A dual‐port dual‐frequency coaxial dual‐helical antenna with high decoupling

In order to obtain a circularly polarized and compact directive antenna for harmonic direction finding (HDF) of small animals using radio‐frequency identification (RFID), a dual‐port, dual‐frequency coaxial dual‐helical antenna is developed. The two frequencies are harmonics (2.45 and 4.9 GHz in our case). The antenna is realized using two coaxial, contradirective helices. Two different principles of realization are tested. The measured decoupling between ports is between 22 and 28 dB for the best antenna. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 1–4, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20883