Patent Application
20110006959
The invention relates generally to RFID antenna assemblies and methods for forming RFID antenna assemblies.
Radio-Frequency Identification (RFID) technology is directed to wireless communication between one object, typically referred to as a RFID tag, and another object, typically referred to as a RFID reader/writer. RFID technology has been adopted, and is increasingly being used, in virtually every industry, including, for example, manufacturing, transportation, retail, and waste management. As such, efficient RFID systems are becoming increasingly important as the demand for RFID technology increases.
RFID tags typically include two components: a RFID antenna assembly and an RFID integrated circuit (IC). RFID antennas can be used to receive and/or transmit an electromagnetic signal from a RFID reader/writer. A RFID IC (sometimes referred to as a RFID chip) can be used to store and/or process information (e.g., modulate/demodulate a radio-frequency (RF) signal).
Typically, RFID systems that operate in the ultra-high frequency (UHF) range utilize a standard dipole antenna configuration for the RFID antenna assembly. The performance of a standard dipole UHF transponder depends on the orientation between the transponder antenna and the reader antenna, because dipole antennas can only emit radio signals in one direction. To achieve two-dimensional readability, two or more dipole antennas can be used in a single antenna assembly. For example, two dipole antennas can be arranged perpendicular to each other to form a “double-dipole” antenna, which takes the shape of a cross. Standard “double-dipole” antennas require RFID chips with at least three electrical contact points: two antenna inputs and one ground contact. In other words, RFID chips require a separate channel for each dipole of the antenna assembly.
One approach to providing two-dimensional readability is to couple a near-field loop antenna with a dual polarized far-field antenna. In one aspect, there is an antenna assembly for two-dimensional readability. The antenna assembly includes a dual polarized far-field antenna and a near-field loop antenna electromagnetically coupled to the dual polarized far-field antenna. The near-field loop antenna includes two contacts for electrically connecting to a chip.
In another aspect, there is a method for forming an antenna assembly. The method includes forming, on a first side of a first substrate, a dual polarized far-field antenna, and forming, on a second side of a second substrate, a near-field loop antenna on a-second layer. The near-field loop antenna includes two contacts for electrically connecting to a chip. The dual polarized far-field antenna is electromagnetically coupled to the near-field loop antenna.
In other examples, any of the aspects above can include one or more of the following features. The chip can include an RFID device. The dual polarized far-field antenna can be a UHF antenna. The near-field loop antenna can be inductively coupled to the dual polarized far-field antenna. The near-field loop antenna can be ohmically coupled to the dual polarized far-field antenna. The near-field loop antenna can be capacitively coupled to the dual polarized far-field antenna. The near-field loop antenna can be coupled to the dual polarized far-field antenna inductively, ohmically, capacitively, or any combination thereof.
In some embodiments, the dual polarized far-field antenna can include a far-field loop antenna. The far-field loop antenna can include a rectangular geometry, a fractal geometry or a symmetrical geometry. The antenna assembly can further include the chip. The chip can be a one-channel chip. The chip can be a multi-channel chip comprising three or more contact pads. The antenna assembly can further include a first layer, a second layer, and a third layer. The first layer can include metallization of the dual polarized far-field antenna. The second layer can include a carrier material. The third layer can include metallization of the near-field loop antenna.
In other examples, the antenna assembly can further include a first layer and a second layer. The first layer can include a carrier material. The second layer can include metallization of the dual polarized far-field antenna and metallization of the near-field loop antenna. The antenna assembly can further include a first carrier material including the dual polarized far-field antenna, and a second carrier material including the near-field loop antenna.
In yet other embodiments, the method can further include ohmically coupling the dual polarized far-field antenna to the near-field loop antenna. The method can further include forming segments of the dual polarized far-field antenna and the near-field loop antenna, wherein the segments inductively couple the dual polarized far-field antenna to the near-field loop antenna. The method can further include forming segments of the dual polarized far-field antenna and the near-field loop antenna, wherein the segments capacitively couple the dual polarized far-field antenna to the near-field loop antenna.
In yet other examples, the first and second substrates can be different and the method can further include positioning the first and second substrates together using lamination, dispensing, bonding, or any combination thereof. The first and second substrates can be the same and the first and second sides can be the same. The first and second substrates can be the same and the first and second sides can be different. The method can further include attaching the second substrate to a device, wherein forming the dual polarized far-field antenna can include printing the dual polarized far-field antenna over the second substrate attached to the device.
Any of the above implementations can realize one or more of the following advantages. By coupling a near-field loop antenna to a dual polarized far-field antenna, two-dimensional readable RFID tags can be made compatible with single-channel RFID chips. In addition, the RFID tags can remain compatible with multi-channel RFID chips.
The details of one or more examples are set forth in the accompanying drawings and the description below. Further features, aspects, and advantages of the invention will become apparent from the description, the drawings, and the claims. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention.
The advantages of the invention described above, together with further advantages, will be better understood by referring to the following description taken in conjunction with the accompanying drawings. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention.
The chip 110 illustrated in
The near-field loop antenna 120 illustrated in
The near-field loop antenna 120 can be positioned into a corner 212 of the dual polarized far-field antenna 210 such that the two antennas are magnetically coupled to each other. For example, the near-field loop antenna 120 can be magnetically coupled to the dual polarized far-field antenna 210 via the magnetic induction that results from the proximity of segments of the two antennas in corner 212. In some configurations, the near-field loop antenna 120 can overlap with the dual polarized far-field antenna 210 or a gap can exist between the two. In a supplemental or alternative embodiment to inductive coupling, the near-field loop antenna 120 can be ohmically and/or capacitively coupled to the dual polarized far-field antenna 210. For example, the antenna assemblies 200b and 200c include a dual polarized far-field antenna 220 that is ohmically connected to the near-field loop antenna 120 via connections in corners 222b and 222c. Generally, the far-field antenna 210 can connect to at least one point anywhere on the near-field antenna 120 (e.g., the point that is substantially opposite to the chip's position).
In the antenna assembly configurations 200a-c, the dual polarized far-field antennas 210 and 220 are configured as rectangular loops, but other configurations can also be used. In one embodiment, for example, a dual polarized far-field antenna can be configured as any rotationally symmetric loop. More generally, a dual polarized far-field antenna can be configured in any arbitrary loop path. In some embodiments, for example, an antenna assembly configuration 200d or 200e can include a rectangularly-shaped dual polarized far-field antennas 230d or 230e with semi-circle indentations 232 located on each side. In an alternative embodiment, an antenna assembly configuration 240 can include a dual polarized far-field antenna 240 with a fractal geometry. The near-field loop antenna 120 can be positioned, for example, in the center of the dual polarized far-field antenna 240, which would allow substantially all segments of the near-field loop antenna 120 to be magnetically coupled to segments 242 of the dual polarized far-field antenna 240.
In general, near-field loop antennas and dual polarized far-field antennas can be formed on one or more substrates. Formation of an antenna can include metallization of a side of the substrate. Suitable substrates can include a non-conductive carrier material such as, for example, PET (polyester), FR-4 (or any other printed circuit board (PCB) material), PI (polyimide), BT (bismaleimide-triazine), PE (polyethylene), PVC (polyvinylchloride), PC (polycarbonate), Teslin (silica-filled polyethylene), paper and/or other suitable antenna substrate materials. In addition, substrates can be flexible or rigid. In one embodiment, a near-field loop antenna and a dual polarized far-field antenna can be formed on the same side of a substrate. In an alternative embodiment, a near-field loop antenna and a dual polarized far-field antenna can be formed on different sides of a substrate. In yet another embodiment, a near-field loop antenna and a dual polarized far-field antenna can be formed on different substrates and subsequently brought together using lamination, dispensing, bonding, and/or any other substrate binding process.
In another embodiment, a RFID chip can be bonded to a near-field loop (e.g., an antenna on a carrier material like PET), and the far-field antenna can be printed on the top-side or bottom-side of the carrier material. In yet another embodiment, a RFID chip can be bonded to a near-field loop (e.g., an antenna on a carrier material like PET), and the near-field loop can be laminated, dispensed, bonded, or otherwise attached to any device (e.g., a cardboard box or other housing). A far-field loop antenna can be printed on top of the device to which the near-field loop is attached to.
In some embodiments, a dual polarized far-field antenna can be coupled to one or more additional dual polarized far-field antennas via inductive, capacitive, and/or ohmic coupling.
One skilled in the art will realize the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting of the invention described herein. Scope of the invention is thus indicated by the appended claims, rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
