広角放射特性を有する4線巻き巻き戻しヘリカルアンテナとその最適支持構造

摘要

本稿では，第一に，軸比特性に優れた4線巻きヘリカルアンテナを取り上げ，広角放射特性を有する設計法の明確化と，試作機での実験評価を行う．ヘリカル高さ0.92波長という低姿勢，かつ，ヘリカル素子途中に巻き戻しを装荷することで比帯域9.5％，±80度範囲内で0dBi以上の広角放射特性を実現することを明示する．第二に，振動を伴う劣悪環境下でフイルム樹脂基板を筒状に巻いて構成したヘリカル形状を保持しつつ，特性劣イヒの小さいアンテナ支持構造について検討する．円筒軸上に配した軸棒と，特定間隔で軸棒に固定された円盤状部位とで構成される串型の支持構造を提案している．また，ヘリカル上端部が開放の場合，そこからヘリカル素子線路に沿って電気長で1／4波長分下がった位置から，同じく電気長で半波長の間隔で，円筒フイルム樹脂基板を押さえる円盤状部位を配置する最適構造を示している．%In this report, first a quadrifilar helical antenna is adopted due to its good performance in the axial ratio, and its design method in order to realize a broad beamwidth is clarified and then experimental estimation of antenna performances by a prototype is carried out. It is specified that the antenna achieves remarkable performances, which are a fractional bandwidth of 9.5 % and 0 dBi or more within the range of ± 80 degrees, by installing rewind of wires under the condition of a low profile, 0.92 λ (λ: wavelength at design frequency in the free space) in height. Second, an antenna support structure to maintain the helical form that rolls the film resin substrate cylindrical, and to suppress deterioration in antenna performances under poor surroundings with vibrations is examined. We propose a new type of support structure composed of the stick arranged on the cylinder axis and disks fixed to it, which have a function that holds the cylindrical film, at specific intervals. Additionally, the optimized structure is investigated that its disks are arranged from the position that fell down from the top of the helical opened by 0.25 λ_g (λ_g: electricity wavelength) along on the helical element at 0.5 λ_g intervals.