A novel, compact, and highly selective ultra-wideband （UWB） bandpass filter with a narrow notched band is presented. Apart from having a basic structure of a slotline multiple-mode resonator （MMR） and microstrip f...A novel, compact, and highly selective ultra-wideband （UWB） bandpass filter with a narrow notched band is presented. Apart from having a basic structure of a slotline multiple-mode resonator （MMR） and microstrip feed lines, this novel design introduces a cross-coupling between the input and output feed lines to enhance the filter selectivity. The design strictly follows the theory and verified by electromagnetic （EM） simulation and experiments. In addition, the narrow notched band is introduced by embedding a pair of split ring resonators （SRR） in order to reject any undesired existing radio signals that may interfere with the Federal Communications Commission （FCC）-defined UWB band. By changing the structural parameters of SRR, it can be easily tuned to any desired frequency. This filter can be integrated in UWB communication systems and efficiently improve the interference immunity from undesired signals such as wireless local area network （WLAN）.展开更多
The developments of the high speed analog to digital converters （ADC） and advanced digital signal processors （DSP） make the smart antenna with digital beamforming （DBF） a reality. In conventional M-elements arra...The developments of the high speed analog to digital converters （ADC） and advanced digital signal processors （DSP） make the smart antenna with digital beamforming （DBF） a reality. In conventional M-elements array antenna system, each element has its own receiving channel and ADCs. In this paper, a novel smart antenna receiver with digital beamforming is proposed. The essential idea is to realize the digital beamforming receiver based on bandpass sampling of multiple distinct intermediate frequency （IF） signals. The proposed system reduces receiver hardware from M IF channels and 2M ADCs to one IF channel and one ADC using a heterodyne radio frequency （RF） circuitry and a multiple bandpass sampling digital receiver. In this scheme, the sampling rate of the ADC is much higher than the summation of the M times of the signal bandwidth. The local oscillator produces different local frequency for each RF channel The receiver architecture is presented in detail, and the simulation of bandpass sampling of multiple signals and digital down conversion to baseband is given. The principle analysis and simulation results indicate the effectiveness of the new proposed receiver.展开更多
Wavelength conversion based on four-wave mixing （FWM） has been demonstrated using a 40-m dispersion flattened highly nonlinear photonic crystal fiber （HNL-PCF）. A conversion efficiency of -26 dB for a pump power o...Wavelength conversion based on four-wave mixing （FWM） has been demonstrated using a 40-m dispersion flattened highly nonlinear photonic crystal fiber （HNL-PCF）. A conversion efficiency of -26 dB for a pump power of 19.5 dBm and a conversion bandwidth of 28 nm have been obtained, which are limited by the continuous wave （CW） laser wavelength range and tunability of optical band pass filters （OBPFs）.展开更多
Two-dimensional metallic photonic crystal slabs with square lattice are proposed to be used for the design of waveguide bandpass filters operating in millimeter to terahertz region. Filter characteristics are studied ...Two-dimensional metallic photonic crystal slabs with square lattice are proposed to be used for the design of waveguide bandpass filters operating in millimeter to terahertz region. Filter characteristics are studied when rod radii and lattice constants are changed. Based on the frequency scaling technique, a series of higher frequency filters has been designed. By using laser drilling and welding processing techniques, a compact waveguide filter embedded in an EIA-WR10 waveguide with central frequency 145.5 GHz and 3-dB bandwidth of 5.26 GHz is fabricated and measured. The measurement data agree well with the simulation prediction.展开更多
The application of frequency selection surfaces(FSSs)is limited by large area,narrow bandwidth,low stopband inhibition and large ripple in the passband.A method for designing high-order wide band miniaturized-element ...The application of frequency selection surfaces(FSSs)is limited by large area,narrow bandwidth,low stopband inhibition and large ripple in the passband.A method for designing high-order wide band miniaturized-element frequency selective surface(MEFSS)with capacitance loading is introduced.The proposed structure is composed of multiply sub-wavelength interdigital capacitance layer,sub-wavelength inductive wire grids separated by dielectric substrates.A simple equivalent circuit model,composed of short transmission lines coupled together with shunt inductors and capacitors,is presented for this structure.Using the equivalent circuit model and electromagnetic(EM)model,an analytical synthesis procedure is developed that can be used to synthesize the MEFSS from its desired system-level performance indicators such as the center frequency of operation,bandwidth and stopband inhibition.Using this synthesis procedure,a prototype of the proposed MEFSS with a third-order bandpass response,center frequency of 2.75 GHz,fractional bandwidth of 8%is designed,fabricated,and measured.The measurement results confirm the theoretical predictions and the design procedure of the structure and demonstrate that the proposed MEFSS has a stable frequency response with respect to the angle of incidence of the EM wave in the±30°range incidence,and the in-band return loss is greater than 18 dB,and the rejection in the stopband is greater than 25 dB at the frequency of 3.2 GHz.展开更多
Wind loads have instantaneity and turbulence characteristics that will lead to pointing errors in antenna structures,and these errors cannot be ignored in high-frequency observations.Using the Tianma 65 m radio telesc...Wind loads have instantaneity and turbulence characteristics that will lead to pointing errors in antenna structures,and these errors cannot be ignored in high-frequency observations.Using the Tianma 65 m radio telescope(TMRT)as an example object,the pointing errors caused by wind loads are investigated using an accelerometer system.First,the resonant frequency range of the antenna structure is used for reference to acquire useful signals through the bandpass filtering method.Then,the direct current(DC)component of these signals is filtered out using the fast discrete Fourier transform method,and the baseline of the acceleration is corrected using the least-squares method.Finally,the acceleration integral is solved approximately using the discrete trapezoidal area method,and the structural vibration displacement of the antenna is determined using a double integral of acceleration.The pointing errors are then obtained based on the displacement relationship between the primary and subreflector surfaces.When the wind speed is 3.2 m/s,the antenna pitch angle is 61.7°and the wind direction angle is 80°,the generated pitch pointing error is 3.05'',and the azimuth pointing error is 1.14''.These results are consistent with those obtained via inclinometer measurements,thus validating the signal processing method and the pointing error calculation method proposed in this paper.The research methods and data analysis results reported here provide a basis for further wind-induced pointing error correction studies.展开更多
With the diversified development of big data,detection and precision guidance technologies,electromagnetic(EM)functional materials and devices serving multiple spectrums have become a hot topic.Exploring the multispec...With the diversified development of big data,detection and precision guidance technologies,electromagnetic(EM)functional materials and devices serving multiple spectrums have become a hot topic.Exploring the multispectral response of materials is a challenging and meaningful scientific question.In this study,MXene/TiO_(2)hybrids with tunable conduction loss and polarization relaxation are fabricated by in situ atomic reconstruction engineering.More importantly,MXene/TiO_(2)hybrids exhibit adjustable spectral responses in the GHz,infrared and visible spectrums,and several EM devices are constructed based on this.An antenna array provides excellent EM energy harvesting in multiple microwave bands,with|S11|up to−63.2 dB,and can be tuned by the degree of bending.An ultra-wideband bandpass filter realizes a passband of about 5.4 GHz and effectively suppresses the transmission of EM signals in the stopband.An infrared stealth device has an emissivity of less than 0.2 in the infrared spectrum at wavelengths of 6-14μm.This work can provide new inspiration for the design and development of multifunctional,multi-spectrum EM devices.展开更多
We propose and experimentally demonstrate a scheme of high-Q microwave photonic filter （MPF） using the techniques of self-phase modulation （SPM） spectrum broadening and third-order dispersion （TOD） compensation....We propose and experimentally demonstrate a scheme of high-Q microwave photonic filter （MPF） using the techniques of self-phase modulation （SPM） spectrum broadening and third-order dispersion （TOD） compensation. The optical pulses from a mode-locking laser are spectrally broadened by the SPM in the highly nonlinear fiber. A wideband optical frequency comb with 365 spectral lines within 10-dB power variation from the highest spectral power is obtained. By applying a cubic phase modulation via a waveshaper, the effect of TOD which broadens the MPF passband is eliminated. The final implemented MPF has a Q-value as high as 296 and a tuning range of 700 MHz.展开更多
A phase-shift fiber Bragg grating (FBG) with sampling is proposed to generate a multi-channel bandpass filter in the background of multi-channel stopbands.The sampled moiré fiber gratings are analyzed by Fourier ...A phase-shift fiber Bragg grating (FBG) with sampling is proposed to generate a multi-channel bandpass filter in the background of multi-channel stopbands.The sampled moiré fiber gratings are analyzed by Fourier transform theory first,and then simulation and experiment are performed,the results show that transmission peaks are opened in every reflective channel,the spectrum shape of every channel is identical.It can be used to fabricate multi-wavelength distributed feedback (DFB) fiber laser.展开更多
We propose a novel and simple all-optical 160-Gb/s orthogonal frequency division multiplexing（OFDM） symbol generator which is based on discrete triangle waveform driving-LiNbO_3 modulators to realize large-range lin...We propose a novel and simple all-optical 160-Gb/s orthogonal frequency division multiplexing（OFDM） symbol generator which is based on discrete triangle waveform driving-LiNbO_3 modulators to realize large-range linear optical shift.The entire system needs 64 discrete modulators：at the transmitter,a 2.5-Gb/s optical duobinary（ODB） modulator for data modulation and a 2.5-Gb/s triangle waveform driving-LiNbO_3 phase modulator for phase shift to generate each subcarrier;and at the receiver,a 2.5-GHz optical band pass filter（OBPF） using Faraday anomalous dispersion optical effect to separate them.Excellent bit error rate（BER） is observed after 1060 km of transmission without any dispersion compensation.展开更多
In this paper,a 5G wideband power amplifier(PA)with bandpass filtering response is synthesized using a bandwidth-extended bandpass filter as the matching network(MN).In this structure,the bandwidth(θ_(C))is defined a...In this paper,a 5G wideband power amplifier(PA)with bandpass filtering response is synthesized using a bandwidth-extended bandpass filter as the matching network(MN).In this structure,the bandwidth(θ_(C))is defined as a variable in the closedform equations provided by the microstrip bandpass filter.It can be extended over a wide range only by changing the characteristic impedances of the structure.Different from the other wideband MNs,the extension of bandwidth does not increase the complexity of the structure(order n is fixed).In addition,based on the bandwidth-extended structure,the wideband design of bandpass filtering PA is not limited to the fixed bandwidth of the specific filter structure.The theoretical analysis of the MN and the design flow of the PA are provided in this design.The fabricated bandpass filtering PA can support almost one-octave bandwidth(2-3.8 GHz),covering the two 5G bands(n41 and n78).The drain efficiency of 47%-60%and output power higher than 40 dBm are measured.Good frequency selectivity in S-parameter measurements can be observed.展开更多
Spectral bandpass filters serving as crucial signal processing components are widely applied in various electromagnetic/optical systems.However,the filtering of reflection signal always faces problems of notably accom...Spectral bandpass filters serving as crucial signal processing components are widely applied in various electromagnetic/optical systems.However,the filtering of reflection signal always faces problems of notably accompanied transmission or strict angular limit.Here,we propose novel transmissionless metagratings for specular-reflection bandpass filtering under wide oblique incidence angles.The metagratings are composed of metallic groove gratings and high-refractive-index dielectric particles,which of them respectively provide continuum of localized cavity mode and discrete magnetic dipole resonance under oblique transverse magnetic waves,and produce broadband and narrowband anomalous reflection.Their destructive interference gives rise to a Fano-type narrow bandpass filter in the specular reflection.By integrating CaTiO3ceramic particles with metallic groove gratings,we experimentally demonstrate a single-bandpass metagrating filter at microwave frequency which exhibits a low insertion loss and narrow bandwidth under wide-angle oblique incidence,and agrees with simulations well.Furthermore,by arranging two different sized CaTiO3ceramic particles or changing the temperature,the metagrating filter is endowed with dual-bandpass or thermally tunable feature,respectively.Finally,the design is extended to terahertz frequencies by improving the structure to a double-groove configuration.The proposed composite metagratings with novel bandpass filtering function and angular insensitivity not only enrich the category of spatial filter but have promising applications in microwave communication systems and optical devices.展开更多
A scheme for all-fiber clock enhancement of non-return-to-zero (NRZ) data based on cross-phase modulation (XPM) effect in nonlinear fibers is proposed and demonstrated in simulation. The simulation results indicate th...A scheme for all-fiber clock enhancement of non-return-to-zero (NRZ) data based on cross-phase modulation (XPM) effect in nonlinear fibers is proposed and demonstrated in simulation. The simulation results indicate that the clock-to-data ratio of NRZ signals at 64 Gb/s can be increased to 22.94 dB by using this scheme, and the pattern effect in clock enhanced signals is very weak. The ability of high speed operation up to 140 Gb/s of this scheme is also proved in our simulation.展开更多
Compared with binary diffractive super-resolving elements, programmable super-resolution pupil filters permit the analysis of various filter designs and allow the filters to be changed rapidly to modify the response o...Compared with binary diffractive super-resolving elements, programmable super-resolution pupil filters permit the analysis of various filter designs and allow the filters to be changed rapidly to modify the response of an optical system. In this Letter, a deformable mirror is employed as a programmable super-resolution pupil phase filter. Continuous phase-only filters based on the Zernike polynomial series are designed by the genetic algorithm and fitted through closed-loop adaptive optics with a piezoelectric deformable mirror. Experimental superresolution results are in agreement with the theoretical predictions. This method has no polarization light requirement and is convenient for application.展开更多
基金supported by the Natural Science Foundation of CQ CSTC(CSTC2010DD2412)Chongqing Municipal Science and Technology Commission of Natural Science Foundation Project(KJ100512)the Research Fund Project of Chongqing University of Posts and Telecommunications(A2011-51)
文摘A novel, compact, and highly selective ultra-wideband （UWB） bandpass filter with a narrow notched band is presented. Apart from having a basic structure of a slotline multiple-mode resonator （MMR） and microstrip feed lines, this novel design introduces a cross-coupling between the input and output feed lines to enhance the filter selectivity. The design strictly follows the theory and verified by electromagnetic （EM） simulation and experiments. In addition, the narrow notched band is introduced by embedding a pair of split ring resonators （SRR） in order to reject any undesired existing radio signals that may interfere with the Federal Communications Commission （FCC）-defined UWB band. By changing the structural parameters of SRR, it can be easily tuned to any desired frequency. This filter can be integrated in UWB communication systems and efficiently improve the interference immunity from undesired signals such as wireless local area network （WLAN）.
基金Supported by the Foundation of Aeronautics Science (No. 03F52042)
文摘The developments of the high speed analog to digital converters （ADC） and advanced digital signal processors （DSP） make the smart antenna with digital beamforming （DBF） a reality. In conventional M-elements array antenna system, each element has its own receiving channel and ADCs. In this paper, a novel smart antenna receiver with digital beamforming is proposed. The essential idea is to realize the digital beamforming receiver based on bandpass sampling of multiple distinct intermediate frequency （IF） signals. The proposed system reduces receiver hardware from M IF channels and 2M ADCs to one IF channel and one ADC using a heterodyne radio frequency （RF） circuitry and a multiple bandpass sampling digital receiver. In this scheme, the sampling rate of the ADC is much higher than the summation of the M times of the signal bandwidth. The local oscillator produces different local frequency for each RF channel The receiver architecture is presented in detail, and the simulation of bandpass sampling of multiple signals and digital down conversion to baseband is given. The principle analysis and simulation results indicate the effectiveness of the new proposed receiver.
基金the National Natural Science Foundation of China(No.60678043)Beijing Education Committee Common Build Foundation(No.XK100130637).
文摘Wavelength conversion based on four-wave mixing （FWM） has been demonstrated using a 40-m dispersion flattened highly nonlinear photonic crystal fiber （HNL-PCF）. A conversion efficiency of -26 dB for a pump power of 19.5 dBm and a conversion bandwidth of 28 nm have been obtained, which are limited by the continuous wave （CW） laser wavelength range and tunability of optical band pass filters （OBPFs）.
基金supported by the National Natural Science Foundation of China(No.11075032)the National High Technology Research and Development Program of China(No.2011AA010204)
文摘Two-dimensional metallic photonic crystal slabs with square lattice are proposed to be used for the design of waveguide bandpass filters operating in millimeter to terahertz region. Filter characteristics are studied when rod radii and lattice constants are changed. Based on the frequency scaling technique, a series of higher frequency filters has been designed. By using laser drilling and welding processing techniques, a compact waveguide filter embedded in an EIA-WR10 waveguide with central frequency 145.5 GHz and 3-dB bandwidth of 5.26 GHz is fabricated and measured. The measurement data agree well with the simulation prediction.
基金This work was financially supported by the 2023 Shaanxi College Students Innovation and Entrepreneur-Ship Training Program Project(S202311664066)supported by the Xi'an Science and Technology Association Youth Talent Lifting Program Project(959202313012).
文摘The application of frequency selection surfaces(FSSs)is limited by large area,narrow bandwidth,low stopband inhibition and large ripple in the passband.A method for designing high-order wide band miniaturized-element frequency selective surface(MEFSS)with capacitance loading is introduced.The proposed structure is composed of multiply sub-wavelength interdigital capacitance layer,sub-wavelength inductive wire grids separated by dielectric substrates.A simple equivalent circuit model,composed of short transmission lines coupled together with shunt inductors and capacitors,is presented for this structure.Using the equivalent circuit model and electromagnetic(EM)model,an analytical synthesis procedure is developed that can be used to synthesize the MEFSS from its desired system-level performance indicators such as the center frequency of operation,bandwidth and stopband inhibition.Using this synthesis procedure,a prototype of the proposed MEFSS with a third-order bandpass response,center frequency of 2.75 GHz,fractional bandwidth of 8%is designed,fabricated,and measured.The measurement results confirm the theoretical predictions and the design procedure of the structure and demonstrate that the proposed MEFSS has a stable frequency response with respect to the angle of incidence of the EM wave in the±30°range incidence,and the in-band return loss is greater than 18 dB,and the rejection in the stopband is greater than 25 dB at the frequency of 3.2 GHz.
基金provided by the TMRT operators during the observations.This work was supported by the National Key Basic Research and Development Program(2018YFA0404702)the National Natural Science Foundation of China(U1631114,11873015,and 11203062)+2 种基金the CAS Key Technology Talent Program,the Knowledge Innovation Program of CAS(KJCX1-YW-18)the Scientific Program of Shanghai Municipality(08DZ1160100)the Key Laboratory for Radio Astronomy of CAS,the Key Laboratory of Planetary Sciences of CAS,and the CAS Scholarship.
文摘Wind loads have instantaneity and turbulence characteristics that will lead to pointing errors in antenna structures,and these errors cannot be ignored in high-frequency observations.Using the Tianma 65 m radio telescope(TMRT)as an example object,the pointing errors caused by wind loads are investigated using an accelerometer system.First,the resonant frequency range of the antenna structure is used for reference to acquire useful signals through the bandpass filtering method.Then,the direct current(DC)component of these signals is filtered out using the fast discrete Fourier transform method,and the baseline of the acceleration is corrected using the least-squares method.Finally,the acceleration integral is solved approximately using the discrete trapezoidal area method,and the structural vibration displacement of the antenna is determined using a double integral of acceleration.The pointing errors are then obtained based on the displacement relationship between the primary and subreflector surfaces.When the wind speed is 3.2 m/s,the antenna pitch angle is 61.7°and the wind direction angle is 80°,the generated pitch pointing error is 3.05'',and the azimuth pointing error is 1.14''.These results are consistent with those obtained via inclinometer measurements,thus validating the signal processing method and the pointing error calculation method proposed in this paper.The research methods and data analysis results reported here provide a basis for further wind-induced pointing error correction studies.
基金supported by the National Natural Science Foundation of China(Grant Nos.52373280,52177014,51977009,52273257).
文摘With the diversified development of big data,detection and precision guidance technologies,electromagnetic(EM)functional materials and devices serving multiple spectrums have become a hot topic.Exploring the multispectral response of materials is a challenging and meaningful scientific question.In this study,MXene/TiO_(2)hybrids with tunable conduction loss and polarization relaxation are fabricated by in situ atomic reconstruction engineering.More importantly,MXene/TiO_(2)hybrids exhibit adjustable spectral responses in the GHz,infrared and visible spectrums,and several EM devices are constructed based on this.An antenna array provides excellent EM energy harvesting in multiple microwave bands,with|S11|up to−63.2 dB,and can be tuned by the degree of bending.An ultra-wideband bandpass filter realizes a passband of about 5.4 GHz and effectively suppresses the transmission of EM signals in the stopband.An infrared stealth device has an emissivity of less than 0.2 in the infrared spectrum at wavelengths of 6-14μm.This work can provide new inspiration for the design and development of multifunctional,multi-spectrum EM devices.
基金the National Key Basic Research Program of China(Nos.2012CB315603 and 2012CB315604)the National Natural Science Foundation of China(Nos.61025004,61032005,and61321004).
文摘We propose and experimentally demonstrate a scheme of high-Q microwave photonic filter （MPF） using the techniques of self-phase modulation （SPM） spectrum broadening and third-order dispersion （TOD） compensation. The optical pulses from a mode-locking laser are spectrally broadened by the SPM in the highly nonlinear fiber. A wideband optical frequency comb with 365 spectral lines within 10-dB power variation from the highest spectral power is obtained. By applying a cubic phase modulation via a waveshaper, the effect of TOD which broadens the MPF passband is eliminated. The final implemented MPF has a Q-value as high as 296 and a tuning range of 700 MHz.
文摘A phase-shift fiber Bragg grating (FBG) with sampling is proposed to generate a multi-channel bandpass filter in the background of multi-channel stopbands.The sampled moiré fiber gratings are analyzed by Fourier transform theory first,and then simulation and experiment are performed,the results show that transmission peaks are opened in every reflective channel,the spectrum shape of every channel is identical.It can be used to fabricate multi-wavelength distributed feedback (DFB) fiber laser.
基金supported by the National"973"Program of China(Nos.2010CB328300 and 2010CB328303)the National Natural Science Foundation of China(No. 60772013)+1 种基金the National"863"Program of China(No. 2009AA03Z408)the Open Fund of Key Laboratory of Optical Communication and Lightwave Technologies Beijing University of Posts and Telecommunications, Ministry of Education,China.
文摘We propose a novel and simple all-optical 160-Gb/s orthogonal frequency division multiplexing（OFDM） symbol generator which is based on discrete triangle waveform driving-LiNbO_3 modulators to realize large-range linear optical shift.The entire system needs 64 discrete modulators：at the transmitter,a 2.5-Gb/s optical duobinary（ODB） modulator for data modulation and a 2.5-Gb/s triangle waveform driving-LiNbO_3 phase modulator for phase shift to generate each subcarrier;and at the receiver,a 2.5-GHz optical band pass filter（OBPF） using Faraday anomalous dispersion optical effect to separate them.Excellent bit error rate（BER） is observed after 1060 km of transmission without any dispersion compensation.
基金supported by National Natural Science Foundations of China (No.61971052 and No.U20A20203)Key Research and Development Project of Guangdong Province (2020B0101080001)
文摘In this paper,a 5G wideband power amplifier(PA)with bandpass filtering response is synthesized using a bandwidth-extended bandpass filter as the matching network(MN).In this structure,the bandwidth(θ_(C))is defined as a variable in the closedform equations provided by the microstrip bandpass filter.It can be extended over a wide range only by changing the characteristic impedances of the structure.Different from the other wideband MNs,the extension of bandwidth does not increase the complexity of the structure(order n is fixed).In addition,based on the bandwidth-extended structure,the wideband design of bandpass filtering PA is not limited to the fixed bandwidth of the specific filter structure.The theoretical analysis of the MN and the design flow of the PA are provided in this design.The fabricated bandpass filtering PA can support almost one-octave bandwidth(2-3.8 GHz),covering the two 5G bands(n41 and n78).The drain efficiency of 47%-60%and output power higher than 40 dBm are measured.Good frequency selectivity in S-parameter measurements can be observed.
基金supported by the National Natural Science Foundation of China(Grant No.51902175)the Fundamental Research Funds for the Central Universities(Grant No.06500174)the National Postdoctoral Program for Innovative Talents(Grant No.BX20180153)。
文摘Spectral bandpass filters serving as crucial signal processing components are widely applied in various electromagnetic/optical systems.However,the filtering of reflection signal always faces problems of notably accompanied transmission or strict angular limit.Here,we propose novel transmissionless metagratings for specular-reflection bandpass filtering under wide oblique incidence angles.The metagratings are composed of metallic groove gratings and high-refractive-index dielectric particles,which of them respectively provide continuum of localized cavity mode and discrete magnetic dipole resonance under oblique transverse magnetic waves,and produce broadband and narrowband anomalous reflection.Their destructive interference gives rise to a Fano-type narrow bandpass filter in the specular reflection.By integrating CaTiO3ceramic particles with metallic groove gratings,we experimentally demonstrate a single-bandpass metagrating filter at microwave frequency which exhibits a low insertion loss and narrow bandwidth under wide-angle oblique incidence,and agrees with simulations well.Furthermore,by arranging two different sized CaTiO3ceramic particles or changing the temperature,the metagrating filter is endowed with dual-bandpass or thermally tunable feature,respectively.Finally,the design is extended to terahertz frequencies by improving the structure to a double-groove configuration.The proposed composite metagratings with novel bandpass filtering function and angular insensitivity not only enrich the category of spatial filter but have promising applications in microwave communication systems and optical devices.
文摘A scheme for all-fiber clock enhancement of non-return-to-zero (NRZ) data based on cross-phase modulation (XPM) effect in nonlinear fibers is proposed and demonstrated in simulation. The simulation results indicate that the clock-to-data ratio of NRZ signals at 64 Gb/s can be increased to 22.94 dB by using this scheme, and the pattern effect in clock enhanced signals is very weak. The ability of high speed operation up to 140 Gb/s of this scheme is also proved in our simulation.
基金supported by the National Natural Science Foundation of China (No.61378064)the National High Technology Research and Development Program of China (No.2015AA020510)
文摘Compared with binary diffractive super-resolving elements, programmable super-resolution pupil filters permit the analysis of various filter designs and allow the filters to be changed rapidly to modify the response of an optical system. In this Letter, a deformable mirror is employed as a programmable super-resolution pupil phase filter. Continuous phase-only filters based on the Zernike polynomial series are designed by the genetic algorithm and fitted through closed-loop adaptive optics with a piezoelectric deformable mirror. Experimental superresolution results are in agreement with the theoretical predictions. This method has no polarization light requirement and is convenient for application.
