Luquire et al. ' s impedance change model of a rectangular cross section probe coil above a structure with an arbitrary number of parallel layers was used to study the principle of measuring thicknesses of multi-l...Luquire et al. ' s impedance change model of a rectangular cross section probe coil above a structure with an arbitrary number of parallel layers was used to study the principle of measuring thicknesses of multi-layered structures in terms of eddy current testing voltage measurements. An experimental system for multi-layered thickness measurement was developed and several fitting models to formulate the relationships between detected impedance/voltage measurements and thickness are put forward using least square method. The determination of multi-layered thicknesses was investigated after inversing the voltage outputs of the detecting system. The best fitting and inversion models are presented.展开更多
Bound states in the continuum(BICs)have gained considerable attention for their ability to strengthen light-matter interactions,enabling applications in lasing,sensing,and imaging.These properties also show great prom...Bound states in the continuum(BICs)have gained considerable attention for their ability to strengthen light-matter interactions,enabling applications in lasing,sensing,and imaging.These properties also show great promise for intensifying free-electron radiation.Recently,researchers realized momentum-mismatch-driven quasi-BICs in compound grating waveguides.This category of quasi-BICs exhibits high Q factors over a broad frequency spectrum.In this paper,we explore the possibility of achieving multi-frequency terahertz Smith-Purcell radiation empowered by momentum-mismatch-driven quasi-BICs in silicon compound grating waveguides.By leveraging the low-loss properties of silicon in the terahertz range,quasi-BICs are achieved through guided-mode resonance,delivering exceptionally high Q factors over a broad frequency spectrum.The broadband nature of these quasi-BICs enables efficient energy extraction from electron beams across varying voltages,while their multimode characteristics support simultaneous interactions with multiple modes,further boosting radiation intensity.The findings demonstrate significant enhancement of free-electron radiation at multiple frequencies,addressing the limitations of narrowband methods and high-loss metallic systems.By integrating broadband performance with the advantages of low-loss dielectric platforms,this work advances the development of compact,tunable terahertz free-electron radiation sources and provides valuable insights into optimizing quasi-BIC systems for practical applications.展开更多
This paper presents a low power tunable active inductor and RF band pass filter suitable for multiband RF front end circuits. The active inductor circuit uses the PMOS cascode structure as the negative transconductor ...This paper presents a low power tunable active inductor and RF band pass filter suitable for multiband RF front end circuits. The active inductor circuit uses the PMOS cascode structure as the negative transconductor of a gyrator to reduce the noise voltage. Also, this structure provides possible negative resistance to reduce the inductor loss with wide inductive bandwidth and high resonance frequency. The RF band pass filter is realized using the proposed active inductor with suitable input and output buffer stages. The tuning of the center frequency for multiband operation is achieved through the controllable current source. The designed active inductor and RF band pass filter are simulated in 180 nm and 45 nm CMOS process using the Synopsys HSPICE simulation tool and their performances are compared. The parameters, such as resonance frequency, tuning capability, noise and power dissipation, are analyzed for these CMOS technologies and discussed. The design of a third order band pass filter using an active inductor is also presented.展开更多
Microwave chips are widely utilized in modern communication,national defense,and various technological domains.However,effective signal identification remains challenging due to complex multi-frequency microwave inter...Microwave chips are widely utilized in modern communication,national defense,and various technological domains.However,effective signal identification remains challenging due to complex multi-frequency microwave interference.To address this issue,we propose an advanced optical imaging framework based on nitrogen-vacancy(NV)center near-field microscopy.This framework enables the separation and imaging characterization of mixed multi-frequency microwave signals across a wide field of view(2000μm×1600μm,spatial resolution of 5μm)on chip surfaces.By leveraging the NV color center as a mixer,combined with a multi-frequency hybrid model and fast Fourier transform(FFT)analysis,we convert the invisible electromagnetic waves into visible optical information.Using a wide-field microscopy system equipped with a high-speed optical camera,our approach effectively enables the separation and imaging of mixed microwave signals across two complex scenarios.Comparative analysis with finite element simulation validates the accuracy of this approach.Experimental results reveal m Hz frequency resolution for GHz microwaves andμT-level signal intensity resolution,showcasing its superior capability for imaging mixed signals with multi-frequency.These findings provide critical technical support for microwave chip characterization,interference signal identification,and diagnostic testing,highlighting the broad applicability of this technique.展开更多
文摘Luquire et al. ' s impedance change model of a rectangular cross section probe coil above a structure with an arbitrary number of parallel layers was used to study the principle of measuring thicknesses of multi-layered structures in terms of eddy current testing voltage measurements. An experimental system for multi-layered thickness measurement was developed and several fitting models to formulate the relationships between detected impedance/voltage measurements and thickness are put forward using least square method. The determination of multi-layered thicknesses was investigated after inversing the voltage outputs of the detecting system. The best fitting and inversion models are presented.
基金National Natural Science Foundation of China(62271011,U21A20458)National Key R&D Program of China(2021YFA1600302)Beijing Science Foundation for Distinguished Young Scholars(JQ21011)。
文摘Bound states in the continuum(BICs)have gained considerable attention for their ability to strengthen light-matter interactions,enabling applications in lasing,sensing,and imaging.These properties also show great promise for intensifying free-electron radiation.Recently,researchers realized momentum-mismatch-driven quasi-BICs in compound grating waveguides.This category of quasi-BICs exhibits high Q factors over a broad frequency spectrum.In this paper,we explore the possibility of achieving multi-frequency terahertz Smith-Purcell radiation empowered by momentum-mismatch-driven quasi-BICs in silicon compound grating waveguides.By leveraging the low-loss properties of silicon in the terahertz range,quasi-BICs are achieved through guided-mode resonance,delivering exceptionally high Q factors over a broad frequency spectrum.The broadband nature of these quasi-BICs enables efficient energy extraction from electron beams across varying voltages,while their multimode characteristics support simultaneous interactions with multiple modes,further boosting radiation intensity.The findings demonstrate significant enhancement of free-electron radiation at multiple frequencies,addressing the limitations of narrowband methods and high-loss metallic systems.By integrating broadband performance with the advantages of low-loss dielectric platforms,this work advances the development of compact,tunable terahertz free-electron radiation sources and provides valuable insights into optimizing quasi-BIC systems for practical applications.
文摘This paper presents a low power tunable active inductor and RF band pass filter suitable for multiband RF front end circuits. The active inductor circuit uses the PMOS cascode structure as the negative transconductor of a gyrator to reduce the noise voltage. Also, this structure provides possible negative resistance to reduce the inductor loss with wide inductive bandwidth and high resonance frequency. The RF band pass filter is realized using the proposed active inductor with suitable input and output buffer stages. The tuning of the center frequency for multiband operation is achieved through the controllable current source. The designed active inductor and RF band pass filter are simulated in 180 nm and 45 nm CMOS process using the Synopsys HSPICE simulation tool and their performances are compared. The parameters, such as resonance frequency, tuning capability, noise and power dissipation, are analyzed for these CMOS technologies and discussed. The design of a third order band pass filter using an active inductor is also presented.
基金National Natural Science Foundation of China(52435011,51821003,62175219,62103385)。
文摘Microwave chips are widely utilized in modern communication,national defense,and various technological domains.However,effective signal identification remains challenging due to complex multi-frequency microwave interference.To address this issue,we propose an advanced optical imaging framework based on nitrogen-vacancy(NV)center near-field microscopy.This framework enables the separation and imaging characterization of mixed multi-frequency microwave signals across a wide field of view(2000μm×1600μm,spatial resolution of 5μm)on chip surfaces.By leveraging the NV color center as a mixer,combined with a multi-frequency hybrid model and fast Fourier transform(FFT)analysis,we convert the invisible electromagnetic waves into visible optical information.Using a wide-field microscopy system equipped with a high-speed optical camera,our approach effectively enables the separation and imaging of mixed microwave signals across two complex scenarios.Comparative analysis with finite element simulation validates the accuracy of this approach.Experimental results reveal m Hz frequency resolution for GHz microwaves andμT-level signal intensity resolution,showcasing its superior capability for imaging mixed signals with multi-frequency.These findings provide critical technical support for microwave chip characterization,interference signal identification,and diagnostic testing,highlighting the broad applicability of this technique.
