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This work is focused on how to efficiently shrink a patch antenna operating in the UHF band. Five typical independent methods are first introduced that were solely used to realize a small patch antenna. A potential combination method is further discussed utilizing two or more of these five methods. One miniature patch antenna is experimentally demonstrated operating at 735 MHz using the combination method, in which both of shorting wall and complementary split ring resonators are applied in a reconciling way. A two-step optimization procedure is given to show how the antenna sizes can be significantly reduced with this combination method. The antenna is fabricated on a simple dielectric with a low εr of 2.2. The patch size is only 0.127λ x 0.123λ. The antenna efficiency is considerably high as 77% in measurement. [ABSTRACT FROM AUTHOR]

This paper presents a new coplanar waveguide (CPW)-fed circularly polarized square slot antenna (CPSSA). The proposed antenna uses an inverted Z-shaped feedline protruded from the signal line of the feeding CPW. Circularly polarized (CP) radiation can be achieved by adequately inserting the arc-shaped grounded strip into the upper right corner of the square slot. The widened vertical tuning stub on the L-shaped grounded strip can improve impedance matching and axial ratio (AR) performance. The measured results indicate that the 10 dB impedance bandwidth is 620 MHz (652-1272 MHz), and the 3 dB axial ratio bandwidth is 320 MHz (840-1160 MHz), which has a broadband characteristic. In the range of the universal UHF RFID band, the measured peak gain is about 4.4 dBi. The proposed CPSSA uses low-cost FR4 material as the dielectric substrate. The overall size of the antenna is 119 × 119 × 0.5 mm³. The proposed antenna has a simple structure, easy processing, good performance, wide operating bandwidth, and dual circular polarization characteristic. It can be applied to the universal UHF RFID handheld reader environment. [ABSTRACT FROM AUTHOR]

A novel compact printed broadband circularly polarized slot antenna is proposed in this paper. The antenna consists of an inverted L-shaped coplanar waveguide feed structure and a square ground plate loaded with three rectangular slots. The antenna achieves good impedance matching and circular polarization characteristics by adjusting the size of the L-shaped band and the rectangular slot. The simulation results show that the antenna has a 10-dB impedance bandwidth of 1360 MHz (690-2050 MHz) and a 3 dB axial ratio (AR) bandwidth of 490 MHz (770-1260 MHz). Additionally, the maximum gain reached 4.02 dBi. The antenna proposed in this paper can be applied to UHF RFID and GPS frequency bands. [ABSTRACT FROM AUTHOR]

Size-reduction techniques are applied to a circular UHF patch antenna, by varying parameters to better predict its desired resonant frequency. Specifically, slits are introduced into the patch, which are parametrically varied to determine the optimum slit dimensions for maximum size reduction. Further studies determine the optimum location for the probe feed, to achieve 50? input impedance for different slit lengths. [ABSTRACT FROM AUTHOR]

We compare the performance of equal-sized dipole and folded dipole wearable passive UHF RFID tags using three different body models for the torso of an adult male: cuboid and anatomical models with and without internal structures. The results show that all models estimate the antenna impedance matching appropriately, but only the anatomical models predict the full spatial coverage of the tags properly. We present a novel metrics for analysing the coverage in simulations and compare the simulated and measured tag read ranges to validate our modelling results. [ABSTRACT FROM AUTHOR]

A new compact slotted triangular monopole antenna for ultra-high frequency (UHF) radio frequency identification (RFID) applications is presented. The antenna exhibits an omnidirectional radiation pattern and has a bandwidth (BW) of more than 13%. It covers the global UHF RFID band and has a maximum gain of around 2.6 dBi. An overview of the antenna design along with the full wave simulation is provided. A prototype of the antenna is fabricated and tested. Good agreement is obtained between simulated and measured results. Moreover, the antenna is used with a UHF RFID reader in real use cases where read range and read rate with different commercial tags are used to evaluate the antenna performance. [ABSTRACT FROM AUTHOR]

This paper describes a compact printed Quasi-Yagi antenna for ultra high frequency (UHF) radio frequency identification (RFID) reader that can be used in both Europe and US regions. The proposed antenna is a Yagi type structure with a microstrip-tocoplanar stripline transition, a meander dipole, a folded finite-size ground plane and a rectangle ground plane. The proposed antenna has compact size (0.18?×0.24?). The proposed antenna has an endfire radiation pattern within operation bandwidth, with peak gain values of more than 3 dBi and return loss is less than -10 dB in approximately 100 MHz band that can cover European and US RFID bands (860 MHz - 960 MHz). We described the antenna structure and presented the comparison of simulation results with experimental data. Good return loss and radiation pattern characteristic are obtained, measured results are presented to validate the usefulness of the proposed antenna structure for RFID reader. [ABSTRACT FROM AUTHOR]

A new circular shaped patch antenna loaded with vertical slots and fed by meanderedstripline on a high dielectric material substrate is proposed in this paper, and experimentally verified the performance of the printed prototype. With the deployment of meandered-stripline structure to excite in the assistant of partial ground plane, the experimental results show that the proposed antenna has achieved wider bandwidth with satisfactory gain. The measured impedance bandwidth (voltage wave stand ratio, VSWR <= 2) of the proposed antenna at lower band is 400 MHz (600 MHz - 1 GHz) and at upper band is 700 MHz (2.25 GHz - 2.95 GHz). The peak gains of -1.18 dBi and 4.87 dBi have measured with topmost radiation efficiencies of 82.0% and 92.6% and have observed at lower band and upper band respectively. The performance criteria and almost consistent radiation pattern make the proposed antenna as a suitable candidate for UHF RFID, WiMAX and WLAN applications. The designing of antenna model and the parametric study have been performed with commercially available EM simulation software on 64-bit windows PC. The proposed antenna model has been validated by comparing the obtained experimental results with the output from the numerical simulation and apparently shows good agreement between them. [ABSTRACT FROM AUTHOR]

In this paper, a Circularly Polarised (CP) universal Ultra-High-Frequency (UHF) RFID reader antenna based on coupled line power divider is firstly proposed. The antenna features compact size, simple structure and low-cost and achieves Return Loss (RL)=25.5 dB, gain=5.5 dBic and Axial Ratio (AR)=1.8 dB, over the universal UHF RFID band of 840 to 955 MHz and the 3-dB AR beam-width is more than 110°. Then, an improved bandpass filter based on coupled lines and a ring resonator is proposed for achieving extremely narrow frequency response. A CP filter reader antenna using this narrow bandpass filter is proposed for enhancing the reliability of the communication and reducing the cost of the microwave front end in RFID system. The filter antenna exhibits the measured 1-dB gain (gain>6.4 dBic) bandwidth from 905 to 930 MHz and RL=15 dB, AR=1.4 dB in the band. [ABSTRACT FROM AUTHOR]

The impact of tag antenna and chip impedance tolerances on power transfer between these components is investigated analytically. Means for efficient computation of the minimum and maximum power transmission coefficient under given impedance tolerances are developed. The presented sensitivity analysis is employed to quantify the design uncertainty of single and double T-matched short dipole tag antennas for UHF RFID systems. The simulated and measured performance of the two tag antennas is analyzed and compared. [ABSTRACT FROM AUTHOR]