Examining Food Quality via RFID Tag Array

Radio-frequency identification (RFID) tags are widely used in the food supply chain where they can be used to hold identification data of tagged objects. They can also be used to provide information related to the quality and safety of the tagged object. This can be achieved by analyzing the RF signals emitted by the tag which couples with the tagged objects, and hence can be used to acquire useful information related to the safety and quality of that object. This paper investigates the correlation between the radiated signals from the tags and the quality characteristics of the tagged objects. It focuses on analyzing the mutual coupling between the tags in an array, in particular, of orthogonal polarization configuration, which shows that more information can be extracted by an array of tags compared to the use of a single RFID tag emitter

In-House Made Inverted Microstrip Line Phase Shifter Based on Nematic Liquid Crystal

Nematic liquid crystals are anisotropic dielectrics whose properties could be controlled by surface anchoring, exter-nal electric or magnetic fields. A typical design method of tunable inverted microstrip line phase shifter based on liquid crystal for microwave application is investigated. Two phase shifter designs based on the proposed method were introduced with the center operation frequency of 10 GHz and 20 GHz respectively. The prototype design operating at 20GHz is manufactured. The dielectric anisotropy of the liquid crystal used for the prototype is 0.45. A differential phase shift of 27.2° was achieved at 20 GHz with the physical length of 20 mm, connected to two coplanar waveguide ports of 50 ohms through vias, and under an external bias of 7 V

Equivalent Circuit of Metamaterial Formed by Array of Conductive Disks

The use of metamaterials to obtain a wideband wide angle impedance matching (WAIM) for compact phased array of interconnected crossed rings is investigated. The metamaterial layer above the planar array is formed by array of conductive disks in contrast to the conventional multilayer homogeneous dielectric structure. The equivalent circuit of the metamaterial layer to enhance wideband array antenna design is derived based on a hybrid technique. The values of the components in the equivalent circuit to represent metamaterial layer is given. The response from the equivalent circuit is verified by using the full-wave numerical simulations on the metamaterial structure. The results show the effectiveness of the method in analyzing the electromagnetic characteristics of the structure and improving the performance of the whole array system

Calibration of Aperture Arrays in Time Domain Using the Simultaneous Perturbation Algorithm

Online calibration is desired in antenna arrays of ultrawide bandwidth. This study proposes a time domain calibration method based on the simultaneous perturbation algorithm. Two objective functions were established: power of the received signal at array output; or combination of power and correlation coefficient between the signal at array output and a target signal. For both criteria, the convergence settings require only two measurements at each iteration. One advantage of the method is that the entire signal operation for calibration is performed in the time domain. This is achieved by resolving the effects of distortion on time delay of each channel, which accounts for both amplitude and phase distortions at different frequencies. Therefore, the proposed method significantly increased the calibration efficiency for ultra-wideband antenna arrays. Since time delay coefficients for calibration associated with array elements were determined independently due to characteristic of the simultaneous perturbation, estimation accuracy of the method is tangential to the number of elements in the array, and is mainly dependent on the convergence conditions. This gives the method an additional distinct advantage for calibrating large-scale antenna arrays with ultrawide bandwidth. An estimation accuracy of 99% on time delay adjustments has been achieved and demonstrated