GB2265052A - Antenna mounting units - Google Patents

Abstract

An antenna base mounting unit for use in a mobile vehicle is adapted at a first end 3 to be connected to any one of a range of antennae and at a second end 2 to be connected to a cable. The mounting unit includes a matching unit 1 including a predetermined amount of coiled conducting material which is wound onto a toroid so as to match a large range of antennae to a connecting cable and ensure that a low standing wave ratio is achieved so as to maximize functioning of a radio receiver. The unit is particularly for use with a GRP vehicle body. <IMAGE>

Description

IMPROVEMENTS IN ANTENNA MOUNTING UNITS The invention relates to a mounting unit for use with an antenna and in particular for use with a radio antenna.

To be efficient in a normal mobile structure when operating vertically polarised, an antenna must work against its electrical "reflection" which is known as a ground plane. This is generally of the electrical dimension of one quarter wavelength and is mounted beneath the antenna. This is usually supplied by the metal body work of the vehicle, but in the case of for example, a GRP body, this is entirely absent.

It is known to provide antennae with a coiled end wherein the coiling effectively extends the functional length of the antennae whilst keeping the physical length within acceptable parameters. It will be appreciated that the degree of coiling will be related to the operating frequency of the antennae and will be specifically adapted accordingly.

This however decreases the efficiency of the antenna.

Another disadvantage of this prior art development is that each antenna can only operate at a given frequency and therefore different lengths of antennae having differentially coiled regions must be purchased if a user wishes to receive electromagnetic signals, that is radio signals, over a wide range of frequencies.

Accordingly it can be seen that there is a need to provide a more flexible system to overcome these disadvantages - especially the problems that come with modern all-GRP body construction - for use with coiled or uncoiled radio antennae and being adapted to connect with a wide range of antennae and provide for the optimaI functioning of same.

According to the invention there is therefore provided an antenna base mounting unit adapted for connection to an antenna and incorporating a matching unit whereby the unit is adapted to connect for example with a range of different antennae and to match each antenna's impedance to that of a connecting cable.

Such a unit is therefore of a wide band type and so can match a large range of antennae to a connecting cable whilst at the same time keeping a low standing wave ratio, that is the ratio between the impedance of the cable and that of the antennae. As will be known to those skilled in the art the attainment of a low standing wave ratio is important to the optimal functioning of a radio receiver.

One such unit, provided with a predetermined amount of coiled conducting material, is shown by way of example in the drawing of this present patent specification.

In this unit the coil is wound on a toroid which is preferably made of iron granules mixed with an inert material.

Preferably the windings ratio of the coil for a 50 ohm cable is 3:7.

This an other embodiments of the invention will now be described by way of example only with reference to the accompanying drawings wherein: Figure 1 represents a perspective view of a first unit in accordance with the invention; and Figure 2 represents a perspective view of a second unit in accordance with the invention.

Referring firstly to Figure 1 there is shown a matching unit 1 which is of cylindrical construction and sealed at ends la and Ib.

End ib is provided with a socket 2 for connecting to a cable.

End la is provided with a mounting. 3 comprising an. upstanding hollow cylindrical portion 3a and a hexagonal base 3b.

In use, an antenna is mounted in mounting portion 3 and by virtue of the conductive nature of the inner base of mounting portion 3 the aerial is functionally coupled to matching unit 1.

The inner chamber of matching unit 1 contains a conventional toroid made from iron granules mixed with an inert material to form a ring structure.

A predetermined amount of coil is wound on the ring structure so as to provide for a matching unit which is adapted to be connected to a wide range of antennae, which antennae are selected from a group functional over a wide range of frequencies.

It is a surprising advantage of the invention that a single toroid can be used with a wide number of different antennae.

The functional significance of the invention can be explained as follows.

One international standard fqr a conducting cable connected to an antenna is met by a cable having an impedance of 50 ohms.

The operating frequency of an antenna is determined by, amongst other things, its length, which in turn determines its feedpoint impedance. Thus for a given antenna with a given length there will exist a given impedance. The standing wave ratio, as mentioned, is a function of cable impedance. For example an antenna having an impedance of 200 ohms has a standing wave ratio of 50:200 which is 4.

As is well known to those skilled in the art antennae operate most efficiently when the standing wave ratio is low and is accordingly approaching one.

The matching unit in accordance with the invention matches the cable to the antenna by reducing the standing wave ratio.

An alternative embodiment of a unit in accordance with the invention is shown in Figure 2 wherein a square shaped matching unit 5 is provided with an upper surface 5a a lower surface (not shown) and sides 5a, 5b, Sc and 5d.

Upper surface 5a is provided with a mounting portion 6 which is similar to that shown in Figure 2. Mounting portion 6 comprises an upstanding hollow cylindrical portion which is adapted to accommodate an end of an antenna.

Side - Sc is provided with a socket (not shown) to which is connected a standard cable.

Within matching unit 5 there is provided a toroid as afore described about which is coiled a predetermined amount of conductive material so as to enable the matching unit to match a wide range of antennae to the antennae cable 7.

As previously stated, the units illustrated and specifically described above are only individual examples of forms which the invention might take within its broadest aspect. The invention as a whole is generally embodied in a matching device built into an antenna base mounting which is adapted to accept (eg) mobile antennae (or purpose-built antennae) and forms a wide-band unit electrically matching a wide range of antenna types and over a wide range of frequencies.

Claims (8)

1. An antenna base mounting unit adapted for connection to an antenna and incorporating a matching unit whereby the unit is adapted to connect with any one of a range of different antenna-so as to match each antenna's impedance to that of a connecting cable.

2. A unit according to Claim 1, wherein the matching unit includes a pre-determined amount of conducting material.

3. A unit according to Claim 2, wherein the material is coiled.

4. A unit according to Claim 2 or Claim 3, wherein the conducting material is wound onto a toroid.

5. A unit according to Claim 4, wherein the toroid is made of iron granules mixed with an inert material.

6. A unit according to Claim 5, wherein the winding ratio of the conducting material for a 50 ohm cable is 3:7.

7. A vehicle including an antenna base mounting unit in accordance with any of the preceding Claims.

Amendments to the claims have been filed as follows 1. An antenna base mounting unit adapted for connection to an antenna and incorporating a matching unit including a mounting means on which a pre-determined amount of conducting material can be mounted so that any one of a range of different antennae can be attached to the unit and the impedance of each antenna can be matched to that of a connecting cable.

2. A unit according to Claim 1, wherein the ratio of the input cable to the ouput cable is 3:7.

3. A unit according to Claim 1, wherein the ratio of the input cable to the output cable is 5:6.

4. A unit according to Claim 1, wherein the ratio of the input cable to the output cable is 2:8.

5. A unit according to Claims 1, 2, 3 or 4, wherein the material is coiled.

6. A unit according to Claims 1 to 5, wherein the conducting material is wound onto a toroid.

7. A unit according to Claim 6, wherein the toroid is made of iron granules mixed with an inert material.

8. A vehicle including an antenna base mounting unit in accordance with any of the preceding Claims.