GB1307496A - Wide-band antenna - Google Patents

Abstract

1307496 Aerials TOKYO SHIBAURA ELECTRIC CO Ltd 25 May 1971 [25 May 1970] 17001/71 Heading H4A In a wideband dipole aerial of overall length 2l 2 cms. a series capacitor C 1 is disposed in each arm at a distance l 1 cms. from the feed centre, and the following relationships hold: l 1 /l 2 =0À4 to 0À6; 2log e 2l 2 /p<12 (p = radius in cms. of any portion of the dipole arms); C 1 = 0À025l 2 to 0À3l 2 pico-farads. As described, each dipole arm may comprise two tubular portions 8, 9, Fig. 3, a coaxial rod portion 10, and inner and outer insulating portions 11, 12 of, for example, phenol resin or ABS terpolymer. The capacitor C 1 is formed between the arm portions and the central conductor as well as between the facing ends of the arm portions. In a second embodiment, a rod-like first portion of each arm is located for an appropriate distance within a tubular second portion, with insulating material intervening (Fig. 4, not shown). In a third embodiment, first and second portions of each arm overlap, with insulating material between (Fig. 5, not shown). In a fourth embodiment, the ends 19, 20, Fig. 6, of first and second tubular arm portions 17, 18 are compressed flat and are inclined in opposite directions with respect to the axis. The said ends are spaced apart, and insulating material 11 is moulded around them. A Yagi-type aerial may incorporate an active dipole element of the kind described, together with a reflector and directors (Fig. 11, not shown). In order to increase the operating bandwidth, each dipole arm may comprise a plurality of rods in parallel (Fig. 12, not shown).