Editor in chief：Jun-Hao CHU
International standard number：ISSN 1001-9014
Unified domestic issue：CN 31-1577
Domestic postal code：4-335
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Abstract:A Schottky diode model for the mixer’s design is presented in this paper. According to the physical structure of the Schottky diode, a novel 3D electromagnetic (EM) model was built and analyzed by finite element method. A wide-band equivalent circuit up to 110 GHz was proposed taking the parasitic effects distributed in the diode into account. Based on the proposed equivalent circuit, a Ka-band balanced mixer was designed and optimized. The measured conversion loss is 7.5 dB to 10 dB from 32 GHz to 37 GHz, which agreed well with the simulated one.
Abstract:A new type of miniaturized microstrip diplexer is initially proposed based on the combined technology of fractal geometry and composite right/left handed transmission line (CRLH TL). The diplexer which is synthesized by combining two 3-port networks operating at a pair of different frequencies consists of lumped elements for the left handed (LH) part and Sierpinski-shaped microstrip lines (MLs) for the right handed (RH) part. Sierpinski curve allows miniaturized dimensions of the diplexer mainly attributing to its strong space-filling capability. CRLH TL enables dual-band design due to its unique hyperbolic-linear dispersion relation. For demonstration, three CRLH diplexers using Siepinski curves of different iteration orders are successfully designed. For verification, a CRLH diplexer sample by adopting a Sierpinski curve of second order was fabricated and measured. Consistent numerical and experimental results have confirmed the design. The fabricated diplexer operating at 0.9 and 1.8 GHz, respectively achieves good in-band performances and a maximal 76.3% size reduction compared to the conventional CRLH diplexer without fractal geometry.
Abstract:Dempster-Shafer evidence theory is an important tool in the fields of information fusion. However Dempster’s rule of combination cannot efficiently handle highly conflicting evidence combination for it can arouse counter-intuitive behaviors. To deal with such a problem, a novel weighted average evidence combination approach is proposed. Not only the distance of evidence but also the uncertainty measure is utilized to determine the weights of the bodies of evidence. Based on the weighted averaged BOE and Dempster’s rule of combination, the rational combination results can be obtained. The experimental results show that the method proposed can effectively handle conflicting evidence combination with better convergence.
Abstract:Different composition Hg1-xCdxTe crystals were grown by THM method. The optical properties of Hg1-xCdxTe crystals were investigated by using the Fourier transform infrared spectroscopy and transmission mode THz time-domain spectroscopy. The transmission was approached to zero in 0.2~1.5 THz frequency range as Cd composition of Hg1-xCdxTe crystal was lower than 0.279. A TA phonon model of Hg1-xCdxTe crystal was observed at 0.9 THz. Drude model was applied for simulation, which fitted well with the experimental results. The carrier densities of the Hg1-xCdxTe (x=0.388 and 0.326) were also characterized, which agreed with the experimental results.
Abstract:The growth of mid-wavelength infrared InAs/GaSb superlattice on GaSb substrates by molecular beam epitaxy (MBE)was studied. We optimized the substrate temperature and interface structures to obtain high quality material. The InAs/GaSb superlattice layers were characterized by Atomic Force Microscope(AFM), high resolution X-ray diffraction (XRD) and Fourier Transform Infrared Spectrum. We found the optimal substrate temperature for GaSb and superlattice is 485℃ and 450℃ respectively. We finally obtained highly lattice matched InAs/GaSb materials with 50% cut-off wavelength at 4.84 μm at 77 K.
Abstract:256*1 element front-illuminated InGaAs detector arrays were fabricated by using MBE-grown p-InP/n-InGaAs/n-InP double-heterostructure epitaxial materials and were wire-bonded to 128*1 element odd and even readout integrated circuits(ROICs) in order to form near-infrared 256?1 element InGaAs focal plane arrays(FPAs).The inoperable pixels exist in the near-infrared InGaAs FPAs. In this paper, the inoperable pixels were classified and analyzed by the optical microscope, SEM and electrical measurements. The results show that the lower resistance of photosensitive detectors at the bias voltage of 0V, the damage and false bonding, and the thinner profile of passivation film cause the inoperable pixels. The near-infrared 256*1 element InGaAs FPAs without inoperable pixels were obtained by improving the structure of photodetectors and the technics of passavition film.
Abstract:The variable-area HgCdTe/Si photovoltaic detector was investigated in this paper. By analyzing the relationship of dark current density (J) and the ratio of perimeter to area (p/A) under different reverse bias, it is indicated that the n-on-p type HgCdTe/Si photovoltaic detector has a significant surface leakage current under larger reverse bias. The minority carrier diffusion length at different temperature can be obtained by fitting the relationship between the product of zero-bias resistance and area (R0A) and p/A. It shows that the minority carrier diffusion length increases with the increase of temperature below 200 K, while the minority carrier diffusion length decreases with the increase of temperature above 200 K. The minority carrier lifetime of Hg-vacancy p-type HgCdTe on Si substrate was calculated from the minority diffusion length at different temperature. It was concluded that the lifetime of HgCdTe/Si minority carrier and its relationship with the temperature is the same as that of HgCdTe/CdZnTe material by comparing the minority carrier lifetime for these two kinds of materials.
Abstract:The distribution of electromagnetic field of 2D metal grating in the Long-Wavelength Quantum Well Infrared Photodetectors (LW-QWIPs) was studied by Finite Time Domain Method (FDTD). The result shows that making good use of the surface plasmons can remarkably improve the optical coupling efficiency in the LW-QWIPs. It also shows that using a metal grating with the ratio of the hole diameter to the grating period ranged from 0.8 to 0.9, optimal optical coupling can be achieved.
Abstract:Under the background of safety inspection, the key technologies of near-range passive millimeter wave focal plane array imaging are studied. The analysis of the system quasi-optics were carried out using fundamental Gaussian beam method combined with geometrical optics method. A multi-beam wide-angle scanning lens antenna was designed. A new dielectric rod antenna was devised, which is prone to be aligned in close arrays and provide good radiation to the lens. Miniaturized direct-detection radiometers were fabricated with high-sensitive in Ka-band . Experimental results of the 20-channel passive millimeter wave focal plane array imaging system are presented, which can be used to detect hidden objects on human bodies in near range indoors.
Abstract:Vector modulator can be employed in active phased array antenna(APAA)as a replacement of conventional digital phase shifter and attenuator for its capability of simultaneously realizing millimeter-wave direct carrier modulation on phase and amplitude.A millimeter wave vector modulator was realized with advanced GaAs pHEMT process, and onchip measurement has shown that -12~-40 dB amplitude modulation and 360? phase modulation was achieved. A Ka band 1?8 array experimental APAA composed of vector modulators was designed and proved to steer the beam scanning effectively. It was demonstrated that APAA based on vector modulation technique is feasible.
Abstract:A quasi-optical mode converter transforming TE6,2 mode to Gaussian-like mode is proposed to be employed in 94 GHz Gyrotron. A simulation code is written to model electromagnetic behaviour related to the converter based on the geometric optics and vector diffraction theory. Initial geometry parameters of the converter obtained according to the geometric optics are optimized to make the converter high efficient. Optimization gives a Gaussian mode content of more than 70% and an approximate transmission efficiency 85% for TE6,2 mode at 94 GHz.
Abstract:A model of solar irradiation on sensors onboard the FY-4 geostationary satellite in the case of solar intrusion was proposed. Solar radiation and the angle of incidence of the sun light on arbitrary surface of satellite can be calculated at any given time. Considering structure of baffle, the solar radiation, angle of incidence and the solar intrusion duration on scanning mirror of atmosphere vertical sounder on any day of the year can be given. The changes in one year are also given. The simulation results are similar with the measured data of GOES-8 (Geostationary Operational Environmental Satellites), and proved the accury of the simulation data.
Abstract:A numerical method, used for infrared radiative transmission and spectrum characteristics in participating medium with particles, was developed in this paper. Decomposition form of radiative transfer equation was deduced using spherical harmonics (PN-Approximation) method. Arbitrary order PN-Approximation method for solving infrared transmission in nonlinear anisotropic scattering medium was established. Based on the coupled radiation and conduction model, the calculation accuracy of high-order PN-Approximation method was verified through comparison with theoretical solution. Compassion shows that the arbitrary order PN-Approximation method established in this paper has a high accuracy, and it can easily treat the nonlinear anisotropic scattering phase functions with high order. Therefore, this method is very suitable for solving the problem of atmospheric infrared transmission. Atmospheric transmission characteristics with aerosols in the spectrum band ranging from 2μm to 5μm were calculated, and the influence of anisotropic scattering on atmospheric infrared transmission characteristics was studied. The results show that nonlinear anisotropic scattering can reduce both the atmospheric infrared spectral radiation intensity and the direction radiation intensity in strong absorptive bands.
Abstract:To overcome the deficiency of the robustness and real-time performance of traditional Kalman filter used for changeable target tracking, a new Kalman algorithm based on multi-scale feature extraction was proposed. After the feature points of a frame matched ones of the follow-up frame in the target area of image, the latter feature points centroid was took as the center from which the searching area was located so as to avoid traversing the whole image. So the stable signals and residuals of observations were provided to the Kalman filter equations to calculate accurately the posteriori state value. Experiment show that the multi-scale feature extraction technology introduced into the traditional Kalman filter equation as constrained conditions reduced filtering time and restrained divergence. Thus improved filter has good convergence.
Abstract:The cotton field infected by Verticillum wilt was investigated with both the multi-temporal TM images and the field survey simultaneously. A model of evaluating disease severity of the cotton was established by analyzing the correlation between spectral indices of TM image and severity level (SL) of the disease. The results indicated that with an increase of disease SLs, the values of spectral indices B2，B4，SATVI，OSAVI，MSAVI，TSAVI，SVNSWI，SNSWIa，SNSWIb，SVNI，DNSIa，DNSIb，NDSWIa，NDSWIb，RNSWIa，RNSWIb，DVNI，EVI，TVI，SAVI，DVI，NDVI，RVI and PVI declined slowly, B1，B3，B7 and RI increased gradually，NDGI increased at first and then decreased，while B5 exhibited a trend of decrease-increase with an increase of disease SLs. The SLs of disease were highly significantly positive correlated with the spectral indices values of B1，B3 and RI, highly significantly negative correlated with the spectral indice values of B4，OSAVI，MSAVI，TSAVI，SVNSWI，SNSWIa，SNSWIb，SVNI，DNSIa，DNSIb，NDSWIa，NDSWIb，RNSWIa，RNSWIb，DVNI，EVI，TVI，NDGI，SAVI，DVI，NDVI，RVI and PVI, significantly negative correlated with the spectral indice values of SATVI, and no significantly correlated with the spectral indice values of B2，B5 and B7. All of the eight spectral indices of TM image selected achieved significant correlation level. However, the linear models on the basis of DVI and DNSIb had the best estimating precision. This study demonstrated that it is feasible to estimate quantitatively the SL of cotton disease using the spectral indices of TM satellite image.
Abstract:To improve and simplify the NIR prediction model of the soluble solid content (SSC) of strawberry, backward interval partial least squares (BiPLS) and simulated annealing algorithm (SAA) were combined to select the efficient wavelengths. The strawberry spectra were divided into 21 intervals, among which 4 subsets, i.e. No.8, 13, 16 and 17 were selected by BiPLS. Then SAA was used to select variables in these informative regions, which were used for regression variables of MLR model. Finally, 7565 cm-1, 7706 cm-1, 8289 cm-1, 8489 cm-1, 8499 cm-1, 8724 cm-1 and 8807 cm-1 were used to build a MLR model. The MLR model performs well with root mean standard error of prediction (RMSEP) of 0.428 for SSC, which out performs models using PLS and BiPLS. This work proved that the BiPLS-SAA could determine optimal variables in NIR spectra and improve the accuracy of model.
Abstract:Goos-Hanchen shift at the surface of dielectric/anisotropic metamaterials/metal sandwich structures was investigated using the stationary-phase method. The analytical expressions of Goos-Hanchen shift are presented for both total reflection and partial reflection condition at the first interface. Moreover, the necessary conditions for the existence and the sign of Goos-Hanchen shift for the sandwich structure containing four kinds of metamaterials are discussed. The influences of the incident angle φ, the angle between the optical axis and the interface α and the material thickness d on Goos-Hanchen shift are studied by numerical calculation, which is agree well with the theoretical analysis. The investigation of GH shift in the structure containing of metamaterial will benefit the application of metamaterial in microwave and optics system.
Abstract:By adjusting the effective permittivity of the unit cell, a new method of constructing metamaterial band-pass frequency selective surface was proposed. The effective permittivity of continuous conducting wires is negative below the plasma frequency and thus a stop-band occurs. By combining the continuous conducting wires with cut wires, we realized a one-dimensional frequency selective surface. Both the theory analysis and simulation results demonstrated the facility and feasibility of the method. We also designed a wide-angle and polarization-independent frequency selective surface based on this method. Two samples were fabricated to validate the proposed method; the experiment results were fairly consistent with the simulation results. The proposed method eliminates the complicated calculation and excessive parameter optimization process. It paves a new way of designing frequency selective surfaces and is of important reference values for fabricating THz frequency selective surface as well as multi-band, tunable and miniaturized frequency selective surfaces.
Abstract:The impacts of on-chip metal connective lines, power grids, heat sink along with packaging, and dummy fills on a 2 mm-long, 30 μm-wide on-chip dipole antenna pair characteristics were investigated with qualitative analysis. On-chip antenna pair transmission gain has been improved by 9 dB at 20 GHz by employing a 0.35 mm thick diamond layer between silicon substrate and heat sink. Extensive simulations were performed by three-dimensional software HFSS to explore the interfering effects of these metal structures and placements on the transmission gain, phase, impedance and radiation pattern for integrated dipole antenna pair. According to the results of experiment and simulations, several empirical linear formulas for antenna pair gain and phase in interfering circumstances were obtained using numerical fit. A set of design rules for on-chip antenna was summarized for wireless interconnection.
Editor in chief：Jun-Hao CHU
International standard number：ISSN 1001-9014
Unified domestic issue：CN 31-1577
Domestic postal code：4-335