AU710276B3 - Multi-band antenna - Google Patents

Description

MULTI-BAND ANTENNA The present invention relates to radio communication systems and, in particular, to a multi-band antenna for use with multiple frequency bands such as those allocated to cellular phone systems, ie AMPS (Analogue Mobile Phone System), GSM (Global System for Mobile Communication), PCS (Personal Communication Services) cellular systems and any future frequency spectrum allocations.

BACKGROUND TO THE INVENTION With the introduction of several different bands for use by cellular mobile phone and other like radio transmission systems, there is a need for a multi-band antenna for use with micro cell base-station sites. The invention will avoid the need to have individual antennas to cater for each system frequency. The present invention is specifically designed to be suitable for indoor building installations.

OBJECT OF THE INVENTION It is the object of the invention to provide an antenna for use with a communication system which allows for at multiple frequency bands to be operational thereon. At the very least the object of the present invention is to provide an alternative method of coupling between radiating elements of known antennae.

DISCLOSURE OF THE INVENTION According to one aspect of the present invention there is provided an omni-directional antenna apparatus for use with a communication system which allows multiple frequency bands to be operational thereon, said antenna apparatus comprising at least two substantially co-axial radiating elements which are straight elements placed end to end and which are capacitively coupled with the first radiating element being connected to an antenna cable and received within an insulated antenna body, wherein the radiating elements are individually tuned to operate at their required frequencies.

hi 7 150 Preferably, the system provides an omni-directional radiation pattern in the plane operating on two or more frequencies.

BRIEF DESCRIPTION OF THE DRAWINGS One embodiment of the present invention will now be described with reference to the drawings in which: Fig. 1 is a schematic view of the installation of antenna apparatus of a preferred embodiment; Fig. 2 is a typical return loss diagram of the operation of the antenna apparatus of Fig. 1; and Fig. 3 is a explanatory RF diagram.

BEST MODE OF CARRYING OUT THE INVENTION A brief theoretical consideration is referred to in respect of Fig. 3 which shows radiation elements 1 and 2. The radiating element 1 which is connected to an inner conductor 3 of a co-axial input line 4, forms a broadband co-axial dipole with the ground plane 5. This radiating element 1 is designed to radiate an upper frequency band.

Radiation element 2 is placed above the element 1 and is capacitively coupled via an electric field in a gap 6 between the two elements 1 and 2. The length of the element 2 and the degree of coupling are designed to permit radiation at the lower frequency band.

With regard to the preferred embodiment, an antenna apparatus 10 is illustrated installed into a ceiling 11 in Fig. 1. The antenna apparatus 10 is a multi-band antenna. The apparatus 10 is a 0dB ground plane dependent antenna designed to be fitted through plasterboard, foam or metal ceiling panels.

The antenna apparatus 10 has at least two, ie first and second antenna radiation elements 12 and 13 which operate in the required frequency bands.

The first antenna radiation element 12 is soldered to a cable 14 which in turn is connected to radio communication circuitry (not illustrated) by means of a co-axial connector 15. The elements 12 and 13 are designed to minimise intermodulation when used with two or more frequency bands operating in duplex, ie each system operating with transmitting and receiving frequencies. The connection end 16 of the first element 12 is received within an insulated tubular antenna body 17 which is a two part arrangement.

The second antenna radiation element 13 is co-axially mounted with the first radiation element 12 via an electric insulator A ground plane formed by an annular metal disc 21 is fitted over the body 17 and is located at the junction between body portions 18 and 19. The disc 21 is adapted to abut against a panel of the ceiling 11 as the body portion 19 protrudes through a hole 22 in the ceiling 11.

The disc 21 is insulated from the body 17 by means of insulated washers 23 and 24 which are male and female respectively which mate together.

A locking nut 25 and mounting locking ferrule 26 interlock with the threaded portions 18 and 19 of the antenna body 17 such that the antenna is locked to the ceiling 11. The insulation of the washers 23 and 24 as well as the plastics to plastics connection of the portion 19 and ferrule 26 ensure that the antenna apparatus is inter-modulation free and does not resonate at any other frequencies when operating.

When tested the apparatus 10 provided the return loss frequency response as shown in Fig. 2.

The foregoing describes only one embodiment of the present invention, and modifications obvious to those skilled in the art can be made thereto without departing from the scope of the present invention.

Claims (3)

1. An omni-directional antenna apparatus for use with a communication system which allows multiple frequency bands to be operational thereon, said antenna apparatus comprising at least two substantially co-axial radiating elements which are straight elements placed end to end and which are capacitively coupled with the first radiating element being connected to an antenna cable and received within an insulated antenna body, wherein the radiating elements are individually tuned to operate at their required frequencies.

2. The antenna apparatus according to claim 1, wherein the apparatus provides an omni-directional radiation pattern in the "IT' plane operating on two or more frequencies.

3. The antenna apparatus according to claims 1 or 2, wherein the apparatus is fitted to a ceiling panel. DATED this TWENTIETH day of JULY 1999 BENELEC PTY LTD Patent Attorneys for the Applicant WILSON YOUNG C