The present invention relates to a luminary which incorporates a wireless transmitter.
Luminaries (or luminaires) constitute a basic component of many lighting solutions, particularly intelligent lighting solutions incorporating light emitting diode (LED) lighting. Another important component of intelligent lighting systems is control modules which are equipped with a radio and antenna to provide wireless connectivity. The control modules operate in a communication mesh, where each module constitutes a node of the mesh. Presently, control modules are often integrated in luminaries. Luminaries are typically manufactured with metal and plastic materials. In particular, any metal parts can have a high impact on the radiation properties of the antenna. The quality of the communication (propagation distance and package error rate (PER)) within the mesh depends very much on the radiation properties of the antenna as integrated into the illumination system.
Currently, specifically designed gaps and holes are provided in the luminaries in order to enable electromagnetic energy to propagate properly to the environment.
An alternative solution to the provision of gaps and holes is to provide external (e.g. patch) antennas on an outer surface of the luminary. Such external antennas are expensive.
According to one aspect of the invention there is provided a luminary configured for attachment to a ceiling of a space to be illuminated, the luminary comprising: a casing; a fixture for securing a lighting component to the casing: a wireless transmitter module comprising an antenna located in the casing; and
a securing component arranged to secure the luminary with respect to a ceiling plate and configured to space the casing from the ceiling plate to provide an air-gap between the casing and the ceiling plate, whereby the casing constitutes a resonant cavity for RF energy transmitted from the antenna, the air-gap dimensioned to radiate RF energy from the antenna to the environment externally of the casing.
Another aspect of the invention provides an illumination system configured for attachment to a ceiling of a space to be illuminated, the illumination system comprising: at least one luminary as hereinabove defined, and a ceiling plate secured to the luminary by the securing component.
The illumination system can comprise multiple luminaries spaced apart in an array, each luminary being as hereinabove defined and intended to communicate with each other through the radiation of RF energy from their respective antennas.
For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made by way of example to the accompanying drawings.
In the present disclosure, an air-gap is used between a metal luminary and a metal ceiling plate on which the luminary is installed. The inventors have noticed that the use of an air-gap between the metal luminary and the ceiling plate results in better radiation properties than by using holes in the luminary itself. Moreover, efficient radiation properties can be achieved without the need for such holes in the luminaries, and also without having to resort to external antennas which can be expensive. It is advantageous to avoid the use of holes in the external walls of the luminaries, because holes require additional production steps to manufacture, and additional measures for safety requirements in use.
The luminary 1 has a reflector 16 secured to the underside of the base, with sloping walls having a reflective material on their inner side.
The luminary 1 is equipped with at least one lighting component secured to the underside of the base 4 using one or more suitable fixture, such that the lighting component emits light to be reflected downwardly by the reflector. The lighting components can be arranged to be under the control of the control signals which are exchanged between luminaries of the system, via a control module at each luminary.
The rectangular channel is provided at each upper edge by longitudinally extending portions which support inwardly angled walls 18. The side wall 6, the longitudinally extending portions and the inwardly angled walls 18 are all solid, that is they are formed of a continuous material, without gaps or holes. It is understood in this context that there may be matters of construction which have led for example, to screw holes or other fixtures and fittings to be inserted into the luminary, but there are no specially designed gaps and holes for the purposes of radiation emission.
The luminary is provided with a securing component (not shown) which secures the luminary 1 with respect to a ceiling plate 20, for example, of metal. The ceiling plate 20 is a substantially planar continuous sheet of material, for example, metal, secured to the ceiling or forming part of the ceiling. The luminary can be secured to the ceiling plate 20 itself, or to another part of the ceiling such that it is secured with respect to the ceiling plate. Either way, an air-gap 22 is formed between the upper edge of the inwardly directed walls 18 of the luminary channel and the lower surface of the ceiling plate 20.
As mentioned, the inventors have noted that the use of an air-gap between the metal luminary and ceiling plate results in better radiation properties than by using holes in the luminary itself. Besides the positive effect that this air-gap enables the electromagnetic energy radiated from the antenna 10 to radiate efficiently to the environment, use of the air-gap also provides a radiation pattern with useful directivity properties.
In
The material of the ceiling 24 can be either metal or concrete, and by use of a metal ceiling plate both situations can be coped with. The air-gap principle works particularly well for luminaries shaped as shown in
The mechanism of the air-gap concept is based on a resonant cavity. The metal channel 2 of the luminary 1 forms, with the ceiling plate 20, a resonant cavity. The control module 8 including the antenna 10 is a source of RF energy inside the cavity and the energy is distributed according to a transversal magnetic (TM) field pattern over the casing as shown in
However, as the concept is based on a resonant cavity, the exact shape of the luminary and the location of the control module 8 within the luminary are not critical for the efficiency of radiation as long as the typical field distribution (TM) remains dominant. This should be the case as long as the luminary cross-section does not exceed a few (≈1 to 4) wavelengths of the emitted radiation. For example, with the 2.4 GHz ISM band (wavelength =12.5 cm), the cross-section should be smaller than 15 to 50 cm.
The radiation pattern can be slightly influenced by the longitudinal positioning of the transmitter module in the luminary, but this does not have a negative impact on the radiation efficiency nor on the gear-tray communication mesh performance. Moreover, the length of the luminary can have an effect on the radiation pattern, but nevertheless the overall advantages remain.
The unique benefit of the concept of using an air-gap between a metal luminary and a metal ceiling plate is that it combines an efficient pathway for the electromagnetic energy to the environment (including the nodes of the connectivity mesh) as well as directivity properties which are optimal for luminaries placed in an arrayed grid such as in offices and parking garages. Especially for metal gear-tray-types of luminaries, the air-gap principle is very effective for achieving excellent radiation properties. Moreover, it prevents additional measures in the luminary, such as holes, as well as the use of external antennas, resulting in a cost-effective solution.
Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practice of the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are cited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.
Number | Date | Country | Kind |
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13181607.6 | Aug 2013 | EP | regional |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2014/067601 | 8/18/2014 | WO | 00 |