A new directional coupler for UHF RFID reader

A conventional microstrip directional coupler has poor isolation due to its unequal phase velocity between the even and odd modes. In this article, a compact dual-stub microstrip directional coupler for the UHF RFID reader is proposed. The operating frequency band is 902–928 MHz. It is found that the coupler can obtain a good isolation of −65 dB at 920 MHz. Modeling and simulation results are also presented which are in good agreement with measurement data. © Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1973–1975, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23495

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