Inverted F antenna system and RFID device having same

An RFID device, comprising:

• a substrate;
• a first active portion of a first inverted F antenna extending along a topside of the substrate;
• a first feed electrically coupled to the first active portion;
• a second active portion of a second inverted F antenna extending along an underside of the substrate such that the first active portion of the first inverted F antenna and the second active portion of the second inverted F antenna lie along parallel but spaced apart planes, wherein the second active portion of the second inverted F antenna is arranged in an opposite orientation relative to an orientation of the first active portion of the first inverted F antenna, such that the second active portion is rotated about 180 degrees from the orientation of the first active portion relative to a central axis perpendicular to a face of the substrate;
• a second feed electrically coupled to the second active portion;
• a ground plane spaced from the active portions;
• an RFID controller coupled to the feeds;
• and
• a battery coupled to the RFID controller, wherein the battery is positioned between the active portions of the inverted F antennas and the ground plane, such that the active portions of the inverted F antennas are on a first side of the battery and the ground plane is on a second side of the battery that is opposite of the first side.