Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
1999-08-16
2001-11-20
Trieu, Van T. (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S572800, C343S823000
Reexamination Certificate
active
06320509
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to radio frequency (RF) transponders such as radio frequency identification (RFID) transponders, and more specifically, to an RFID transponder having a high gain antenna configuration.
2. Description of Related Art
In the automatic data identification and collection industry, the use of RFID transponders (also known as RFID tags) has grown in prominence as a way to track data regarding an object to which an RFID transponder is affixed. An RFID transponder generally includes a semiconductor memory in which information may be stored. An RFID interrogator containing a transmitter-receiver unit is used to query an RFID transponder that may be at a distance from the interrogator. The RFID transponder detects the interrogating signal and transmits a response signal containing encoded data back to the interrogator. RFID systems are used in applications such as inventory management, security access, personnel identification, factory automation, automotive toll debiting, and vehicle identification, to name just a few.
RFID systems provide certain advantages over conventional optical indicia recognition systems (e.g., bar code symbols). For example, the RFID transponders may have a memory capacity of several kilobytes or more, which is substantially greater than the maximum amount of data that may be contained in a bar code symbol. The RFID transponder memory may be re-written with new or additional data, which would not be possible with a printed bar code symbol. Moreover, RFID transponders may be readable at a distance without requiring a direct line-of-sight view by the interrogator, unlike bar code symbols that must be within a direct line-of-sight and which may be entirely unreadable if the symbol is obscured or damaged. An additional advantage of RFID systems is that several RFID transponders may be read by the interrogator at one time.
One important consideration in an RFID system is the range at which the radio frequency transponder may be read. A known method to increase the range of a radio frequency transponder is to increase the power of the interrogating signal, which necessitates a greater use of energy. A drawback of this method is that increasing the energy of the interrogating signal may involve adding additional and more costly components to an RF transmitter-receiver unit of the interrogator. This may prove costly not only to manufacture, but also to utilize in its intended environment. Another consideration in an RFID system is that, in some instances, it is desirable to selectively orient the field-of-view of an RFID transponder relative to an interrogating source, receiver, or the like. For example, the radio frequency transponder might be oriented so that it would respond to only one of two interrogating sources.
Consequently, it would be advantageous to provide an RF transponder with an increased effective range and/or a selective field-of-view in a cost effective and efficient manner.
SUMMARY OF THE INVENTION
It is the intention of the present invention to provide an improved radio frequency transponder system with a reflector that increases the effective range of the radio frequency transponder so that the radio frequency transponder may be utilized over an increased distance.
A radio frequency identification transponder assembly in accordance with a first embodiment of the invention includes a radio frequency transponder disposed next to a reflector. The reflector may comprise any sort of radio frequency reflective material. The reflector may be formed with the radio frequency transponder at its focus region so as to enhance the reception of transmitted energy (for power or information transfer), and/or the transmission of signal energy by the radio frequency transponder. In this manner, the reflector provides increased range of useful energy transfer between the radio frequency transponder and a base station or the like. For example, the reflector may increase the effective range by focusing an increased reception area of the reflector to a radio frequency transponder so as to increase the distance at which the radio frequency transponder may receive an interrogating signal or other energy, and/or transmit data.
In accordance with a second embodiment of the invention, a radio frequency transponder is disposed next to a reflector that may selectively orient the radio frequency transponder with respect to a base station or the like. For example, a reflector may be formed or positioned relative to the radio frequency transponder so as to supply an interrogating signal from one source while excluding a signal from a second source. Alternatively, the reflector may selectively reflect a radio wave so as to reflect a wave from one specific source to the transponder yet exclude transmissions from other sources.
In accordance with a third embodiment of the invention, the radio frequency transponder includes an radio frequency identification integrated circuit coupled to a horn antenna. The integrated circuit may be directly coupled to the interior walls of a waveguide portion of the horn antenna. Alternatively, the integrated circuit may be electrically coupled to the waveguide portion by an inductive coupler. The horn antenna provides increased gain and directivity for the radio frequency transponder.
In accordance with a fourth embodiment of the invention, the radio frequency transponder includes a multi-layer patch antenna. The patch antenna includes a feeder patch coupled to a radio frequency identification integrated circuit, and a radiating patch spaced from the feeder patch. The patch antenna may further include a hybrid coupler electrically connecting the radio frequency identification integrated circuit with the feeder patch, so that the feeder patch is driven by two signals having a 90° phase difference and a 90° difference in orientation. The patch antenna provides increased gain and circular polarization for the radio frequency transponder.
In accordance with a fifth embodiment of the invention, the radio frequency transponder includes a patch antenna array. The patch antenna array includes a plurality of patch antennas coupled to a radio frequency identification integrated circuit through at least one impedance transformer. The patch antenna array may be adapted to provide linear polarization or circular polarization.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention and together with the general description, serve to explain the principles of the invention.
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Brady Michael John
Duan Dah-Weih
Kodukula Venkata S. R.
Martinez Rene D.
Moskowitz Paul Andrew
Intermec IP Corp.
O'Melveny & Myers LLP
Trieu Van T.
LandOfFree
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