Radiating coaxial cable

Details Radiating coaxial cable Radiating coaxial cable

1998-08-18

2001-06-12

Dinkins, Anthony (Department: 2831)

Electricity: conductors and insulators

Conduits, cables or conductors

Conductive armor or sheath

C174S1020SP

Reexamination Certificate

active

06246005

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates to a radiating coaxial high-frequency cable with openings in the outer conductor which are in the form of slots arranged substantially perpendicular to the cable axis and which are configured in sections which are arranged consecutively without gaps in the longitudinal direction of the cable and whose axial length is dimensioned according to the high-frequency energy to be transmitted, wherein the number of slots is greater in the sections which are farther away from the feed location of the high-frequency energy than in the sections which are closer to the feed location.
2. Description of the Prior Art
Radiating coaxial high frequency cables—hereinafter called “RHF-cables—operate essentially as antennae as a result of the electromagnetic energy which is transmitted to the outside through the slots in the outer conductor. These cables enable communication between transmitters and receivers which move relative to each other. The intensity of the radiated power decreases along the length of the RHF cable due to cable damping (longitudinal damping) and because HF energy is radiated (coupling damping). Consequently, the so-called “system damping” which is the sum of the longitudinal damping and coupling damping—for example between an antenna of a vehicle and a RHF cable—increases with increasing cable length measured from the location where the HF energy is fed into the RHF cable. To keep the field strength which is received by a receiver moving along the RHF cable, at least approximately constant, the effect of the longitudinal damping of the RHF cable described in DE 41 06 890 A1 is compensated with the help of a special slot configuration. The number of the slots along the cable increases here according to a predetermined rule. The cable with this configuration can then made longer than a RHF cable with a uniform slot arrangement. Nonetheless, the length of the RHF cable along which a “usable” signal can be received or coupled in, remains relatively short, in particular at higher operating frequencies.
A conventional RHF cable can operate over a greater length by using the cable design according to EP 0 643 438 A1. This RHF cable has consecutive sections wherein each section has a different number of slots. The electrically effectual size of the openings formed by the slots increases with increasing distance from the location where the HF energy is injected into the cable. The longitudinal damping of the longer RHF cable is also compensated, providing greater flexibility for tuning important properties of the transmission system. The cable also requires a lesser number of amplifiers and feed locations along the cable run. This RHF cable has proven effective in practice. However, the “usable” length of the cable—as defined above—is still limited, in particular at higher frequencies.
SUMMARY OF THE INVENTION
It is an object of the invention to improve the RHF cable described above so as to further increase its length without additional amplifiers and feed locations, in particular at higher frequencies.
This object is solved with the invention by arranging several sections with an identical number of slots consecutively without gaps, provided that the effectual opening of subsequent sections is increased when the system damping between the high-frequency cable and an antenna located outside the cable reaches a predetermined value.
The distance which can be covered with the RHF cable designed in this fashion, can be readily increased without requiring additional amplifiers or additional injection of HF energy. The effectual opening in the outer conductor of the RHF cable can be enlarged with increasing distance from the location where the HF energy is injected, by providing more slots which can be made of different size. In each section a sufficient number of larger slots can then advantageously be arranged on the outer conductor even if the sections of the RHF cable are relatively short in the axial direction and frequency-dependent. The original goal of attaining a “larger opening with increasing distance from the feed location” can thereby be met. In the sections which have a greater distance from the feed location, only slots which are quite long in the direction of the circumference, are provided in the outer conductor. A RHF cable designed in this fashion is easier to manufacture since, for example, only two different stamping tools are required to machine the slots. The smaller slots can be stamped first, while the longer slots are stamped later. It is possible to interleave sections with slots of different slot lengths.


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