IE62259B1

IE62259B1 - Means for transmitting high frequency signals

Info

Publication number: IE62259B1
Application number: IE220288A
Authority: IE
Inventors: Helmut Hagg; Karl Schulze-Buxloh; Gunter Thoenneben; Peter Zamzow
Original assignee: Rheydt Kabelwerk Ag
Priority date: 1987-07-20
Filing date: 1988-07-19
Publication date: 1995-01-11
Also published as: NO172778C; EP0300147B1; FI883186A0; FI92891B; IE882202L; FI883186A; DE3723951A1; DK255388A; FI92891C; IN170111B; DE3877445D1; NO883211L; ATE84640T1; NO172778B; PT88031B; PT88031A; DK168779B1; ES2038237T3; EP0300147A1; DK255388D0

Abstract

In an arrangement for the transmission of radio frequency signals between a radio frequency line emitting waves and a mobile antenna, the radio frequency line having an inner conductor (1), a coaxial outer conductor (2) and a dielectric (3), and openings being provided in the outer conductor of the radio frequency line for the emission or reception of waves, it is provided that different types of groups of openings (4, 5) are located in the longitudinal direction of the radio frequency line, on different sleeve lines, and that the individual opening in the longitudinal direction of the radio frequency line in the case of one group of openings is at least twice as long as in the case of another group. <IMAGE>

Description

The invention relates to an arrangement for the transmission of high-frequency signals according to the preamble of claim 1.

Radiation coaxial cables are in use for transmitting high-frequency signals in regions with unfavourable propagation conditions for radio waves. Waves are radiated from these cables, for example by reason of the fact that the outer coaxial conductor is provided with openings. A high-frequency radiation coaxial cable of this type is known from DE-OS 28 12 523. In order to achieve a uniform progression of the radiation intensity in the axial direction, a number of holes is provided in the outer conductor. These holes form a pattern which is periodically repeated (leaky cable).

US-PS 3 795 915 discloses a similar cable. By the application of many slots of different lengths and inclinations to the cable axis, the arrangement of which is periodically repeated, such a cable can be operated in a wide frequency range.

In the previously known leaky cables, in the first place, leak waves are emitted through the openings above a limiting frequency which is characteristic of the cable construction. Below the limiting frequency of the cable only a weak surface wave is generated on account of the ' relatively small openings.

V High-frequency lines are also known which have a continuous longitudinal slot (slotted cables). Surface waves are t generated through the longitudinal slot. A limiting frequency that is characteristic of the construction does not exist, but by reason of the steep increase in cable damping with rising frequency, the field of application of these slotted cables is restricted to the frequency range below 200-300 MHz. In addition, the cable damping and the broadcast properties of the slotted cable are adversely affected by environmental influences, such as deposits on the cable coating.

The problem which the invention seeks to solve is to provide an emitter cable with improved broadcast properties. A high-frequency conductor of this kind should be largely unaffected by environmental influences in its broadcast properties, and should emit a broad frequency band. This problem is solved according to the invention, in an arrangement for the transmission of high-frequency signals between a high-frequency line that emits waves, and a mobile antenna, in which the high-frequency line comprises an inner conductor, a coaxial outer conductor and a dielectric, and in which openings are provided in the outer conductor of the high-frequency line for emitting or receiving waves, characterized in that, at least two types of openings of respectively different shape are located on different envelope lines in the longitudinal direction of the high frequency line, in each case a first type of openings being arranged on a first envelotje^Vine, while a second type of openings is located on a second envelope/, in that the ’ openings of the first type are in each case at least twice as long in the longitudinal direction of the high-frequency line than is the case for the second type, and in that the first type of openings is provided for transmission in a lower frequency band, and the second type for transmission in a higher frequency band. The invention represents a combination of a the constructional features of both principles, so that the good properties of the slotted cable come into play in the lower frequency region, and those of the leaky cable in the upper frequency region. The combination of both principles permits the longitudinal slot to be designed narrower (30° radial angle as against 80°) compared with the slotted cable properly so called.

Preferably the openings of the second type are holes, and the openings of the first type are slots which extend esentially in the longitudinal direction of the high-frequency line.

Preferably the length of the slots is greater than the diameter of the high-frequency line, and the radial aperture angle of the slots is from 10 to 40 degrees.

Preferably the openings of the second type have a smaller and longitudinal extenty consist of circular holes, which are arranged essentially parallel to the axis of the nigh- frequency line.

Preferably the openings of each type form a pattern which repeats itself.

One embodiment of the invention will be described in greater detail with reference to the drawing, in which the figure shows a high-frequency cable which consists of the high-frequency line 6 and the sheath 7. The high-frequency line is made up of an inner conductor 1, an outer conductor 2 and a dielectric 3. The outer conductor is provided with openings. The latter have on one side the form of periodic configurations of holes 4, whose diameter is smaller than that of the high-frequency line, and on the other side the form of slots 5, which have a length greater than the diameter of the high-frequency line 6. The long slots have a width which, in a cross-section perpendicular to the axis, corresponds to a radial angle of for example 30°. Holes and slots are, for example, disposed so as to extend helically around the axis with a large pitch, so that both holes and slots are respectively located on the travel pathway side of the high-frequency line at centres spaced a few meters apart.

A protective sheath 7 is extruded around the high-frequency line, and consists of a material with the smallest possible dielectric losses. Such a material is, for example, po1yethy1ene.

A further preferred embodiment of the invention consists in designing the slots very long compared with the diameter of the high-frequency line, and in providing, for example, only short conducting bridges between the slots at large spacings apart. In the limiting case of vanishingly small bridges or very long slots, only a single slot remains present. This can be preferred for reasons of manufacturing technology. In a further embodiment it is provided that the long slot is likewise designed in helical shape, so that the outer conductor embraces the dielectric better. Apart from that, the helical arrangement ensures that the slot is at one time on the side averted from the travel pathway, and can at another time broadcast on the side facing the travel pathway.

The radiation cable according to the invention is capable of generating the best available and most uniform emissions, for example in the most commonly used bands (4m, 2m, 0.7m bands), with reduced sensitivity to its environment. The invention will mainly be used for the transmission of information in tunnels, and for the transmission of signals to the traffic control centre in railways, but in future it will also be applied on streets and motorways.

It is envisaged that a cable of this type will also be employed as a receiving antenna for data exchange purposes.

As is known from antenna technology, it is desirable to dispose the high-frequency line spaced apart from conducting surfaces. Conducting surfaces in this sense include rails, conductor boards or the like, which serve as reflectors or directors with respect to the receiving or transmitting antenna.

The radiation cable treated by way of example in the description can of course comprise more than two groups of longitudinally extending openings. For example, with three groups the radial angle of separation of any two groups is 120".

Claims

1. Arrangement for the transmission of high-freguency signals between a high-frequency line, which transmits waves, and a mobile antenna, the high-frequency line having an inner conductor, a coaxia 11 outer conductor and a dielectric, and openings for the transmission or reception of waves being provided in the outer conductor of the high-frequency line, characterised in that at least two types of openings of respectively different shape are located on different envelope lines in the longitudinal direction of the high-frequency line, in each case a first type of openings being arranged on a first envelope line, while a second type of openings is located on a second envelope line, in that the openings of the first type are in each case at least twice as long in the longitudinal direction of the high-frequency line than is the case for the second type, and in that the first type of openings is provided for transmission in a lower frequency band, and the second type for transmission in a higher frequency band.

2. Arrangement according to Claim 1, characterised in that the openings of the second type are holes, and in that the openings of the first type are slots which extend essentially in the longitudinal direction of the high-frequency line.

3. Arrangement according to Claim 2, characterised in that the length of the slots is greater than the diameter of the high-frequency line, and in that the radial aperture angle of the slots is 10 to 40°.

4. Arrangement according to one of Claims 1 to 3, characterised in that the openings of the second type having a smaller longitudinal extent consist of circular holes which are arranged essentially parallel to the axis of the high-frequency line.

5. Arrangement according to one of Claims 1 to 4, characterised in that the openings of each type form a pattern which repeats itself. - 8

6. Arrangement according to one of Claims 1 to 4, characterised in that the openings of the first type are replaced by a longitudinally running slot.

7. Arrangement according to one of Claims 1 to 6, characterised in that each type of openings is located alternately on the one hand on the one side and, in an adjacent section, on the opposite side of the high-frequency line.

8. Arrangement as defined in Claim 1, substantially as described herein with reference to and as shown in the accompanying drawings.