Microstrip antenna for rfid device

A radio frequency identification transponder comprising:

• a first patch antenna and a second patch antenna;
• an integrated circuit having a first pair of terminals and a second pair of terminals;
• and
• a first matching circuit for coupling the first patch antenna to the first pair of terminals, wherein the first matching circuit resonates at a first frequency;
• and
• a second matching circuit for coupling the second patch antenna to the second pair of terminals, wherein the second matching circuit resonates at a second frequency.

In a radio frequency identification transponder for physical association with an object and for storing and communicating data regarding the object, the improvement comprising:

• a first patch antenna and a second patch antenna;
• an integrated circuit having a first pair of terminals and a second pair of terminals;
• a first matching circuit for coupling the first patch antenna to the first pair of terminals, wherein the first matching circuit resonates at a first frequency;
• and
• a second matching circuit for coupling the second patch antenna to the second pair of terminals, wherein the second matching circuit resonates at a second frequency.

A radio frequency identification transponder comprising:

• a microstrip patch antenna providing electromagnetic coupling for far-field operation;
• an integrated circuit;
• and
• a matching circuit coupling the microstrip patch antenna with the integrated circuit includes a circuit loop that is sufficiently large to provide inductive coupling for near-field operation.

A radio frequency identification transponder comprising:

• a first layer including a substrate and a ground plane;
• a second layer including
• first and second microstrip patch antennas, with each patch antenna extending toward a different side of the second layer,
• an integrated circuit, and
• first and second matching circuits coupling the first and second microstrip patch antennas, respectively, to the integrated circuit.

In a radio frequency identification transponder for physical association with an object and for storing and communicating data regarding the object, the radio frequency identification transponder having an integrated circuit, the improvement comprising:

• a first layer including a substrate and a ground plane;
• a second layer including
• first and second microstrip patch antennas, with each patch antenna extending toward a different side of the second layer,
• an integrated circuit, and
• first and second matching circuits coupling the first and second microstrip patch antennas, respectively, to the integrated circuit;
• and
• a third layer including a superstrate for protecting the second layer from an adverse condition of an operating environment.

A radio frequency identification transponder comprising:

• a microstrip patch antenna having an annular shape with an inner edge and an outer edge;
• an integrated circuit;
• a first feed and a second feed, each feed being coupled with an edge of the microstrip patch antenna, and the first feed being approximately 180 degrees out of phase with the second feed;
• and
• a matching circuit coupling the first and second feeds with an integrated circuit, the matching circuit including a transmission line coupling the first feed with the second feed and creating a virtual short between the feeds.

In a radio frequency identification transponder for physical association with a cylindrical object having a stem and for storing and communicating data regarding the object, the radio frequency identification transponder having a microstrip patch antenna and an integrated circuit, the improvement comprising:

• the microstrip patch antenna having an annular shape with an inner edge and an outer edge;
• a first feed and a second feed, each feed being coupled with an edge of the microstrip patch antenna, and the first feed being approximately 180 degrees out of phase with the second feed;
• and
• a matching circuit coupling the first and second feeds with the integrated circuit, the matching circuit including a transmission line coupling the first feed with the second feed and creating a virtual short between the feeds, wherein the matching circuit is coupled with the inner edge of the microstrip patch antenna.

In a radio frequency identification transponder for physical association with a cylindrical object having a stem and for storing and communicating data regarding the object, the radio frequency identification transponder having a microstrip patch antenna and an integrated circuit, the improvement comprising:

• the microstrip patch antenna having an annular shape with an inner edge and an outer edge;
• a first feed and a second feed, each feed being coupled with an edge of the microstrip patch antenna, and the first feed being approximately 180 degrees out of phase with the second feed;
• and
• a matching circuit coupling the first and second feeds with the integrated circuit, the matching circuit including a transmission line coupling the first feed with the second feed and creating a virtual short between the feeds,
• wherein the matching circuit is coupled with the outer edge of the microstrip patch antenna.