Different types of antennas and their applications pdf writer
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The handheld device is used for the mobile reading and writing of BIS M data carriers, particularly in poor lighting conditions and harsh
This guide is ideal for those new to RFID and who want to learn about what the technology is, how it is used, about the different types, and about the necessary tags and equipment. Tagging items with RFID tags allows users to automatically and uniquely identify and track inventory and assets. Not only does the technology continue to improve year over year, but the cost of implementing and using an RFID system continues to decrease, making RFID more cost-effective and efficient. The Federal Communications Commission FCC is the governing body in the United States that sets and upholds country-wide standards for communicating via multiple channels including Radio Waves. The FCC regulations state that RFID tags and equipment can only operate between - MHz, because, like Europe, other communication types are allocated to the remaining portions of the larger range of - MHz.
This application is related to and claims priority under 35 U. The invention is better understood by reading the following detailed description with reference to the accompanying drawings in which:. An RFID encoder may be incorporated, for example, into a device such as a printer or the like that, in addition to encoding information in RFID tags, prints information on the tags.
In other applications, the RFID labels are provided in sheets that may be fed through a sheet-feeding mechanism. These labels, as they are provided on a roll or sheet of labels, may be blank, partially programmed, or programmed with manufacturing test data.
Accordingly, typically at least one encoding step is required before an RFID label is useful for identifying an object to which it will be applied. A wide variety of different types of RFID labels that vary in their choice of integrated circuitry, shape, size, or electromagnetic performance have been developed to deal with the varied application scenarios for RFID labels.
Due to rapid growth in RFID applications, there is a corresponding proliferation of different label antenna types. For example, two different label types are shown in FIGS. Label type-I, denoted in FIG. Some RFID labels may have folded-dipole type antenna elements, while others may have inductively loaded dipole elements or patch elements.
Because it is often desirable to produce orientation-independent labels, there may be more than one antenna element on the label, connected to the tag's circuitry, as shown in the example of FIG.
Furthermore, in the case of complex roll-fed or sheet-fed label forms, there may be more than one tag present on the same portion of the label medium. This is most often the case when a sheet-fed multipart form is produced, although it may also apply to roll-fed applications. In such cases the inter-tag spacing may vary between any two regions on the same form, or between a tag on one form and a tag on adjacent form, and additionally, the orientation of each tag may be different from the next.
For example, on a multipart form of two parts, one tag may be oriented horizontally with respect to the direction of label travel through the printer or encoder, while another may be oriented vertically with respect to the direction of label travel.
It should be appreciated that labels may also be interspersed with each other for certain specialized applications, as when a smaller label is partially or wholly contained within a larger label.
In such cases, if the tags disposed on the labels have different antenna types, one tag may be substantially surrounded by another tag. This single, fixed-configuration encoder antenna poses a problem when the RF field surrounding the antenna does not properly excite the label's antenna, or when the encoder antenna's field reaches beyond a single label to excite multiple labels simultaneously.
The latter is a particular problem when attempting to encode labels that contain RFID tag integrated circuits that employ communication protocols that do not distinguish among labels when performing the encode operation.
In this case, if two such labels are present in the field surrounding the encoder's antenna, as often happens in the case of adjacent labels, they may both be programmed simultaneously, even if the user's intent was to encode only one label.
Two different types of fixed-configuration encoder antennas , are shown in FIGS. In both cases there is a single coupling element microstrip present on an antenna substrate.
This copper region is fed with the RF signal from an attached RFID reader, and a wave is coupled along the length of the copper region, before being terminated in resistor , also denoted Rterm. In FIG. In both Type-I and Type-II single element antennas, the traveling or standing wave present on the microstrip element results in an electric field gradient in the region of space near to the element, which couples capacitively into an RFID label's antenna when the label is proximate.
In one aspect, this invention provides an RFID encoder antenna that can be dynamically reconfigured to properly excite many different types of RFID labels. In some aspects, this invention comprises of a multiple-element near-field antenna, as contrasted with the conventional single-element near-field antennas. Each element of an antenna according to embodiments of the invention can be configured to couple signals from an associated transmission line, resulting in the formation of a localized electric field, a localized magnetic field, or it can be grounded to provide a localized ground reference.
As these regions of electric or magnetic field are controlled by the switching logic, a configurable excitation field results. In other aspects, the antenna elements of this invention may be employed in a far-field antenna mode, wherein each antenna element radiates an electromagnetic wave that propagates to one tag without exciting an adjacent tag.
In these cases, the antenna elements of this invention are of substantially the same type as those disclosed herein but their far-field behavior is employed rather than their near-field behavior. Both types of signal coupling are explicitly contemplated herein. In some preferred embodiments of the present invention, the structure of the antenna is a multi-layer printed circuit making use of microstrip transmission lines and etched antenna element regions, although it may alternatively be made of a single- or two-layer printed circuit containing only the radiating elements, which are then connected to the switching circuitry by means of coaxial or other standard transmission line types as are well known in the art.
Suitable multi-layer printed circuit materials include, e. The latter dielectric materials, although more costly than FR4 material, have the advantages of better controlled dielectric properties dielectric constant as well as lower loss tangent and better dimensional stability over temperature and under mechanical stress.
It should be understood that this invention also contemplates the use of alternative dielectric materials such as air, glass, plastics or foam. Furthermore, the conductive elements may be constructed of any conductor, such as aluminum, brass, copper, or other sheet metals, or conductive inks or paints such as silver loaded conductive ink. Still further, the structure of conductors and dielectrics may be laminated together as in the case of a printed circuit board, or the antenna structure may be comprised of separate layers that are held together with fasteners such as spacers, rivets, screws and the like.
The pattern of the antenna element regions according to preferred embodiments of the invention may be one of two types. These antenna elements may be formed, e. In some embodiments, the antenna elements may be formed on the top layer of the PC, while in some other embodiments, the antenna elements may be located on an inner layer of the multi-layer printed circuit.
In these latter cases, the region above the elements is preferably a dielectric layer or a slot aperture rather than an uninterrupted ground plane. Although only one switch p is shown in FIG.
In some embodiments, the elements may be grouped so that more than one element is connected to the same switch. In other embodiments, each element may have its own switch. In general, in a Type-I embodiments of the present invention, antenna elements are preferably arranged in a regular repeating pattern, such as a grid of square, rectangular, circular, or diamond-shaped conductive areas or slot apertures , each of which is connected via a switch either to a transmission line or to ground.
This type of antenna element arrangement is quite flexible because it allows a fine granularity of field geometry selection, and allows for tag antennas of widely varying size and shape to be properly excited by the encoder's RF field. In general, if there are N antenna elements, there will be between one and N switches. Although the number of elements and switches is not limited, presently preferred values of N are 2, 3, 4, 5 and 6, and presently preferred element shapes are squares and rectangles.
Further, preferred embodiments have a one-to-one relationship between switches and antenna elements i. In a presently preferred implementation of a Type-I antenna system according to the present invention, there are four square-shaped antenna elements formed in a two-by-two grid, each element having its own switch.
In Type-II antennas according to embodiments of the present invention, the antenna elements are predetermined shapes that are designed to excite certain commonly used types of RFID label antennas.
For example, the antenna elements may be configured as a group of dipoles of varying sizes or shapes to better accommodate dipole-type label antennas. Alternatively the antenna elements may be a mixture of dipole, folded dipole, triangular, slot, leaky microstrip, patch, or slot elements as desired to achieve excitation of various label types.
Alternatively the antenna elements may also be comprised of shapes that produce grounded regions of varying size to better separate one tag from its neighbors by minimizing the RF field outside a desired region.
It should be further appreciated that, in addition to being directly fed by means of an ohmic electrical connection, the antenna elements may themselves be parasitically or capacitively fed, as by excitation from a radiating transmission line or slot located in proximity to the antenna element.
Alternatively the antenna element itself may be a slot aperture in a conductive plane, rather than an isolated conductive region, as is this is well known to be the dual of the conductive element itself. The switches employed in some embodiments of this invention may be silicon or gallium arsenide RF switches such as, e.
RF relays such as microelectromechanical switches MEMS may also be employed where the switching losses of silicon or GaAs switches are too high. The drive signals for the switches are obtained from a controller e. These settings may be determined, e. Once determined, the look-up table may be stored as hard-wired combinational logic, embodied as a finite state machine, or stored in RAM or Flash memory as when it is embodied as a software program running on a processor. In one presently preferred implementation, as shown in FIG.
In another preferred implementation, as shown in FIG. In present exemplary embodiments, these control messages may take one of two forms. In one form, the control message is a specific directive from the RFID reader module to open or close certain of the attached switches.
In another form, the control message is a pointer to a structure of tag types that is stored in the PIC16F microprocessor's memory. This pointer is effectively an indication of the label type to be read or written, although there may not be a one-to-one correspondence between the label type indicator sent via this connection.
Instead, the pointer may reference an abstraction of the desired RF field profile to be generated by the antenna unit under the control of the controller.
In this way a selection of a desired RF field profiles from a library of such profiles may be made in order to accommodate variations in RFID tags as may occur subsequent to the initial design of the antenna system. In another aspect, this invention may make use of a dynamic optimization in which an iterative or randomized search is made through many possible switch configurations in order to maximize a certain variable, e. This determination may be made once when a roll or sheet of tags is first inserted into the RFID label encoder, and the same determination may stored, e.
In some embodiments, this process is repeated for multiple possible configurations of the dynamically configurable antenna. The measurements may be, e. The configurations may be determined by a computer program executing on a processor, they may be extracted from a database of configurations or they may be input or determined in some other manner.
In some embodiments of the present invention, the configurations are determined by a finite element or harmonic balance simulation. Additionally, information from the label stock itself may be used to configure the antenna unit described herein. This information may be, for example, an alpha-numeric code entered by the user of the label encoder based on information shown on the label itself or packaging of the label stock. Alternatively or in addition , a bar code or other automatic identification symbology may be read from either the label itself or its packaging and used to select a field profile to be employed by the antenna unit.
In one preferred embodiment a small mark e. In this case the mark is detected by means of a photodetector and the input from that photodetector is used to determine the field profile to be employed preferentially for encoding the label. This information is communicated from the form design software to the label printer-encoder, e.
Those skilled in the art will realize that information used to configure an antenna unit may take many forms, and that various forms may be used alone or in combinations. For example, a bar code on a label itself may be used in conjunction with a user input. When more than one form or source of information is provided, a hierarchy may be imposed in order to resolve conflicts in the information.
For example, a code or mark on the stock itself may override a user-input code or a code on some packaging. Control signals may also be transferred to the antenna controller through a separate digital interface with their control logic, such as via a synchronous serial bus such as I2C or SPI, or via a standard serial transport such as RS, via USB or an Ethernet network, or via any other digital interface mechanism as is known in the art.
This may also provide power to operate the switches and associated control logic. Further, the control signals may be communicated via the amplitude, frequency, or phase of the RF signal itself from the reader, as extracted at the antenna unit. This implementation has the advantage that no additional cables beyond the RF interconnecting cable are needed. The transmission lines shown may take any form known in the art, including microstrip, buried microstrip, or coplanar waveguide types, in the case of planar transmission lines.
Alternatively, a coaxial transmission line or a waveguide may also be employed. To provide a good RF impedance match between the transmission line and the antenna element, and to avoid RF reflections, a terminating switch may be employed which would produce a constant impedance on the attached transmission line regardless of whether a given antenna element is connected or disconnected at any given time.
Such a terminating switch may be, e. HMC or any number of others that are now common in the RF industry. In this case, the transmission line is always properly terminated regardless of whether the antenna element is connected or not. An example switching arrangement for one embodiment of this invention is shown in FIG.
The latter connection allows for a larger field gradient to be generated between two elements than is possible with only single-phase excitation of array elements.
How RFID Works & Antenna Design
RFID Systems enable non-contact reading and writing of data. Related Contents. ID Identification usually refers to unique identification of people and objects. RFID, like barcodes and two-dimensional codes, is used for identifying objects. Biometrics for uniquely identifying people includes fingerprints, and the iris of the eye.
Nfc Module Nxp. Email: [email protected][email protected]. NFC is a short-range, wireless communications technology that connects. Transmission module. It has a simple instruction set and memory addressing along with a reduced code size compared to existing architectures.
How To Create A PDF From Your Web Application
This application is related to and claims priority under 35 U. The invention is better understood by reading the following detailed description with reference to the accompanying drawings in which:. An RFID encoder may be incorporated, for example, into a device such as a printer or the like that, in addition to encoding information in RFID tags, prints information on the tags. In other applications, the RFID labels are provided in sheets that may be fed through a sheet-feeding mechanism.
Rachel Andrew is a web developer, writer and speaker. Many web applications have the requirement of giving the user the ability to download something in PDF format. In the case of applications such as e-commerce stores , those PDFs have to be created using dynamic data, and be available immediately to the user. If you have a favorite tool or any experiences of your own to share, please add them to the comments below.
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