Guo-Min Yang

Small Ultra-Wideband (UWB) Bandpass Filter With Notched Band

A compact ultra-wideband (UWB) bandpass filter (BPF) with notched band has been proposed and implemented in this letter. H-shaped slot is studied and adopted to tighten the coupling of inter-digital capacitor in order to improve the BPFs performance. Three pairs of tapered defected ground structures (DGS) are formed to assign their transmission zeros towards the out of band signal, thereby suppressing the spurious passband. Combining these two structures we obtain a small sized UWB BPF. Meander line slot is developed to reject the undesired wireless local-area network (WLAN) radio signals. An experimental UWB filter with notched band was fabricated with 35% less length as compared to an embedded open-circuited stub. The measured BPF insertion loss is less than 1.0 dB throughout the pass band of 2.8 to 10.8 GHz, the variation of group delay less than 0.20 ns in this band except for the notched band, and a wide stopband bandwidth with 20 dB attenuation up to at least 20.0 GHz.

Electrical tuning of magnetism in Fe3O4/PZN–PT multiferroic heterostructures derived by reactive magnetron sputtering

Strong magnetoelectric (ME) coupling was demonstrated in Fe3O4/PZN–PT (lead zinc niobate–lead titanate) multiferroic heterostructures obtained through a sputter deposition process. The dependence of the magnetic anisotropy on the electric field (E-field) is theoretically predicted and experimentally observed by ferromagnetic resonance spectroscopy. A large tunable in-plane magnetic anisotropy of up to 600 Oe, and tunable out-of-plane anisotropy of up to 400 Oe were observed in the Fe3O4/PZN–PT multiferroic heterostructures, corresponding to a large ME coefficient of 100 Oe cm/kV in plane and 68 Oe cm/kV out of plane, which match well with predicted results. In addition, the electric field manipulation of magnetic anisotropy is also demonstrated by the electric fields dependence of magnetic hysteresis loops, showing a large squareness ratio change of 44%. These Fe3O4/PZN–PT multiferroic heterostructures exhibiting large E-field tunable magnetic properties provide great opportunities for novel electrostatic...

Wideband vibration energy harvester with high permeability magnetic material

A vibration energy harvester based on a high permeability cantilever beam was demonstrated, which overcomes the limitation of the existing approaches in output power and working bandwidth. Magnetostatic coupling between the vibrating highly permeable beam and bias magnetic field leads to maximized flux change and large induced voltage. The coexistence of magnetostatic and elastic potential energy results in the nonlinear oscillation with wide bandwidth. The harvester showed a maximum power of 74 mW and power density of 1.07 mW/cm3 at 54 Hz under acceleration of 0.57 g (with g=9.8 m/s2), and bandwidth of 10 Hz (or 18.5% of the operating frequency).

Planar Annular Ring Antennas With Multilayer Self-Biased NiCo-Ferrite Films Loading

With their high relative permeability, magneto-dielectric materials show great potential in antenna miniaturization. This paper presents an annular ring antenna with self-biased magnetic films loading in the gigahertz frequency range. The annular ring antenna was realized by cascading a microstrip ring and a tuning stub. Self-biased NiCo-ferrite films were adopted to load an annular ring antenna on a commercially available substrate that operates at 1.7 GHz. Novel antenna designs with self-biased NiCo-ferrite films on one side and both sides of the substrate were investigated. Antennas with self-biased magnetic films loading working at 1.7 GHz showed a down shift of 2-71 MHz of the central resonant frequency. An antenna gain enhancement of up to 0.8 dB was observed over the non-magnetic antenna.

Tunable Miniaturized Patch Antennas With Self-Biased Multilayer Magnetic Films

Magneto-dielectric substrates with thin magnetic films show great potential in realizing electrically small tunable antennas with enhanced bandwidth, improved directivity, and high efficiency. This communication introduces self-biased NiCo-ferrite magnetic films as a practical mean to tune a patch antenna by loading single layer and multilayer self-biased ferrite films. The central resonant frequency of the unloaded patch antenna is measured at 2.1 GHz with a bandwidth of 18 MHz. However, with ferrite loading of the alumina substrate, this frequency is shown to be tunable within a range of 12 MHz-40 MHz, and the antenna efficiency is increased from 41% of the non-magnetic antenna to 56%, 65%, and 74% for the three magnetic antennas. Theomnidirectional radiation pattern is significantly enhanced with the -5 dBic gain beamwidth increased from 140deg to 155deg, 156deg and 160deg, respectively for the three ferrite loaded antennas. In addition, the gains of the three magnetic antennas are enhanced by 0.32, 0.77, and 1.1 dB, respectively, over the unloaded antenna.

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.

Recent advances in multiferroic oxide heterostructures and devices

The increasing demand for realizing ultra-fast, compact, and ultra-low power electronics/spintronics has propelled the creation of novel multiferroic heterostructures which enable voltage control of magnetism in an energy efficient way. In this progress report, we present an overview of recent advances and future prospects of the most attractive oxide multiferroic heterostructures, with an emphasis on the development of strong magnetoelectric coupling effects and their device applications. In particular, we review the recent progress in spinel/ferroelectric and garnet/ferroelectric multiferroic oxide heterostructures.

Ultrawideband (UWB) Antennas With Multiresonant Split-Ring Loops

Novel ultrawideband (UWB) antennas with multiresonant split-ring loops and with coplanar waveguide (CPW) feed are presented in this communication. Dual concentric microstrip split-ring loops with different geometrical ground planes have been analyzed and compared. UWB antennas are designed, of which the dimension of each split-ring loop varies proportionally to the arithmetic progression sequence. The dimensions of the rectangular ground planes and the split-ring loops are tuned for achieving a very wide bandwidth. A tapered transmission line is adopted to improve the return loss performance in the required band. Measurement results show that the proposed UWB antennas have a wide bandwidth from 2 to 20 GHz, and the measured return losses are less than -10 dB in this band combined with relative stable radiation characteristics.

Compact UWB Bandpass Filter With Dual Notched Bands Using Defected Ground Structures

This letter proposes a novel ultra-wideband (UWB) bandpass filter (BPF) with dual notched bands using triangular defected ground structures (DGS). Two symmetrical dumbbell-shaped interdigital capacitors are formed to improve the BPFs performance. Three pairs of tapered defected ground structures are studied and adopted to suppress the spurious passband by assigning their transmission zeros towards the out of band signal. A small UWB BPF is obtained by combining these two structures. One of the arms in coupled-line sections is extended and folded to create a notched band at 5.3 GHz, and a meander line slot is developed to create another notched band at 7.8 GHz. Simulated and measured results are in good agreement indicating that the proposed BPF has a passband from 2.8 to 11.0 GHz and a wide stopband bandwidth with 20 dB attenuation up to 30.0 GHz.

Optimal Design of an Antenna Array for Energy Harvesting

A high-gain, linear polarized microstrip antenna array for energy harvesting at 915 MHz is studied in this letter. The optimization theory for wireless power transmission efficiency has been used to design the feeding network of the antenna array to achieve the maximum power transmission efficiency with a given antenna configuration. As a demonstration, a light emitting diode (LED) is used as the resistive load of the rectifier (a three-stage Dickson charge pump circuit) connected to the antenna array terminal. For a given input power of 10 dBm fed into a circularly polarized transmitting antenna with 6 dBi gain, the maximum distance for lighting the LED is 51 cm.