Introduction to the detector
A detector is a device that detects some useful information in a heartbeat. A device used to identify the presence or variation of a wave, oscillation, or signal. The detector is usually used to extract the information carried. The detector is divided into an envelope detector and a synchronous detector. The output signal of the former is in correspondence with the envelope of the input signal, and is mainly used for demodulation of the standard amplitude modulation signal. The latter is actually an analog multiplier. In order to obtain demodulation, an additional oscillating signal (coherent signal) identical to the carrier of the input signal is required. Synchronous detectors are mainly used for demodulation of single sideband amplitude modulated signals or demodulation of vestigial sideband amplitude modulated signals.