GB2194394A - Co-axial connector with inbuilt electrical circuit - Google Patents

Abstract

A coaxial connector comprises: an outer body in contact with the outer conductor of co-axial cable; a pin (10) forming the inner contact of the connector; and an insulator (19) which separates the pin and the outer conductor of the cable and which carries a circuit. The insulator may be a p.c.b. carrying a filter circuit and contacts for contacting the pin, the outer body, the central conductor of the cable, and a ferrule (9) in contact with the outer conductor of the cable. <IMAGE>

Description

SPECIFICATION Co-axial connector This invention relates to a co-axial connector.

The invention arose in relation to the design of a-radio transceiver having a housing and a co-axial socket mounted on the housing. It was found desirable to include a filter or limiter to remove interference which could be picked up by circuits inside the housing and, more particularly, by a link between those circuits and the aforementioned socket. Naturally it was necessary to minimise the length of any connection between the filter and the socket which connection could itself pick up interference and it was thereore necessary to locate the filter as close as possible to the socket: a requirement which was difficult to meet because of the limited space available.

This invention provides a co-axial connector comprising: an outer body which, in use, makes contact with the outer conductor of a co-axial cable; a pin forming an inner contact of the connector: and an insulator for separating the pin from the outer conductor of the cable; characterised in that the insulator carries a circuit connecting the pin to the inner and/or outer conductor.

Because the connector is effectively part of a co-axial line to which it is connected, it is possible, by using the invention, to eliminate any link between the aforementioned circuit, which will normally be a filter or limiter, and the co-axial line.

The insulator is preferabiy a sheet or board carrying conductive tracks which join elements of the said circuit. Such construction is conducive to mass-production in a method where: printed circuit board techniques are used to form conductive tracks on a relatively large sheet, circuit components e.g. inductors and capacitors are attached to the tracks, and the sheet is then split up to form a large number of small individual boards each carrying one of the said circuits.

One of the conductive tracks is preferably arranged on the board so as to be pressed against the outer body of the plug or socket during assembly thereof to form an earth connection. A compressed rubber ring or other resilient member may be used to maintain the required pressure. In one embodiment of the invention a ferrule is screwed onto the outer body. During assembly one end of a cable is passed through the ferrule and the outer conductor of the cable is then splayed out. The ferrule is then screwed onto the outer body, this process serving to compass the aforementioned resilient body, whose compression then (a) holds the splayed end of the cable outer conductor in contact with the outer body (or another element connected electrically to it) and (b) holds the insulating element against the outer body, ferrule, or other element such as a washer connected electrically to it.It may be desirable to form two earth connections in this way at opposite ends of the insulator. For example, where the circuit is a filter comprising an inductor and two capacitors connecting respective ends of the inductor to earth, both capacitors can be earthed in this way at different positions. This arrangement enables the connections between the capacitors and the earth to be of equal length, avoiding undesirable inbalance at high frequencies.

One way of performing the invention will now be described by way of example with reference to the accompanying drawings in which: Fig. 1 shows an axial cross section through a conventional co-axial socket; Fig. 2 shows an axial cross section through a co-axial socket with an integral filter constructed in accordance with this invention corresponding parts in Figs. 1 and 2 being denoted by the same reference numerals; Fig. 3 shows an enlarged view-of one face of an insulator carrying the filter of Fig. 2; Fig. 4 shows a view of the opposite face of the same insulator; Fig. 5 shows an equivalent circuit to that mounted on the insulator in Figs. 3 and 4; and Figs. 6 to 10 show steps in the manufacture of an insulator like that shown in Figs. 3 and 4.

Fig. 1 shows, for purposes of comparison a known co-axial socket comprising a conductive main body 1 connected to one end of a co-axial cable 2. The latter consists of a signal-carrying inner conductor 3 and shielding braid 4 separated by an insulating layer 5 and surrounded by an outer insulating layer 6.

The inner conductor 3 and insulator 5 of the co-axial cable pass through a compression washer 7, metallic washer 8 and a ferruled metallic washer 9. The ferruled washer 9 has a ferrule or sleeve that is forced between the braid 4 and insulator 5 of the co-axial cable.

This ferrule passes through washers 7 and 8.

The outer insulator 6 is removed from the coaxial cable so that the braid 4 can make contact with the conductive main body. To make this contact the braid 4 is splayed out, passed between ferruled washers 9 and metallic washer 8 and then folded over compression washer 7. Thus when compression washer 7 is compressed it will press braid 4 against the conductive main body 1.

After passing through ferruled washer 9 the inner conductor 3 of the co-axial cable is soldered to the end of contact pin 10, which is female in this illustration but could of course be male. Contact pin 10 is kept central in the main body 1 by insulator 11. Insulator 12 prevents the ferruled metallic washer 9 making contact with the contact pin 10. All the parts are kept in place by shoulder 13 on the main body and flange 14 on the contact pin and by gland nut-15, which when screwed in compresses compression washer 7 and keeps braid 4 in contact with the main body 1.

In use, a screw-threaded section 16 of the main body 1 is used to link up with a male co-axial connector. Also a screw-threaded section 17 together with a nut (not shown) and a flange 18 are used to secure the connector to a housing.

Fig. 2 shows a co-axial connector containing a filter and constructed according to this invention. A co-axial cable is connected through a compression washer 7, a metal washer 8 and a ferruled washer 9 as before.

Between a contact pin 10 and the ferruled washer 9 there is a printed circuit board (P.C.B.) 19 carrying a filter. The filter is formed by a coil 20 and chip capacitors 21 and 22.

Referring to Figs 3, and 4 the P.C.B. 19 has a number of metal plated areas 24 over an insulating substrate 23. In use the contact pin 10 is soldered into a slot 25, the sides of which are metal plated, and the inner conductor 3 of the co-axial cable is soldered to a metal plated area 26.

The P.C.B. 19 is earthed by soldering the ferruled washer 9 (Fig. 2) to the metal plated ends of legs 27 and by the metal plated edges 28 of the P.C.B. abuting the shoulder 29 of the main body 1.

The metal plated areas and components on the P.C.B. are arranged to form an equivalent circuit to that shown in Fig. 5 where the coil 20 and the capacitors 21 and 22 form a filter between two co-axial sections 2 and 32.

The contact pin 10 is held central in the main body 1 by an insulator 11 as in the known arrangement to Fig. 1.

The parts are kept in place by: the insulator 11 and P.C.B. 19 resting on shoulders 13 and 29 respectively: by the flange 14 on the contact pin 10: and by the gland nut 15 which compresses compression washer 7.

The main body 1 has screwthreads 16 and 17 and a flange 18 similar to those denoted by the same reference numerals on Fig. 1.

Although a female connector is shown, a male connector could be constructed in a similar way, requiring only minor changes to the contact pin 10, the insulator 11 and the main body 1.

The P.C.B. 19 is manufactured by a massproduction method as follows. A conventional P.C.B. substrate coated with copper on both sides is drilled and routed, removing the shaded areas, to form the shape shown in Fig. 6 which shows a block of four P.C.B.'s 19 formed in pairs. Resist is then applied to areas 30 where no metal is wanted on the final P.C.B. 19, as shown in Fig. 7, using some standard method such as photo-lithography. Only one face of each P.C.B. 19 is shown because the processing is the same for both faces. The P.C.B.'s 19 are then electroplated with a tin-lead alloy. This forms a metal layer over the exposed edges of the P.C.B.'s 19 as well as the faces. The resist and the metal over it is then removed and the exposed copper etched away, a known technique which need not be detailed. A central hole 31 is then drilled and routed out as shown in Fig. 8. The coil 20 and chip capacitors 21 and 22 are then soldered in position as shown in Fig. 9 and then the P.C.B. 19 is cut free as shown in Fig. 10 and fitted into a co-axial connector.

Although a discrete coil 20 is shown one could, alternatively, be defined on the P.C.B.

19 by appropriately placed metalized areas and through plated holes.

Claims (14)

1. A co-axial connector comprising: an outer body which, in use, makes contact with the outer conductor of a co-axial cable; a pin forming an inner contact of the connector; and an insulator for separating the pin from the outer conductor of the cable; characterised in that the insulator carries a circuit connecting the pin to the inner and/or outer conductor.

2. A co-axial connector according to claim 1 characterised in that the circuit is connected to a contact, also carried by the insulator, which contact is passed against the outer body, or a conductive element in contact with it, to form an earth connection for the circuit.

3. A co-axial connector according to claim 2 characterised by a screw-threaded ferrule which, when tightened, urges the said contact against the outer body.

4. A co-axial connector according to claim 3 characterised by a resiliently compressible member which is compressed when the ferrule is tightened and which, when compressed serves to press the contact against the outer body.

5. A co-axial connector according to claim 3 or 4 characterised by two contacts at opposite ends of the insulator, each of which forms an earth connection to the circuit.

6. A co-axial connector as claimed in any preceding claim characterised in that the insu lator is in the form of a sheet or board and the circuit is formed at least in part by conductive tracks on the sheet or board.

7. A co-axial connector as claimed in claim 6 when dependent on claim 2 characterised in that the contact is formed by a conductive area on the sides of the sheet or board.

8. A co-axial connector as claimed in claim 7 when dependent on claim 3 characterised in that the said conductive area is arranged at an angle to the direction of a force exerted by tightening of the ferrule so as to make good contact with a correspondingly tapered inner surface of the outer body.

9. A co-axial connector as claimed in any preceding claim characterised in that the cir cuit is a filter.

10. A co-axial connector according to claim 9 when dependent on claim 6 in which the filter includes a coil formed by conductive tracks and through plated holes on the sheet or board.

11. A method of producing a circuit for use in a co-axial connector including the steps of; taking an insulating substrate coated with conductive metal on both sides and machining it to cut out the shapes of a plurality of circuit boards; metal plating to provide through plated holes and plated areas on the sides of the circuit boards; etching to form the required conductive and non-conductive areas on the circuit boards; machining holes and edges required to be unplated; attaching circuit components; and then separating the circuit board.

12. A co-axial connector constructed in accordance with claim 1 in which the circuit is constructed in accordance with the method of claim 11.

13. A co-axial connector substantially as illustrated in figure 2 of the accompanying drawings and substantially as described with reference thereto.

14. A method of producing circuit boards for use in co-axial connectors substantially as described with reference to Figs. 6 to 10 of the accompanying drawings.