Wireless communications device

#The present invention relates to a wireless system; and, more particularly, to a wireless system for use in a low power data communications in a sub-millimeter wave zone whose effective channels are increased in number within a limited frequency range.

#Low power data communications systems capable of non-licensed wireless communications are already in practical use. Such systems do not need any license and are convenient to use. However, when such systems are being used, it is difficult to find out who are using them and how they are being used. Therefore, conventionally, such systems try to detect an interference, and if an interference is found, communications are performed through other channels or stopped until the interference disappears (see, for example, Japanese Laid-Open Applications No. 2001-45538, No. H5-300047 and No. H5-206942). Therefore, additional communications become practically impossible to be performed with such systems when the number of users thereof reaches a certain level.

#This is inevitable in that, since any non-occupied channels can be used by anybody, users of the wireless systems for non-licensed communications, unlike ones for licensed communications, cannot secure specific communications channels for their exclusive use, causing inconveniences to the users thereof.

#The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments, given in conjunction with the accompanying drawings, in which:

#FIGS. 1A and 1B show graphs illustrating antenna gains of an exemplary antenna in a wireless system with respect to H plane and E plane, respectively;

#FIG. 2 illustrates an exemplary arrangement of a wireless system;

#The present invention makes use of a feature of the electromagnetic wave that two electromagnetic waves whose planes of polarization are mutually orthogonal can be used without influencing each other. Thus, it is possible to increase the number of effective channels for a wireless system for a non-licensed communications in a sub-millimeter wave zone by using an antenna having an improved polarization characteristic.

#FIGS. 1A and 1B show graphs illustrating antenna gains of an exemplary antenna in a wireless system with respect to H plane and E plane, respectively. The antenna is a beam antenna of a sharp directivity, having an absolute gain of 31 dBi and a half power angle of 4 degrees. FIGS. 1A and 1B represent normalized antenna gains with respect to H plane and E plane, respectively, when an antenna is set to be orthogonal to a plane of polarization of the wireless system, wherein the normalized antenna gains are obtained by normalizing the antenna gains by a maximum of the antenna gain on the plane of polarization, i.e., the antenna gain at the center of the beam. The targeted value of the antenna gain, which is represented by line segments between −20 dB and −30 dB, can be achieved easily, since the antenna cross-polarization discrimination of 30 dB or more can be secured easily by using current technologies.

#FIG. 2 illustrates an exemplary arrangement of a wireless system. The wireless system 1 includes wireless communications devices 11 and 12 respectively having an antenna and arranged in a direction opposite to each other to perform wireless communications therebetween. Additionally, another wireless system 2 including wireless communications devices 21 and 22 is arranged in parallel with the wireless system 1 in a manner that the wireless communications devices 12 is in line with the wireless communications devices 22, wherein the wireless system 2 uses a channel of a same frequency as that of the wireless system 1. In this case, since the wireless communications devices 11 and 21 are arranged to confront the wireless communications devices 12 and 22, respectively, a considerable degree of interference occurs therebetween. However, by setting the plane of polarization for the wireless system 2 to be different from that for the wireless system 1, interference can be reduced by the cross-polarization discrimination.