Artificially engineered metasurfaces provide extraordinary wave control at the subwavelength scale. However, metasurfaces proposed so far suffer due to limited bandwidths. In this paper, extremely thin metasurfaces made of single metallic layer is experimentally presented for ultra-wideband operation from 9.3 to 32.5 GHz (with a fractional band of 112%), working at both transmission and reflection modes simultaneously. The phase control is achieved by azimuthally rotating the scatterer based on Pancharatnam-Berry phase principle. Nearly uniform efficiency (≈25%), approaching the theoretical limit of the infinitely thin metasurface, is achieved throughout the operation band. Finally, the proposed design is implemented for applications, e.g., the generation of electromagnetic waves carrying orbital angular momentums as well as anomalous reflections and refractions. The metasurfaces are characterized numerically and experimentally and the results are in good agreements.

Ultrathin Single Layer Metasurfaces with Ultra-Wideband Operation for Both Transmission and Reflection.

Geometric metasurfaces primarily follow the physical mechanism of Pancharatnam-Berry (PB) phases, empowering wavefront control of cross-polarized reflective/transmissive light components. However, inherently accompanying the cross-polarized components, the copolarized output components have not been attempted in parallel in existing works. Here, a general method is proposed to construct phase-modulated metasurfaces for implementing functionalities separately in co- and cross-polarized output fields under circularly polarized (CP) incidence, which is impossible to achieve with solely a geometric phase. By introducing a propagation phase as an additional degree of freedom, the electromagnetic (EM) energy carried by co- and cross-polarized transmitted fields can be fully phase-modulated with independent wavefronts. Under one CP incidence, a metasurface for separate functionalities with controllable energy repartition is verified by simulations and proof-of-principle microwave experiments. A variety of applications can be readily expected in spin-selective optics, spin-Hall metasurfaces, and multitasked metasurfaces operating in both reflective and transmissive modes.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/advs.202001437

A Fully Phase-Modulated Metasurface as An Energy-Controllable Circular Polarization Router.

Regarding miniaturized and integrated systems, a single flat device that possesses diversified functionalities is highly desirable in optical to microwave regimes. With this perspective, bifunctional metalenses constructed by meta-atoms with integrated response to propagation phase and geometric phase are proposed for independent manipulation of right-handed and left-handed circularly polarized waves. The derived general criterion is verified in the microwave region from three bifunctional metalenses operating in transmission manner. The proof-of-concept measurements show that all these metalenses exhibit two independent functionalities that can be switched by flipping the helicity of the incident illumination. Very high efficiencies of around 80%, with peak value of 91%, are achieved by the ultrathin metasurfaces of thickness 0.15λ0. The proposed metasurfaces provide a promising route for the realization of reconfigurable lenses and antennas in wireless communication systems.

High-Efficiency Metalenses with Switchable Functionalities in Microwave Region.

Broadband high-efficiency cross-polarization conversion and multi-functional wavefront manipulation based on chiral structure metasurface for terahertz wave

Polarization-Engineered Noninterleaved Metasurface for Integer and Fractional Orbital Angular Momentum Multiplexing

In this paper, ultra-thin metalenses are proposed to generate converging and non-diffractive vortex beam carrying orbital angular momentum (OAM) in microwave region. Phase changes are introduced to the transmission cross-polarized wave by tailoring spatial orientation of Pancharatnam-Berry phase unit cell. Based on the superposition of phase profile of spiral phase plate and that of a converging lens or an axicon, vortex beam carrying OAM mode generated by the metalens can also exhibit characteristics of a focusing beam or a Bessel beam. Measured field intensities and phase distributions at microwave frequencies verify the theoretical design procedure. The proposed method provides an efficient approach to control the radius of vortex beam carrying OAM mode in microwave wireless applications for medium-short range distance.

Phase-engineered metalenses to generate converging and non-diffractive vortex beam carrying orbital angular momentum in microwave region

This paper proposes a channelized receiver based on microwave photonic, the system generated two coherent optical frequency comb with different free spectral ranges. By adjusting carrier frequency, a different frequency interval is formed between the local frequency comb and the optical comb modulating the signal to be measured. After the two optical combs pass through the optical demultiplexer respectively, the corresponding channel is beat frequency and the heterodyne detection is realized by converting the signal to intermediate frequency.The scheme proposed in this paper realizes the measurement frequency range of 2GHz~18GHz, has the instantaneous bandwidth of more than 7GHz, and the average error is less than 50MHz

Research on channelized receiver based on microwave photonic with large instantaneous bandwidth

Generalized FRM-Based P-L Band Multi-Channel Channelizers for Array Signal Processing System

Design and Implementation of FRM-based Filter Bank with Low Complexity for RJIA

The traditional multi-subband radar signal fusion method based on pole information fits nonlinear signals via linear models. It is very important to accurately estimate the order of the pole model, as the wrong order will lead to errors in the resulting fusion signal. In the case of low signal-to-noise ratio (SNR), it is difficult to obtain accurate pole values. When a noise suppression method is included in the algorithm, the influence of noise on the pole order may be effectively avoided. However, traditional methods have many complex links, and only a few samples can be tested each time. Also, approximating a linear model onto a nonlinear signal will inevitably have errors. Therefore, this paper proposes a method based on the deep neural network (DNN) that applies nonlinear fitting of deep learning to complete the fusion process. The multi-subband distance envelopes are input into the DNN, and the fusion full-band distance envelopes are obtained as the output. Using DNN for subband fusion could improve the radar range resolution and obtain high-resolution one-dimensional range profiles.

/pdf/multi-subband-radar-signal-fusion-processing-based-on-deep-1zcn4t6f.pdf

Manjun Lu

Papers

Phase-engineered metalenses to generate converging and non-diffractive vortex beam carrying orbital angular momentum in microwave region

Research on channelized receiver based on microwave photonic with large instantaneous bandwidth

Generalized FRM-Based P-L Band Multi-Channel Channelizers for Array Signal Processing System

Design and Implementation of FRM-based Filter Bank with Low Complexity for RJIA

Multi-Subband Radar Signal Fusion Processing Based on Deep Neural Network in Low Signal-to-Noise Ratio