Multiport Circular Polarized RFID-Tag Antenna for UHF Sensor Applications

Abstract

A circular polarized patch antenna for UHF RFID tag-based sensor applications is presented, with the circular polarization (CP) generated by a new antenna shape, an asymmetric stars shaped slotted microstrip patch antenna (CP-ASSSMP). Four stars etched on the patch allow the antenna’s size to be reduced by close to 20%. The proposed antenna is matched with two RFID chips via inductive-loop matching. The first chip is connected to a resistive sensor and acts as a sensor node, and the second is used as a reference node. The proposed antenna is used for two targets, serving as both reference and sensor simultaneously, thereby eliminating the need for a second antenna. Its reader can read the RFID chips at any orientation of the tag due to the CP. The measured reading range is about 25 m with mismatch polarization. The operating frequency band is 902–929 MHz for the two ports, which is covered by the US RFID band, and the axial-ratio bandwidth is about 7 MHz. In addition, the reader can also detect temperature, based on the minimum difference in the power required by the reference and sensor.

Architecture Characteristics and Technical Trends of UHF RFID Temperature Sensor Chip

“…Two antennas [49][50][51] were studied, one connected to the RFID chip to receive/transmit data from the reader and the other for RF energy harvesting, to power the digital circuits of sensors and microcontroller units (MCUs). In order to eliminate the need of two antennas, a circularly polarized patch antenna (CPPA) [52] was proposed, which utilizes the circular polarization (CP) generated by the new antenna shape to match the two chips with an asymmetric star-shaped slot microstrip patch antenna; one is as a reference node and the other can be connected to the sensor.…”

Design of Dual Circularly Polarized Sequentially-Fed Patch Antennas for Satellite Applications

“…Circularly polarized (CP) antennas [1][2][3][4] at relatively low frequencies (higher UHF band) have been profitably adopted in several satellite applications such as CubeSats [5,6], MEO satellites [7], telemetry tracking and command (TTC) antennas [8], near-field focusing [9][10][11] only to mention a few. In particular, CP patch antennas combine the advantages of fabrication easiness and of CP: the antenna does not need to be oriented along a particular direction, it is insensible to Faraday rotation, and the channel capacity is inherently duplicated by using the two orthogonal circular polarizations.…”

A Telemetry, Tracking, and Command Antennas System for Small-Satellite Applications

“…In [7] an S-band TT&C antenna employing bow-tie dipoles excited by an appropriate feeding network has been presented. To avoid complicated feeding networks, CP can also be generated with perturbation technologies [10][11][12][13][14]. This approach results in compact single-feed antennas, but such design generally has very limited bandwidth.…”