Journal of Electronics (China)

Based on dual-frequencies dual-apertures spaceborne SAR (Synthetic Aperture Radar), a new SAR system with four receiving channels and two operation modes is presented in this paper. SAR imaging and Moving Target Indication (MTI) are studied in this system. High resolution imaging with wide swath is implemented by the Mode I, and MTI is completed by the Mode II. High azimuth resolution is achieved by the Displaced Phase Center (DPC) multibeam technique. And the Coherent Accumulation (CA) method, which combines dual channels data of different carrier frequency, is used to enhance the range resolution. For the data of different carrier frequency, the two aperture interferometric processing is executed to implement clutter cancellation, respectively. And the couple of clutter suppressed data are employed to implement Dual Carrier Frequency Conjugate Processing (DCFCP), then both slow and fast moving targets detection can be completed, followed by moving target imaging. The simulation results show the validity of the signal processing method of this new SAR system.

In this report the diffusion of Zn into Ge is investigated. The experiments are accomplished in an evacuated and sealed quartz ampoule using Zn as the diffusion source. The relation of theX j-t and $$C_5 - \frac{l}{T}$$ is given. The influence of the source temperature on the surface micrograph is investigated. It is found that using the two-temperature process a smooth surface layer can be obtained. The effect of the thickness of the SiO2 films on the mask ability for Zn is given. The leakage current can be reduced by evacuation annealing.

In this paper, starting from the theory of the base widening effect, it is demonstrated by a simple calculation that the critical current density of a collector followsT −1.3 law. And it is confirmed by experiment. We obtain from the temperature characteristics of the transistors. That the physical reason for the current gain fall-off at high current levels is the base widening effect.

This paper proposes a Real-Valued Time-Delay Recurrent Radial Basis Function (RVTDRRBF) model suitable for dynamic modeling of the strongly nonlinear behaviors of the Doherty Power Amplifiers (DPAs). This model has four Tapped Delay Lines (TDLs), which account for the memory effect of the DPA. The structure of the RVTDRRBF model is simpler than the traditional FeedForward Neural Networks (FFNNs) model. Weights and centers of the proposed model can be resolved by the Orthogonal Least Square (OLS) and Singular Value De-composition (SVD) algorithm. A three-carrier Wideband Code Division Multiple Access (WCDMA) signal is taken as the test signal. The simulation results in frequency-domain and time-domain for a DPA with 51 dBm output illustrate a good agreement between the RVTDRRBF model and measurement data. Moreover, comparing the Normalized Mean Square Error (NMSE) of RVTDRRBF model, memory polynomial model and RVTDRBF model, it can be noticed that the proposed RVTDRRBF model is more accurate than the RVTDRBF model and the memory polynomial model in modeling the strong dynamic nonlinearity of the DPAs.

The partial charge—simulation method is presented for calculating the capacitances of rectangular shielded lines with offset inner conductors. The capacitances calculated by using this method are in good agreement with those of other available methods. This method can improve the accuracy by increasing the term numberN of series.

After extending the forgery attacks to Nyberg-Rueppel’s signatures with message recovery, Atsuko Miyaji in 1997 proposed two suitable message recovery signatures, (F1) and (F2). In this paper, another new forgery attacks to (F1), (F2) and Nyberg-Rueppel’s signatures are presented.

This paper presents the system design and experimental results of a 35GHz coherent LFM-CW radar for use in near range two-dimensional imaging. Special techniques, including FM sweep linearization, range-segment processing, system background voltage suppression and dynamic range compression are also presented.