Abstract: Microstrip patch antenna (46), feed structure (48), and matching circuit (50) designs for an RFID tag (10) are disclosed. A balanced feed design using balanced feeds coupled by a shorting stub (56) creates a virtual short between the two feeds so as to eliminate the need for physically connecting the substrate to the ground plane. A dual feed structure design uses a four-terminal IC connected to two antennas (46a,46b) resonating at different frequencies to provide directional and polarization diversity. A combined near-field/far-field design using a microstrip antenna provides electromagnetic coupling for far-field operation, and a looping matching circuit provides inductive coupling for near-field operation. A dual-antenna design uses first and second microstrip antennas providing directional diversity when affixed to a cylindrical or conical object, and a protective superstrate (66) is applied. An annular antenna (46c) design for application to the top of a metal cylinder around a stem is disclosed.

Abstract: Microstrip patch antenna (46), feed structure (48), and matching circuit (50) designs for an RFID tag (10). A balanced feed design using balanced feeds coupled by a shorting stub (56) to create a virtual short between the two feeds so as to eliminate the need for physically connecting the substrate to the ground plane. A dual feed structure design using a four-terminal IC can be connected to two antennas (46a,46b) resonating at different frequencies so as to provide directional and polarization diversity. A combined near-field/far-field design using a microstrip antenna providing electromagnetic coupling for far-field operation, and a looping matching circuit providing inductive coupling for near-field operation. A dual-antenna design using first and second microstrip antennas providing directional diversity when affixed to a cylindrical or conical object, and a protective superstrate (66). An annular antenna (46c) design for application to the top of a metal cylinder around a stem.

Abstract: The present invention encompasses an antenna (12) for use with a radio-frequency identification transponder (10) that performs optimally in free space and near optimally when near a conductive surface. The radio-frequency identification transponder (10) broadly comprises an antenna (12); an integrated circuit (14); a matching circuit (16) interposed between the antenna (12) and integrated circuit (14); and a substrate (18). The antenna (12) is designed with a length so the antenna (12) as a microstrip resonates at a starting frequency and a matching circuit is constructed. The antenna (12) is placed near a conductive surface and the length of the antenna is adjusted until the antenna reactance is approximately the opposite of the integrated circuit reactance.

Abstract: Microstrip patch antenna (46), feed structure (48), and matching circuit (50) designs for an RFID tag (10). A balanced feed design using balanced feeds coupled by a shorting stub (56) to create a virtual short between the two feeds so as to eliminate the need for physically connecting the substrate to the ground plane. A dual feed structure design using a four-terminal IC can be connected to two antennas (46a,46b) resonating at different frequencies so as to provide directional and polarization diversity. A combined near-field/far-field design using a microstrip antenna providing electromagnetic coupling for far-field operation, and a looping matching circuit providing inductive coupling for near-field operation. A dual-antenna design using first and second microstrip antennas providing directional diversity when affixed to a cylindrical or conical object, and a protective superstrate (66). An annular antenna (46c) design for application to the top of a metal cylinder around a stem.

Abstract: Microstrip patch antenna (46), feed structure (48), and matching circuit (50) designs for an RFID tag (10). A balanced feed design using balanced feeds coupled by a shorting stub (56) to create a virtual short between the two feeds so as to eliminate the need for physically connecting the substrate to the ground plane. A dual feed structure design using a four-terminal IC can be connected to two antennas (46a,46b) resonating at different frequencies so as to provide directional and polarization diversity. A combined near-field/far-field design using a microstrip antenna providing electromagnetic coupling for far-field operation, and a looping matching circuit providing inductive coupling for near-field operation. A dual-antenna design using first and second microstrip antennas providing directional diversity when affixed to a cylindrical or conical object, and a protective superstrate (66). An annular antenna (46c) design for application to the top of a metal cylinder around a stem.

Abstract: The present invention overcomes the above-described and other problems by providing an improved edge-fed microstrip patch antenna, a dielectric substrate with integrated ground plane and enclosure that with a printable surface. An RFID microstrip patch antenna (21) system produces an antenna that is significantly less expensive to manufacture and install than existing commercial solutions. In doing so, the present invention enables the use of commodity, low cost products such as corrugated paperboard foils and extruded polystyrene and assembly methods such as graphics printing.

Abstract: Microstrip patch antenna (46), feed structure (48), and matching circuit (50) designs for an RFID tag (10). A balanced feed design using balanced feeds coupled by a shorting stub (56) to create a virtual short between the two feeds so as to eliminate the need for physically connecting the substrate to the ground plane. A dual feed structure design using a four-terminal IC can be connected to two antennas (46a,46b) resonating at different frequencies so as to provide directional and polarization diversity. A combined near-field/far-field design using a microstrip antenna providing electromagnetic coupling for far-field operation, and a looping matching circuit providing inductive coupling for near-field operation. A dual-antenna design using first and second microstrip antennas providing directional diversity when affixed to a cylindrical or conical object, and a protective superstrate (66). An annular antenna (46c) design for application to the top of a metal cylinder around a stem.

Abstract: Microstrip patch antenna (46), feed structure (48), and matching circuit (50) designs for an RFID tag (10). A balanced feed design using balanced feeds coupled by a shorting stub (56) to create a virtual short between the two feeds so as to eliminate the need for physically connecting substrate to the ground plane. A dual feed structure design using a four-terminal IC can be connected to two antennas (46a,46b) resonating at different frequencies so as to provide directional and polarization diversity. A combined near/field-far/field design using a microstrip antenna providing electromagnetic coupling for far-field operation, and a looping matching circuit providing inductive coupling for near-field operation. A dual-antenna design using first and second microstrip antennas providing directional diversity when affixed to a cylindrical or conical object, and a protective superstrate (66). An annual antenna (46c) design for application to the top of a metal cylinder around a stem.

Abstract: The present invention encompasses an antenna (12) for use with a radio-frequency identification transponder (10) that performs optimally in free space and near optimally when near a conductive surface. The radio-frequency identification transponder (10) broadly comprises an antenna (12); an integrated circuit (14); a matching circuit (16) interposed between the antenna (12) and integrated circuit (14); and a substrate (18). The antenna (12) is designed with a length so the antenna (12) as a microstrip resonates at a starting frequency and a matching circuit is constructed. The antenna (12) is placed near a conductive surface and the length of the antenna is adjusted until the antenna reactance is approximately the opposite of the integrated circuit reactance.

Abstract: A feed structure (18) and matching circuit (20) for inductively coupling an antenna (16) with an IC (22) in an RFID tag (10). The tag (10) includes first and second feed structures (26,28) coupled with the antenna (16), a first transmission line (30) coupling the feed structures (26,28), and a matching circuit (20) including a second transmission line (32) having a portion that is substantially parallel to and spaced apart from the first transmission line (30) such that the first and second transmission lines (30,32) inductively couple. Where two or more antenna elements (56,57) are used, the elements (56,57) are sufficiently loosely coupled by inductive coupling that they can operate at nearly the same frequency without forming a single resonant antenna. Thus, for example, different elements can operate at approximately 905 MHz and approximately 925 MHz, respectively, to effectively cover the FCC range of 900-930 MHz.

Abstract: An RFID tag (10) including a virtual short circuit using a stepped impedance transformation from an open circuit or other known impedance point to provide a reference signal to an integrated circuit (22). The stepped impedance transformer (28) does not consist solely of a quarter wavelength transmission line. The stepped impedance transformer (28) may consist of first and second transmission lines (30,32) having different lengths and widths. The RFID tag (10) may also include an impedance matching circuit (20) which does not consist solely of a three-section transmission line. The matching circuit (20) may include a shorting stub transmission line.

Abstract: A method and system for a device to embed a low signal to interference plus noise ratio (SINR) communications signal into the backscatter of an illuminating signal. The illuminating signal may be acoustic or electromagnetic (EM) such as radio frequency (RF), light, or infrared (IR). The embedded communications signal may be recovered at a desired receiver.

Abstract: An RFID tag (20) associated with a container (22) having a container wall (24) constructed of a container material (26). The RFID tag (20) includes a microstrip antenna (32) associated with an exterior surface of the wall (24) of the container (22) and a ground plane (30) associated with an interior surface of the wall (24) of the container (22). The container material (26) is interposed between the microstrip antenna (32) and the ground plane (30) and acts as a dielectric substrate. The microstrip antenna (32) may be embedded below, substantially flush with, or affixed to the exterior surface. Similarly, the ground plane (30) may be embedded below, substantially flush with, or affixed to the interior surface. Use of the microstrip antenna (32) reduces or eliminates detuning, while locating the components below or flush with the surfaces of the container (22) protects them from damage.