It is of particular interest to characterize the frequency spectrum of signal sources at submillimeter wavelengths.The heterodyne-mixing and direct-detection(Fourier transform spectrometer,FTS) methods were introduced to measure thefrequency spectrum of a submillimeter CW source(phase-locked and tunable from 460-520 GHz).A 500-GHz supercon-ductor-insulator-superconductor(SIS) tunnel junction was employed as a mixer for the former method but a direct detectorfor the latter.The measurement results are compared.

Optical properties and surface structures of InAs/GaAs selfassembled quantum dots(QDs) grown on 2 nm In~~(0.2)Ga~~(0.8)As and x ML GaAs combined strain-buffer layer were investigated systematically by photoluminescence(PL) and atomic force microscopy(AFM).The QD density increased from ~1.7×10~9 cm~(-2) to ~3.8×10~9 cm~(-2) due to the decreasing of the lattice mismatch.The combined layer was of benefit to increasing In incorporated into dots and the average height-to-width ratios,which resulted in the red-shift of the emission peaks.For the sample of x= 10 ML,the ground state transition is shifted to 1350 nm at room temperature.

According to the effective medium theory,the average field inside a cell suspension was calculated by Maxwell-Wagner effective equation.Then,based on the second-order model for calculating the transmembrane voltage(ΔΨ) on a single cell exposed to an alternating field,an analytical model was derived for the ΔΨ on the cells in suspensions exposed to millimeter waves.The model shows that the ΔΨ on a cell in suspensions depends on the frequency and amplitude of the external field,cell arrangement,and cell volume fraction.

Raman spectra of a batch of potassium lithium niobate(KLN) crystals with different compositions were investigated.The analysis results show the striking effects of Li content on these Raman peaks.For the KLN sample with small Li content,the three character peaks belong to ~(7-) O~~h octahedron show simple peak,and the weak peaks in the wavelength range of 100~400 cm~(-1) are regarded to relate to the Li ions in C lattice.With the raise of Li content in crystal,the peaks belong to ν~~2 mode are partly split, and the peak belongs to ν~~5 mode is broadened in the spectrum corresponding to scattering geometry X(ZY)Z.When the Li content approaches to chemical composition,the peaks belong to ν~~5 mode are split,the peaks belong to ν~~1 mode and ν~~2 mode are partly split too.

The cause of the target fade-out and the ghosting artifact in NN nonuniformity correction scheme for infrared focal plane array(IRFPA) was studied.It was found that ignoring target edge and updating correction coefficients blindly in the NN-NUC scheme were the cause of the problems.Based on this consideration,an edge-directed NN-NUC scheme(ED-NN-NUC) was proposed to eliminate the ghosting artifact and the target fade-out.The comparison experiment with simulated data and real IRFPA infrared data shows that our viewpoint is correct,and the proposed scheme is effective.

A novel left-handed microstrip transmission line(LH-TL) structure was presented.Based on this structure,feed lines with composite right/left-handed transmission line(CRLH-TL) structure for microstrip arrays were also presented.By controlling the lengths of LH-TL.and RH-TL parts in CRLH-TL, naught phase shifts of the transmission line can be obtained.As an application,the CRLH-TL has been used as feed line in series fed millimeter wave microstrip arrays.Numerical results show that,by means of the CRLH-TL,the insertion phase shifts at excited ports of microstrip elements can be eliminated.As a result,the inherent beam shifts disappear.

MMW Costas frequency-coded radar is a kind of high-range-resolution radar,and motion compensation is the key to realize high range resolution.A motion compensation method based on time domain was proposed,and the accuracy of estimating velocity was also analyzed.Simulations show that this method is feasible and fast.

In the millimeter Linear FMCW radar system,the echo Doppler signal quadratic modulated by the target acceleration will cause the Doppler spectrum aberration and reduce the detection performance and parameter estimation precision.In this study,an optimal model based on the Maximum Likelihood(ML) method and its fast algorithm for velocity and acceleration estimation fitted for Gaussian noise were presented.Furthermore,the CRB of the parameter estimation of LFM under normal gauss circumstance was also derives.It provides the real low bounds for variance of estimated parameter.

Thermoelectric cooler has dynamic thermoelectric performance under complex environment.A linear dynamic model of the thermoelectric cooler was derived by using small-signal linearization method.It shows that the dynamic model of the thermoelectric cooler has one zero and two poles.The dynamic model of the thermoelectric cooler is showed to vary with operating conditions.Based on average linear dynamic model of a thermoelectric cooler,a temperature control system was designed for the cold end temperature of the thermoelectric cooler by using fuzzy-PID algorithm and Pulse Width Modulator.The step response tests show that the controller has satisfying dynamic and static performance.In room temperature environment,the response time for cooling down 10℃ is around 70s and the steady error is very small.the cold-end temperature can be maintained at the setting value within 0.1℃.Experiment results also show that the setting temperature can be 23℃ below the environment temperature.And the setting value is smaller,the

The pre-launch calibration of the water vapor channel onboard FY-2B geostationary meteorological satellite was made in the Lab's vacuum container.The change of sensor's characteristics post-launch is normally monitored by the onboard blackbody.However,since the blackbody calibration path adopts different objective optic path,it is hard to make the in-orbit absolute calibration for the WV channel of the satellite.The pre-launch calibration of FY-2B's WV channel was introduced,and the calibration processing method with the quantized relation derived from in-orbit electronic calibration,as well as the inter-calibration for the channel 12 of HIRS/3 aboard NOAA-17 was also deseribed.

For the absorbing-scattering semitransparent coatings with smooth surface and diffuse opaque substrate,the propagation model of the incident spectrum was derived and the spectral radiative transfer was solved by Monte Carlo method.The effects of the optical thickness,medium scattering and substrate reflection on the bi-directional reflection of the coating surface were analyzed.The results show that the reflection of an absorbing-scattering semitransparent coating is obviously anisotropic even if the Fresnel reflection on surface is not taken into account,and its BRDF is quite different from that of an absorbing coating.

According to the theory of H~~∞ filter,an approach of small target motion prediction and tracking in infrared images was presented based on H~~∞filter technology.In order to reduce the rank of the model for speeding up the velocity of image process,the filter process was analysed along horizontal orientation and vertical orientation,that is,the filter was decomposed into two filters along x and y orientation.H~~∞filter is a filter technology based on the optimization of worst condition which doesn't require too much about the noise sources and it can be applied to target motion prediction and tracking in complex and clutter background.The experiments demonstrate that H~~∞ filter is more exact for IR small target motion prediction and resistible to the disturbance than Kalman filter in the system which has the uncertain or unknown noise sources.

In order to detect objects accurately,an image thresholding approach named two dimensions(2-D) maximum entropy was proposed to do infrared image segmentation.By using the 2-D histogram of image,the 2-D maximum entropy method not only considers the distribution of gray information,but also takes advantage of the spatial neighbor information.However,its great computation was often an obstacle in application.The threshold vector was obtained by using a new optimization algorithm,namely,the particle swarm optimization algorithm (PSO).The new way was proposed to realize the 2-D maximum entropy method instead of exhaustive search method.And it is 300~400 times faster than the traditional method.Through the example of segmenting the infrared image,the proposed method has been proved to be a fast method of segmenting infrared image.

A PLKF(pseudo-linear Kalman filter) was presented for tracking a moving target by using multi-stations of IRST systems.The initial value of the filter was attained from the pseudo-linear equations,which improves the tracking accuracy and speed of the filter.Results of the simulation of tracking a moving target by PLKF and EKF(extended Kalman filter) illustrate: for 3 or 4 stations,the tracking accuracy of PLKF is more advantage than that of EKF at the beginning of the tracking;for 6 stations,the PLKF and the EKF have the same tracking accuracy.

By using the compact density matrix approach and displacement harmonic variant and numerical calculation methods,the linear and nonlinear intersubband refractive index changes(RICs) in a semi-parabolic quantum well with applied electric field were investigated in detail.Numerical calculations on GaAs were performed for the dependence of RIC on the incident optical intensity,the frequency of confined potential of the semi-parabolic quantum well and the strength of applied electric field.Results reveal that the RICs in the semi-parabolic quantum well system sensitively depend on these factors.

Characteristics of atmosphere and emissivities are the major influencing factors in land surface temperature retrieval.Different split window expressions can result in different retrievals of land surface temperature.Among them,the split window algorithm with linear combination of two channels' radiance has the least atmospheric influence.Retrieved temperature errors are correlated with emissivities and downwelling atmospheric radiance,not correlated with transmittance and upwelling atmospheric radiance.Retrieved coefficients(a and b) of split window method(B(λ′,T~°~~s)=a·I(λ~~1)+b·I(λ~~2)+c) have not relations with upwelling atmospheric radiance,but have inverse ratio with transmittance of two channels,respectively.When the land surfaces for calibration have different emissivities,the retrieved coefficients a and b have relations with downwelling atmospheric radiance,however,if the land surfaces for calibration have the same emissivities,the retrieved coefficients a and b will bear no relation to downwelling at

The Primary design of a Ka-band fundamental wave TE~~(01) gyro-traveling wave tube(gyroTWT) amplifier was present.Employing a PIC code,gyroTWT was simulated numerically,and the details and the relations of parameters were presented.The results indicate that an over 450 kW output power and 50dB gain can be obtained from the amplifier by simulating under the condition of 100 kV voltage,20 A current,1.27 T magnetic field.The efficiency exceeds 22.5 percent and the bandwidth is about 5 percent.

The borophosphosilicate glass(BPSG) layers as the filling coatings to silica-based planar lightwave circuits were obtained by using plasma enhanced chemical vapor deposition with SiH~~4/N~~2O and PH~~3,B~~2H~~6.The influence of dopants on refractive index of BPSG layers was discussed and the methods related the refractive index of BPSG layers to PH~~3 and B~~2H~~6 gases flows were suggested.The annealing effects of BPSG layers were studied on its optical features and surface map at different annealing conditions.By using multiple deposition followed by annealing,the perfect BPSG layers,which are without void and gap and with fine smoothness,were fabricated.

A simple self-seeding scheme was demonstrated for tunable dual-wavelength optical short pulse generation with enhanced sidemode suppression ratio.The two wavelengths and their separation can be tuned in a flexible manner by adjusting two fiber Bragg gratings and an optical delay line.The sidemode suppression ratio of the output pulses achieved is close to or better than 30 dB over the wavelength-tuning range of 20.7 nm.The system is simple and robust and convenient for dual-wavelength tuning.

Automatic image thresholding segmentation based on two-dimensional Maximum Correlation Criterion(MCC) was proposed.On the base of two-dimensional histogram,this method maximizes the correlations associated with the distributions of the background and object classes to obtain the optimal threshold, and it has greater resistance capability to noise than one-dimensional MCC.At the same time,Genetic Algorithms(GA) was used in the establishment of the optimal threshold based on the two-dimensional MCC.The experimental results show that the proposed algorithm achieves a good segmentation quality and shorten the computational time.