Sheet antenna apparatus

Abstract

A sheet antenna apparatus capable of favorably receiving vertically polarized electromagnetic waves is provided which includes an antenna element 11 comprising a main antenna portion 15 having a vertical segment 19, a pair of upper and lower lateral segments 20 and 21 respectively extending laterally from opposite ends of the vertical segment 19 and a pair of feeder segments 22 respectively extending inwardly from the terminating ends of the lateral segments 20 and 21, and a parasitic antenna element comprising an inner loop portion 16 and an outer loop portion 17 which form a double loop and are disposed as adjoining to one of the lateral segments 20 and 21. The vertical segment 19 of the antenna element 11 substantially coincides with the direction of vertically polarized electromagnetic waves and hence receives vertically polarized electromagnetic waves favorably. Further, when the frequency of received electromagnetic waves is high, the inner loop portion 16 becomes resonant with the main antenna portion 15, while when the frequency of received electromagnetic waves is low, the outer loop portion 17 becomes resonant with the main antenna portion 15. Thus, the antenna apparatus can successfully receive vertically polarized electromagnetic waves within an extensive frequency range.