Method for supplying power over a coaxial cable and corresponding connector

Description

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a method for supplying power supply over a coaxial cable.

[0002] Methods for supplying power over a coaxial cable are usually used for supplying power up through a coaxial cable to power an antenna mounted preamplifier, the DC power source being located at the bottom of the antenna mast. In addition to power supply, the coaxial cable is used for transmitting the signal to be sent through the antenna.

[0003] A specific Bias T arrangement is necessary for feeding simultaneously DC power and RF signal through the coaxial cable. A bias T is shown on figure 1.

[0004] The bias T shows 2 inputs +DC, RF signal and one output ANT. Input +DC is connected to one wire of the power supply cable, preferably the non ground wire. Input RF signal is a coaxial cable end connector adapted to be connected to a RF signal. Output ANT is also a coaxial cable end connector to which the coaxial cable leading to the antenna can be connected. The function of the Bias T consist in avoiding the DC power supplied to input +DC from looping back to input RF signal and reciprocally to avoid the RF signal from looping back to the DC power input. For this purpose, 2 inductors are connected between input +DC and output ANT which block the 900 1200 MHz RF signal while passing the DC power. Similarly a capacitor is connected between the RF signal input and the antenna output to block the DC power while passing the RF signal.

[0005] The second DC power wire, as well as the outer conductors of all coaxial cable end connectors are put to the ground on the Bias T housing.

[0006] This solution is advantageous since no extra wires are needed to be run toward the antennas for supplying power. One single coaxial cable combines the functionality of power supply and RF supply.

[0007] Since recently remote radio heads where developed where the whole or at least part of the base station hardware needs to be installed close to the antenna making the transport of RF signal through a coaxial cable obsolete. The remote radio heads have to be connected to power supply and to an optical fibre for the digital data transmission which have to run up to the tower. The DC power to be supplied in this configuration has a voltage is in the range of 48 V and a current is in the range of 25 A. The required cable for the power supply may have wires with a cross section of 16 mm².

[0008] The Bias T arrangements presented above have nevertheless the disadvantage not to be able to handle DC current of 25A and more. They are also not designed to connect a 2 wire shielded cable with wire cross sections of 16mm² and more.

[0009] Patents US 5 928032, US 6039 609 and patent applications US 2006/292925 disclose known connector arrangements adapted to connect a two wire cable to a coaxial cable. Patent applications DE 196 53 998 disclose a connector arrangement to be adapted on a coaxial cable.

[0010] It is a particular object of the present invention to provide a solution for supplying power over a coaxial cable mitigating the drawbacks mentioned above.

[0011] Another object of the invention is to provide a corresponding connector for connecting a power supply cable to coaxial cable.

SUMMARY OF THE INVENTION

[0012] These objects, and others that appear below, are achieved by a connector for connecting a 2 wire power supply cable to a coaxial cable according to claim 1, and a method for supplying power over a coaxial cable according to claim 10.

[0013] According to the present invention, the method consists in connecting the one wire of the power cable to the inner conductor of the coaxial cable and connecting the second wire of the power cable to the outer conductor of the coaxial cable.

[0014] This invention presents the advantage that when existing base stations sites of traditional system approach shall be replaced by a remote radio head system, the already installed coaxial cables can be reused for the power supply. Consequently, coaxial cables are reused even if no RF signal is transported any more through the coaxial cable for supplying power to antennas and their associated remote radio heads. Additionally, the coaxial cable can be reused as protection tube of the optical fibre in case the coaxial cable has a hollow inner conductor.

[0015] This invention further presents the advantage that a quite solid connection can be established between both wires of the power cable and both conductors of the coaxial cable so that moisture and dust sealing can be reached easily. This is especially required for DC power with a voltage about 48 V and a current about 25A. The connector presents good contact in term of contact area and contact pressure to the coaxial cable.

[0016] Such connectors avoid the installation of additional power supply cables. At the same time the down time of a base station is reduced when installing the remote radio head system.

[0017] Further advantageous features of the invention are defined in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Other characteristics and advantages of the invention will appear on reading the following description of a preferred embodiment given by way of non-limiting illustrations, and from the accompanying drawings, in which:

• Figure 1 shows a Bias T arrangement known from prior art;
• Figure 2 shows an arrangement power supply cable/connector/coaxial cable according to the present invention;
• Figure 3 shows the different parts of a connector for connecting a power cable to a coaxial cable in their installation position according to the present invention;
• Figure 4a, 4b, 4c show the different parts of a connector for connecting a power cable to a coaxial cable according to the present invention;
• Figure 5 shows another embodiment of the connector according to the present inventon.

DETAILED DESCRIPTION OF THE INVENTION

[0019] Figure 1 has already been described in relation to prior art.

[0020] Figure 2 shows an arrangement comprising a power supply cable a connector and a coaxial cable according to the present invention. The three elements are represented: the power supply cable 21, the coaxial cable 22 and connector 23.

[0021] Power supply cable 21 comprises 2 wires, 211, 212 and optionally braided shield not shown on the figure. Preferably the power supply cable transport power with a voltage of about 48 V and a current of about 25 A. The contact surface of the wire is preferably about 16 mm².

[0022] Coaxial cable 22 comprises an inner conductor 221, an outer conductor 222, a dielectric 223.

[0023] Connector 23 will be further detailed thanks to figures 3 and 4a, 4b, 4c. For the part of the description relating to the connection of the power supply cable respectively the coaxial cable, figure 2 should be preferably referred to.

[0024] Connector 23 comprises a connector front part 231, a connector middle part 232 and a connector back part 233. Connector front part 231 is the interface with the power supply cable 21 while connector back part 233 is the interface with the coaxial cable 22.

[0025] Connector front part 231 are externally preferably cylindrical or conic with an axial hole for power supply cable 21 to be lead thought the hole.

[0026] Connector front part 231 further comprises fixation means to connector middle part 232. Preferably the diameters of both parts are adjusted to each other so that connector middle part 232 can be inserted into connector front part creating a fixed and sealed liaison.

[0027] Connector middle part 232 comprises contacting means preferably in the form of 2 soldered or crimped or clamped contact bushes 2322 each adapted to receive one of the wires 211, 212.

[0028] Connector middle part 232 comprises contacting means preferably in form of a conic inner surface 2321 cooperating with a conic clamping ring 2331 of the connector back part 233. These contacting means are enabling a clamped contact of outer conductor 222 to the middle connector part 232. The connector middle part 232 is arranged to establish a solid contact C1 been one contact bush 2322 and the outer conductor 222 on the one hand and a solid contact C2 between the second contact bush 2322 and the inner conductor221 on the other hand.

[0029] Contact bushes 2322 for the wires of the power supply cables could be separated parts which could be pressed into appropriate holes in the connector middle part 232. Alternatively, the contact bush that contacts the outer conductor of the coaxial cable and connector middle part may be manufactured as one single piece. (Both bushes have to be electrically isolated). The contact bushes 2322 can be made either such that the power supply cable wires are soldered, crimped or fixed with a screw inside them.

[0030] Both contact bushes 2322 are electrically isolated from each other preferably by an isolating material as but not restricted to a plastic ring 2323 Connector middle part 232 is adapted to be fixed thanks to fixations means 2324 as for example spring fingers or screwed contact to coaxial cable 22. Preferably, the fixation is performed in the center of the coaxial cable 22 in the area of the inner conductor 221. Preferably, the contact to the inner conductor 221 of the coaxial cable 22 is made with a self-tapping screw type inner conductor 221. The self-tapping contact would allow using the same connector for coaxial cables made from different suppliers having certain variations of dimensions and wall thicknesses.

[0031] The connector back part 233 may comprises in addition to the clamping ring 2331, o-rings 2332 for establishing a sealed contact with the outer part of the coaxial cable 22.

[0032] Coaxial cable outer conductor 222 is pressed against conic surface 2321 when the connector back part 233 is tightened on coaxial cable 22.

[0033] In the following, the different steps of the process of realizing an arrangement as shown on figure 2 will be detailed:

1. The jacket of coaxial cable 22 is removed to a certain length. Coaxial cable 22 is cut perpendicular to the cable axis.

2. Connector back part 233 is pushed over coaxial cable 22.

3. Coaxial cable outer conductor 222 is flared.

4. fixation means 2324 of connector middle part 232 is screwed/clipped into coaxial cable 22.

5. The connector middle part 232 is pushed on the fixation means.

6. Connector back part 233 is screwed on connector middle part. Other coupling mechanisms are possible

7. Connector front part 231 including gland 2311 is pushed over power supply cable 21.

8. The gland 2311 is closed. Fixation and sealing could also be made by other means.

9. The jacket of power supply cable 21 is stripped to a certain length.

10. The braided shield of the power supply cable is cut to leave only a short section free close to the jacket.

11. The braid is clamped inside the connector front part 231 with nut and washer or similar.

12. Both wires 211, 212 of power supply cable 21 are stripped as required by the bushes 2322.

13. Both wires 211, 212 are formed to a bow to enable some movement of the connector front part 231 relative to the other parts 232, 233 of the connector. Some freedom in relative movement is required for the attachment of both connector parts.

14. The wire ends 211, 212 are attached to the bushes 2322 by either crimping, screwing, soldering or similar.

15. The connector front part 231 is attached to connector middle part 232. The coupling mechanism could be made by a kind of bayonet, thread or similar.

[0034] In another embodiment of the present invention showed on figure 5, it is foreseen to have a optical fiber cable 24 being fed through connector 23. It would be especially advantageous to have the optical fiber cable being inserted in an axial opening of the inner conductor 221 of coaxial cable 22. Coaxial cable 22 would constitute a further protection for the optical fiber cable 24 and would limit the size used for having the optical fiber cable being connected to a remote radio head. The digital signal being forwarded towards the remote radio head through this optical fiber cable. The connector middle part 232 would show an hollow finger resp screw 2324 for letting the coaxial cable go through the connector middle part. In addition, bush 2322 connected to the inner conductor 221 would no more be in the axis of the coaxial cable but ex-centred and electrically connected to finger resp. screw 2324.

Claims

1. Connector (23) adapted to be used for connecting a 2-wire power supply cable (21) to a coaxial cable (22) with an inner (221) and an outer (222) conductor, said connector comprising

- a connector middle part (232) comprising two contact bushes (2322), each of one being adapted for receiving one of the wire (211, 212) of said power cable (21), said connector middle part (232) further comprising means (2321) for connecting electrically one of said contact bushes (2322) to said outer conductor (222) of said coaxial cable (22) and means (2324) for connecting electrically the other contact bush (2322) to the inner conductor (221) of said coaxial cable (22);

- fixation means (233, 2324) for fixing said connector middle part on said coaxial cable (22), and fixation means (231) for fixing said connector middle part on said power supply cable (21);

- wherein said electrical connection between said other contact bush (2322) and said inner conductor (221) of said coaxial cable (22) is obtained by inserting a metallic finger (2324) in an opening of the inner conductor (221) having the size of said metallic finger, said metallic finger being connected to said other contact bush (2322), said metallic finger comprises fixation means (2324) to be fixed in said inner conductor, said fixation means (2324) being in form of spring fingers or a screwed contact.

2. Connector according to claim 1, wherein said electrical connection between said contact bush (2322) and said outer conductor (222) of said coaxial cable (22) is obtained by the cooperation of a conic surface (2321) of said connector middle part electrically connected to said contact bush (2322) and a clamping ring (2331), the outer conductor extremity being flared and pressed between said clamping ring (2331) and said conic surface (2321).

3. Connector according to claim 1, wherein said fixation means for fixing said connector middle part (232) on said power supply cable (21) consists in a connector front part (231) with an opening for letting said power cable being inserted in said connector front part (231), said connector front part being attached to the connector middle part (232).

4. Connector according to claim 1, wherein said fixation means for fixing said connector middle part (232) on said coaxial cable (22) consists in a connector back part (233), said connector back part showing an opening for letting said coaxial cable (22) being inserted in said connector back part, said connector back part being adapted to press said clamping ring (2331) on said outer conductor (222).

5. Connector according to claim 1, wherein said electrical connection between said contact bush (2322) and said inner conductor (221) of said coaxial cable (22) is obtained by screwing a screw (2324) part of said connector middle part in an opening of the inner conductor (221).

6. Connector according to claim 1, further comprising means (2323) for isolating electrically said two contact bushes (2322) from each other.

7. Connector according to claim 1, further comprising an additional opening in said connector middle part (232) for inserting an optical fiber cable through said connector middle part.

8. Connector according to claim 87, wherein said connector middle part comprises a hollow metallic finger (2324) for inserting an optical fiber through said connector middle part.

9. Method for supplying power over a coaxial cable (22), said power being transported by a power supply cable (21) comprising 2 wires, said method comprising the steps of:

- fixing each of said two wires (211, 212) of said power supply cable (21) in a contact bush (2322) of a connector (23);

- fixing and connecting electrically one of said bush (2322) to said inner conductor (221) of the coaxial cable (22) by inserting a metallic finger (2324) in an opening of the inner conductor (221) having the size of said metallic finger, said metallic finger being connected to said contact bush (2322), said metallic finger comprising fixation means (2324) to be fixed on said inner conductor, said fixation means (2324) being in form of sprint fingers or a screwed contact;

- fixing and connecting electrically the other bush (2322) to said outer conductor (222) of the coaxial cable (22).

Ansprüche

1. Konnektor (23), ausgelegt für seine Verwendung zum Verbinden eines Zweileiter-Spannungsversorgungskabels (21) an ein Koaxialkabel (22) mit einem inneren (221) und einem äußeren (222) Leiter, wobei besagter Konnektor umfasst:

- ein Konnektormittelteil (232), welches zwei Kontaktbuchsen (2322) umfasst, von denen jede ausgelegt ist für die Aufnahme eines der Leiter (211, 212) besagten Spannungsversorgungskabels (21), wobei besagter Konnektormittelteil (232) weiterhin Mittel (2321) für das elektrische Verbinden einer der besagten Kontaktbuchsen (2322) mit besagtem äußerem Leiter (222) besagten Koaxialkabels (22) und Mittel (2324) für das elektrische Verbinden der anderen Kontaktbuchsen (2322) mit dem inneren Leiter (221) besagten Koaxialkabels (22);

- Befestigungsmittel (233, 2324) für das Befestigen besagten Konnektormittelteils auf besagtem Koaxialkabel (22) und Befestigungsmittel (231) für das Befestigen besagten Konnektormittelteils auf besagtem Spannungsversorgungskabel (21).

- wobei besagte elektrische Verbindung zwischen besagter anderer Kontaktbuchse (2322) und besagtem inneren Leiter (221) besagten Koaxialkabels (22) erreicht wird durch das Einführen eines Metallfingers (2324) in eine Öffnung des inneren Leiters (221), welche die Größe des besagten Metallfingers hat, wobei besagter Metallfinger mit besagter anderer Kontaktbuchse (2322) verbunden wird, wobei besagter Metallfinger Befestigungsmittel (2324) zur Befestigung in besagtem innerem Leiter umfasst, wobei besagte Befestigungsmittel (2324) Federfinger oder Schraubkontakte sind.

2. Konnektor nach Anspruch 1, wobei besagte elektrische Verbindung zwischen besagter Kontaktbuchse (2322) und besagtem äußerem Leiter (222) besagten Koaxialkabels (22) erreicht wird durch das Zusammenwirken einer konischen Oberfläche (2321) besagten Konnektormittelteils, das elektrisch mit besagter Kontaktbuchse (2322) verbunden ist, und einem Klemmring (2331), wobei das äußere Leiterende sich verdickt und zwischen besagtem Klemmring (2331) und besagter konischer Oberfläche (2321) eingeklemmt wird.

3. Konnektor nach Anspruch 1, wobei besagte Befestigungsmittel zum Befestigen besagten Konnektormittelteils (232) auf besagtem Spannungsversorgungskabel (21) aus einem Konnektorvorderteil (231) mit einer Öffnung bestehen, die dazu dient, besagtes Spannungsversorgungskabel in besagtes Konnektorvorderteil (231) einzuführen, wobei besagtes Konnektorvorderteil am Konnektormittelteil (232) befestigt ist.

4. Konnektor nach Anspruch 1, wobei besagte Befestigungsmittel zum Befestigen besagten Konnektormittelteils (232) auf besagtem Koaxialkabel (22) aus einem Konnektorhinterteil (233) mit einer Öffnung bestehen, die dazu dient, besagtes Koaxialkabel (22) in besagtes Konnektorhinterteil einführen zu können, wobei besagtes Konnektorhinterteil dafür ausgelegt ist, um besagten Klemmring (2331) auf besagten äußeren Leiter (222) zu pressen.

5. Konnektor nach Anspruch 1, wobei besagte elektrische Verbindung zwischen besagter Kontaktbuchse (2322) und besagtem innerem Leiter (221) besagten Koaxialkabels (22) erreicht wird durch das Einschrauben eines Schraubteils (2324) besagten Konnektormittelteils in eine Öffnung des inneren Leiters (221).

6. Konnektor nach Anspruch 1, weiterhin Mittel (2323) für das elektrische Isolieren der besagten zwei Kontaktbuchsen (2322) voneinander umfassend.

7. Konnektor nach Anspruch 1, weiterhin eine zusätzliche Öffnung in besagtem Konnektormittelteil (232) umfassend, das dem Einführen eines Glasfaserkabels durch besagten Konnektormittelteil dient.

8. Konnektor nach Anspruch 7, wobei besagter Konnektormittelteil einen hohlen Metallfinger (2324) umfasst, der dem Einführen eines Glasfaserkabels durch besagten Konnektormittelteil dient.

9. Verfahren zur Spannungsversorgung über ein Koaxialkabel (22), wobei besagte Spannung von einem Zweileiter-Spannungsversorgungskabel (21) transportiert wird, wobei besagtes Verfahren die folgenden Schritte umfasst:

- das Befestigen eines jeden der beiden Leiter (211, 212) besagten Spannungsversorgungskabels (21) in einer Kontaktbuchse (2322) eines Konnektors (23);

- das Befestigen an und elektrische Verbinden einer der besagten Kontaktbuchsen (2322) mit dem besagten, inneren Leiter (221) besagten Koaxialkabels (22) durch das Einführen eines Metallfingers (2324) in eine Öffnung des inneren Leiters (221), welche die Größe des besagten Metallfingers hat, wobei besagter Metallfinger mit besagter Kontaktbuchse (2322) verbunden wird, wobei besagter Metallfinger Befestigungsmittel (2324) zur Befestigung auf dem besagten inneren Leiter umfasst, wobei besagte Befestigungsmittel (2324) Federfinger oder Schraubkontakte sind.

- das Befestigen an und elektrische Verbinden der anderen Buchse (2322) mit besagtem äußerem Leiter (222) des Koaxialkabels (22).

Revendications

1. Connecteur (23) adapté à une utilisation pour raccorder un câble d'alimentation électrique à 2 fils (21) à un câble coaxial (22) avec un conducteur intérieur (221) et un conducteur extérieur (222), ledit connecteur comprenant :

- une partie centrale du connecteur (232) comportant deux douilles de contact (2322), chacune d'entre-elles étant adaptée pour recevoir l'un des fils (211, 212) dudit câble électrique (21), ladite partie centrale du connecteur (232) comprenant en outre des moyens (2321) pour raccorder électriquement l'une desdites douilles de contact (2322) audit conducteur extérieur (222) dudit câble coaxial (22) et des moyens (2324) pour raccorder électriquement l'autre douille de contact (2322) au conducteur intérieur (221) dudit câble coaxial (22) ;

- des moyens de fixation (233, 2324) destinés à fixer ladite partie centrale du connecteur audit câble coaxial (22), et des moyens de fixation (231) destinés à fixer ladite partie centrale du connecteur audit câble d'alimentation électrique (21) ;

- dans lequel ledit raccordement électrique entre ladite autre douille de contact (2322) et ledit conducteur intérieur (221) dudit câble coaxial (22) est obtenu en insérant un doigt métallique (2324) dans une ouverture du conducteur intérieur (221) de la taille du doigt métallique, ledit doigt métallique étant raccordé à ladite autre douille de contact (2322), ledit doigt métallique comprenant des moyens de fixation (2324) destinés à être fixés dans ledit conducteur intérieur, lesdits moyens de fixation (2324) se présentant sous la forme de languettes faisant ressort ou de contact vissé.

2. Connecteur selon la revendication 1, dans lequel ledit raccordement électrique entre ladite douille de contact (2322) et ledit conducteur extérieur (222) dudit câble coaxial (22) est obtenu par l'action conjointe d'une surface conique (2321) de ladite partie centrale du connecteur électriquement reliée à ladite douille de contact (2322) et d'une bague de serrage (2331), l'extrémité du conducteur extérieur étant évasée et serrée entre ladite bague de serrage (2331) et ladite surface conique (2321).

3. Connecteur selon la revendication 1, dans lequel lesdits moyens de fixation destinés à fixer ladite partie centrale du connecteur (232) sur ledit câble d'alimentation électrique (21) consistent en une partie avant du connecteur (231) disposant d'une ouverture pour permettre l'insertion dudit câble d'alimentation électrique dans ladite partie avant du connecteur (231), ladite partie avant du connecteur étant reliée à la partie centrale du connecteur (232).

4. Connecteur selon la revendication 1, dans lequel lesdits moyens de fixation destinés à fixer ladite partie centrale du connecteur (232) sur ledit câble coaxial (22) consistent en une partie arrière du connecteur (233), ladite partie arrière du connecteur disposant d'une ouverture pour permettre l'insertion dudit câble coaxial (22) dans ladite partie arrière du connecteur, ladite partie arrière du connecteur étant adaptée pour appuyer ladite bague de serrage (2331) contre ledit conducteur extérieur (222).

5. Connecteur selon la revendication 1, dans lequel ledit raccordement électrique entre ladite douille de contact (2322) et ledit conducteur intérieur (221) dudit câble coaxial (22) est obtenu en vissant une pièce filetée (2324) de ladite partie centrale du connecteur dans une ouverture du conducteur intérieur (221).

6. Connecteur selon la revendication 1, comprenant en outre des moyens (2323) destinés à isoler électriquement lesdites deux douilles de contact (2322) l'une de l'autre.

7. Connecteur selon la revendication 1, comprenant en outre une ouverture supplémentaire dans ladite partie centrale du connecteur (232) destinée à insérer un câble à fibre optique à travers ladite partie centrale du connecteur.

8. Connecteur selon la revendication 7, dans lequel ladite partie centrale du connecteur comprend un doigt métallique creux (2324) destiné à insérer une fibre optique à travers ladite partie centrale du connecteur.

9. Procédé destiné à alimenter en énergie électrique un câble coaxial (22), ladite énergie électrique étant transportée par un câble d'alimentation électrique (21) comportant 2 fils, ledit procédé comprenant les étapes suivantes :

- fixer chacun desdits deux fils (211, 212) dudit câble d'alimentation électrique (21) dans une douille de contact (2322) d'un connecteur (23) ;

- fixer et raccorder électriquement l'une desdites douilles (2322) audit conducteur interne (221) du câble coaxial (22) en insérant un doigt métallique (2324) dans une ouverture du conducteur intérieur (221) de la taille dudit doigt métallique, ledit doigt métallique étant raccordé à ladite douille de contact (2322), ledit doigt métallique comprenant des moyens de fixation (2324) destinés à être fixés sur ledit conducteur intérieur, lesdits moyens de fixation (2324) se présentant sous la forme de languettes faisant ressort ou de contact vissé ;

- fixer et raccorder électriquement l'autre douille (2322) audit conducteur extérieur (222) du câble coaxial (22).

Drawing