Atmospheric aerosols are the primary contributors to environmental pollution.As such aerosols are micro-to nanosized particles invisible to the naked eye,it is necessary to utilize LiDAR technology for their detection...Atmospheric aerosols are the primary contributors to environmental pollution.As such aerosols are micro-to nanosized particles invisible to the naked eye,it is necessary to utilize LiDAR technology for their detection.The laser radar echo signal is vulnerable to background light and electronic thermal noise.While single-photon LiDAR can effectively reduce background light interference,electronic thermal noise remains a significant challenge,especially at long distances and in environments with a low signal-to-noise ratio(SNR).However,conventional denoising methods cannot achieve satisfactory results in this case.In this paper,a novel adaptive continuous threshold wavelet denoising algorithm is proposed to filter out the noise.The algorithm features an adaptive threshold and a continuous threshold function.The adaptive threshold is dynamically adjusted according to the wavelet decomposition level,and the continuous threshold function ensures continuity with lower constant error,thus optimizing the denoising process.Simulation results show that the proposed algorithm has excellent performance in improving SNR and reducing root mean square error(RMSE)compared with other algorithms.Experimental results show that denoising of an actual LiDAR echo signal results in a 4.37 dB improvement in SNR and a 39.5%reduction in RMSE.The proposed method significantly enhances the ability of single-photon LiDAR to detect weak signals.展开更多
The optically transparent antenna is becoming a very attractive proposition for various applications, such as wearable devices and vehicle radars. The fabrication of transparent flexible/conformal antennas is a long-l...The optically transparent antenna is becoming a very attractive proposition for various applications, such as wearable devices and vehicle radars. The fabrication of transparent flexible/conformal antennas is a long-lasting interest in academia and industry.However, the preparation of radio-frequency radiators with excellent conductivity and optical transmittance is still quite challenging. Herein, we introduce a facile approach to directly fabricate optically transparent flexible and conformal coplanar waveguide-fed antennas using programmable electrohydrodynamic lithography. Metallic meshes with transmittance above 90%have been successfully created based on the conformal electrohydrodynamic printing of high-viscosity photoresist masks, and the corresponding sheet resistance can be tuned down to ~2 Ω/□. Then, the geometrical structure of the proposed transparent antenna has been systematically optimized because of the basic radio frequency components, including the radiator, feeder line,ground plane, and size of metallic meshes. Optically transparent flexible and conformal antennas are finally obtained, presenting an optical transmittance of 92% and 55%, respectively. The simulated and measured results demonstrate that the transparent antennas with a good optoelectronic performance indeed exhibit a nice electromagnetic behavior. We believe that this newly developed conformal electrohydrodynamic lithography method can be utilized to fabricate a variety of other transparent electronic devices, such as transparent electromagnetic shielding meshes on aircraft canopies, in the future.展开更多
基金funded by the National Key R&D Program of China(Grant No.2022YFC3300705)the National Natural Science Foundation of China(Grant Nos.62203056,12202048,and 62201056).
文摘Atmospheric aerosols are the primary contributors to environmental pollution.As such aerosols are micro-to nanosized particles invisible to the naked eye,it is necessary to utilize LiDAR technology for their detection.The laser radar echo signal is vulnerable to background light and electronic thermal noise.While single-photon LiDAR can effectively reduce background light interference,electronic thermal noise remains a significant challenge,especially at long distances and in environments with a low signal-to-noise ratio(SNR).However,conventional denoising methods cannot achieve satisfactory results in this case.In this paper,a novel adaptive continuous threshold wavelet denoising algorithm is proposed to filter out the noise.The algorithm features an adaptive threshold and a continuous threshold function.The adaptive threshold is dynamically adjusted according to the wavelet decomposition level,and the continuous threshold function ensures continuity with lower constant error,thus optimizing the denoising process.Simulation results show that the proposed algorithm has excellent performance in improving SNR and reducing root mean square error(RMSE)compared with other algorithms.Experimental results show that denoising of an actual LiDAR echo signal results in a 4.37 dB improvement in SNR and a 39.5%reduction in RMSE.The proposed method significantly enhances the ability of single-photon LiDAR to detect weak signals.
基金supported by the National Key Research and Development Program of China (Grant No. 2021YFB3200703)the National Natural Science Foundation of China (Grant Nos. 52175537, 51975235, and52188102)。
文摘The optically transparent antenna is becoming a very attractive proposition for various applications, such as wearable devices and vehicle radars. The fabrication of transparent flexible/conformal antennas is a long-lasting interest in academia and industry.However, the preparation of radio-frequency radiators with excellent conductivity and optical transmittance is still quite challenging. Herein, we introduce a facile approach to directly fabricate optically transparent flexible and conformal coplanar waveguide-fed antennas using programmable electrohydrodynamic lithography. Metallic meshes with transmittance above 90%have been successfully created based on the conformal electrohydrodynamic printing of high-viscosity photoresist masks, and the corresponding sheet resistance can be tuned down to ~2 Ω/□. Then, the geometrical structure of the proposed transparent antenna has been systematically optimized because of the basic radio frequency components, including the radiator, feeder line,ground plane, and size of metallic meshes. Optically transparent flexible and conformal antennas are finally obtained, presenting an optical transmittance of 92% and 55%, respectively. The simulated and measured results demonstrate that the transparent antennas with a good optoelectronic performance indeed exhibit a nice electromagnetic behavior. We believe that this newly developed conformal electrohydrodynamic lithography method can be utilized to fabricate a variety of other transparent electronic devices, such as transparent electromagnetic shielding meshes on aircraft canopies, in the future.
