Design of a compact CPW‐fed UHF RFID tag antenna for metallic objects

Abstract

number of right-hand sides to be solved for the complete monostatic RCS calculation is 91 for each example. It can be seen that the number of MVPs of the SAI-GMRES method varies largely with respect to incident angles (i.e., right-hand sides), while that of the GMRESE methods are more similar and almost constant for each example. This is another advantage of the GMRESE method proposed in this article. More detailed comparisons can be found in Table 5, in which the cumulated number of matrix-vector products and the total elapsed solution time for a complete monostatic RCS calculation are summarized using both the SAI-GMRES method and the GMRESE methods. In this table, it can be observed that the overall gain ranges from a factor of 3.5 to 5.9 when compared in terms of CPU time. CONCLUSIONS AND COMMENTSIn this article, we have described an enhanced GMRES method combined with MLFMA for solving linear systems from electromagnetic wave scattering problems. We explicitly compute and save the approximate eigenvectors associated with the eigenvalues close to the origin, either by the ARPACK software in a preprocessing phase or by the GMRES-DR method as a byproduct during the iteration process. The spectral information is then augmented into the Krylov subspace of the GMRES method to recover global information in the MLFMA context. Numerical experiments of typical examples are performed and comparison is made with the SAI preconditioned GMRES method, which shows the GMRESE method proposed in this article is more efficient and can reduce significantly both the iteration number and the overall simulation time.The novelty of this approach presented in this article compared to the augmentation techniques in Ref. 9 is that the proposed method induces a global deflation in the spectrum of the preconditioned matrix. The combined effect of the preconditioning techniques that cluster most of the eigenvalues to one, coupled with the augmentation technique that shifts the rest of the smallest eigenvalues of the spectrum can be very beneficial for the convergence of the Krylov iterative methods. Moreover, the price of augmenting eigenvectors into the Krylov subspace in the classical augmented GMRES method, that is the k additional matrix vector products, is avoided, since the spectral information is explicitly saved and applied at every cycle. Recently, radio frequency identification (RFID) in the UHF band has gained popularity in many applications, because it provides a long reading distance, fast reading speed, and large information storage capability. In RFID systems, tags are usually attached to objects having various material properties. Among them, metallic objects strongly affect the performance of a tag antenna including radiation efficiency and gain levels. To overcome these problems, planar inverted-F and microstrip patch antennas have been proposed for RFID tag applications. However, these antennas have a narrow bandwidth and thick height, and the resonant frequency can easily be shifted depending on the characteristics o...

Planar UHF tag antenna with bandwidth enhancement

“…2(a), it is seen that a resonant mode near 910 MHz band can be excited with good matching to the input impedance of the IC microchip. For the realization of impedance matching between the tag antenna and IC chip, the half-power (3 dB return loss) bandwidth specification had been adopted in the proposed designs [1,8]. From the related results shown in Fig.…”

Bandwidth Enhancement Design of Planar F-Shaped Tag Antenna With Parasitic Strips

“…Therefore, it is found that a new matching mode close to the fundamental matching mode of the regular F-shaped dipole antenna is obtained to enhance the operating bandwidth for RFID UHF band. For the realization of impedance matching between the tag antenna and IC chip, the half-power (3 dB return loss) bandwidth specification had been adopted in the proposed designs [3,9]. From the experimental results, the measured bandwidth .…”

“…The detection range and accuracy are directly dependent on the performance of reader/tag antennas. Some tag antennas for UHF RFID system have been proposed using planar unsymmetrical antenna [2], symmetrical dipole antenna [3][4][5][6], meander antenna [7] and slit antenna mounted on metal materials [8,9]. However, tag antenna applied for the glass object of the car is very scant in the literature.…”

Planar inverted-E antenna for UHF RFID tag on metallic objects with bandwidth enhancement

“…However, the above presented designs need larger dimensions and are unable to meet the dimensional considerations of the product. Moreover, the half-power matching bandwidth of the above tag designs cannot meet the specification of the UHF band (860-960 MHz) [4,6]. In this Letter, a compact UHF tag antenna with bandwidth enhancement is proposed.…”

“…However, there are some problems to be overcome for UHF label tags attached to the surface of metallic objects owing to electromagnetic wave scattering from the metal plane. Some metal tag antennas have been presented by using PIFA structures [1,2], dipole antennas [3], slit structures [4][5][6] and T-matching networks [7]. However, the above presented designs need larger dimensions and are unable to meet the dimensional considerations of the product.…”