Yue-Long Lyu

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.

A Detached Zero Index Metamaterial Lens for Antenna Gain Enhancement

In this paper, a detached zero index metamaterial lens (ZIML) consisting of metal strips and modifled split ring resonators (MSRRs) is proposed for antenna gain enhancement. The efiective permittivity and permeability of the detached ZIML are designed to synchronously approach zero, which leads the ZIML to having an efiective wave impedance matching with air and near-zero index simultaneously. As a result, neither does the detached ZIML need to be embedded in horns aperture nor depends on auxiliary re∞ectors in enhancing antenna gain, which is quite difierent from conventional ZIMLs. Moreover, the distance between antenna and the detached ZIML slightly afiect the gain enhancement, which further conflrms that the ZIML can be detached from antennas. Simulated results show that the efiective refractive index of the detached ZIML is near zero in a broad frequency range where the efiective relative wave impedance is close to 1. The detached ZIML is fabricated and tested by placing it in front of an H-plane horn antenna. One flnds that evident gain enhancement is obtained from 8.9GHz to 10.8GHz and the greatest gain enhancement reaches up to 4.02dB. In addition, the detached ZIML can also work well at other frequencies by adjusting its geometric parameters to scale, which is demonstrated by designing and simulating two detached ZIMLs with center frequencies of 2.4GHz and 5.8GHz, respectively.

Leaky-Wave Antennas Based on Noncutoff Substrate Integrated Waveguide Supporting Beam Scanning From Backward to Forward

In this paper, we propose an approach to realize substrate integrated waveguide (SIW)-based leaky-wave antennas (LWAs) supporting continuous beam scanning from backward to forward above the cutoff frequency. First, through phase delay analysis, it was found that SIWs with straight transverse slots support backward and forward radiation of the -1-order mode with an open-stopband (OSB) in between. Subsequently, by introducing additional longitudinal slots as parallel components, the OSB can be suppressed, leading to continuous beam scanning at least from -40° through broadside to 35°. The proposed method only requires a planar structure and obtains less dispersive beam scanning compared with a composite right/left-handed (CRLH) LWA. Both simulations and measurements verify the intended beam scanning operation while verifying the underlying theory.

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.

Periodic SIW Leaky-Wave Antenna With Large Circularly Polarized Beam Scanning Range

In this letter, we propose and demonstrate a periodic leaky-wave antenna (P-LWA) by loading transverse slot pairs (TSPs) and longitudinal slots (LSs) along substrate integrated waveguide. The proposed P-LWA is able to yield a circularly polarized beam, which scans continuously from backward, through broadside, and to forward. Furthermore, it is shown that a large circularly polarized beam scanning range requires maximally coinciding radiation patterns of TSPs and LSs. Hence, within the design and optimization of the proposed P-LWA, the radiation pattern of the TSP should be adjusted to match the radiation pattern of the LS. A resulting large circularly polarized beam scanning range from −40° to 25° has been predicted by simulations and experimentally verified. This circularly polarized beam scanning range turns out to be larger than in most of the previously reported works.

Frequency splitting elimination in wireless power transfer using nonidentical resonant coils

We propose an approach to eliminate frequency splitting in wireless power transfer (WPT). Two nonidentical resonant coils (NIRCs) are used in this method as 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 NIRCs. Therefore, frequency splitting caused by over-coupling can be eliminated. Experimental measurement of the NIRCs shows that frequency splitting is completely eliminated and uniform voltage across the load is achieved.

Electrically steerable leaky-wave antenna capable of both forward and backward radiation based on liquid crystal

In this paper, a electrically beam scanning leaky-wave antenna (LWA) based on composite right/left-handed (CRLH) rectangular waveguide (RWG) is presented. In the proposed LWA, liquid crystal (LC) is chosen as tunable material, which could be controlled by applied electric and magnetic field. The beam of LWA proposed can be steered at a fixed frequency as the electromagnetic parameters of LC change under different bias voltages. The designed antenna supports the backward-to-forward beam scanning. It is found from simulations that the antenna has a beam scanning angle from -19° to 12° at 9.7 GHz.

A half-mode substrate integrated waveguide based leaky-wave antenna with open-stopband suppression

This paper presents a leaky-wave antenna (LWA) based on half-mode substrate integrated waveguide (HMSIW). The proposed LWA consists of transverse and longitudinal slots in one unit cell, by properly adjusting the structure parameters of the slots, open-stopband can be suppressed and hence the proposed LWA features continuous beam scanning from backward, through broadside, and to forward. Additional transverse slots are also implemented to suppress the cross polarization level. Numerical simulations are conducted and the results verify the theory very well.

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.