Jianhao Wang

Electronically Tunable Miniaturized Antennas on Magnetoelectric Substrates With Enhanced Performance

Achieving relative permeability larger than 1 in antenna substrates can lead to antenna miniaturization, enhanced bandwidth, and tunable resonant frequency. Metallic magnetic films and self-biased ferrite films were introduced as a practical means to tune a patch antenna by loading a commercially available substrate in this paper. Novel antenna designs with metallic magnetic films and self-biased NiCo-ferrite films were investigated. Magnetic patch antennas were demonstrated at 2.1 GHz with a tuning resonant frequency range of 5-10 MHz (with the metallic magnetic films) and 7-23 MHz (with self-biased ferrite films). Three different cases of annular ring antennas with NiCo-ferrite films loading were also designed and analyzed. Antennas with self-biased magnetic films loading working at 1.7 GHz with a tuning range of 3-20 MHz were achieved.

High Performance Compact Microstripline Phase Shifter at C-Band Using Yttrium Iron Garnet

We report the fabrication of planar microstripline reciprocal phase shifter using a bulk Yttrium Iron Garnet (YIG) material. The propagation direction of the microstripline and magnetization direction of the YIG is collinear, and the length of the microstripline and the YIG was 50 mm in length. The proposed design shows large differential phase shifts of 100 degrees for applied magnetic fields varying from 0 to 0.56 times 104 A/m over the frequency range of 1.2 GHz between 5.4 GHz and 6.6 GHz. The average insertion loss, ~ 2.5 dB, was measured to have a 20% bandwidth at 6 GHz. The planar phase shifter presented here demonstrates a compact design, low loss, and an especially large phase shift with a relatively small bias field.

Size-dependent structure and magnetic properties of co-evaporated Fe-SiO2 nanoparticle composite film under high magnetic field

Composite film of Fe nanoparticles embedded in a SiO2 matrix has been prepared by the co-evaporation of Fe and SiO2. Both source temperature and in-situ high magnetic field (HMF) have been used to adjust the Fe particle size and the growth of Fe-SiO2film. The size of Fe particle decreased with increasing the source temperature without HMF. When HMF was presented during the growth of the film, the size of Fe particle was enlarged and reduced for source temperatures of 1300 °C and 1400 °C, respectively. Meanwhile, the preferred orientation of the filmgrown at 1400 °C became uniform with the application of HMF. In addition, it is also found that the film was formed in two layers. One layer is formed by the Fe particle, while the other is free of Fe particles due to the existence of more SiO2. The structural variation has a significant effect on the magnetic properties. The coercivity (90 Oe) of the 1300 °C film is much higher than that (6 Oe) of the 1400 °C film with a small particle size and uniform orientation. The saturation magnetization can be increased by increasing the Fe particle volume fraction. This study develops a new method to tune the soft magnetic properties by the co-evaporation of Fe and SiO2.