An antenna is a well known arrangement for radiating or receiving electromagnetic waves. While antennas are available in a variety of shapes and sizes, they all function based on the same basic principles. In the reception mode, an antenna intercepts a propagating electromagnetic wave, which then induces an electronic signal within the antenna. The electronic signal can be then fed into an integrated circuit that deciphers the signal. In the transmission mode, an antenna receives an electronic signal through a feed line, which then induces a field surrounding the antenna that results in the formation of a free-space propagating electromagnetic wave. The antenna's features such as its dimensions can be obtained by reference to its operation frequency, radiation patterns, loss, gain, and the like. Antennas are typically made from metallic materials and have a wide variety of configurations. One known configuration is a dipole antenna that includes two conductive bodies of equal length each receiving an input signal at one end thereof. The two conductive bodies of a typical dipole antenna are elongated bodies that are aligned with one another. Each body may be one-quarter of the wavelength of the target wavelength which is to be transmitted or received by the antenna.
Antennas are prevalently used in wireless devices such as cell phones and the like to direct incoming and outgoing electromagnetic waves between a free space and a transmission line. Antennas are also used in radio frequency identification device (RFID) applications.
An RFID device that includes an antenna is usually referred to as an inlay. An inlay may include an antenna as well as a transponder, which is an integrated circuit for deciphering signals sent to the inlay and received by the antenna and also for sending a signal to the antenna which is then transmitted by the antenna. The inlay antenna may be tuned (i.e. sized) to communicate at a certain target frequency with a transceiver which is sometimes referred to as the interrogator. The interrogator typically includes an antenna for communication with the RFID inlay. An inlay may be active or passive. An active inlay would include its own power source such as a battery, while a passive inlay would receive its power from an external source such as an interrogator.
A magnetic coupler that employs a terminated transmission line can be used in encoding of RFID-enabled labels, tickets, tags, cards or other media. U.S. Pat. Nos. 7,425,887 and 7,190,270 disclose RFID printers/encoders which employ single transmission line couplers for communication with RFID inlays.    PTL 1: U.S. Pat. No. 7,425,887 U.S. Pat. No. 7,190,270 U.S. Pat. No. 7,348,885