Human body communication device having single electrode

1. A human body communication device comprising:

an electrode;

a matching circuit connected to the electrode and configured to provide an impedance matching;

a switch configured to provide a first path that is electrically connected to the matching circuit in a first state, and to provide a second path that is electrically connected to the matching circuit in a second state;

a sensor, in the first state, connected to the matching circuit through the first path of the switch, configured to output a first sensing signal to the matching circuit through the switch, and configured to output a second sensing signal when a difference between a signal that is generated from the matching circuit in response to the first sensing signal and the first sensing signal is greater than or equal to a threshold;

a transmitter, in the second state, connected to the matching circuit through the second path of the switch, and configured to output a data signal to the matching circuit through the switch; and

a controller configured to control the switch from the first state to the second state in response to receiving the second sensing signal from the sensor, in the first state.

2. The human body communication device of claim 1 , wherein, in the first state, the controller is further configured to control the sensor in an active mode and control the transmitter in a power saving mode.

3. The human body communication device of claim 1 , wherein, in the second state, the controller is further configured to control the sensor in a power saving mode and control the transmitter in an active mode.

4. The human body communication device of claim 1 , wherein the transmitter is further configured to output fixed information as the data signal in response to that the switch enters the second state from the first state.

5. The human body communication device of claim 1 , wherein, in the second state, the controller is further configured to control the switch from the second state to the first state in response to that the transmitter completes an output of the data signal.

6. A human body communication device comprising:

an electrode;

a matching circuit connected to the electrode and configured to provide an impedance matching;

a switch configured to provide a first path that is electrically connected to the matching circuit in a first state, and to provide a second path that is electrically connected to the matching circuit in a second state;

a sensor, in the first state, connected to the matching circuit through the first path of the switch, configured to output a first sensing signal to the matching circuit through the switch, and configured to output a second sensing signal when a difference between a signal that is generated from the matching circuit in response to the first sensing signal and the first sensing signal is greater than or equal to a threshold;

a receiver, in the second state, connected to the matching circuit through the second path of the switch, and configured to receive a data signal from the matching circuit through the switch; and

a controller configured to control the switch from the first state to the second state in response to receiving the second sensing signal from the sensor, in the first state.

7. The human body communication device of claim 6 , wherein, in the first state, the controller is further configured to control the sensor in an active mode and control the receiver in a power saving mode.

8. The human body communication device of claim 6 , wherein, in the second state, the controller is further configured to control the sensor in a power saving mode and control the receiver in an active mode.

9. The human body communication device of claim 6 , wherein, in the second state, when an idle time for which the data signal is not received is longer than a threshold, the controller is further configured to control the switch from the second state to the first state.

10. A human body communication device comprising:

an electrode;

a matching circuit connected to the electrode and configured to provide an impedance matching;

a switch configured to provide a first path that is electrically connected to the matching circuit in a first state, and to provide a second path that is electrically connected to the matching circuit in a second state;

a sensor, in the first state, connected to the matching circuit through the first path of the switch, configured to output a first sensing signal to the matching circuit through the switch, and configured to output a second sensing signal when a difference between a signal that is generated from the matching circuit in response to the first sensing signal and the first sensing signal is greater than or equal to a threshold;

a transceiver, in the second state, connected to the matching circuit through the second path of the switch, and configured to output a first data signal to the matching circuit through the switch or to receive a second data signal from the matching circuit; and

a controller configured to control the switch from the first state to the second state in response to receiving the second sensing signal from the sensor, in the first state.

11. The human body communication device of claim 10 , wherein, in the first state, the controller is further configured to control the sensor in an active mode and control the transceiver in a power saving mode.

12. The human body communication device of claim 10 , wherein, in the second state, the controller is further configured to control the sensor in a power saving mode and control the transceiver in an active mode.

13. The human body communication device of claim 10 , wherein, in the second state, when an idle time for which the first data signal is not output and the second data signal is not received is longer than a threshold, the controller is further configured to control the switch from the second state to the first state.