Showing papers by "Zhen Liao published in 2019"

Broadband Band-Absorptive Frequency-Selective Rasorber With a Hybrid 2-D and 3-D Structure

Abstract: A novel frequency-selective rasorber (FSR) with a broad absorption band is proposed in this letter. The proposed FSR is realized by vertically cascading a two-dimensional (2-D) lossy layer with a 3-D band-stop frequency-selective structure (FSS). The 2-D lossy layer is composed of meandered square loops loaded with lumped resistors, and the 3-D band-stop FSS is constructed by parallel-plate waveguide arrays (PPWAs) stacked along the TE polarization direction (linear polarization perpendicular to the PPW). The band-absorptive FSR exhibits an absorption band (| S 11| ≤ –10 dB and | S 21| ≤ –10 dB) from 7.85 to 12.85 GHz and a low-pass band (| S 21| ≥ –1 dB) up to 3.8 GHz. Its transition efficiency of the transition band (FRap) is 2.1. A prototype is fabricated, and its measured results show that the proposed FSR has a low loss and flat low-pass band, a wide absorption band with high selectivity, and a steep transition band between the low-pass band and absorption band.

3D Band-Absorptive Frequency Selective Rasorber: Concept and Analysis

Abstract: This paper presents a 3D band-absorptive frequency selective rasorber (FSR). Such an FSR is absorptive within a specific band and almost transparent below the absorption band. The definition and evaluation of the band-absorptive FSR is initially provided and followed by the design concept of 3D FSR. An example is then proposed, whose unit cell is composed of 3D absorber and 3D band-stop FSS. An equivalent circuit model is established for understanding its operating principle. A prototype of the proposed 3D band-absorptive FSR is fabricated. The measured results show that it has an absorption band ( $\vert S_{11}\vert \le -10$ dB and $\vert S_{21}\vert \le -10$ dB) from 4.21 to 6.51 GHz, with a thickness of 0.17 wavelength at 4.21 GHz. Moreover, $\vert S_{21}\vert $ is higher than −1 dB at the frequencies below 1.28 GHz. The proposed band-absorptive FSR can be used as radomes for low-frequency antennas in military communications or spectrum monitoring systems.

Subwavelength negative-index waveguiding enabled by coupled spoof magnetic localized surface plasmons

Abstract: Magnetic localized surface plasmon modes are supported on metallic spiral structures. Coupling mechanisms for these metamaterial resonators, which are the joint action of magnetic and electric coupling, are studied. Based on the strong coupling, spoof magnetic plasmon modes propagating in the backward direction are proposed along a chain of subwavelength resonators. The theoretical analysis, numerical simulations, and experiments are in good agreement. The proposed novel route for achieving negative-index waveguiding has potential applications in integrated devices and circuits.

Concentric designer plasmon hybridization in deep subwavelength metamaterial resonator

Abstract: Concentric spoof surface plasmon hybridization in the microwave frequency is physically realized with subwavelength plasmonic metamaterials. The hybridization is generated with two concentric spoof localized surface plasmon (LSP) particles, where the overlap of the two spoof LSP particles could be tuned to manipulate the resonance. Such spoof plasmon hybridization could increase the Q factor effectively up to 965, and decrease the electric dimension of the particle down to 1/7 wavelength. The coupled-resonator circuit theory is applied to analyze the interaction mechanism of the structure with strong electric and magnetic coupling. Near electric-field distributions are mapped in the simulation and experiment to characterize the resonant property. Both the bonding mode and the antibonding mode are observed. A free space measurement system is adopted to improve the measurement of the spoof LSP resonant spectra.

Wideband Direction-of-Arrival Estimation With Arbitrary Array via Coherent Annihilating

Abstract: In this paper, a new wideband DOA estimation method for arbitrary array application is proposed. The arbitrary array manifold is approximately decomposed under the concept of manifold separation technique (MST) and a linear combination of the equal interval sampling complex exponentials (EISCE) can be synthesized. Since the EISCEs at all frequencies contain the same DOA information, they can be annihilated by the same spatial annihilating filter. So, the coherent annihilating scheme is proposed, and all narrowband components are coherently combined to construct an optimization problem under the structural total least squares framework. During the optimization problem construction, the general solution method is proposed to enable the model approximation error in MST to be reduced to a negligible level. Finally, the optimization problem is solved through the multiple measurement vectors structural total least norm (MMV-STLN) approach and the DOAs are estimated from the reconstructed spatial annihilating filter. The new method is free of frequency focusing and is capable of handling both incoherent and coherent signals. The simulation results verify that the proposed method surpasses the existing methods largely in resolution and estimation performance under the low SNR, snapshot deficient, and closely spaced sources scenarios.

Three-dimensional band absorption-type absorptive frequency selective structure

Abstract: The invention discloses a three-dimensional band absorption-type absorptive frequency selective structure, which is a periodically distributed structure. A structure unit adopts a mode of stacking oftwo layers of step-impedance parallel plate waveguides, loading of lumped capacitors and resistors is combined, and the performance of low-frequency wave transmission and high-frequency wave absorption is realized. The structure unit is composed of an upper parallel plate waveguide and front and rear loading parts, and a lower parallel plate waveguide and the rear loading part. The structure disclosed in the invention can be used for a stealth radome of a low frequency antenna in a military field. The three-dimensional band absorption-type absorptive frequency selective structure can transmitelectromagnetic waves at low frequencies without loss and can realize the wave absorption function in a wide frequency band at high frequencies, thereby reducing reflection of out-of-passband electromagnetic waves and realizing good stealth characteristics.

A Novel Tri-Beam Antenna System Based on U-Shaped Dipole

Abstract: Consisting of 6 radiating elements and a 3 × 3 Butler matrix, a novel tri-beam antenna system is proposed in this paper. The radiating element consists of two U-shaped arms and coupled strips, which shows a wide impedance characteristic. Three branch line couplers and four –90° phase shifters are combined into 3 × 3 Butler matrix as a beam-forming network (BFN). In order to avoid the crossover of transmission lines, one main line of a 1.76 dB coupler is designed and located between two 3 dB couplers. With this arrangement, the signal from one input port can be divided into three output signals with equal amplitude and specified phase differences of 0°, +120° and –120°. Furthermore, a 2 × 3 antenna array is connected with this BFN for three orthogonal beams. Measured results show that three beams at θ = 0°, 40° and –40° are produced when different input ports are excited.

The Coupling Mechanism In Two Magnetic Localized Surface Plasmons Modes

Abstract: Magnetic localized surface plasmons modes are supported on metallic spiral structures. Coupling mechanisms for these metamaterial resonators are studied, which are the joint action of magnetic and electric coupling.