An improved compact ultra-wideband(UWB)microstrip antenna with metamaterials is proposed.The total size is slightly reduced and the measured impedance bandwidth operates from 3.84 to 22.77 GHz for a return loss of les...An improved compact ultra-wideband(UWB)microstrip antenna with metamaterials is proposed.The total size is slightly reduced and the measured impedance bandwidth operates from 3.84 to 22.77 GHz for a return loss of less than-10 dB.Compared with the original patch antenna,the bandwidth of this antenna is about six times broader.Moreover,the antenna has an average gain of 6.2 dB,which is 1.2 dB larger than the original one.Both strong radiation in the horizontal direction and practical characteristics are observed.Thus,this antenna would have some specific applications for UWB wireless communications in the future.展开更多
Colorless and transparent thin films of collodion are prepared on silicon wafers and K9 optical glass substrates by using spin-coating technique.The visible light transmittance,IR absorption spectra and optical consta...Colorless and transparent thin films of collodion are prepared on silicon wafers and K9 optical glass substrates by using spin-coating technique.The visible light transmittance,IR absorption spectra and optical constants of collodion thin film are measured by UV-3501Spectrophotometer,Fourier transform infrared spectrometer(FTIR)and spectroscopic ellipsometry.The measured results show that its average visible light transmittance is 91.9%,and its average infrared absorptivity is better than 0.69/um.In the visible light region,the refractive index of collodion thin film changes in the range of 1.5—1.53,which accords with normal dispersion.The collodion films are etched using oxygen gas plasma.The surface morphology and thickness of etched thin film are measured by the polarizing microscope and MP-100S thickness measurement system,respectively.The results show that the collodion thin film is etched out in the oxygen gas plasma.展开更多
The nearly single phase(R_(0.4)Pr_(0.6))_(0.5)Ca_(0.5)Ba_(2)Cu_(3)O_(7-δ)compounds(R=La,Pr,Nd,Sm,Eu,Gd and Y)with Tc about 100 K were prepared under high pressure and high temperature using the cubic anvil apparatus....The nearly single phase(R_(0.4)Pr_(0.6))_(0.5)Ca_(0.5)Ba_(2)Cu_(3)O_(7-δ)compounds(R=La,Pr,Nd,Sm,Eu,Gd and Y)with Tc about 100 K were prepared under high pressure and high temperature using the cubic anvil apparatus.The Tc is much higher than that of the traditional R-123 superconductors without doping Ca on the rare-earth site.For various rare earths with different ionic radius,the(R_(0.4)Pr_(0.6))_(0.5)Ca_(0.5)Ba_(2)Cu_(3)O_(7-δ)compounds have almost the same critical temperature.This is different from the result of the ion-size effect of rare-earth ions in R1-xPrxBa2Cu3O7-δcompounds.Our results show that Pr has the same properties as other rare earths in the 123-phase compounds due to the doping of Ca.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 61172115,60872029the High-Tech Research and Development Program of China(No 2008AA01Z206)the Aeronautics Foundation of China(No 20100180003).
文摘An improved compact ultra-wideband(UWB)microstrip antenna with metamaterials is proposed.The total size is slightly reduced and the measured impedance bandwidth operates from 3.84 to 22.77 GHz for a return loss of less than-10 dB.Compared with the original patch antenna,the bandwidth of this antenna is about six times broader.Moreover,the antenna has an average gain of 6.2 dB,which is 1.2 dB larger than the original one.Both strong radiation in the horizontal direction and practical characteristics are observed.Thus,this antenna would have some specific applications for UWB wireless communications in the future.
基金supported by Shaanxi Province Education Department Key Lab Project(2010JS003,1JS041)Chinese PLA General Armament Department Special Photoelectric Project(40405030104)Basic Research Project of National Defense(A0920110019)
文摘Colorless and transparent thin films of collodion are prepared on silicon wafers and K9 optical glass substrates by using spin-coating technique.The visible light transmittance,IR absorption spectra and optical constants of collodion thin film are measured by UV-3501Spectrophotometer,Fourier transform infrared spectrometer(FTIR)and spectroscopic ellipsometry.The measured results show that its average visible light transmittance is 91.9%,and its average infrared absorptivity is better than 0.69/um.In the visible light region,the refractive index of collodion thin film changes in the range of 1.5—1.53,which accords with normal dispersion.The collodion films are etched using oxygen gas plasma.The surface morphology and thickness of etched thin film are measured by the polarizing microscope and MP-100S thickness measurement system,respectively.The results show that the collodion thin film is etched out in the oxygen gas plasma.
基金Supported by the Ministry of Science and Technology of China(NKBRSF-G19990646).
文摘The nearly single phase(R_(0.4)Pr_(0.6))_(0.5)Ca_(0.5)Ba_(2)Cu_(3)O_(7-δ)compounds(R=La,Pr,Nd,Sm,Eu,Gd and Y)with Tc about 100 K were prepared under high pressure and high temperature using the cubic anvil apparatus.The Tc is much higher than that of the traditional R-123 superconductors without doping Ca on the rare-earth site.For various rare earths with different ionic radius,the(R_(0.4)Pr_(0.6))_(0.5)Ca_(0.5)Ba_(2)Cu_(3)O_(7-δ)compounds have almost the same critical temperature.This is different from the result of the ion-size effect of rare-earth ions in R1-xPrxBa2Cu3O7-δcompounds.Our results show that Pr has the same properties as other rare earths in the 123-phase compounds due to the doping of Ca.
