A compact (50 × 50 × 4 mm3) dual-band radio frequency identification (RFID) tag antenna mountable on metallic objects is proposed for the ultra-high frequency (UHF) band (917∼923.5 MHz) and the microwave (MW) band (2.4∼2.45 GHz). With the proximity-coupled feed loop, the proposed antenna consists of two symmetric planar inverted-F antenna (PIFA) elements for the UHF band passive tag and a meander microstrip patch antenna for the MW band active tag. The performance of the proposed antenna is verified by mounting it on the different sizes of the metallic object. Furthermore, the passive tag antenna in the UHF band furthermore may be used for energy harvesting techniques to improve the lifetime of the active tag in the MW band. The measured maximum read range is 5.50 m in the UHF band and 14.15 m in the MW band when the proposed tag antenna is mounted on the metallic objects. The total efficiency for all operating frequency bands is higher than 50%. High isolation (>12 dB) between tag antennas in the UHF band and the MW band is achieved.

One of the most important design parameters in a microwave radio transmitting system is to reduce the spurious response from an output spectrum. The spurious signal is primarily due to local oscillator (LO) leakage. Applying the leakage reduction (LR) signal that has the same magnitude and is 180° out of phase with respect to the LO leakage signal, the spurious response can be significantly reduced. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 379–381, 2002.

ABSTRACT:The mutual coupling between cylindrical-rectangular microstrip patch antennas with a cylindrical superstrate is analyzed with the use of the conformal FDTD (CFDTD) method. The method is also applied to antennas mounted on flat structures for comparison. The effects of superstrate permittivity and thickness on the mutual coupling between cylindrical-rectangular microstrip patch antennas are presented. Curvature effects on the mutual coupling are also shown.