| 摘要 |
Relatively small omnidirectional antennas ( 2,3 ) with sufficient antenna impedance for exchanging radio frequency signals are provided with two parallel elements ( 21,22 ) coupled to each other via their outer ends. Each element ( 21,22 ) comprises two subelements ( 23,24,25,26 ) separated by a gap ( 27,28 ). The elements ( 21,22 ) have lengths smaller than half the wavelength of the radio frequency signals. The antennas ( 2,3 ) do not need to be operated against a ground surface, and can be used in a non-horizontal position. The elements ( 21,22 ) are planar elements. The antennas ( 2,3 ) further comprise two further elements ( 41,42 ) located in a plane parallel to a plane of the elements ( 21,22 ). This increases the impedance and improves the return loss of the antennas ( 2,3 ). One of the further elements ( 41 ) comprises two sub-elements ( 43,44 ) separated by a gap ( 47 ), to realise a simulated return loss with one dip. Alternatively, the other further element ( 42 ) comprises a gap, to realise a simulated return loss with two dips for dual-band environment.
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