Signal transceiver with enhanced return loss in power-off state

A signal transceiver with enhanced return loss in a power-off state, comprising:

• a connector, for receiving a signal;
• a band-pass filter, coupled to the connector for filtering the signal;
• a front-end module, for de-modulating the signal;
• and
• an impedance transformation circuit, coupled between the band-pass filter and the front-end module for transforming an input impedance of the signal transceiver according to a power state of a power source, comprising:
• an input terminal, coupled to the band-pass filter for receiving the signal;
• an output terminal, coupled to the front-end module for outputting the signal to the front-end module;
• an impedance transforming unit including a first node and a second node;
• and
• a first power source input circuit, coupled to the first node of the impedance transforming unit for providing the power source;
• wherein an impedance at the first node is equivalent to a short circuit and an impedance at the second node is equivalent to an open circuit when the power source is in a power-on state, and the impedance at the first node is equivalent to the open circuit and the impedance at the second node is equivalent to the short circuit when the power source is in a power-off state.