A monopulse angle measurement method for polarization array radar is studied in this paper.The receiving signal model is established and then a monopulse angle measurement method based on virtual polarization matching...A monopulse angle measurement method for polarization array radar is studied in this paper.The receiving signal model is established and then a monopulse angle measurement method based on virtual polarization matching is proposed.To analyze the estimation performance,the Cramer-Rao Lower Bound(CRLB)of angle estimation is derived.Both theoretical analysis and simulation show that:firstly,the proposed method is superior to the traditional angle measurement methods based on the single polarization.Secondly,the performance of the new method is unrelated to the echo polarization.Thirdly,angle estimation of this method is asymptotically optimal.The results show that this method has great potential to be used in polarization array radar.展开更多
Hydrogen atom transfer(HAT)is an elementary mechanistic step in organic synthesis.The photoredox-catalyzed HAT has transformed organic synthesis by enabling the activation and subsequent cross-coupling of traditionall...Hydrogen atom transfer(HAT)is an elementary mechanistic step in organic synthesis.The photoredox-catalyzed HAT has transformed organic synthesis by enabling the activation and subsequent cross-coupling of traditionally inert yet ubiquitous C(sp^(3))-H bonds.展开更多
A high power continuous-wave single-frequency green fiber laser by second-harmonic generation of a Yb-doped fiber amplifier（YDFA）is developed.A linearly polarized single-mode fiber amplifier produces a 60 W infrared...A high power continuous-wave single-frequency green fiber laser by second-harmonic generation of a Yb-doped fiber amplifier（YDFA）is developed.A linearly polarized single-mode fiber amplifier produces a 60 W infrared laser at 1064 nm with a 103 W incident diode pump laser at 976 nm,corresponding to an optical conversion efficiency of 58%.An external bow-tie enhancement cavity incorporating a noncritically phase-matched lithium triborate crystal is employed for second-harmonic generation.A 33.2 W laser at 532 nm is obtained with a 45 W incident 1064 nm fundamental laser,corresponding to a conversion efficiency of 74%.展开更多
文摘A monopulse angle measurement method for polarization array radar is studied in this paper.The receiving signal model is established and then a monopulse angle measurement method based on virtual polarization matching is proposed.To analyze the estimation performance,the Cramer-Rao Lower Bound(CRLB)of angle estimation is derived.Both theoretical analysis and simulation show that:firstly,the proposed method is superior to the traditional angle measurement methods based on the single polarization.Secondly,the performance of the new method is unrelated to the echo polarization.Thirdly,angle estimation of this method is asymptotically optimal.The results show that this method has great potential to be used in polarization array radar.
基金We are grateful for financial support from the National Key R&D Program of China(2021YFA1502500)National Natural Science Foundation of China(22071203)Fundamental Research Funds for the Central Universities(20720210014).
文摘Hydrogen atom transfer(HAT)is an elementary mechanistic step in organic synthesis.The photoredox-catalyzed HAT has transformed organic synthesis by enabling the activation and subsequent cross-coupling of traditionally inert yet ubiquitous C(sp^(3))-H bonds.
文摘A high power continuous-wave single-frequency green fiber laser by second-harmonic generation of a Yb-doped fiber amplifier（YDFA）is developed.A linearly polarized single-mode fiber amplifier produces a 60 W infrared laser at 1064 nm with a 103 W incident diode pump laser at 976 nm,corresponding to an optical conversion efficiency of 58%.An external bow-tie enhancement cavity incorporating a noncritically phase-matched lithium triborate crystal is employed for second-harmonic generation.A 33.2 W laser at 532 nm is obtained with a 45 W incident 1064 nm fundamental laser,corresponding to a conversion efficiency of 74%.
