GB2207286A - Dipole antenna - Google Patents

Abstract

A half-wave notch fed dipole 1 comprises four parallel arms e.g 1A, 1B, formed from extensions of the outer conductors, e.g 3, of a triplate feed structure 2. The dipole is fed directly from the inner conductor 5 of the triplate. <IMAGE>

Description

An Antenna This invention relates to antennas including dipoles of the type known as half wave notch fed dipoles.

Such dipoles are formed by two arms X/4 long and separated by a slot X/2 deep, where X is the wavelength of the radiation the dipole is intended to transmit or receive, and are described in our co-pending U.K. patent application No. 8616576.

Such dipoles are at present fed by a co-axial line with its earthed outer conductor connected to one dipole arm and its inner conductor connected to the other dipole arm.

This invention was intended to give an arrangement for feeding such a dipole from a triplate feed structure.

This invention provides a dipole comprising a half wave notch fed dipole, fed from a triplate feed system, the arms of the dipole being formed from extensions of the outer conductor of the triplate and the dipole being fed directly from the central conductor of the triplate.

One way of performing the invention .i.ll now be described with reference to the accompanying figures, in which, Figure 1 shows a side view of a dipole constructed in accordance with the invention and, Figure 2 shows a top view of the dipole of Figure 1, identical parts having the same reference numerals.

An antenna is formed by a dipole which is, in turn, formed by four parallel arms, 1A, 1B, 1C and 1D. The dipole 1 is fed by a triplate feed system 2. The triplate feed system 2 consists of two parallel outer conductors 3 and 4 formed from metal plates and a central conductor 5 between outer conductors 3 and 4 and formed from a metal strip.

A ground reflector is formed at the base of the dipole 1 by a pair of metal sheets 7 and 8 mechanically and electrically connected to the outer conductors 3 and 4 respectively.

The dipole arms 1A, 1B, 1C and 1D are all formed as extensions of the ground planes 3 and 4. The dipole arms 1A and 1B are formed from the ground plane 3 and the dipole arms 1C and 1D are formed from the ground plane 4.

The dipole arms are each A/4 in width and project /2 from the edge of their respective outer conductors and dipole arms 1A and 1B are separated by a slot 11 and dipole arms 1C and 1D are separated by a slot 12. The width of slots 11 and 12 is small compared with X .

Where X is the intended transmission or reception wavelength of the dipole 1.

The central signal carrier 5 of the triplate feed 2 passes up one side of the dipole 1 between the dipole arms 1B and 1D and then crosses over the slot 11 and is electrically connected to the dipole arms 1A and 1C by a conductive pin 9. This connection is made approximately half way up the arms 1A and 1C, that is, approximately h/4 from the edges of the outer conductors of the triplate.

This distance is only approximate because the precise feed point can be altered to vaty the impedance of the dipole.

Thus the dipole arms 1A and 1B and slot 11 form a first half wave notch fed dipole and the dipole arms 1C and 1D and slot 12 form a second half wave notch fed dipole, however because the dipole arms 1A, 1B, 1C and 1D are parallel and the dipole arms 1A and 1B are close to the dipole arms 1C and 1D and both of these notch fed dipoles are fed in phase by the same feed 5 they behave as a single half wave notch fed dipole 1.

Signals transmitted or received by the dipole 1 are supplied from a transmitter (not shown) or to a receiver (not shown) via a co-axial connector 10 linked to the central conductor 5.

It should be noted that a half wave notch fed dipole is protected by our co-pending U.K. patent application no.

8616576.

Claims (4)

1. An antenna comprising a half wave notch fed dipole fed from a triplate feed system, the arms of the dipole being formed from extensions of the outer conductors of the triplate and the dipole being fed directly from the central conductor of the triplate.

2. An antenna as claimed in claim 1 in which the dipole is formed two pairs of arms, one pair of arms being formed from extensions of each of the outer conductors of the triplate and the central conductor of the triplate passing between the two pairs of arms.

3. An antenna as claimed in claim 1 or 2 in which the central conductor of the triplate passes between one pair of arms and is connected to the other pair of arms.

4. An antenna substantially as illustrated in and as described with reference to the accompanying drawings.