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A novel design for a radio-frequency identification (RFID) tag antenna mounted on a metallic plane is presented. The tag antenna has a rectangular radiating plate with a Z-shaped slot, which enables it to function like a half-wavelength slot resonator and a dipole-type ground radiator. A conjugate match to an Alien Higgs-3 chip with an impedance of 8 – j142 $\Omega$ at 925 MHz is obtained by etching a half-wavelength slot resonator in the center of the rectangular radiating plate (120 \text{ mm}\times60\text{ mm}). The tag antenna resistance and inductive reactance can be matched to the desired chip impedance by simply tuning the length and width of the Z-slot resonator. The space between the half-wavelength resonant radiating plate (dipole-type ground radiator) and the metallic plane enhances the antenna gain by increasing the reflection from the metallic plane. A horizontal electric dipole placed above the perfectly flat electric metallic plane enables a maximum gain of 8.7 dBi over a short distance, which is fourfold higher than that of an isolated half-wavelength dipole. Tests of an RFID reader with an effective isotropic radiated power of 4.0 W showed that the maximum read coverage of the proposed tag antenna mounted on a metallic plane exceeded 10 m. Measurement data were in good agreement with the simulation results. [ABSTRACT FROM AUTHOR]

ABSTRACT A compact dual open-loop antenna is proposed to provide enhanced bandwidth in near-field applications in the ultra-high frequency band. The antenna generates a strong and uniform magnetic field in a near-field zone of the smaller open-loop antenna. For increased bandwidth, two open loops with individual half-wavelength perimeters are etched on each side of an FR4 printed circuit board. The antenna was fabricated in a compact overall size (dimensions, 60 × 60 × 0.8 mm3) and achieves an interrogation zone of 50 × 50 mm2 with good impedance matching and uniform magnetic field distribution in a 888-932 MHz band. Performance tests indicate that the proposed antenna has a reading distance of up to 130 mm for near-field applications and is suitable for radio frequency identification reader applications. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2008-2012, 2015 [ABSTRACT FROM AUTHOR]

A novel, compact X-shaped slotted square-patch antenna is proposed for circularly polarized (CP) radiation. A cross-strip is embedded along the X-shaped slot for a novel proximity-fed technique to produce CP radiation in the UHF band. In the proposed design, two pairs of T-shaped slots are etched orthogonally on the square patch, connected to the center of the X-shaped slot for CP radiation and antenna size reduction. Proper adjustment of the length and coupling gap of the cross-strip will excite two orthogonal modes with 90^\circ phase difference for good CP radiation. Simulated and measured results indicate that the proposed structure can achieve circular polarization. A measured impedance bandwidth (VSWR\leq 2) of about 3.0% (909–937 MHz) and a 3-dB axial-ratio (AR) bandwidth of about 1.3% (917–929 MHz) were obtained. [ABSTRACT FROM AUTHOR]

An UHF RFID tag antenna which is comprised of a trapezoidal loop and a dual-dipole radiator with an L-slit for omnidirectional polarized reading patterns is designed, fabricated and measured. For a conjugate match to the Monza 3 microchip impedance of 44-j231 at 915 MHz, an orthogonal dual-dipole tag antenna (91 mm \times 91 mm) with L-slit on each dipole arm was designed. Simple size adjustments of the L-slit and dipole radiator of the antenna allow for easy control of the antenna resistance and inductive reactance, from which the microchip impedance requirement may be readily satisfied. The read range of the prototype attached on a different glass can reach more than 9 m, which has been tested for an RFID reader with 4.0 W of EIRP. Good tag sensitivity and near omnidirectional radiation patterns were obtained in the desired frequency band. [ABSTRACT FROM PUBLISHER]

A microstrip-to-slotline transition technique is presented, for the coupling of a circularly polarized circular slot antenna in the ultrahigh frequency band.The fundamental TE11 mode of the circular slot antenna is investigated, using the magnetic current flow in the slot. In the proposed design, circular polarization (CP) is generated using a proper c-strip metal, within the circular slot structure, and connecting a strip metal to the circular slot edge, at −45° to the feeding slotline. The direct slotline feed is coupled to a 50-Ω microstrip line, on the opposite side of the substrate. Simulated and measured results indicate that the proposed structure achieves good CP radiation, in the TE11 mode. The impedance bandwidth and the 3-dB axial-ratio bandwidth for the design are approximately 22.1% and 2.5%, respectively. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2016-2023, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27013 [ABSTRACT FROM AUTHOR]

To produce circularly polarized (CP) radiation, a small, double-sided, crossed dipole antenna with two metal strips loaded for phase delay is proposed. The proposed antenna uses two orthogonal, unequal length dipoles, connected in parallel to a coaxial probe feed. It requires no matching network. The required power and phase relationships are obtained by proper choice of dipole lengths and the metal strips attached to them. The antenna also operates at its half wavelength orthogonal modes, for the UHF band. The phase delay metal strip generates the two resonant modes for CP radiation. Simulated and measured results indicate that the crossed dipole structure can produce CP radiation. An impedance bandwidth (VSWR \leq 2) of about 11.8% and a 3-dB axial-ratio (AR) bandwidth of about 3.3% around the center frequency of 925 MHz were measured. [ABSTRACT FROM PUBLISHER]

A compact circularly polarized coplanar crossed dipole antenna with an unequal length of arms for RFID reader is designed and measured in this paper. It uses two unequal length dipoles connected in parallel to a coaxial cable feed and requires no matching network. The impedance bandwidth of the proposed antenna for S <10 dB is about 6.9% and it has a 3-dB CP bandwidth of about 1.0%. Experimental results and simulations reveal that the proposed antenna features total size of 0.15 λ in side of square substrate and 0.005 λ in height at the center frequency 924 MHz. In addition to this, the compact antenna is easily to be embedded in the holding box as transmitting antenna in handheld RFID reader. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1172-1176, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25937 [ABSTRACT FROM AUTHOR]