Cable modem

A cable modem comprising:

• an amplifier;
• a switch circuit comprising a P-channel MOS (PMOS) transistor and a first electronic switch;
• a power module configured for providing operating power for the amplifier via the PMOS transistor;
• a monitor module comprising a monitoring signal source coupled to the first electronic switch configured for outputting control signals to the first electronic switch;
• a radio frequency (RF) matching circuit coupled to the first electronic switch, the radio frequency comprising a second electronic switch coupled to the first electronic switch, and an electronic matching device coupled between the second electronic switch and ground;
• and
• a duplexer coupled between the second electronic switch and a signal receiving/transmitting circuit;
• wherein when the monitoring signal source outputs a control signal, both the first electronic switch and the PMOS transistor are turned on, and the power output provides operating power for the amplifier, the second electronic switch is turned off, and the RF matching circuit is electrically isolated from the switch circuit, when the monitoring signal source stops outputting the control signal, both the first electronic switch and the PMOS transistor are turned off to cut off the power to the amplifier, the second electronic switch is turned on, and conducts the RF signal received by the signal receiving/transmitting circuit to the duplexer which further conducts the RF signal to the radio frequency matching circuit.