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2. ENGINEERING AND TECHNOLOGY
A dual-band antenna with right-hand circular polarization for the first frequency and the counter polarization at the second frequency is realized with compact printed spiral slots. The coupled spiral slots are fed by a 50 Ω microstrip line. Dual-sense circularly-polarized performance is achieved by realizing oppositely-directed current rotation for the two frequency bands. A parametric study shows that the additional slot significantly improves the bandwidth for both frequency bands. Measured results show that the fractional impedance bandwidth is greater than 18% for both bands. The 3 dB axial-ratio bandwidths are 4.5% and 3.5% for the RHCP and LHCP bands, respectively.
X. L. Bao, and M. J. Ammann, "Monofilar Spiral Slot Antenna for Dual-Frequency Dual-Sense Circular Polarization", IEEE Transactions on Antennas & Propagation, vol. 59, issue 8, pp. 3061-3065, 08/2011.