GB2244870A - Aerial cable terminal device - Google Patents

Abstract

A terminal device for connecting a coaxial cable (7) to an aerial consisting of printed conductor (6a, 6b) comprises a fitting (10a) to fix the braided outer conductor (7b) of the coaxial cable to the printed conductor (6b). The braided outer conductor (7b) of the coaxial cable may be secured to the fitting (10a) by soldering. Leg portions of the fitting (10a) are soldered (8a, 8b) onto the printed conductor (6b). A similar fitting (10b) may be provided for securing the inner conductor (7a) of the coaxial cable. A cover (not shown) may be provided to enclose and protect the terminal device. <IMAGE>

Description

CA3LE TERMINAL DEVICE 1. Field of Invention This invention relates to a terminal device for a print antenna, more specifically, to a terminal device which is preferably applied to a terminal portion of a glass print antenna of an automobile.

2. Description of the Prior Art A double loop antenna as a UHF band antenna to be attached on a window glass of an automobile is known (Japanese Patent application laid open No. 69704/87 or U.S.

Patent No. 4,721,964). The double loop antenna consists of a pair of semiloop conductors of half wavelength branched from a feed terminal laterally in both right and left directions along a grounded conductor. Both ends of respective semiloop conductors are grounded and the feed terminal is unbalanced power feed.

Fig. 11 shows prior art in which the abovementioned double loop antenna is formed on a glass window of an automobile with a printing process.

In Fig. 11, a numeral 1 denotes a transmission/reception antenna for a mobile telephone. The double loop antenna is printed on a rear window glass 2 together with defogging heater wires 3 and an antenna conductor 4 for receiving radio frequency (FM and AM). The transmission/reception antenna 1 is arranged along a body 5 and composed of a pair of semiloop elements la and ib branched from a feed termna 6a in right and eft directions.A ine conductor ic is coupled between both ends of respective elements la and ib so as to close recesses of the elements la and ib. A core conductor of a coaxial feeder cable 7 is connected to the feed terminal portion 6a. An outer conductor of the feeder cable 7 is connected to a terminal portion 6b on the line conductor Ic.

Unbalanced power feed is thus performed.

The transmission/reception antenna has characteristics with sufficient gain and is almost nondirectional in an UHF band from 850 to 950 MHz.

Fig. 12 shows an enlarged view of an example of a feeding portion of the transmission/reception antenna 1 of Fig. 11. The core conductor 7a is soldered to the feed terminal portion 6a and the outer conductor 7b (braided wire) is solder-connected to the terminal portion 6b.

The construction of the feed terminal portion of Fig. 12 is weak in. strength by for example a vibration of the cabie, resulting in breaking of wires. Impedance varies at an untwisted end of the outer conductor 7b which results in variation of VSWR and uncertain impedance matching between the cable 7 and the antenna 1. It is also unsightly due to solder connection by hand.

SUMMARY OF THE INVENTION It is an object of this invention to provide a terminal device for a printed antenna from which the above problems are removed.

The terminal device according to the present invention makes a coaxial cable to be connected tightly to the antenna consisting of printed conductors (la,lb, ic, 6a, 6b) and comprises a fitting portion 11 to fix and/or insert an outer conductor 7b of the coaxial cable 7 and leg portions 12a, 12b each extending from or carrying the fitting portion 11; the outer conductor 7b of the coaxial cable 7 being secured to the fitting portion 11 and said leg portions 12a, 12b being soldered onto one of the printed conductor. In accordance with an aspect of the present invention, the terminal device is fixed securely to the flexible cable, and provides a uniform connecting construction, resulting in little variation of VSWR for a stable transmission/reception.

BRIEF DESCRIPTION OF THE DRAWINGS Figs. 1 - 3 are a plane view, side view and a sectional view respectively illustrating a connection feature according to this invention; Fig. 4 is a perspective view of the terminal device; Fig. 5 is a view showing an end portion of a coaxial feeder cable; Fig. 6A is a graph of VSWR; Fig. 6B is a view showing a connection o a coaxial cable used in the VSWR measurement; Figs. 7A and 7B are plane view and a side view of an example with a waterproof cap provided to the terminal portion; Fig. 8 is a view showing a modification of the terminal device; Figs. 9 and 10 are a plane view and a side view showing another modification of Figs. 1 and 2; Fig. 11 is view showing a conductor pattern of a glass window antenna of an automobile according to prior art;; Fig. 12 is a detailed view showing a terminal connection of a coaxial cable of Fig. 11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Figs. 1 - 3 respectively show a plane view, a side view and a sectional view along the X-X line in Fig. 2 illustrating a terminal device according to this invention which is applied to a glass print antenna. A conductor pattern of the antenna is identical to that in Fig. 11, though the pattern is not limited to this illustration.

In this embodiment, large and small metal members 10a and 10b each shaped into a letter "Q" as shown in a perspective view of Fig. 4 are employed. The large metal member or fitting 10a is used with an outer or clad conductor 7b of a flexible cable 7 while the small metal member or fitting 10b is used with an inner or core conductor 7a of the cable. These metal members 10a and 10b have figures similar to each other, and formed of copper or copper alloy such as brass or phosphor bronze in view of good solderability. The respective terminal metal members 10a and 10b consists of a cable fixing portion 11 having "U" shape and a pair of leg portions 12a and 12b each extending from the fixing portion.The U-shaped fixing portion II of the large terminal metal member 10a has an inner diameter corresponding to the outer diameter of the outer or clad conductor (braided wires) 7b of the coaxial feeder cable 7 as shown in Fig. 5. The U-shaped fixing portion 11 of the small terminal metal member 10b has an inner diameter corresponding to the outer diameter of the core conductor 7a of the feeder cable 7.

As shown in Fig. 5, the outer insulator, the clad conductor 7b and an intermediate insulator 7c are peeled off at end portion thereof so that respective top portion of the clad conductor 7b, intermediate insulator 7e and core conductor 7a is exposed in predetermined length. The terminal metal members 10a and 10b are fixed onto the feed terminal portion 6a and terminal portion 6b of the antenna 1 with solder. The end portion of the feeder cable 7 is inserted into the terminal metal members Ga and lOb so the core conductor 7a and the clad conductor 7b are connected to the terminal metal members 'Ga and 1Gb respectively with solder.

In this example, as shown by a sectional vie of Fig. 3, solder connections 8a and 8b are provided between the leg portions 12a and 12b of the terminal metal member IOa and the terminal portion 6b while a solder connection Sc is provided between the outer conductor 7b of the feeder cable 7 and the U-shaped fixing portion 11. For strong fixing, each of the solder connections 8a and 8b is preferably made without an excess of solder.

Tt is therefore desirable to provide an interval or space from 0.5 to 1 mm between the solder connections Sa and 8b and the terminal portion 6b.

A similar constItution of solder connection between the small terminal metal member 10b and the core conductor 7a may be applied. As shown in Fig. 2, the Ushaped fixing portion 11 of the terminal metal member iOb is located above the leg portions 12a and 12b with an interval corresponding to radius of the cable 7.

Only the large terminal metal member 10a may be used without the small terminal metal member 10b so that the core conductor of the cable 7 is directly connected on to the terminal portion 6a by solder.

A tensile strength along the cable was tested or measured for five times for such a direct connection as shown in Fig. 12 and the present indirect connection as shown in Figs. 1 to 3. The average tensile strength for the direct connection is 10 Kg while that of the indirect connection is 30 Kg.

In the terminal constitution of the embodiment, it is preferable to set the length from the top of the clad conductor 7b to the end of the core conductor 7a to be within 5 mm in order to neglect influence on VSWR. The connecting configuration between the outer conductor 7b and the terminal metal member 10a is regulated for every products free from untwisting the braided wires, resulting in less variation of VSWR to allow a stable transmission/reception of a signal.

Fig. 6A shows a graph of VSWR for various length Q of the core conductor 7a as to a test sample in which a core conductor 7a and an outer conductor 7b of a coaxial feeder cable 7 are directly connected to a receptacle 20 which is terminated by a load 21 of 50 ohm as shown in Fig. 6B. It is apparent from the graph that effect on VSWR is eliminated for Q less than 5 mm.

Figs. 7A and 7B show an example in which a cap 14 made of synthetic resin is attached to the terminal portion by a bonding agent for improving waterproofing and anticorrosion.

Fig. 8 shows an example of a terminal metal member consisting of a cylindrical fixing portion 15 and a pair of leg portions 16a and 16b attached to the fixing portion. In this example, the feeder cable 7 is inserted Lte the cylindrical fixing portion 15, then the fixing portion is caulked at the position corresponding te tne ouzer conouctor 7b of the cable 7 to connect the cable 7 with the terminal metal member. The fixing portion 15 may be cauiked at a position corresponding to an outer insulation to increase fastening strength.

Figs. 9 and 10 show respectively a plane view and a side view illustrating another example for connecting the core conductor 7a. In this example, clip terminal member 13 is employed for connecting the core conductor 7a of the coaxial feeder cable to the feed terminal portion 6a of the antenna conductor. The terminal member consists of a pair of leg portions 13a and 13b to be solder-connected to the terminal portion 6a and a clipping portion 13c to clamp the core conductor 7a. The outer conductor 7b is connected bv the terminal metal member 10 shown in Figs. 1 and 2.After the outer conductor 7b is fixed to the terminal metal member 10a by solder, the core conductor 7a of the coaxial cable is forced into the clipping portion 13c to be fixed therebetween. The clipping portion 13c may be soldered for securing connection with the core conductor 7a at need.

According to the terminal device for a printed antenna of this invention, connection strength of a coaxial cable to an antenna conductor is increased to provide a reliable terminal connection with little possibility of breaking of wire. As the outer conductor (braided wire) is connected to the antenna conductor without unbraiding the outer mesh conductor, variation of VSWR is little to allow stable and reliable transmission/reception of a signal.

Having described a specific preferred embodiment of the present invention with reference to the accompanying drawings, it is to be understood that the invention is not limited to that precise embodiment, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims.

Claims (5)

1. A terminal device for connecting a coaxial cable to an antenna consisting of printed conductor comprising a fitting means to fix an outer conductor of the coaxial cable and a leg means carrying the fitting means the outer conductor of the coaxial cable being secured to the fitting means and said leg means being soldered onto the printed conductor.

2. A terminal device according to claim 1; In which said fitting means has a cylindrical form.

3. A terminal device according to claim 1; in which said fitting means comprises a clip to clamp the said outer conductor of the coaxial cable.

4. A terminal device according to any of claims 1 to 3, in which another fitting means fixes an core conductor of the coaxial cable, and the core conductor of the coaxial cable being secured to said another fitting means.

5. A cap to conceal and to protect a terminal device according to any of claims 1 to 4.