SYSTEM FOR NON-CONTACT SENSING AND SIGNALLING USING HUMAN BODY AS SIGNAL TRANSMISSION MEDIUM

摘要

The wireless system includes a transmitter 14 and a receiver 22 coupled through a user 10 and an indoor floor 11. The transmitter generates low frequency, low power signals that pass as capacitive current 13 into and out of the user's body through capacitive coupling. Shared indoor floors provide a return path for the current. The transmitter includes an internal electrode 18 and an external electrode and a signal generator 16 for generating a modulation signal and for varying the voltage between the electrodes. The internal electrode is capacitively coupled to the user's body so that the "quasi-electrostatic" field generated from the electrode level causes the displacement current to pass through the user's body. The outer electrode is oriented such that its coupling to the interior floor is stronger than that of the interior electrode, such that the interior floor acts as a return path for current from the receiver. The receiver similarly includes a pair of electrodes 24 and 26 and also includes a detector / demodulator 28 that acquires and tracks the transmitted signal. One of the receiver electrodes 24 is capacitively coupled to the user's body so that a displacement current passing from the body passes through the electrode. This current then flows through the detector circuit to another electrode 26 which is asymmetrically capacitively coupled to the indoor floor to complete the path to the current. The detector circuit operates in a conventional manner to detect current and recover transmission information therefrom. One or more receivers may be carried by the user or may be located in fixed locations around the room, and the return path may be a combination of air and ground. Thus, the user does not need to physically contact the receivers to pass information to the receivers. Alternatively, the receivers can be mounted as an array on a computer screen and the transmitter is placed on a keyboard.