Electromagnetic coupler, wireless terminal including same, and method for designing electromagnetic couplers

A wireless terminal comprising:

• an electromagnetic coupler that communicates signals by using at least one of a longitudinal electrostatic field and a longitudinal induced electric field, the electromagnetic coupler including:
• a ground conductor;
• a radiation conductor composed of a plurality of rectangular conductors connected in series;
• and
• a feeding point formed at one point in a connection of the plurality of rectangular conductors, and
• a communication transmitter and receiver module for modulating and demodulating signals,
• wherein:
• the plurality of rectangular conductors is connected such that each pair of adjacent rectangular conductors form an angle other than π rad;
• a length from the feeding point to either end of the radiation conductor is an integral multiple of λ/4 in electrical length with respect to a wavelength λ of a central frequency of a frequency band of interest of the electromagnetic coupler;
• and
• a signal line of the transmitter and receiver module is connected to the feeding point of the radiation conductor.

A method for designing an electromagnetic coupler that communicates signals by using at least one of a longitudinal electrostatic field and a longitudinal induced electric field, comprising the steps of:

• selecting an initial configuration composed of a ground conductor, a radiation conductor composed of a plurality of rectangular conductors connected in series, and a feeding point formed at one point in connection with the plurality of rectangular conductors;
• assessing whether the selected initial configuration satisfies a desired value of coupling strength in a center of a coupling range or not;
• and
• assessing whether the configuration judged to satisfy the desired value of coupling strength in the center of the coupling range satisfies the desired value of coupling strength throughout the coupling range.