PURPOSE: To improve the wide band characteristic and frequency characteristics and to simplify the production of structure by using a folding dipole element and providing passive elements consisting of a linear conductor in parallel with the electrostatic axis in the area surrounded by the elements. ;CONSTITUTION: A folding dipole element 1 is formed by folding a bar-like conductor. The length L in the longitudinal direction (electric-field axis direction) is formed 1/2 of the wave length corresponding to the central frequency of the used frequency band, and when an element 1 is shared by a plurarity of frequency band, it is formed 1/2 of the wave length corresponding to the central frequency of the lower frequency band. A power supply circuit 2 consisting of a balance line and a passive element 3 are provided. The element 3 is placed in parallel with the length of the element 1 in the surface surrounded by the element 1. In the equivalent circuit of the antenna, a serial resonance circuit is formed by a high frequency power supply connection terminal T-T, effective inductance LD of the element 1, effective electrostatic capacity CD, and effective resistance RD. A serial resonance circuit is formed by effective inductance LP of the element 3, effective electrostatic capacity CP and effective resistance RP. Both circuits are coupled by mutual inductance to operate as a complex tuning circuit.;COPYRIGHT: (C)1993,JPO&Japio
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