Phase-locked amplifier

Abstract

The invention provides a lock-in amplifier. The lock-in amplifier comprises an input channel module, an analog-to-digital conversion module and a digital processing module, the input channel module is used for amplifying a to-be-detected input signal to obtain a to-be-detected analog signal, and the input channel module comprises a voltage input mode and a current input mode; the analog-to-digital conversion module is used for converting a to-be-detected analog signal according to a preset sampling conversion rate to obtain a to-be-detected digital signal; the digital processing module is used for processing a to-be-detected digital signal to obtain a phase-locked detection result, the phase-locked detection result comprises an X demodulation component and a Y demodulation component, a chip-based phase-locked amplifier can be realized by adopting a CMOS (Complementary Metal-Oxide-Semiconductor Transistor) technology, the size of the chip-based phase-locked amplifier is centimeter-level, and the chip-based phase-locked amplifier has multiple working modes and configurable gains so as to realize weak signal detection; the weak signal detection scene with strict requirements on the size can be met, and the problem that the size of an existing commercial phase-locked amplifier is usually decimeter-level and the application scene is limited is solved.

Claims

1. A lock-in amplifier, characterized in that: include: Input channel module, analog-to-digital conversion module and digital processing module; The input channel module is used to amplify the input signal to be measured to obtain the analog signal to be measured, and the input channel module includes a voltage input mode and a current input mode; The analog-to-digital conversion module is used to convert the analog signal to be tested into a digital signal to be tested according to a preset sampling conversion rate; The digital processing module is used to process the digital signal to be tested to obtain a phase-locked detection result, and the phase-locked detection result includes an X demodulation component and a Y demodulation component.

2. The lock-in amplifier according to claim 1, characterized in that: The input channel module includes: a primary amplification module, an AC / DC coupling switching module, a secondary amplification module and a filtering module; The primary amplification module is connected to the filtering module via the AC / DC coupling switching module and the secondary amplification module in sequence; The input end of the first-stage amplification module serves as the receiving end of the input channel module to receive the input signal to be measured; the output end of the filtering module serves as the output end of the input channel module to output the analog signal to be measured.

3. The lock-in amplifier according to claim 2, characterized in that: The first-stage amplification module includes: a first resistor, a second resistor, a third resistor, an operational amplifier, a first switch and a second switch; The fixed end of the first switch serves as the input end of the first-stage amplification module; the first moving end of the first switch is connected to one end of the first resistor; the second moving end of the first switch is respectively connected to the other end of the first resistor, the fixed end of the second switch and the inverting input end of the operational amplifier; the first moving end of the second switch is connected to one end of the second resistor; the second moving end of the second switch is connected to one end of the third resistor; the in-phase input end of the operational amplifier is grounded; the output end of the operational amplifier is respectively connected to the other end of the second resistor and the other end of the third resistor, and the connection point serves as the output end of the first-stage amplification module.

4. The lock-in amplifier according to claim 2, characterized in that: The AC / DC coupling switching module includes: a third switch and a capacitor; The fixed end of the third switch serves as the input end of the AC / DC coupling switching module; the first moving end of the third switch is connected to one end of the capacitor; the second moving end of the third switch is connected to the other end of the capacitor, and the connection point serves as the output end of the AC / DC coupling switching module.

5. The lock-in amplifier according to claim 2, characterized in that: The secondary amplification module includes: a differential amplifier, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a fourth switch and a fifth switch; One end of the fourth resistor serves as the input end of the secondary amplification module; the other end of the fourth resistor is respectively connected to the fixed end of the fourth switch and the inverting input end of the differential amplifier; the first moving end of the fourth switch is connected to one end of the fifth resistor; the second moving end of the fourth switch is connected to one end of the sixth resistor; the inverting output end of the differential amplifier is respectively connected to the other end of the fifth resistor and the other end of the sixth resistor, and the connection point serves as the first output end of the secondary amplification module; The in-phase input terminal of the differential amplifier is respectively connected to one end of the seventh resistor and the fixed end of the fifth switch; the other end of the seventh resistor is grounded; the first moving end of the fifth switch is connected to one end of the eighth resistor; the second moving end of the fifth switch is connected to one end of the ninth resistor; the in-phase output terminal of the differential amplifier is respectively connected to the other end of the eighth resistor and the other end of the ninth resistor, and the connection point serves as the second output terminal of the secondary amplification module.

6. The lock-in amplifier according to claim 2, characterized in that: The filtering module includes: a sixth switch, a first filter and a second filter; The fixed end of the sixth switch serves as the input end of the filtering module; the first movable end of the sixth switch is connected to the input end of the first filter; the second movable end of the sixth switch is connected to the input end of the second filter; the output end of the first filter is connected to the output end of the second filter, and the connection point serves as the output end of the filtering module.

7. The lock-in amplifier according to claim 1, characterized in that: The analog-to-digital conversion module includes: an analog-to-digital converter; the input end of the analog-to-digital converter serves as the input end of the analog-to-digital conversion module to receive the analog signal to be tested; the output end of the analog-to-digital converter serves as the output end of the analog-to-digital conversion module to output the digital signal to be tested.

8. The lock-in amplifier according to claim 1, characterized in that: The digital processing module includes: a first mixer, a second mixer, a third filter, a fourth filter, a first signal generator and a second signal generator; The first mixer is connected to the first signal generator and the third filter respectively, an input end of the first mixer receives the digital signal to be measured, and an output end of the third filter outputs the X demodulation component; The second mixer is connected to the second signal generator and the fourth filter respectively. The input end of the second mixer receives the digital signal to be measured, and the output end of the fourth filter outputs the Y demodulation component.

9. The lock-in amplifier according to claim 8, characterized in that: The first signal generator and the second signal generator are direct digital frequency synthesizers.

10. The lock-in amplifier according to claim 8, characterized in that: The first mixer and the second mixer are digital multipliers.

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