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Based on the theory of microstrip antenna design and electromagnetic radiation, a kind of tag antenna with a bent meandered dipole and two short-circuited strips is studied in ultra high frequency (UHF) RFID bands to provide broadband and omni-directional performance simultaneously. The proposed antenna was fabricated with a thin copper layer printed on a thin lossy PET substrate for low-cost production. Our simulation and measurement results show the proposed antenna provides a quasi-isotropic radiation pattern and can obtain 200 MHz bandwidth under the condition of voltage standing wave ration (VSWR) less than 2, which is 1.5 dBi for worldwide UHF RFID bands. It is confirmed this kind of antenna is suitable for all different UHF RFID tags in passive RFID applications.

With the implementation of China Compulsive Certification (CCC), more and more manufacturers realize that they must improve their product quality on EMC. In this paper, one system of Electromagnetic Interference (EMI) Pre-Measuring is developed to meet the product designer's demand for EMI diagnoses. The system is applied to measure the unsymmetric interferential signal of supply line quantitatively based on the spectrum analyzer, line impedance stabilization network (LISN) and automatic test system. The structure of the test system is described firstly. Then the circuit diagram of V-LISN for the unsymmetric interferential signal test is showed. A designing method of automatic test system based on LabVIEW is commented in detailed. At last, a test is carried out to demonstrate the system is rational and applied.