplification step by amplifying the low frequency signal. By using the character that capacitance impedance is inversely proportional to signal frequency, the present invention shifts a fingerprint sensing signal with a high frequency into a signal with a low frequency through frequency spectrum shifting and performs signal amplification on the signal with a low frequency, which can overcome the difficulty in amplifying the high frequency fingerprint sensing signal and thus improves the signal-to-noise ratio SNR.

Claims

1. A method for processing fingerprint sensing signals by a circuit, wherein the circuit comprises a frequency mixer and a capacitive feedback amplifier, the method comprising:

mixing, by the frequency mixer, a collected high frequency fingerprint sensing signal with a first high frequency signal to obtain a low frequency signal; and

amplifying, by the capacitive feedback amplifier, the low frequency signal, wherein the capacitive feedback amplifier includes an inverting input end connected to an output end of the frequency mixer, a non-inverting input end connected to a bias voltage, and an output end, wherein a feedback capacitor is connected between the inverting input end and the output end of the capacitive feedback amplifier.

2. The method according to claim 1, wherein the circuit further comprises a voltage-current converter, and before the frequency mixing step the method further comprises:

converting, by the voltage-current converter, a collected high frequency fingerprint sensing signal in a voltage form into a high frequency fingerprint sensing signal in a current form; and

performing the frequency mixing step based on the high frequency fingerprint sensing signal in the current form.

3. A system for processing fingerprint sensing signals, the system comprising:

a frequency mixer configured to mix a collected high frequency fingerprint sensing signal with a first high frequency signal to obtain a low frequency signal; and

a capacitive feedback amplifier configured to perform amplification of the low frequency signal, wherein an inverting input end of the capacitive feedback amplifier is connected to an output end of the frequency mixer, a feedback capacitor is connected between the inverting input end and an output end of the capacitive feedback amplifier, and a non-inverting input end of the capacitive feedback amplifier is connected to a bias voltage.

4. The system according to claim 3, wherein the system further comprises:

a voltage-current converter configured to convert a collected high frequency fingerprint sensing signal in a voltage form into a high frequency fingerprint sensing signal in a current form and output the high frequency fingerprint sensing signal in a current form to the frequency mixer, so that the frequency mixer performs frequency mixing based on the high frequency fingerprint sensing signal in a current form.

5. The processing system according to claim 4, wherein the voltage-current converter comprises:

a first switch tube, wherein a first end of the first switch tube is connected to a power supply, and a control end of the first switch tube is connected to a bias voltage;

a second switch tube, wherein a first end of the second switch tube is connected to a second end of the first switch tube, a second end of the second switch tube is served as an output end and is connected to an input end of the frequency mixer, and a control end of the second switch tube is configured to input the high frequency fingerprint sensing signal in a voltage form; and

a third switch tube, wherein a first end of the third switch tube is connected to the second end of the first switch tube, a second end of the third switch tube is connected to the ground, and a control end of the third switch tube is configured to input a reference voltage.

6. The processing system according to claim 3, wherein the capacitive feedback amplifier comprises:

a fourth switch tube, wherein a first end of the fourth switch tube is connected to a power supply, and a control end of the fourth switch tube is connected to a bias voltage;

a fifth switch tube, wherein a first end of the fifth switch tube is connected to a second end of the fourth switch, and a control end of the fifth switch tube is served as the non-inverting input end of the capacitive feedback amplifier and is connected to a bias voltage;

a sixth switch tube, wherein both a first end and a control end of the sixth switch tube are connected to a second end of the fifth switch tube, and a second end of the sixth switch tube is connected to the ground;

a seventh switch tube, wherein a first end of the seventh switch tube is connected to the second end of the fourth switch tube, a control end of the seventh switch tube is served as the inverting input end of the capacitive feedback amplifier and is connected to the output end of the frequency mixer, and a second end of the seventh switch tube is served as the output end of the capacitive feedback amplifier and is connected to a control end of the seventh switch tube through a capacitor; and

an eighth switch tube, wherein a first end of the eighth switch tube is connected to the second end of the seventh switch tube, a control end of the eighth switch tube is connected to a bias voltage, and a second end of the eighth switch tube is connected to the ground.

11. The fingerprint identification terminal according to claim 4, wherein the capacitive feedback amplifier comprises:

a fourth switch tube, wherein a first end of the fourth switch tube is connected to a power supply, and a control end of the fourth switch tube is connected to a bias voltage;

a fifth switch tube, wherein a first end of the fifth switch tube is connected to a second end of the fourth switch, and a control end of the fifth switch tube is served as a non-inverting input end of the capacitive feedback amplifier and is connected to a bias voltage;

a sixth switch tube, wherein both a first end and a control end of the sixth switch tube are connected to a second end of the fifth switch tube, and the second end of the sixth switch tube is connected to the ground;

a seventh switch tube, wherein a first end of the seventh switch tube is connected to the second end of the fourth switch tube, a control end of the seventh switch tube is served as the inverting input end of the capacitive feedback amplifier and is connected to the output end of the frequency mixer, and a second end of the seventh switch tube is served as the output end of the capacitive feedback amplifier and is connected to a control end of the seventh switch tube through a capacitor; and

an eighth switch tube, wherein a first end of the eighth switch tube is connected to the second end of the seventh switch tube, a control end of the eighth switch tube is connected to a bias voltage, and a second end of the eighth switch tube is connected to the ground.

12. The fingerprint identification terminal according to claim 5, wherein the capacitive feedback amplifier comprises:

a fourth switch tube, wherein a first end of the fourth switch tube is connected to a power supply, and a control end of the fourth switch tube is connected to a bias voltage;

a fifth switch tube, wherein a first end of the fifth switch tube is connected to a second end of the fourth switch, and a control end of the fifth switch tube is served as a non-inverting input end of the capacitive feedback amplifier and is connected to a bias voltage;

a sixth switch tube, wherein both a first end and a control end of the sixth switch tube are connected to a second end of the fifth switch tube, and the second end of the sixth switch tube is connected to the ground;

a seventh switch tube, wherein a first end of the seventh switch tube is connected to the second end of the fourth switch tube, a control end of the seventh switch tube is served as the inverting input end of the capacitive feedback amplifier and is connected to the output end of the frequency mixer, and a second end of the seventh switch tube is served as the output end of the capacitive feedback amplifier and is connected to a control end of the seventh switch tube through a capacitor; and

an eighth switch tube, wherein a first end of the eighth switch tube is connected to the second end of the seventh switch tube, a control end of the eighth switch tube is connected to a bias voltage, and a second end of the eighth switch tube is connected to the ground.

14. The fingerprint identification terminal according to claim 11, wherein the capacitive feedback amplifier comprises:

a fourth switch tube, wherein a first end of the fourth switch tube is connected to a power supply, and a control end of the fourth switch tube is connected to a bias voltage;

a fifth switch tube, wherein a first end of the fifth switch tube is connected to a second end of the fourth switch, and a control end of the fifth switch tube is served as a non-inverting input end of the capacitive feedback amplifier and is connected to a bias voltage;

a sixth switch tube, wherein both a first end and a control end of the sixth switch tube are connected to a second end of the fifth switch tube, and the second end of the sixth switch tube is connected to the ground;

a seventh switch tube, wherein a first end of the seventh switch tube is connected to the second end of the fourth switch tube, a control end of the seventh switch tube is served as the inverting input end of the capacitive feedback amplifier and is connected to the output end of the frequency mixer, and a second end of the seventh switch tube is served as the output end of the capacitive feedback amplifier and is connected to a control end of the seventh switch tube through a capacitor; and

an eighth switch tube, wherein a first end of the eighth switch tube is connected to the second end of the seventh switch tube, a control end of the eighth switch tube is connected to a bias voltage, and a second end of the eighth switch tube is connected to the ground.

7. A fingerprint identification terminal, comprising a plurality of fingerprint sensing pixels distributed in an array manner, wherein each fingerprint sensing pixel is connected to a processing system for fingerprint sensing signals, and the processing system comprises:

a frequency mixer configured to mix a collected high frequency fingerprint sensing signal with a first high frequency signal to obtain a low frequency signal; and

a capacitive feedback amplifier configured to perform amplification of the low frequency signal, wherein an inverting input end of the capacitive feedback amplifier is connected to an output end of the frequency mixer, a feedback capacitor is connected between the inverting input end and the output end of the capacitive feedback amplifier, and a non-inverting input end of the capacitive feedback amplifier is connected to a bias voltage.

8. The fingerprint identification terminal according to claim 7, wherein the processing system further comprises:

a voltage-current converter configured to convert the collected high frequency fingerprint sensing signal in a voltage form into a high frequency fingerprint sensing signal in a current form, and output the high frequency fingerprint sensing signal in a current form to the frequency mixer, so that the frequency mixer perform frequency mixing processing based on the high frequency fingerprint sensing signal in a current form.

9. The fingerprint identification terminal according to claim 8, wherein the voltage-current converter comprises

a first switch tube, wherein a first end of the first switch tube is connected to a power supply, and a control end of the first switch tube is connected to a bias voltage;

a second switch tube, wherein a first end of the second switch tube is connected to a second end of the first switch tube, the second end of the second switch tube is served as an output end and is connected to an input end of the frequency mixer, and a control end of the second switch tube is configured to input the high frequency fingerprint sensing signal in a voltage form; and

a third switch tube, wherein a first end of the third switch tube is connected to the second end of the first switch tube, a second end of the third switch tube is connected to the ground, and a control end of the third switch tube is configured to input a reference voltage.

10. The fingerprint identification terminal according to claim 7, wherein the capacitive feedback amplifier comprises:

a fourth switch tube, wherein a first end of the fourth switch tube is connected to a power supply, and a control end of the fourth switch tube is connected to a bias voltage;

a fifth switch tube, wherein a first end of the fifth switch tube is connected to a second end of the fourth switch, and a control end of the fifth switch tube is served as a non-inverting input end of the capacitive feedback amplifier and is connected to a bias voltage;

a sixth switch tube, wherein both a first end and a control end of the sixth switch tube are connected to a second end of the fifth switch tube, and the second end of the sixth switch tube is connected to the ground;

a seventh switch tube, wherein a first end of the seventh switch tube is connected to the second end of the fourth switch tube, a control end of the seventh switch tube is served as the inverting input end of the capacitive feedback amplifier and is connected to the output end of the frequency mixer, and a second end of the seventh switch tube is served as the output end of the capacitive feedback amplifier and is connected to a control end of the seventh switch tube through a capacitor; and

an eighth switch tube, wherein a first end of the eighth switch tube is connected to the second end of the seventh switch tube, a control end of the eighth switch tube is connected to a bias voltage, and a second end of the eighth switch tube is connected to the ground.

13. The fingerprint identification terminal according to claim 10, wherein the capacitive feedback amplifier comprises:

a fourth switch tube, wherein a first end of the fourth switch tube is connected to a power supply, and a control end of the fourth switch tube is connected to a bias voltage;

a fifth switch tube, wherein a first end of the fifth switch tube is connected to a second end of the fourth switch, and a control end of the fifth switch tube is served as a non-inverting input end of the capacitive feedback amplifier and is connected to a bias voltage;

a sixth switch tube, wherein both a first end and a control end of the sixth switch tube are connected to a second end of the fifth switch tube, and the second end of the sixth switch tube is connected to the ground;

a seventh switch tube, wherein a first end of the seventh switch tube is connected to the second end of the fourth switch tube, a control end of the seventh switch tube is served as the inverting input end of the capacitive feedback amplifier and is connected to the output end of the frequency mixer, and a second end of the seventh switch tube is served as the output end of the capacitive feedback amplifier and is connected to a control end of the seventh switch tube through a capacitor; and

an eighth switch tube, wherein a first end of the eighth switch tube is connected to the second end of the seventh switch tube, a control end of the eighth switch tube is connected to a bias voltage, and a second end of the eighth switch tube is connected to the ground.