| 摘要 |
1327864 Aerials; radio signalling INSTITUT NATIONAL DES INDUSTRIES EXTRACTIVES 19 April 1971 [18 Feb 1970] 21980/71 Headings H4A and H4L A radio communications system which is particularly suitable for use in confined spaces, such as mine workings, comprises a carrier cable of the type in which an outer conductor surrounds one or more inner conductors. Transverse gaps, constituting interruptions, are provided in the outer conductor, and act as radiators. The system also comprises a transmitter, and a plurality of receivers each of which is located within the working range of a respective one of said gaps. As described, a cable comprises a central inner conductor 1, and an outer conductor 2 in which transverse gaps are provided, and which may have a dielectric sheath. Supplementary capacitances are provided by portions 7, 8 for controlling the insertion losses at the gaps. The radiation diagram of a gap exhibits maximum directivity close to the axis of the cable (Fig. 2, not shown). In use, a transmitted signal may be received at one gap and be reradiated by gaps along the cable (Fig. 5, not shown). In-line bi-directional repeaters may be provided which effect a change of frequency as well as amplifying, to avoid instability (Fig. 6, not shown). |
