Bang-Jun Che

A Method of Using Nonidentical Resonant Coils for Frequency Splitting Elimination in Wireless Power Transfer

In this paper, an efficient method is proposed to eliminate frequency splitting in nonradiative wireless power transfer via magnetic resonance coupling. In this method, two nonidentical resonant coils (NIRCs) are used as wireless power transmitter and receiver, respectively. According to the elliptic integral term in the analytical expression, the pole of the mutual inductance function with respect to transfer distance can be eliminated by using the two NIRCs, and hence overcoupling between transmitter and receiver with close transfer distance is avoided. Therefore, frequency splitting caused by overcoupling can be suppressed and stable output power can be achieved. The NIRCs are analytically calculated, numerically simulated and finally, fabricated and tested to verify the theory. All the calculated and experimental results show that frequency splitting is completely eliminated and uniform voltage across the load is achieved. Furthermore, lateral misalignment between the NIRCs barely introduces frequency splitting, and the suppression level of frequency splitting can also be controlled freely.

Magnetic metamaterial analog of electromagnetically induced transparency and absorption

In this paper, it is theoretically demonstrated that the electromagnetically induced transparency (EIT) and absorption (EIA) can be achieved in a magnetic metamaterial. Unit cell of metamaterial consists of a split ring resonator and an “I” shaped cut-wire pair, which serves as a bright resonator and a dark resonator, respectively. It is found that the EIT effect in metamaterial results from the magnetic interaction between bright and dark resonators. A classical model is also introduced to describe the EIT behavior in magnetic metamaterial, and its analytical results are in good agreement with numerical results. Significantly, by controlling the space separation between resonators, we can obtain the destructive and constructive interferences, and thus observe the transition between EIT and EIA. These results may achieve potential applications on enhancing the nonlinear interaction.

Electrically Controllable Composite Right/Left-Handed Leaky-Wave Antenna Using Liquid Crystals in PCB Technology

A design method for electrically controllable composite right/left-handed (CRLH) leaky-wave antennas (LWAs) with large beam-steering range employing liquid crystal (LC) in printed circuit board technology is proposed. It is demonstrated with detailed mathematical derivation that the design principle enables the LC-CRLH-LWA to keep the balanced condition with all bias states applied to the LC, yielding LC-CRLH-LWAs that feature a steady balanced condition and a broadband property. Based on this principle, an LC-CRLH-LWA prototype is designed, simulated, optimized, and experimentally validated. According to the simulation results, the designed LC-CRLH-LWA operates in the band from 11.14 to 12.77 GHz with a frequency-agile radiation direction. By tuning the permittivity of LC, the radiation direction of the designed antenna scans from −21° to +23° at the fixed operating frequency of 12.4 GHz. The experimental results agree well with the simulated data. Furthermore, sidelobe level suppression of the designed antenna is achieved through decreasing the reflection between the unit cells of the antenna.

A Novel liquid crystal based leaky wave antenna

A Novel electrically controllable composite right/left-handed leaky wave antennas (CRLH-LWAs) based on liquid crystal (LC) is proposed. Simulation results show the antenna exhibits a simulated beam scanning angle of -47° to +56° over the frequency range of from 11.8 GHz to 13 GHz. A simulated bandwidth from 11.78 GHz to 13.09 GHz is achieved. By steering the permittivity of LC, the antenna presents a simulated range of electrically beam steering from -21° to +23° is presented at 12.4GHz.

A dual band CRLH leaky wave antenna with electrically steerable beam based on liquid crystals

A dual band CRLH leaky wave antenna with electrically steerable beam based on liquid crystals is designed and investigated. Lots of full-wave simulations are conducted with CST MW Studio software package to optimize and analyze the performance of the antenna. It shown that the proposed LWA achieves the beam scanning from −16° to + 21° at 7.2 GHz and from −10° to + 19° at 9 GHz simultaneously, through tuning the permitivity of the LC material. Such electrically tunable dual-band LWA can be used as an effective and feasbile common antenna for the signal transmitting and receiving of satellite communication in motion.

A novel method for omnidirectional wireless power transmission

In this paper, a novel method for omnidirectional wireless power transmission (OWPT) via magnetic resonant coupling is proposed. In the proposed OWPT, a pair of cross coil consists of two orthogonal loops with 90° feeding phase difference serve as the wireless power transmitter. Through both theoretical analyses and numerical simulations, it is shown that, rotating magnetic field is generated and wireless power is achieved on receiver moving around the transmitter. Then a cylindrical metamaterial slab with negative permeability is designed to improve the efficiency of the OWPT system, for the unique property of enhancing evanescent wave of metamaterials. The simulation results show that the efficiency of the OWPT can be significantly improved by the metamaterial slab.

A novel method for frequency splitting suppression in wireless power transfer

A novel method using resonant coils of different sizes is proposed to suppress frequency splitting in wireless power transfer (WPT). Frequency splitting is caused by excessive mutual inductance between transmitter and receiver, and can be suppressed by reasonably designing the sizes of the transmitter and receiver to eliminate the pole value of the mutual inductance. Theory calculation are conducted to present the transfer efficiency of WPT adopting the proposed method. Frequency splitting is remarkably suppressed and transfer efficiency maintains high value.