We present optimization results obtained for two type of antennas using evolutionary algorithms. A quadrifilar helical UHF antenna is currently flying aboard NASA’s Mars Odyssey spacecraft and is due to reach final Martian orbit insertion in January, 2002. Using this antenna as a benchmark, we ran experiments employing a coevolutionary genetic algorithm to evolve a quadrifilar helical design in...

A novel method for excitation of RF B1 field in high-field (3-T) magnetic resonance imaging (MRI) systems using a subject-loaded quadrifilar helical antenna as an RF coil is proposed, evaluated, and demonstrated. Design, analysis, characterization, and evaluation of the novel coil when situated in a 3-T MRI bore and loaded with different phantoms are performed and cross-validated by extensive n...

In this letter, a compact circularly polarized (CP) multimode antenna for global navigation satellite system reflectometry (GNSS-R) is presented. The design comprises two quadrifilar helical antennas (QHAs), each fed with ground coplanar waveguide (GCPW) and quarter wavelength power divider (QWPD) integrated feed. A hybrid staircase-shaped (SSR) QHA radial proposed, it formed by serially...

Figure 1 Four sample Quadrifilar Antennas T he Quadrifilar Helix Antenna as shown in Figure 1 has already been described in detail and discussed in references [1], [2], [3], [4]. That discussion will not be repeated here. Unfortunately, very little has been written on how to built a Quadrifilar Helix Antenna to radiate with RHCP (Right Hand Circular Polarization) or with LHCP (Left Hand Circula...

This article surveys the research of the Evolvable Systems Group at NASA Ames Research Center. Over the past few years, our group has developed the ability to use evolutionary algorithms in a variety of NASA applications ranging from spacecraft antenna design, fault tolerance for programmable logic chips, atomic force field parameter fitting, analog circuit design, and earth observing satellite...

A quadrifilar helix antenna (QHA) operating at 0.94GHz is designed and realized in this paper. The designed QHA consists of four helical conductors which are excited in phase quadrature by employing a Wilkinson divider which shows good performance in return loss and transmission characteristic. According to the designed parameters of the helices and Wilkinson divider, a QHA is fabricated and me...

A compact MIMO antenna solution, the intelligent quadrifilar helix antenna for the IEEE 802.11n standard is proposed. Analysis has been made with regard to design considerations and preliminary narrowband measurements have been carried out to evaluate its capacity potential in comparison to conventional spatially separated linear antennas. The results indicate that there is comparable capacity ...