GB2467589A

GB2467589A - Monopole antennas with a common feed arrangement

Info

Publication number: GB2467589A
Application number: GB0902125A
Authority: GB
Inventors: Adrian David Charity
Original assignee: Novar ED&S Ltd
Current assignee: Novar ED&S Ltd
Priority date: 2009-02-09
Filing date: 2009-02-09
Publication date: 2010-08-11
Also published as: GB0902125D0; SG164328A1

Abstract

Apparatus 100 comprises a radio frequency device connected to an antenna with plural antenna elements 10a, 10b which are connected to a common feed. The antenna elements 10a, 10b may be folded wire monopoles which may be fed via a radio frequency signal splitter and/or combiner. The antenna elements 10a, 10b may be folded such that they are spaced, at a constant distance, from the periphery of a ground plane. The apparatus 100 may include radio frequency transmission and/or receiving circuitry and is suitable for a wall-mountable unit for controlling an environmental conditioning device or system or a wireless data communication system.

Description

Apparatus for inclusion in a wall-mountable unit for controlling an environmental conditioning device

Field of the Invention

The present invention relates to the field of

environmental conditioning systems, that is systems provided in buildings to condition the building's internal environment; such a system may include for example lights, fans, (de-)humidifiers, and other air-conditioning apparatus. More particularly, the invention relates to apparatus for inclusion in a wall-mountable unit for controlling an environmental conditioning device. Still more particularly, the wall-mountable unit is controllable by an electromagnetic signal, for example a radio-frequency (RF) signal.

Background of the Invention

Wall-mountable units for controlling an environmental conditioning device controllable by an electromagnetic signal are known, but suffer problems. For example, in the case of wall switches that include metal front plates, the performance of the antenna, used for RF data linking with other wall switches in a common system, is severely limited by the close proximity of the metal front plate and wall-mounting back box. Furthermore, although monopole antennas are used in known wall-boxes, the gain they provide is less than is desirable.

The present invention seeks to mitigate the above-mentioned problems.

Summary of the Invention

The present invention provides, in a first aspect, apparatus for inclusion in a wall-mountable unit for controlling an environmental conditioning device, the apparatus comprising: (a) an antenna for detecting an RF signal from a remote transmitter; (b) a receiver arranged to receive the RF signal from the antenna, and to provide a control signal; and (c) control electronics, arranged to receive the control signal from the receiver, for controlling the environmental conditioning device; wherein said antenna comprises a plurality of monopole antenna elements, said plurality of monopole antenna elements being connected to a common feed.

Thus the monopole antenna elements are connected (directly or indirectly) to a common feed voltage; in contrast, in a dipole antenna one part of the antenna is connected to a feed voltage, and the other part is connected to a different voltage, usually ground. Advantageously, the approach of the invention offers improved gain compared with a single monopole, in particular compared with single monopole designs used by other manufacturers of environmental conditioning systems. Advantageously, the approach also offers a level of antenna diversity, thus mitigating the effect of null spots due to RF signal reflections.

The common feed may consist of a single node to which the antenna elements are connected. The common feed may consist of a plurality of nodes connected directly to each other. The common feed may comprise a plurality of nodes connected indirectly to each other (for example via a plurality of identical capacitors) The common feed may comprise a splitter.

At least one of the monopole antenna elements may be connected to the common feed via a matching element, for example a capacitor. Each of the monopole antenna elements may be connected to the common feed via a matching element, for example a capacitor, there being a different matching element (e.g. a different capacitor) for each antenna element. The antenna elements may be connected to each other directly or immediately following the matching elements.

The apparatus may comprise a matching network and a splitter feed circuit which together couple the monopole antenna elements to an RF receiver, transmitter or transceiver module.

The environmental conditioning device may be for example a light (incandescent or fluorescent), a heater, or an air-conditioning unit.

The RF signal may have a carrier frequency of 500 MI-Iz to 1.5GHz, preferably 700 MHz to 1.25 GHz, more preferably 800 MHz to 1 GHz, still more preferably 868 MHz to 920 MHz.

The receiver may comprise a matching network.

The receiver may comprise signal processing electronics arranged to generate the control signal from the RF signal.

The monopole antenna elements may be wire elements.

The monopole antenna elements may be folded. The monopole antenna elements may be arranged to be folded around the perimeter of the wall-mountable unit. The 4_.

monopole antenna elements may be arranged to be folded behind a front plate of the unit.

The apparatus may comprise a ground plane for the monopole antenna elements. The monopole antenna elements may be folded around the perimeter of the ground plane. It may be that the monopole antenna element is positioned at a constant distance from the ground plane over substantially whole length of the antenna element. The apparatus may comprise a printed circuit board (PCB), which may form the ground plane for the antenna. The antenna may be arranged to be closer to the ground plane than to any back box or front plate of the unit; thus, the ground plane may have a larger de-tuning effect than any back box or front plate, which can for example allow the apparatus to be used interchangeably with a wall-mountable unit having a metal or a plastic front plate, without unduly affecting antenna performance.

It may be that there are two monopole antenna elements.

The present invention provides, in a second aspect, a wall-mountable unit including apparatus according to the first aspect of the invention.

The wall-mountable unit may comprise for example a switch or a dimmer.

The wall-mountable unit may have a metal front plate.

The wall-mountable unit may have a plastic front plate.

The wall-mountable unit may comprise a rear box portion, for mounting in or on a wall.

In an example embodiment of the invention, the wall-mountable unit comprises (i) a rear box portion, having a posterior surface and side walls, (ii) a front plate, attached to the front of the box portion, and (iii) a PCB, arranged inside the box portion, behind the front plate. In this example embodiment, a channel is formed within the rear box portion between the PCB and the side walls, and two monopole antenna elements are arranged within said channel, the antenna elements being folded to maintain a substantially constant distance from the PCB.

The present invention provides, in a third aspect, a wireless data communication system including a unit according to the second aspect of the invention.

It may be that the transmitter is another apparatus according to the first aspect of the invention. It may be that the transmitter is a master unit. It may be that the transmitter is a hand-held remote control.

The present invention provides, in a fourth aspect, apparatus for inclusion in a wall-mountable unit for controlling an environmental conditioning device, the apparatus comprising: (a) signal-generating electronics, arranged to generate a signal for transmission to a receiver that is remote from the apparatus; (b) a transmitter arranged to receive the signal from the signal-generating electronics, and to generate a corresponding RF signal; and (c) an antenna arranged to receive the RF signal from the transmitter and to emit said RF signal, for reception by the remote receiver; wherein said antenna comprises a plurality of monopole antenna elements, said plurality of monopole antenna elements being connected to a common feed.

It may be that the apparatus is arranged to function as both a transmitter and a receiver of RF signals; thus, for example, in some embodiments of the invention, the receiver of the first aspect and the transmitter of the fourth aspect are both comprised in a common transceiver It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated in embodiments of other aspects of the present invention.

Description of the Drawings

Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which: Figure 1 is a diagram showing functional blocks of apparatus for a wall-mountable unit according to an example embodiment of the invention; Figure 2 is schematic diagram illustrating the apparatus of Fig. 1; and Figure 3 is diagram showing the antenna and receiver of the apparatus of Figs. 1 and 2 in more detail.

Detailed Description

Functional blocks within an apparatus 100, according to an example embodiment of the invention, for a wall-mountable unit for controlling an environmental conditioning device, are shown in Fig. 1. A dual monopole antenna 10 receives an RF signal from a remote transmitter, for example a hand-held remote control, or another wall-mountable unit within the environmental conditioning system. A receiver 20 is arranged to receive the RF signal from the antenna 10, -7-.

and to provide a control signal. The receiver 20 comprises a splitter 30, which combines the signals from two antenna elements lOa, lOb of the antenna 10. The combined signal passes through an impedance-matching network 40 to an RF module 50, in which the RF signal is reduced to baseband for further processing in control electronics 60. The control electronics 60 receives the control signal from the receiver 20, processes the signal and controls an environmental conditioning device (in this example, a dimmer switch for a light) in accordance with the received signal.

Fig. 2 shows how the antenna 10 comprises two folded monopole antenna elements lOa, lOb. The apparatus 100 also includes a printed circuit board (PCB) 110, upon which is mounted circuitry, including receiver 20 and control electronics 60, for controlling the environmental conditioning device 70, but which also acts as a continuous ground plane for the monopole antenna elements lOa, lOb.

The antenna elements lOa, lOb are wires folded along the outside edge of a wall-mountable unit, behind the unit's metal front plate (not shown) . The wires follow the edges of PCB 110, so that they are at an approximately constant distance from it over almost all of their length.

The antenna elements lOa, lOb are connected (Fig. 3) to the RF module 50 via two capacitors 42a, 42b (one arranged in line with each of the pair of antenna elements lOa, lob), the splitter 30, where the signals from the two antenna elements lOa, lOb are combined, and matching network 40.

The primary function of capacitors 42a and 42b is impedance matching to the individual quarter-wave elements lOa, lOb.

The matching network 40 comprises: a further capacitor 44, connected in series between the splitter 30 and the RF module 50; an inductor 46, connected between ground and a point between the splitter 30 and the further capacitor 44, and another capacitor 48, connected between ground and a point between the splitter 30 and the RF module 50. The capacitances of the capacitors 42a, 42b, the further capacitor 44, and the capacitor 48, and the inductance of the inductor 46, are chosen to provide matching between the impedances of the antenna 10 and the RF module 50, to prevent unwanted reflections of RF signals travelling from the antenna 10 to the RF module 50.

Using an antenna 10 comprising a plurality of monopole antenna elements lOa, lOb offers improved gain compared with a single monopole antenna. By providing two (or more) antennas each in at least slightly different physical locations and/or configurations, the approach also mitigates the effect of null spots due to RF signal reflections from objects in the environment of the wall-mountable unit.

Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents.

It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.

Claims

-10 -Claims 1. Apparatus for inclusion in a wall-mountable unit for controlling an environmental conditioning device, the apparatus comprising: (a) an antenna for detecting an RF signal from a remote transmitter; (b) a receiver arranged to receive the RF signal from the antenna, and to provide a control signal; and (c) control electronics, arranged to receive the control signal from the receiver, for controlling the environmental conditioning device; wherein said antenna comprises a plurality of monopole antenna elements, said plurality of monopole antenna elements being connected to a common feed.
2. Apparatus as claimed in claim 1, wherein the common feed comprises a splitter.
3. Apparatus as claimed in claim 1 or claim 2, further comprising a matching network.
4. Apparatus as claimed in any preceding claim, wherein the receiver comprises signal processing electronics arranged to generate the control signal from the RF signal.
5. Apparatus unit as claimed in any preceding claim, in which the monopole antenna elements are wire elements.
6. Apparatus as claimed in any preceding claim, in which the monopole antenna elements are folded.
7. Apparatus as claimed in claim 6, in which the monopole antenna elements are arranged to be folded behind a front plate of the unit.
8. Apparatus as claimed in claim 6 or claim 7, in which the unit comprises a ground plane for the monopole -11 -antenna elements, and the monopole antenna elements are folded around the perimeter of the ground plane.
9. Apparatus as claimed in claim 8, in which the monopole antenna element is positioned at a constant distance from the ground plane over substantially whole length of the antenna element.
10. Apparatus as claimed in any preceding claim, comprising a printed circuit board (PCB), which forms the ground plane for the antenna.
11. A wall-mountable unit including apparatus according to any preceding claim.
12. A wireless data communication system including a unit according to claim 11.
13. Apparatus for inclusion in a wall-mountable unit for controlling an environmental conditioning device, the apparatus comprising: (a) signal-generating electronics, arranged to generate a signal for transmission to a receiver that is remote from the apparatus; (b) a transmitter arranged to receive the signal from the signal-generating electronics, and to generate a corresponding RF signal; and (C) an antenna arranged to receive the RF signal from the transmitter and to emit said RF signal, for reception by the remote receiver; wherein said antenna comprises a plurality of monopole antenna elements, said plurality of monopole antenna elements being connected to a common feed.
14. A method of controlling an environmental conditioning device, substantially as herein described with reference to the accompanying drawings.-12 -
15. An apparatus, for controlling an environmental conditioning device, substantially as herein described with reference to the accompanying drawings.