Dimensional Analysis and Physical Similarity of Lossy Electromagnetic Systems

The dimensional analysis is applied to the model measurements of lossy electromagnetic systems.The physical similarity between prototype and model system is given.By this theory,it is predictable that which conditions for the model system should be satisfied in order to get a result similar to the prototype of lossy electromagnetic phenomenon.

Physical Similarity of Lossy Scatterers

The theory of the physical similarity of lossy electromagnetic systems is used to analyze the lossy scatterers.Emphasis is placed on the analysis of the effects for the deviation of the similarity between the scatterers by virtue of dimensional analysis.

Pixel for Passive Terahertz Imaging System （PTIS） at the Base of Josephson Junction in Self-Pumping Regime

The use of Josephson junctions （JJ） in self-pumping mode as one of the heterodyne detection method can stay the new trend for design modern passive terahertz imaging system （PT1S）. Combination superconductive and semiconductor technologies on the one substrate in any case will born principal trend of the critical electronic technologies, including the realization superconductive JJ near the gate of a semiconductor transistor. Further development will allow to realize the PTIS system with electronic tuning of the receiving frequency. At the same time there exists yet additional new possibility to measure the frequency of the receiving signals （very briefly） on JJ.

A Novel Frequency Selective Surface with Improved Miniaturization Performance

Based on previous work, a novel Frequency Selective Surface (FSS) consisting of two metallic layers is proposed. The first layer is inductive-designed to generate the band-pass performance, while the second layer is capacitive-designed so that the miniaturization characteristic can be further improved. As a result, compared with the traditional single-layer structure, the profile of the FSS proposed is relatively small with the cell’s dimension only 0.0814λ × 0.0814λ. Moreover, the structure’s stability corresponding to waves of different polarizations and incident angles are also testified, which ensures the practicability of the proposed structure.

Bi-layered coded metasurface for multi-functional hologram with broadband transmission and efficient reflection

A multi-functional full-space metasurface based on frequency and polarization multiplexing is proposed.The metasurface unit consists of metallic patterns printed on the two faces of a single-layered dielectric substrate.The unit cell can control electromagnetic wavefronts to achieve a broadband transmission with amplitudes greater than 0.4 from 4.4 to 10.4 GHz.Meanwhile,at 11.7 GHz and 15.4 GHz,four high-efficiency reflection channels with a reflection amplitude greater than 0.8 are also realized.When illuminated by linearly polarized waves,five different functions can be realized at five different frequencies,which are demonstrated by theoretical calculations,full-wave simulations,and experimental measurements.

Complementary transmissive ultra-thin meta-deflectors for broadband polarization-independent refractions in the microwave region

Polarization manipulation is a significant issue for artificial modulation of the electromagnetic(EM) wave, but general mechanisms all suffer the restriction of inherent symmetric properties between opposite handedness.Herein, a strategy to independently and arbitrarily manipulate the EM wave with orthogonal circular polarizations based on a metasurface is proposed, which effectually breaks through traditional symmetrical characteristics between orthogonal handedness. By synthesizing the propagation phase and geometric phase, the appropriate Jones matrix is calculated to obtain independent wavefront manipulation of EM waves with opposite circular polarizations. Two transmissive ultra-thin meta-deflectors are proposed to demonstrate the asymmetrical refraction of transmitted circularly polarized waves in the microwave region. Simulated transmitted phase front and measured far-field intensity distributions are in excellent agreement, indicating that the transmitted wave with different polarizations can be refracted into arbitrary and independent directions within a wide frequency band(relative bandwidth of 25%). The results presented in this paper provide more freedom for the manipulation of EM waves, and motivate the realizations of various polarization-independent properties for all frequency spectra.

Birefringent transmissive metalens with an ultradeep depth of focus and high resolution

Depth of focus(DOF) and transverse resolution define the longitudinal range and definition of the focusing lens.Although metasurface axilenses and light-sword metalenses with radial and angular modulations can elongate the DOF, these approaches have inherent limitations in being reliable only for small numerical aperture(NA) cases,which in turn compromises the transverse resolution for the given aperture dimension. To conquer this limitation, we propose and experimentally demonstrate a birefringent metalens, achieving an ultradeep DOF of 41λ in terms of the total scattered field, corresponding to a record-breaking wide NA range from 0.14 to 0.7. Meanwhile,the diffraction limited focal spot size in this NA range can guarantee acquisition of images with high resolution. A hybrid methodology is proposed that utilizes both the accuracy of holography in electromagnetic field reconstruction and the polarization multiplexing to double the DOF. A stratified transmissive meta-atom is utilized to encode a pair of independent phase profiles in two orthogonal polarization channels. Furthermore, we combine the generalized scattering matrix with the multipole expansion theory for the first time to elucidate the mechanism of maintaining high transmittance and widening the transmission phase coverage by using the multilayered structure. The proposed metalens provides a competitive platform for devising high-resolution deep DOF systems for imaging and detection applications.

Complex-amplitude radiation-type metasurface enabling beamform-controlled energy allocation

Fifth-generation(5G)communication requires spatial multiplexing multiple-input multiple-output systems with integrated hardware.With the increase in the number of users and emergence of the Internet of Things devices,complex beamforming devices have become particularly important in future wireless systems to meet different communication requirements,where independent amplitude and phase modulations are urgently required for integrated beamforming devices.Herein,by utilizing the constructive interference between multiple geometricphase responses,the mathematical relation for decoupling amplitude and phase modulations in the radiation-type operational mode is derived.Based on this strategy,complex-amplitude radiation-type metasurfaces(RA-Ms)are implemented,with an integrated feeding network.Such metasurfaces exploit full 2πphase modulation and tailorable radiation amplitude in the circular polarization state.Meanwhile,a complex-amplitude retrieval method is developed to design the RA-Ms,enabling precise beamforming performances.On this basis,several functional devices based on the complex-amplitude RA-Ms,including energy-allocable multi-router,shape-editable beam generator,and complex beamformer,are demonstrated in the microwave region.The amplitude-phase decoupling mechanism with the retrieval method merges amplitude and phase modulations,and energy distribution into one compact and integrated electromagnetic component and may find applications in multi-target detection,5G mobile communication,and short-range ground-to-sea radar.

Dual-band independent phase control based on high efficiency metasurface[Invited]

A general method to realize arbitrary dual-band independent phase control is proposed and demonstrated in this paper.A double-layered C-shape reflective meta-atom is designed to realize independent phase control with high efficiency.As a proof of concept,we propose two functional metasurfaces in the microwave region;the first metasurface performs beam steering in different directions,and the second metasurface generates achromatic beam steering at two distinct frequencies.Both simulation and measurement results agree well with the theoretical pre-setting.The maximum measured efficiency is 88.7%and 92.3%at 6.8 GHz and 8.0 GHz,respectively,for one metasurface,and 91.0%and 89.8%at 6.9 GHz and8.6 GHz,respectively,for the other.

Compact logic operator utilizing a single-layer metasurface

In this paper, we design and demonstrate a compact logic operator based on a single-layer metasurface at microwave frequency. By mapping the nodes in the trained fully connected neural network(FCNN) to the specific unit cells with phase control function of the metasurface, a logic operator with only one hidden layer is physically realized. When the incident wave illuminates specific operating regions of the metasurface, corresponding unit cells are activated and can scatter the incident wave to two designated zones containing logical information in the output layer. The proposed metasurface logic operator is experimentally verified to achieve three basic logic operations(NOT, OR, and AND) under different input signals. Our design shows great application potential in compact optical systems, low-power consumption information transmission, and ultrafast wave-based full signal processing.

Shaped patterns synthesis in time-modulated antenna arrays with static uniform amplitude and phase excitations

Abstract A novel approach for the synthesis of shaped beam patterns in time-modulated antenna arrays(TMAAs)with static uniform amplitude and phase excitations is proposed in this paper.Based on the sideband radiation in TMAAs,shaped beam patterns can be realized by only controlling the switch-on time sequences of the TMAAs.Differential evolution(DE)algorithm is adopted to optimize the time modulation parameters to obtain the desired flat-top and cosecant-squared beams and to suppress the sidelobe levels(SLLs).Simulation results of a time-modulated linear array(TMLA)and a timemodulated semicircular array(TMSA)demonstrate the effectiveness of the proposed approach for the synthesis of shaped beam patterns from TMAAs.