Xianjun Sheng

A Compact Miniaturized Frequency Selective Surface with Stable Resonant Frequency

A compact miniaturized frequency selective surface (FSS) with stable resonant frequency is proposed in this letter. The proposed FSS is composed of four spiral triangles connected in the middle of the unit cell, symmetrically. Simulated results show that the dimension of the element is only 0.0558λ0 × 0.0558λ0, and reduction in FSS size is up to 97.7% with respect to conventional cross-dipole FSS operating at the same frequency of 2.7 GHz. Also, the proposed FSS has great angular stability, and the resonant frequency deviation keeps below 0.4% for both TM and TE polarizations of 60◦ incident angle.

A miniaturized FSS based on tortuous structure design

A miniaturized frequency selective surface (FSS) composed of wire grid and tortuous pattern of cross-dipole element has been proposed to realize a first-order band-pass response. Resonant frequency of the proposed FSS can be adjusted by changing tortuous factor of the cross-dipole element. Sharper one-side roll-off characteristic and better resonant frequency angular stability can be obtained by the proposed FSS with a larger tortuous factor. Also, by cascading the proposed FSS of different tortuous factors, a dualband frequency filter property can be obtained. The proposed FSS is analyzed by equivalent circuit method and full-wave simulations.

Influence of tilt angle on eddy current displacement measurement

For displacement measurement, to explore the influence of tilt angle on sensor’s measured values, the relationship between coil equivalent inductance and lift-off under different tilt angles and the relationship between coil equivalent inductance and tilt angle under different lift-offs were investigated by the finite element method in this article, respectively. Comparing the two variation laws, the increase of tilt angle will lead to smaller sensor’s measured values. Moreover, the applicability of the transformer-equivalent circuit model has nothing to do with the tilt angle. Besides, the experiments also testify that the measuring errors can be compensated well by the Gaussian function.

A dual-band fractal FSS with SZ curve elements

A novel dual-band miniaturized frequency selective surface adopting fractal elements is proposed. The proposed structure is composed of interconnected four SZ curves of second generation. Such a design is to provide two pass-bands with stable performance, the first band resonates at S-band with a center frequency of 3.02GHz and the second band is at C-band centered at 7.22GHz. In addition, the compact structure employing the space filling curve can further reduce the size of the FSS. The dual-band FSS achieves better miniaturization compared with other single layer FSS in previous literature, the dimension of the unit cell is only 0.072λ × 0.072λ, where λ represents the free space wavelength at first resonant frequency. Furthermore, the proposed FSS exhibits great resonance stability for different polarizations and incidence angles. Both the simulation and measurement verify the stable performance of the FSS.

A Miniaturized Dual-Band FSS With Controllable Frequency Resonances

A novel dual-band miniaturized frequency-selective surface (FSS) is proposed in this letter. The proposed FSS is composed of cross dipole aperture element combined with meandered monopole aperture element. The single layer FSS provides two pass-bands centered at 5.13 and 8.85 GHz with bandwidth of 1.27 and 1.33 GHz, respectively. The two pass-band frequencies of the designed FSS can be controlled independently by simply changing structure parameters of the unit cell. In addition, the dual-band FSS designed using the miniaturized element exhibits excellent resonance stability for different polarizations and incident angles. A prototype of the proposed FSS is fabricated and measured. A good agreement between the simulation and the measured results is obtained, which demonstrates the stable performance of the FSS.

Reconfigurable frequency selective surface with multiband characteristic

In this paper, a reconfigurable frequency selective surface (RFSS) with multiband characteristic has been proposed. The proposed RFSS is composed of two FSS layers separated by a thin dielectric substrate. The top FSS layer is composed of modified cross-dipole element and the bottom layer is wire grid of the same periodicity. By placing high frequency switch PIN diodes between the modified cross-dipole elements in the top FSS layer, controllable frequency response can be obtained. Simulated results show that the proposed RFSS structure can provide two pass-bands operating at 2.2GHz and 3.5GHz when the PIN diodes at ON state. On the contrary, when the PIN diodes turn OFF, the proposed RFSS can provide three pass-bands operating at 1.2GHz, 2.6GHz and 4.1GHz, respectively.

Design of FSS radome using binary particle swarm algorithm combined with pixel-overlap technique

Abstract An optimization method for designing frequency selective surface (FSS) radome using binary particle swarm optimization (BPSO) algorithm combined with pixel-overlap technique is proposed, in this paper. The proposed method takes the connectivity condition of adjacent conductors within FSS element into consideration. With the help of pixel-overlap technique, lattice points in FSS element are avoided by overlapping adjacent conductors, which improves the manufacturability of the FSS layers. Also, structure parameters of the FSS radome can be obtained according to the desired frequency selective property using the BPSO algorithm. To verify the validity of the proposed method, a sandwich-structured FSS radome is designed, fabricated, and measured. Good agreements between the simulation and measurement results can be observed, which demonstrate that the proposed method can be applied to design FSS radome.

A feasible bandwidth compensation technique for FSS radome design

In this paper, a feasible compensation technique has been proposed to improve the bandwidth angular stability of FSS radome. Stacked structure composed of different mechanical suitable materials has been adopted to construct the bandwidth compensation layer in the proposed technique. Hence, the problem that mechanical suitable materials with lower permittivity are not available in the classic bandwidth compensation technique has been solved. The validity of the proposed technique is verified by designing an FSS radome composed of modified second-order miniaturised FSS (MFSS) and bandwidth compensation layers. Simulation results show that the proposed technique has equal performance in stabilizing the bandwidth of FSS radome under oblique incidence with the classic one.

A Miniaturized Triband Frequency Selective Surface Based on Convoluted Design

A novel miniaturized tri-band frequency selective surface (FSS) based on convoluted design has been proposed in this letter. The proposed FSS is a low-profile structure, and it is composed of two periodic metallic arrays separated by a thin dielectric substrate. The top metallic array is composed of four branched spiral triangles connected in the center, and the bottom one is consisting of gridded tortuous cross-dipole. The proposed FSS can provide three passbands operating at 3.28, 4.2, and 5.4 GHz, respectively. The unit cell is only 0.066 λ0 × 0.066 λ0 in size, where λ0 is the wavelength of the first resonant frequency in free space. In addition, the proposed FSS provides a stable performance under oblique incidence for both TE and TM polarizations. For verification, an FSS prototype has been fabricated and measured. Good agreements between the simulated and the measured results can be observed.

Identification for Active Vibration Control of Flexible Structure Based on Prony Algorithm

Flexible structures have been widely used in many fields due to the advantages of light quality, small damping, and strong flexibility. However, flexible structures exhibit the vibration in the process of manipulation, which reduces the pointing precision of the system and causes fatigue of the machine. So, this paper focuses on the identification method for active vibration control of flexible structure. The modal parameters and transfer function of the system are identified from the step response signal based on Prony algorithm, while the vibration is attenuated by using the input shaping technique designed according to the parameters identified from the Prony algorithm. Eventually, the proposed approach is applied to the most common flexible structure, a piezoelectric cantilever beam actuated by Macro Fiber Composite (MFC). The experimental results demonstrate that the Prony algorithm is very effective and accurate on the dynamic modeling of flexible structure and input shaper could significantly reduce the vibration and improve the response speed of system.