Simulated signals illustrating vari

Simulated signals illustrating various stages of the lock-in detection process. (A) Transmitted (reference)
signal; (B) signal attenuated by 10 times after passing through the test sample; (C) attenuated signal completely
embedded in noise at a level of 100 times the received signal magnitude; (D) received noisy signal multiplied by the
reference signal, demonstrating successful detection. The mean of the signal in (D) is then used to obtain a final DC
output.