FIELD OF THE INVENTION

The invention relates to PCB designs for providing an antenna module. In particular, the invention relates to PCB designs for antennae for use in communicating signals to (and optionally from) a driver of a luminaire.

BACKGROUND OF THE INVENTION

Some designs of driver for a luminaire are provided with a metal outer casing, such as a metal linear driver housing. If an antenna is to be used to communicate received wireless signals to the driver (to control the light source of the luminaire), the metal housing will shield the wireless signal if the antenna is within the metal housing. As a result, the antenna can only be placed outside the metal housing. However, as the antenna is treated as a live part, it is not possible to leave the bare printed circuit board (PCB) of the antenna exposed.

It is known to provide an antenna, such as a near-field communication (NFC) antenna, as a separate module outside the metal housing, and the antenna has its own plastic cover. The plastic cover allows the antenna to meet the communication requirements and approbation requirements.

Figure 1 illustrates an antenna covered by a plastic cover 106. The antenna comprises a printed circuit board formed of conductive layers 102 placed between insulating layers 104. The top and bottom conductive layers 102 are exposed to the environment if the antenna is not covered by the plastic cover 106.

However, the addition of the plastic cover increases the number of manufacturing steps as well as increasing the overall cost of the LED driver.

Other options include the use of plastic shells for example used in radio frequency identification (RFID) antennas. Figure 2 illustrates an RFID antenna covered by a plastic shell 206. The conductive layers 202 of the RFID antenna are placed between insulating layers 204. Similarly to the previous example using plastic covers, the top and bottom conductive layers 202 would be exposed to the environment if the antenna was not covered by the plastic shell 206. However, the addition of the plastic shell also increases the number of manufacturing steps as well as increasing the overall cost of the LED driver. Thus, there is a need for an improved antenna design.

CN 204834882U discloses a chip type NFC antenna.

US 20160205752A1 discloses a lighting apparatus includes a communication module including an antenna device.

EP 3576499A1 discloses a light driving device includes a housing and a driving unit.

SUMMARY OF THE INVENTION

The invention is defined by the claims.

According to examples in accordance with an aspect of the invention, there is provided an antenna module, comprising a multi-layer printed circuit board, PCB, wherein the multi-layer PCB comprises: conductive layers forming an antenna; at least one insulating layer between the conductive layers; a top protective layer above the conductive layers of the antenna; a bottom protective layer below the conductive layers of the antenna; and an electrical connection to the antenna, wherein the top protective layer, the bottom protective layer and the at least one insulating layer are made of dielectric composite materials, and the top and bottom protective layers are for exposure to the ambient surroundings around the antenna module.

The top and bottom protective layers function as protection for the antenna. In particular, the top and bottom layers serve to electrically insulate the traces of the antenna as well as to protect them from the environment to which the top and bottom layers are exposed.

Typically, wireless antennae are protected with plastic covers (or with covers formed from other non-metallic materials). However, this solution adds cost to the wireless antenna as well as adding additional manufacturing steps.

Having the protective layers directly formed as part of the multi-layer PCB of the antenna module can reduce the overall cost and increase manufacturing efficiency whilst ensuring proper functioning of the antenna. The top and bottom protective layers may be for protecting the conductive layers from the environment (e.g. moisture, dust etc.). By designing the top and bottom layers for exposure to the ambient surroundings, the antenna module is not intended to be positioned within a device housing or within its own housing, but instead the antenna module is for positioning outside a device housing and exposed to the ambient surroundings around the device which incorporates the antenna module. In this way, the cost of a cover for the antenna module is avoided, and attenuation of RF signals is prevented. The edges of the multi-layer PCB of the antenna module are similarly exposed to the ambient surroundings.

The top protective layer preferably fully covers the top conductive layer of the antenna. Similarly, the bottom protective layer preferably fully covers the bottom conductive layer of the antenna.

Two-layer wireless antenna designs, and four-layer wireless antenna designs will be well known to the skilled person. They are formed using two or more conductive layers of a multi-layer PCB separated by insulating layers. Wireless signals for reception or transmission by the antenna can pass through the top and bottom protective layers.

The thickness of both the top protective layer and the bottom protective layer is for example more than 0.05mm, so they are structural PCB layers (e.g. a pre-preg layer) rather than, for example, solder mask layers.

Using dielectric composite materials for the insulation layers as well as the protective layers improves manufacturing efficiency as the addition of the protection layers can be achieved in the same manner as the addition of the insulation layers (i.e. using conventional multi-layer PCB manufacturing methods).

The dielectric composite materials are electrically insulating and typically comprise woven, or non-woven, materials such as glass fibers or paper with a resin. The resin can be fully cured in core/laminate layers or it may be only partially cured in pre-preg layers.

The multi-layer PCB may comprise an antenna portion defining at least a portion of the antenna and a hidden portion defining the electrical connection.

The antenna portion of the PCB is intended to be exposed to the environment. This is possible by the addition of the top and bottom protective layers. Conventionally, the outer conductive layers of a PCB are only covered by a thin layer of solder mask which does not provide adequate protection to the conductive layers. The protective layers mean that no conductive layers are exposed in the antenna portion.

The hidden portion is intended to be used as a connector and, thus, the electrical connection in the hidden portion will not be exposed to the external environment when the antenna module is in use. The hidden portion is for example shielded or covered by a main PCB of a luminaire driver.

Exposed vias between the conductive layers may be positioned at the hidden portion. This enables the vias to be hidden when the antenna module is connected to, for example, an LED driver. Multi-layer PCBs comprise vias between the conductive layers to electrically connect the different conductive layers as required.

The electrical connection may comprise a set (e.g. two) of exposed conductive pads.

The top protective layer, the bottom protective layer and the at least one insulating layer may be made of the same material.

Both the top protective layer and the bottom protective layer may be a prepreg layer. Pre-preg layers are made from insulating materials typically used in PCB manufacturing as the insulating layers between the conductive traces. These materials can also function as a protective layer to the conductive parts of the antenna which still enable the wireless antenna to function as intended. These layers are formed as part of the manufacture of the PCB.

Four conductive layers may form the antenna. The antenna may be a near-field communication, NFC, antenna. The antenna module may further comprise a structural support portion for providing a mounting to the antenna module.

The invention also provides a luminaire driver comprising a power source for powering one or more light sources, a metal housing containing the power source, the antenna module as defined above outside the metal housing and a driver electrical connection between the antenna of the antenna module and the power source.

This enables the power source to be covered by a metal housing whilst still having access to wireless communication with the wireless antenna.

In particular, conventional PCB materials can be used for the antenna module without the need of any further protection as the top and bottom protective layers provide the necessary protection, for example for indoor use.

The luminaire driver is for example a linear LED driver.

The metal housing may comprise a metal chassis on which the power source is mounted and a metal cover.

The invention also provides a luminaire comprising the luminaire driver defined above and one or more light sources powered by the power source of the luminaire driver. An antenna portion of the antenna module of the luminaire driver is exposed to the ambient surroundings around the luminaire. Thus, no protective cover is provided over the antenna portion.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment s) described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

Figure 1 illustrates a prior art antenna covered by a plastic cover;

Figure 2 illustrates a prior art RFID antenna covered by a plastic shell;

Figure 3 shows a first example cross section of the PCB layers in an antenna module;

Figure 4 shows an example top-down view of the antenna module;

Figure 5 shows a second example cross section of the PCB layers in an antenna module;

Figure 6 shows an antenna connected to an external PCB assembly;

Figure 7 shows an electrical connection between the antenna and the external PCB assembly of Figure 6;

Figure 8 shows a linear driver housing with a metal housing;

Figure 9 shows a close-up of the antenna of Figure 8;

Figure 10 shows a side-view of the linear driver housing of Figure 8; and

Figure 11 shows a close-up of the antenna of Figure 10.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The invention will be described with reference to the Figures.

It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

The invention provides an antenna module comprising a multi-layer printed circuit board, PCB. The multi-layer PCB comprises conductive layers forming an antenna, at least one insulating layer between the conductive layers and an electrical connection to the antenna. Additionally, a top protective layer is provided above the conductive layers of the antenna and a bottom protective layer is provided below the conductive layers of the antenna, where the top protective layer, the bottom protective layer and the at least one insulating layer are made of dielectric composite materials.

Figure 3 shows a first example cross section of the PCB layers in an antenna module. The antenna module is formed of four conductive layers 302, three insulating layers 304 placed between the conductive layers 302, a top protective layer 306 and a bottom protective layer 308. The conductive layers 302 are connected using vias and through holes through the insulating layers 304 to form an NFC antenna. Note that Figure 3 is meant to show the ordering of the layers. In practice, the conductive layers would likely not be exposed at the edges of the antenna.

As shown, the antenna module has an antenna portion 301 and a hidden portion 303 separated by line 312 (which is simply for representation purposes). The antenna portion 301 is intended to be exposed to the environment when the antenna module is in use whilst the hidden portion 303 is intended to be connected to another PCB (e.g. an LED driver) to electrically connect the antenna module to the other PCB and in such a way that the hidden portion 303, where the electrical connections are mode between the PCBs, is not outwardly exposed.

In the example shown, the hidden portion 303 comprises electrical connections 310 which are exposed to enable connection to the other PCB. Once the connection is made to the other PCB, the electrical connections are no longer outwardly exposed to the ambient surroundings.

The electrical connections 310 can be placed above the top protective layer 306 and below the bottom protective layer 308. When the antenna module is connected to the other PCB, the exposed electrical connections 310 will no longer be exposed to the environment. Alternatively, the protective layers 304 and 306 can be removed in the hidden portion 303 to expose the top and bottom conductive layers 302. Of course, it is possible to expose only a single conductive layer 302 above or below the protective layers 304 and 306 instead of exposing both the top and bottom conductive layers 302. Any suitable connection may be used between the other PCB and the antenna PCB which ensures that no electrical contact pads remain exposed outwardly to the ambient surroundings.

The protective layers 306 and 308 serve to protect the conductive layers 302 in the antenna portion 301. The protective layers 306 and 308 can be made from the same dielectric composite material as the insulating layers 304. As such, the protective layers 306 and 308 can be pre-preg layers and/or core layers conventionally used in PCBs. This enables the use of already existing processes in multi-layer PCB manufacturing to add the protective layers 306 and 308, thereby simplifying the manufacturing process.

Many different dielectric composite materials can be chosen to provide different insulating values depending on the requirements of the PCB. Well known pre-preg materials used in the PCB industry include FR-2 (phenolic cotton paper), FR-3 (cotton paper and epoxy), FR-4 (woven glass and epoxy), FR-5 (woven glass and epoxy), FR-6 (matte glass and polyester), G-10 (woven glass and epoxy), CEM-1 (cotton paper and epoxy), CEM- 2 (cotton paper and epoxy), CEM-3 (non-woven glass and epoxy), CEM-4 (woven glass and epoxy) and CEM-5 (woven glass and polyester).

One or more of these dielectric composites may be used for the insulating layers 304 and the protective layers 306 and 308. Of course, other dielectric composites may be used depending on, for example, the required thickness, the required dielectric constant and/or the required thermal expansion etc.

In an example, FR-4 pre-preg layers are used for the protective layers 306 and 308. The insulating layers 304 may comprise one or more copper-clad cores (also referred to as copper-clad laminates) and one or more FR-4 pre-preg layers. FR-4 grade materials are commonly used for their flame resistance and self-extingui shing characteristics. However, the exact materials and resin percentages which are chosen may depend on the required dielectric constant and/or thickness of the layers.

The conductive layers 302 are conventionally made from copper and have a thickness of about 1 OZ or 2 OZ. Of course, other conductive materials and thicknesses may be used.

In summary, Figure 3 shows a six layer PCB design (i.e. with six conductive layers in total) for an NFC antenna, where four of the conductive layers 302 form the antenna and the top and bottom conductive layers (layers 310) are only exposed in the hidden portion 303 of the six layer PCB.

Figure 4 shows an example top-down view of the antenna module. A portion of the antenna 408 is shown exposed in Figure 4 in the antenna portion 402 of the antenna module. Line 403 represents the boundary between the antenna portion 402 and the hidden portion 404. The hidden portion 404 comprises two pads 410 and 412 (on the same side of the antenna PCB in this example) which enable the antenna 408 to be electrically connected to a different PCB. The vias 414 used to connect the conductive layers in the antenna module PCB are all located at the hidden portion 404 such that they are hidden when the antenna module is connected to the different PCB.

The antenna module also comprises a structural support portion 406 which provides a mounting support to the antenna module. The structural support portions 406 helps the antenna module stay mounted to a different PCB when it is connected to the other PCB (e.g. during manufacturing).

The other PCB could be a PCB assembly (PCB A) of a luminaire driver (e.g. an LED driver). As such, the antenna module can be mounted to the PCBA of the LED driver to enable wireless NFC functionality.

The antenna module may be mounted with the antenna parallel with the PCBA of the LED driver (e.g. horizontal) or it may be mounted with the antenna vertical. There may for example be a 90 angle between the plane of the PCBA of the LED driver and the plane of the antenna module PCB. For example, the LED driver may be for mounting horizontally, and the antenna module may be for mounting vertically, so that the radiation pattern extends around a horizontal plane.

Figure 5 shows a second example cross section of the PCB layers in an antenna module. The conductive layers 302 are separated by the insulating layers 304. The protective layers 306 and 308 serve to protect the conductive layers 302 from the environment as well as protecting users from the conductive layers. In this example, the sides 502 and 504 of the PCB are shown as being covered by the insulating layers 304 and the protective layers 306 and 308. Thus, the conductive layers at the sides of the PCB are also protected from the environment as well as the top and bottom surfaces.

Figure 6 shows an antenna 604 connected to an external PCB assembly (PCBA) 602. The antenna 604 is mounted orthogonal to the PCBA 602. The antenna portion 402 of the antenna is exposed to the environment whilst the hidden portion 404 is buried within and under the PCBA 602. Figure 7 shows an electrical connection between the antenna 604 and the external PCBA 602 of Figure 6. Solder 702 is used to provide an electrical connection between the antenna 604, connected to the conductive layers using vias 704, and the PCBA 602.

Figure 8 shows a linear housing driver with a metal housing. Figure 9 shows a close-up of the antenna of Figure 8.

The linear housing driver has a PCBA 802 on which is mounted a power source. The PCBA 802 is mounted on a metal chassis 806 of the metal housing and is covered by a metal cover 808 of the metal housing. A portion of the PCBA 802 is outside of the metal housing. This enables the antenna module 804 to be connected to the PCBA 802 and still provide a wireless NFC connection.

The antenna module 804 cannot be provided within the metal housing as this would prevent the antenna from wirelessly communicating with other antenna modules outside the metal housing.

Typically, the outer conductive layers present in antenna module 804 would mean that there are live parts exposed on the PCB of the antenna module. As such, some sort of protection is needed for the antenna module 804. Conventionally, plastic covers have been used to cover the antenna module 804. However, this increases manufacturing time and cost.

The inclusion of the protective layers previously discussed (layers 306 and 308 from Figure 3) enables the bare antenna module PCB to be connected to the PCBA 802 of the luminaire driver without the need for an additional protective cover.

The hidden portion of the antenna module 804 can be located beneath the PCBA 802 of the luminaire driver, or it may be slotted into a slot of the PCBA 802. An electrical connection is then provided between the power source on the PCBA 802 and the antenna module 804.

For example, the electrical connections (layers 310 in Figure 3) and any exposed vias on the antenna module 804 can be placed at the hidden portion 404 of the antenna module 804 as shown in Figure 4.

As shown in Figure 9, the hidden portion of the antenna is received through a slot in the main PCBA. The structural support portion 406 is also received in a respective slot in the main PCBA.

The hidden portion is thus inserted through the receiving slot of the PCBA 802 so that the electrical connections that need to be made to PCBA 802 are located at the underside of the PCBA. The electrical connection between the antenna PCB and the main PCB A for example comprises connecting pins (of a connector pin block) on one of the PCBs and connecting slots (of a connector slot block) on the other of the PCBs. Any alternative suitable connection type may be used between the contacts of the antenna module and contacts of the main PCB, such as a soldered connection or a wired connection or any suitable electrical connector or mechanical and electrical connector.

In all cases, the electrical connections between the antenna module and the PCBA are not exposed. The structural support portion 406 of the antenna module 804 is used to hold the antenna module in position during manufacture. The antenna portion 402 (unobstructed by metal parts) provides the wireless connection.

Figure 10 shows a side-view of the linear housing driver of Figure 8. Figure 11 shows a close-up of the antenna of Figure 10 with part of the chassis 806 cut away. The PCBA 802 can be mounted on the metal chassis 806 and the metal cover 808 covers the driver to form a linear driver housing. The metal cover 808 covers the power source on the PCBA 802.

As can be seen, the antenna module 804 is visible from the side of the linear housing driver and is not covered by metal. As such, the antenna module 804 can interact with other external antenna modules (e.g. mobile phones with an NFC antenna) to control the power source of the linear housing driver. In particular, the antenna portion 402 of the antenna module 804 is not covered by metal parts. The hidden portion 404 is inserted into the slot in the PCBA 802 and protrudes from the bottom of the PCBA. However, this portion of the driver is shielded by the chassis and thus inherently protected from the environment.

The structural portion 406 provides support for the antenna module when it is mounted on the PCBA 802.

In the example shown, the antenna module is perpendicular to the main PCB, e.g. the main PCB is parallel to the housing bottom (i.e. the chassis part) and the antenna PCB stands up perpendicularly to the housing bottom. The housing is for example horizontal and the antenna is vertical. However, the main PCB and the antenna PCB may extend in parallel planes, for example with the main PCB overlapping the antenna PCB in the region of the hidden portion of the antenna PCB.

The antenna module 804 is for example for use as part of an indoor luminaire. There is no need for an additional housing outside the antenna module.

Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing 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.

The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. If the term "adapted to" is used in the claims or description, it is noted the term

"adapted to" is intended to be equivalent to the term "configured to". If the term "arrangement" is used in the claims or description, it is noted the term "arrangement" is intended to be equivalent to the term "system", and vice versa.

Any reference signs in the claims should not be construed as limiting the scope.