There is provided a three band whip antenna. More precisely there is provided a three band whip antenna having a base, and where the whip antenna along its length or part of its length, has a lowest frequency band antenna element and an intermediate frequency band antenna element.

Below, for illustrative reasons, reference are made to the following three bands:

- lowest frequency: L-VHF generally recognized to include the range of 30-88MHz;

- intermediate frequency: UHF generally recognized to include the range of 225-450MHz; and

- highest frequency: L band generally recognized to include the range of 1250-2000MHz .

The above band frequencies are in no way limiting the scope of the invention as other ranges may apply.

As more data signals are transmitted though radio systems, an increasing need for L band antennas has been experienced.

Two band antennas covering the L-VHF and UHF bands have been available for some time. The applicant's antenna VHF30450DB is such an antenna.

In order to avoid having yet another antenna in operation, the antenna manufacturers have experienced interest for a three band whip antenna that in addition to the L-VHF and the UHF also has an L band antenna included.

Problems associated with the inclusion of an L band antenna in a whip antenna may include:

- retaining the characteristics of the L-VHF UHF antenna with the L band antenna added;

- obtaining a good omnidirectional radiation pattern with a high gain for the L band antenna; and

- retain an acceptable diameter for the whip.

The purpose of the invention is to overcome or reduce at lest one of the disadvantages of the prior art.

The purpose is achieved according to the invention by the features as disclosed in the description below and in the following patent claims.

There is provided a three band whip antenna having a base and where the whip antenna along its whole length or part of its length, has a lowest frequency band antenna element and an intermediate frequency band antenna element, wherein a high ^¬ est frequency band antenna is included in the whip antenna at a position closer to base than the intermediate frequency band antenna element.

In a whip antenna, it has proved technically simpler to pass a feed conductor by the highest frequency antenna element and to the intermediate frequency antenna element than to pass the feed conductor by the intermediate frequency antenna ele ^¬ ment and to the highest frequency antenna element. The structure of the antenna according to the invention thus allows for simpler and less costly filters and antenna match ^¬ ing units to be utilized.

The highest frequency band antenna may have more than one an ^¬ tenna element. The more than one highest frequency band an ^¬ tenna elements may be spaced along a part of the whip.

The highest frequency band antenna elements may be positioned diametrically opposite to a feed conductor. Such a layout will maximise the distance between the antenna elements and the feed conductor.

The highest frequency band antenna elements may be placed symmetrically along the whip antenna relative its feed posi ^¬ tion.

The highest frequency band antenna elements may be formed as an arch of a circle. The highest frequency band elements may be concave with respect to the feed conductor. Again, the purpose of this layout is to utilize the space in the whip antenna .

At least two of the lowest frequency, intermediate frequency or the highest frequency band signals may be combined prior to or in the base.

At least two of the lowest frequency, intermediate frequency or the highest frequency band signals may be divided prior to feeding the appropriate antenna element.

The signals to all three band antennas may be passed through a single coaxial cable.

In one embodiment, the shield of the coaxial cable consti ^¬ tutes the antenna element of the end feed lower frequency an ^¬ tenna . Frequency filters and antenna matching units are well known to a skilled person and are not discussed here.

The three band whip antenna according to the invention pro ^¬ vides a high performance antenna with excellent highest fre ^¬ quency band antenna performance in a relatively simple struc ture that is well suited for manufacture.

Below, an example of a preferred device is explained under reference to the enclosed drawings, where:

Fig. 1 shows schematically a three band whip antenna accord ^¬ ing to the invention;

Fig. 2 shows a perspective view of an L band antenna of the whip antenna in fig. 1; and

Fig. 3 shows a signal flow of the whip antenna in fig. 1.

On the drawings the reference number 1 denotes a three band whip antenna, below denoted whip antenna, that has a whip 2 in the form of a none-insulating tube, which is connected to a base 4 via a spring 6.

The whip antenna 1 has an end feed lower frequency band an ^¬ tenna element 8, here corresponding to the L-VHF band, an di pole intermediate frequency band antenna element 10, here corresponding to the UHF band, at its upper end portion and an highest frequency band antenna 12, here corresponding to the L band, positioned closer to the base 4 than the interme diate frequency antenna element 10.

The highest frequency band antenna 12 includes four dipole highest frequency band antenna elements 14 that is symmetri ^¬ cally spaced relative their feed position so that the length of an highest frequency band element feed conductor 16 is equal for all highest frequency band antenna elements 14. In order to achieve an acceptable gain, it is necessary to have more than one highest frequency antenna elements 14. Four highest frequency antenna elements 14 give excellent highest frequency band antenna performance.

A practical design of the highest frequency band antenna 12 is shown in fig. 2. Here the highest frequency band element feed conductor 16 has the form of a printed circuit on a board 18.

The highest frequency band elements 14 are made from conduc ^¬ tive plates and have the form of an arch of a circle.

A whip antenna feed conductor 20 is located at the opposite side of the board 18 relative the highest frequency band an ^¬ tenna elements 14. The highest frequency band antenna ele ^¬ ments 14 are concave relative the antenna feed conductor 20.

In this preferred embodiment the three band signals to the antenna are combined prior to being supplied to the whip an ^¬ tenna 1 through a feed cable 22. In the base 4, a lower fre ^¬ quency band antenna matching unit 24 together with a lower frequency low pass filter 26 for the end feed lowest frequen cy antenna element 8 are positioned, see also fig. 3.

The feed conductor 20 in this embodiment consists of a coaxi al cable that includes a centre conductor and a shield. The shield of the feed conductor 20 constitutes, together with the spring 6 and a metal tube 28, the lowest frequency anten na element 8. The shield of the feed conductor 20 is electri cally connected to the spring 6 and the metal tube 28 in or ^¬ der to improve radiation.

A diplexer 30, that includes an intermediate frequency low pass filter and highest frequency high pass filter, is posi ^¬ tioned at a feed position 32 of the highest frequency band antenna 12. The diplexer 30 is connected to the highest fre ^¬ quency antenna feed conductor 16 and to a feed conductor 34, also in the form of a coaxial cable.

The feed conductor 34 supplies the intermediate frequency band antenna element 10 via an intermediate frequency high pass filter 36.

The shield of the feed conductors 20, 34 constitute earth for the intermediate frequency and the highest frequency antenna elements 10, 12.