Lock-in augmented XIVA significantly improves the sensitivity of the system through the implementation of a lock-in amplifier. The lock-in amplifier modulates the laser signal while sampling the output of the XIVA sensor. Utilizing this technique, we are able to realize a Q greater than 100,000.
The lock-in amplifier system consists of five major components:
- Input Signal
- Reference Signal
- Mixer/Multiplier
- Integrator/Low Pass Filter
- Voltage Amplifier
.
The input signal ( ) is the signal sample from the device or system under test.
The reference signal ( ) is the signal generated by the lock-in amplifier.
The multiplier is essentially a mixer where the input signal and reference signal are mixed to produce the sum and difference signals. The output of this multiplier is can be represented by the following formula: