Envelope detection device and related communication device

A communication device, comprising:

• a physical layer circuit, comprising:
• an envelope detection circuit, for detecting a transmission signal of a high speed serial communication carried out by the communication device, comprising:
• an operation circuit, for receiving the transmission signal and generating a set of operation outputs according to a difference between the transmission signal and at least one reference signal;
• a reference signal generation circuit, coupled to the operation circuit, for providing the reference signal to the operation circuit, wherein the reference signal generation circuit is operable to provide the reference signal with different levels;
• and
• a comparison circuit, coupled to the operation circuit, for comparing the set of the operation outputs to generate a comparison result;
• wherein the envelope detection device detects a transmission state and a disconnect state of the high speed serial communication based on the reference signal at different levels;
• and
• a medium access control layer circuit, coupled to the physical layer circuit, for providing an output state selection signal to the envelope detection device, allowing the envelope detection device to detect one of the transmission state and the disconnect state of the high speed serial communication, and the reference signal generation circuit determines a level of the reference signal according to the output state selection signal, and the envelope detection device correspondingly generates a state indication signal;
• the medium access control layer circuit operates according to the state indication signal.