Conventionally, a technique has been suggested for allowing an electromagnetic field to exist in an interspace area sandwiched between conductive sheets that face each other and for allowing the electromagnetic field to travel in a desired direction by changing the electromagnetic field by changing the voltage between the two conductive sheets or by changing the voltage between the conductive sheets by changing the electromagnetic field so as to transmit an electromagnetic wave. Non-patent document No. 1 shown in the following introduces an electromagnetic wave interface device that transmits/receives signals and receives electric power by electromagnetic wave transmission.
Also, a signal transmission system combined with a signal transmission device is known that transmits signals by changing an electromagnetic field in an interspace area sandwiched between a mesh-like conductor portion and a sheet-like conductor portion and in a transudation area on the outside of the mesh-like conductor portion.
In an electromagnetic wave transmission sheet used for the signal transmission system, the electromagnetic wave intensity in the transudation area is reduced according to the distance from the sheet. For example, the following non-patent document No. 1 discloses that arranging a resistor or an electromagnetic wave absorber at the end of the mesh-like conductor portion of the electromagnetic wave transmission sheet prevents the leakage or reflection of an electromagnetic wave.
[Patent document No. 1] JP 2007-281678
[Non-patent document No. 1] Hiroyuki Shinoda, et al., Method of Simultaneous Signal-Power Transmission Using Surface Microwave (Fundamental theories for ubiquitous and sensor networks, etc.), The Technical Report of The Proceeding of The Institute of Electronics, Information and communication Engineers, Vol. 107, No. 53(20070517) pp. 115-118