GB2332099A

GB2332099A - Hand-held transmitter housing an open-loop radiating element

Info

Publication number: GB2332099A
Application number: GB9826814A
Authority: GB
Inventors: Josef Kraiczyk
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1997-12-05
Filing date: 1998-12-04
Publication date: 1999-06-09
Also published as: GB9826814D0; DE19753999A1; FR2772218A1

Abstract

A hand held transmitter, preferably for remote control of car locks, has a housing 1 6 7 which encloses a transmitter unit (8 fig. 2) and a directional transmitting element 5 which is mounted either within or attached to the housing. The transmitting element 5 is a generally annular but broken by a slot 11 forming a 'C' or 'U' shape (figs 3a-3f). The directivity is controlled by the position of the slot in the element. The slot is on the opposite side to the resultant main lobe of the directivity pattern of the transmitter. Preferably, the transmitter also forms the grip of a mechanical car key which also holds switches, transmitting circuitry and a battery.

Description

2332099 is PORTABLE HAND-HELD TRANSMITTER This invention relates to a

portable hand-held transmitter, in particular for a remote-controllable anti-theft system of a motor vehicle.

A known hand-held transmitter (DE 195 39 939 A1) has a housing in which a transmitting unit is arranged. Coded signals can be emitted with the transmitting unit. In this connection, the transmitting unit is arranged on a printed-circuit board. The transmitting power and the directional characteristic of the transmitting unit thereby depend, among other things, on the geometric shape of the transmitting element. Because the printed-circuit board is accommodated in a small housing, the geometric shape is to a great extent determined by the space which is still free on the printed-circuit board.

The present the invention seeks to provide a portable hand-held transmitter which is constructed simply and with small dimensions and the directional characteristic of which is substantially independent of a transmitting unit.

According to the present invention, there is provided a hand-held transmitter having a housing in which a transmitting unit is arranged, characterised in that the housing has a directional transmitter which receives wireless signals which are generated by the transmitting unit and passes them on in a preferred direction which is substantially conditional upon its geometric shape.

Because the housing is constructed so as to be larger than the printedcircuit board and otherwise has no electrical components, the directional transmitter can be as large as possible and shaped appropriately so that a preferred direction for the signals is obtained, in which direction the signals are transmitted with a range which is as great as possible.

is In a preferred embodiment, the directional transmitter is realised as an electrically conductive metal strip which is arranged on or in the housing. The directional transmitter is provided with a cutout in a direction opposite to the preferred direction. As a result of the geometric shape and the position of the cutout, the directional characteristic having the preferred direction in which the signals are transmitted with the greatest range is established. Apart from this, the cutout prevents.a situation in which an electrical short-circuit occurs on the directional transmitter and the signals which are emitted by the transmitting unit are either not passed on or are passed on with a range which is too small.

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:- Figure 1 shows a view of a portable hand-held transmitter; Figure 2 shows a section through the hand-held transmitter in accordance with Figure 1; and Figure 3 shows exemplary embodiments for a directional transmitter.

A portable hand-held transmitter is preferably used for a remotecontrollable anti-theft system of a motor vehicle. In this connection, coded signals are emitted by the hand-held transmitter, which signals are received by a receiver in the motor vehicle. The signals are tested for their authorisation. Upon authorisation, units in the motor vehicle, such as door locks, immobiliser, interior light, heating, seat adjustment, etc, are electrically or electromechanically controlled.

The hand-held transmitter has a housing 1 (Figure 1) in which a transmitting unit (not shown) is arranged. In this exemplary embodiment, the housing 1 is a grip of a mechanical key, which can have a key bit 2 with a mechanical coding. Arranged on the housing 1 are buttons 3, 4, which can be actuated from the outside and upon the actuation of which signals are emitted. Thus, for example, signals for locking the vehicle doors can be emitted when a first button 3 is actuated, or signals for unlocking the vehicle doors can be emitted when a second button 4 is actuated. '- In accordance with the invention, the housing 1 has a directional transmitter 5 which is fastened in or on the housing 1. The directional transmitter 5 receives wireless signals which are generated by the transmitting unit (the directional transmitter 5 is not, therefore, electrically connected to the transmitting unit) and passes them on in a preferred direction which is conditional upon its geometric shape (see arrow in Figure 1). The geometric shape of the directional transmitter 5 therefore determines its directional characteristic (see dashed line in Figure 1).

The directional transmitter 5 can - as shown in Figure 2 - be arranged inside the housing 1, i.e. enclosed in the housing wall. In the exemplary embodiment according to Figures 1 and 2, the housing 1 comprises a lower housing portion 6 and an upper housing portion 7. Arranged inside the housing is a printed-circuit board 9 which carries a circuit 8. The components of the circuit 8 form the transmitting unit which emits a signal when one of the buttons 3, 4 is actuated. This signal is then received by the directional transmitter 5 and passed on in the preferred direction. The circuit 8 is preferably supplied with power by a battery 10.

The directional transmitter 5 can be arranged both on the upper side and on the lower side of the housing is 1. If the directional transmitter 5 is arranged on both sides, the range of the signals which are emitted is greater in comparison with a directional transmitter 5 on only one side.

The directional transmitter 5 is an electrically conductive component which is fastened on or in the housing 1. A specially shaped metal tape or metal strip is preferably used.

In the exemplary embodiment according to Figure 1, the directional transmitter 5 is constructed so as to be substantially annular with a slit 11, a cutout or an opening in the opposite direction to.the preferred direction. As a result of this, the signals are passed on by the directional transmitter 5 in the direction of the key bit.

In accordance with Figures 3A to 3F, the directional transmitter 5 can have various geometric shapes. Thus, it can be constructed so as to be Ushaped (Figure 3M or substantially horseshoe-shaped (Figure 3B). The geometric shape of the directional transmitter 5 can be varied. It is fundamental to the invention that the directional transmitter 5 is electrically conductive, has a substantially strip-like or tape-like surface which is not closed, the opening of the surface being arranged in the opposite direction to the preferred direction. As a result of this, there is achieved a directional characteristic which has a preferred direction which lies in the opposite direction to the cutout.

The transmitting power is greatest if the directional transmitter 5 is a thin and narrow metal strip, the electrical length of which is matched to the wavelength X/4 of the signals to be emitted. The directional transmitter 5 should therefore be matched in terms of its form to the frequency of the signals to be emitted.

For uses in automotive engineering, frequencies of approximately f = 434 MHz are permitted. At such a frequency, the wavelength X of the signals lies at approximately 70 cm (X = c/f). A good range of the signals would be achieved if the hand-held transmitter had a directional transmitter 5 having an electrical length of X/4 (= approximately 17 cm). Because, however, great efforts are made to make the hand-held transmitter as small as possible, it is sufficient i-f the electrical lengths are integral parts of X/4. This gives electrically shortened X/4 transmitters which pass on signals, the range of which is still sufficiently great. For example, the electrical length of the directional transmitter 5 could be approximately X/16 (i.e. approximately 4.3 cm). A directional transmitter 5 having such a length can easily be put in a small, easily carried key grip. However, the. electrical length must not be too small in comparison with the wavelength X, because otherwise the radiated power would be too low.

The directional transmitter 5 can be inserted into the housing 1 as a metal ring having a slit 11. If the housing 1, as in the exemplary embodiment according to Figure 1, comprises a lower housing portion 6 and an upper housing portion 7, each housing portion 6 and 7 can have a portion of the directional transmitter 5, the two portions being electrically connected to each other as soon as the housing portions 6, 7 are put together.

Because the housing 1 is larger than the printedcircuit board 9 located therein, the electrical length of the directional transmitter 5 can be matched to the external dimensions of the housing 1 and thus as closely as possible to the wavelength X/4. Such a large antenna could not be accommodated on the printedcircuit board 9 itself.

The housing 1 can be injection moulded, in which case the directional transmitter 5 is extrusion-coated by the housing 1. The directional transmitter 5 can even be produced from electrically conductive particles, which are injection moulded together with the housing 1.

The housing 1 can also be produced as a so-called three-dimensional printed-circuit board 9, in which case the directional transmitter 5 is then producedas a strip conductor on the printed-circuit board 9 and thus on the housing 1.

For the invention, it does not matter how the directional transmitter 5 is produced. It is fundamental that it is electrically conductive and comprises a surface which has an operring or cutout in the opposite direction to the preferred direction. In this connection, the directional transmitter 5 can be produced from a material which is very electrically conductive, such as gold, silver, aluminium or copper, for example.

With such a hand-held transmitter, an effective high-frequency radiation is ensured. In this connection, the battery voltage can also be decreased and a sufficient radiation ensured nevertheless. It is then possible to develop a hand-held transmitter, the dimensions of which are small.

The directional transmitter 5 can be embodied as a resonator or waveguide, which as a result of its geometric shape determines the directional characteristic for the signals to be-emitted. As a result of the resonator, waveguide or directional transmitter 5, the signals are admittedly not amplified, but the range is increased in the preferred direction (in comparison with a transmitting unit without a directional transmitter). In the preferred direction, the radiating or transmitting power is increased by 1 to 2 dB in comparison-with a hand-held transmitter without a directional transmitter 5.

The portable hand-held transmitter can be used not only for a remotecontrollable anti-theft system of a motor vehicle, such as, for example, for a remotecontrollable centrallocking system, but can also be used for other applications in which signals are emitted by a portable hand-held transmitter.

In this connection, the housing 1 can - as shown have the shape of a conventional mechanical key grip. Equally, other housing shapes, such as, for example, a cheque-card-sized card (smart card or chip card) or suchlike, are possible.

16 is

Claims

1. Hand-held transmitter having a housing in which a transmitting unit is arranged, the housing having a directional transmitter which receives wireless signals which are generated by the transmitting unit and passes them on in a preferred direction which is substantially conditional upon its geometric shape.

2. Hand-held transmitter according to claim 1,-in which the directional transmitter is realised as an electrically conductive metal layer which is fastened to the housing.

3. Hand-held transmitter according to any one of the preceding claims, in which that the directional transmitter is constructed so as to be substantially annular with a slit in the opposite direction to the preferred direction.

4. Hand-held transmitter according to claim 1 or 2, in which the directional transmitter is constructed so as to be substantially U-shaped or substantially horseshoe-shaped.

5. Hand-held transmitter according to any one of the preceding claims, in which the housing is injection moulded, with the directional transmitter being extrusion-coated by housing material.

6. Hand-held transmitter according to one any of claims 1 to 4, in which the directional transmitter is produced from electrically conductive particles which are injection moulded together with the housing.

7. Hand-held transmitter according to any one of preceding claims, in which the housing is produced as a three-dimensional printed-circuit board and the directional transmitter is produced as strip conductors of this printed-circuit board.

8. A hand-held transmitter as claimed inany one of the preceding claims, in which the wireless signals -g- 1 are radio frequency signals.

9. A hand-held transmitter as claimed in any one of the preceding claims, in which the directional transmitter is a resonator.

10. A hand-held transmitter substantially as described herein, with reference to and as shown in the accompanying drawings.

11. A remote Control anti-theft system of a motor vehicle having a portable hand-held transmitter as claimed in any one of the preceding claims.

12. A vehicle having a remote control anti-theft system as claimed in claim 11.