Active load modulation antenna

摘要

Active load modulation antennas for contactless systems typically require the presence of a battery power source in the transponder device. The transponder typically cannot be powered by the reader device alone and also transmit an active load modulation signal. Embodiments in accordance with the invention are disclosed that allow transponder devices to transmit an active load modulation signal when powered only by the reader in the contactless system.

主权项

1. An active load modulation antenna structure comprising:
a first loop antenna having an outer perimeter that defines a first area on a first face of a substrate having an area, the first loop antenna having two ends with a ground pad at one end and a driver pad at the other end, the driver pad for driving an active load signal; and a second loop antenna having an outer perimeter that defines a second area on a second face opposite to the first face of the substrate, the second loop antenna having two ends with the ground pad at one end and a receiver pad at the other end, the receiver pad for receiving a carrier signal, the ground pad being common to both the first loop antenna and the second loop antenna; wherein the driver pad, the receiver pad, and the ground pad are on the same side of the substrate for connection to an integrated circuit; wherein the outer perimeter of the first loop antenna is the same as the outer perimeter of the second loop antenna and the first area is the same as the second area; wherein the outer perimeter of the second loop antenna is displaced a lateral distance, relative to the first face and the second face of the substrate, from the outer perimeter of the first loop antenna to define an overlapping area of the first area with the second area that is less than the first area and less than the second area; wherein the first loop antenna operates to transmit the active load signal and the second loop antenna operates to receive the carrier signal.