用于RFID读卡器的低旁瓣圆极化微带天线阵的设计

A low-sidelobe circularly-polarized （CP） microstrip patch array for 2.4 GHz radio frequency identification （RFID） readers is presented. The antenna array with a Chebyshev current distribution is composed of 6 microstrip elements. The CP operation is obtained by the quasi-square patch with difference in lengths of the two sides. The antenna has been investigated numerically and experimentally. Measured results show that the array has a Chebyshev pattern with the sidelobe level of -23 dB, the half-power beamwidth of 16° and an impedance bandwidth （S11 ≥-10 dB） of 130 MHz, which is suitable for RFID reader applications.     

单轴孪晶界面上的最大负折射角

Using the Maxwell's equations,we carry out theoretical analysis on the maximum incident and refractive angles at which negative refraction can be realized at the interfaces associated with conventional uniaxial media.In the numerical analysis,the largest incident and refractive angles at which refraction arises are obtained by optimizing directions of the optical axis of the uniaxial bicrystal.Meanwhile,the optical parameters of the ordinary uniaxial bicrystals (including homogeneity- junction and heterogeneity-junction) are given,and some representative laser wavelengths,the largest incident and refractive angles are obtained.The relation between the largest incident angles (or refractive angles) and refractive index is also discussed.