Slot antenna structure for electronic tag

A slot antenna structure for an electronic tag includes a dielectric layer, a conductor layer, a slot area and a capacitance adjustment unit. The electronic tag includes an identification chip. The conductor layer is disposed on the dielectric layer. The slot area is disposed in the conductor layer and includes an open slot, an open end and at least one closed slot. The open end is located at an edge of the conductor layer and extends inwardly to form the open slot for disposing the identification chip. The open slot has two sidewalls, and the two sidewalls have at least one turning point at a bottom portion of the open slot to form the closed slot. The capacitance adjustment unit is disposed on a surface of the dielectric layer different from the conductor layer to correspond to the slot area, thereby generating a capacitance effect.

FIELD OF THE INVENTION

The present invention relates to a slot antenna structure, and more particularly to a slot antenna structure for an electronic tag.

BACKGROUND OF THE INVENTION

Radio frequency identification (RFID), also known as electronic tag, is a wireless communication technology that can be identified or perform data exchange with a read and write device through radio waves. An electronic tag mainly includes an antenna and an identification chip. In order to reduce the size and cost, many electronic tags use passive power design, which means that the power source of the identification chip is generated by microwave resonance or electromagnetic induction by using the antenna or coil to sense the radio waves or magnetic fields sent from the read and write devices.

Many industries use electronic tags. For example, electronic tags may be attached to a car in production, and therefore, the progress of the car in the production line can be tracked; through electronic tags, warehouse can track the location of items and logistics management can be facilitated; electronic tags may be set on the identification card for access control management, installed in the car for collecting road toll and parking fees, installed in livestock or wildlife for identification, or linked to electronic records of patients. The use of electronic tags is very broad.

For longer distance communications, an antenna is used for general wireless transmission. Specifically, radio waves produce microwave resonance first. The antenna, after receiving the radio waves from a read and write device, then transmits the radio waves to the modulation circuit and power control circuit in the identification chip. The power control circuit converts the transmitted AC into DC as the power sources of the components in the identification chip. After obtaining the power source, logic unit starts to process the received data. Once the processing is completed, the logic unit modulates the result by the modulation circuit, and then transmits back to the remote read and write device through the antenna. Thus, the power supply and data exchange functions are completed.

Design of the antenna of an electronic tag requires that the antenna has a frequency band matching with the radio waves, to generate sufficient power by induction, and to consider the gain effect and read field shape. Further, to consider the antenna impedance matching, increase the communication distance, optimize the read rate of data, and consider the application of miniaturization, the type of the antenna must be designed specific to such purposes.

Accordingly, one objective of the present invention to provide a slot antenna structure for use in an electronic tag, which achieves the above-mentioned objectives and solves the problems in the prior art.

SUMMARY OF THE INVENTION

One objective of the present invention is to provide a slot antenna structure for an electronic tag that produces a desired impedance matching in a slot design to achieve a desired communication effect and to minimize the overall volume.

The present invention relates to a slot antenna structure for an electronic tag. The electronic tag has an identification chip. The slot antenna structure includes a dielectric layer, a conductor layer, a slot area and a capacitance adjustment unit.

The conductor layer is disposed on the dielectric layer. The slot area is disposed in the conductor layer and includes an open slot, an open end and at least one closed slot. The open end is located at an edge of the conductor layer and extends inwardly to form the open slot for disposing the identification chip. The open slot has two sidewalls and the two sidewalls have at least one turning point at a bottom portion of the open slot to form the closed slot. The capacitance adjustment unit is disposed in the open slot or on a surface of the dielectric layer different from the conductor layer to correspond to the slot area, thereby generating a capacitance effect.

The aforementioned slot antenna structure can be presented in various embodiments. In the slot antenna structure according to one embodiment, the slot area includes two closed slots, the two sidewalls oppositely extend from the bottom portion of the open slot to form the two closed slots, the conductor layer between the two closed slots and the open slot forms a symmetrical dipole structure, and the capacitance adjustment unit is disposed on the surface of the dielectric layer different from the conductor layer to correspond to the dipole structure.

Further, each of the closed slots has an end and at least two of the turning points, and an area of the end of each of the closed slots is larger than a specific value so that a size of the dipole structure is identical to a size of the capacitance adjustment unit. Moreover, an end of each of the closed slots has a depressed portion so that the dipole structure has a symmetrical L-shape.

In the slot antenna structure according to one embodiment, the slot area further includes a through hole disposed adjacent to the open slot, the conductor layer between the open slot and the closed slot forms a part of the dipole structure, another part of the dipole structure is disposed on the surface of the dielectric layer different from the conductor layer as the capacitance adjustment unit, and the part of the dipole structure is electrically connected to the other part of the dipole structure via the through hole, so that a capacitance effect is formed between the part of the dipole structure and the other part of the dipole structure overlapping with the projection of the part of the dipole structure.

In one embodiment, the capacitance adjustment unit is a conductor structure. In another embodiment, the capacitance adjustment unit is a capacitive element, and the capacitive element is disposed in the opening slot.

Therefore, by utilizing the slot antenna structure for use in the electronic tag of the present invention having the open slot and the closed slot of various designs, the impedance of the slot antenna structure can be adjusted to match the desired impedance matching and the overall volume of the slot antenna structure can be further miniaturized in conjunction with the capacitance effect generated between the dipole structure and the capacitance adjustment unit and further in conjunction with the location of the identification chip.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Please refer toFIG. 1, which is a schematic functional block view of a slot antenna structure12in an electronic tag10in accordance with an embodiment of the present invention. The present invention relates to the slot antenna structure12for use in the electronic tag10. The electronic tag10is disposed in a circuit board (not shown) such as a single-layered printed circuit board or a multi-layered printed circuit board, but the present invention is not limited thereto. Further, a surface of the circuit board is provided with a clearance area disposed on a dielectric layer of the circuit board and at the edge of the circuit board, in addition to a wiring conductor layer with the electronic components disposed on the dielectric layer. The electronic tag10is disposed in the clearance area. The other surface of the circuit board also has a wiring conductor layer with electronic components disposed on the dielectric layer but not having a clearance area. The tag10has an identification chip14in addition to the slot antenna structure12. The slot antenna structure12includes a dielectric layer20, a conductor layer22, a slot area24and a capacitance adjustment unit26. The slot area24is located at the edge of the circuit board. The conductor layer22is disposed on the dielectric layer20. The conductor layer22may be a metal layer such as a copper layer, an aluminum layer, etc. The dielectric layer20is mostly made of an insulating material, such as glass fiber or resin. In one embodiment of the present invention, the conductive layer22and the dielectric layer20of the slot antenna structure12may be a conductor layer and a dielectric layer of a circuit board, respectively.

The slot area24is disposed in the conductor layer22. The slot area24is manufactured in such a manner as to, for example, etch the conductor layer22to expose the dielectric layer20, or avoid the slot area24to form the conductor layer22on the surface of the dielectric layer20by printing. The slot area24further includes an open slot2402, an open end (which will be shown inFIG. 3A) and at least one closed slot2404. The open end is located at the edge of the conductor layer22and extends inwardly to form the open slot2402for disposing the identification chip14. The open slot2402has two sidewalls that have at least one turning point at the bottom portion of the open slot2402for forming the closed slot2404.

The capacitance adjustment unit26is disposed in the open slot2402, or disposed on the surface of the dielectric layer20different from the conductor layer22to correspond to the slot area24, thereby generating a capacitance effect. Further, the capacitance adjustment unit26is disposed on the dielectric layer of the other surface of the circuit board to correspond to the slot area24, thereby generating a capacitance effect, so as to achieve impedance matching of the slot antenna structure12, which benefits the miniaturized design of the slot antenna structure12. The conductor layer22is a radiating element which, after receiving a radio wave from a read and write device, resonates to generate a current supply to operate the identification chip14and transmits the information of the identification chip14as a radio wave. The present invention provides a number of embodiments for the form and disposition of the capacitance adjustment unit26, but is not limited thereto and may vary depending on the needs of the user.

Please refer toFIGS. 2, 3A, 3B and 3C.FIG. 2is a schematic view of the slot antenna structure12in accordance with the first embodiment of the present invention.FIG. 3Ais an enlarged schematic view of the area B inFIG. 2.FIG. 3Bis an enlarged cross-sectional view ofFIG. 2taken along line A-A.FIG. 3Cis an enlarged cross-sectional view ofFIG. 2taken along line C-C. Identical to the slot antenna structure12shown inFIG. 1, the capacitance adjustment unit26of the present embodiment is a conductor structure34, and the slot area24includes an open slot2402, an open end91and two closed slots2404. The open end91is located at the edge90of the conductor layer22and extends inwardly to form the open slot2402for disposing the identification chip14. The open slot2402has two sidewalls93, which oppositely extend from the bottom portion92of the open slot2402and each has two turning points94. The conductor layer22between the two closed slots2404and the open slot2402forms a symmetrical dipole structure35. In the present embodiment, the identification chip14is electrically connected to the dipole structure35.

In the present embodiment, the conductor structure34may be, for example, a metal sheet disposed on the surface of the dielectric layer20different from the conductor layer22and disposed in a range covered by the projection of the dipole structure35, so that a capacitance effect is formed between the conductor structure34and the dipole structure35overlapping with the projection of the conductor structure34. Further, the conductor structure34is disposed on the dielectric layer of the other surface of the circuit board to correspond to the dipole structure35, thereby generating a capacitance effect between the conductor structure34and the dipole structure35, so as to achieve impedance matching of the slot antenna structure12that benefits the miniaturized design of the slot antenna structure12.

Please refer toFIGS. 4A and 4B.FIG. 4Ais an enlarged schematic view of the slot antenna structure12in accordance with the second embodiment of the present invention.FIG. 4Bis a schematic cross-sectional view of the enlarged portion ofFIG. 4A. Identical to the slot antenna structure12shown inFIG. 1and similar to the slot antenna structure12of the first embodiment, the capacitance adjustment unit26of the present embodiment is also a conductor structure34and the slot area24also includes an open slot2402, an open end91and two closed slots2404. Different from the first embodiment, the area of the end40of each closed slot2404of the present embodiment is larger than a specific value so that the size of the dipole structure35between the closed slots2404and the open slot2402is identical to that of the capacitance adjustment unit26, but the present invention is not limited thereto. The user may adjust the area of the end40of the closed slot2404in accordance with the desired impedance of the slot antenna structure12to match the desired impedance matching. In the present embodiment, the identification chip14is disposed in the open slot2402and electrically connected to the dipole structure35.

Please refer toFIG. 5, which is an enlarged schematic view of the slot antenna structure12in accordance with the third embodiment of the present invention. Identical to the slot antenna structure12shown inFIG. 1and similar to the slot antenna structure12of the second embodiment, a depressed portion42may further be formed at the end40of each closed slot2404inFIG. 4Adepending on the requirements of the user42, so that the dipole structure35has a symmetrical L-shape. The conductor structure34should also be designed to have a symmetrical L-shape in accordance with the shape of the dipole structure35to obtain a preferred capacitance effect.

Please refer toFIG. 6and in conjunction withFIGS. 6A and 6B.FIG. 6is a schematic appearance of the slot antenna structure12in accordance with the fourth embodiment of the present invention.FIG. 6Ais a partial enlarged top view ofFIG. 6.FIG. 6Bis a partial enlarged bottom view ofFIG. 6. Identical to the slot antenna structure12shown inFIG. 1, the capacitance adjustment unit26of the present embodiment is also a conductor structure34. As shown inFIG. 6A, the slot area24of the present embodiment includes an open slot2402, an open end91and a closed slot2404. The conductor layer22between the open slot2402and the closed slot2404forms a part of the dipole structure35a. The slot area24further has a through hole50disposed adjacent to the open slot2402. As shown inFIG. 6B, another part of the dipole structure35bis disposed on the surface of the dielectric layer20different from the conductor layer22as the capacitance adjustment unit26, and the part of the dipole structure35ais electrically connected to the other part of the dipole structure35bvia the through hole50. By such design, a capacitance effect is formed between the part of the dipole structure35aand the other part of the dipole structure35boverlapping with the projection of the dipole structure35a. Further, the other part of the dipole structure35bis disposed on the dielectric layer of the other surface of the circuit board, thereby generating a capacitance effect between the part of the dipole structure35aand the other part of the dipole structure35boverlapping with the projection of the dipole structure35a.

Please refer toFIG. 7, which is an enlarged schematic view of the slot antenna structure12in accordance with the fifth embodiment of the present invention. Identical to the slot antenna structure12shown inFIG. 1and similar to the slot antenna structure12of the first embodiment, the slot area24of the present embodiment also includes an open slot2402, an open end91and two closed slots2404, and the conductor layers22between the two closed slots2404and the open slot2402forms a symmetrical dipole structure35. The difference from the first embodiment is that the capacitance adjustment unit26is a capacitive element60and is disposed in the open slot2402, and the identification chip14is also disposed in the open slot2402and between the open end91and the capacitance adjustment unit26. The user may adjust the position of the capacitance adjustment unit26at the opening slot2402as needed to adjust the impedance value of the slot antenna structure12to match the desired impedance matching. In addition, as previously described, the ends40of the closed slot2404of the present embodiment may also have an area larger than a specific value, a depressed portion (not shown) may further be formed at the end40of each closed slot2404, so that the dipole structure35has a symmetrical L-shape, and no redundant detail is to be given herein.

Thus, by utilizing the slot antenna structure12for use in the electronic tag10of the present invention having the open slot2402and the closed slot2404of various designs, the impedance of the slot antenna structure12can be adjusted to match the desired impedance matching and the overall volume of the slot antenna structure12can be further miniaturized in conjunction with the capacitance effect generated between the dipole structure35and the capacitance adjustment unit26and further in conjunction with the location of the identification chip14.