Joint DOA and polarization estimation for unequal power sources based on reconstructed noise subspace

In most literature about joint direction of arrival（DOA） and polarization estimation, the case that sources possess different power levels is seldom discussed. However, this case exists widely in practical applications, especially in passive radar systems. In this paper, we propose a joint DOA and polarization estimation method for unequal power sources based on the reconstructed noise subspace. The invariance property of noise subspace（IPNS） to power of sources has been proved an effective method to estimate DOA of unequal power sources. We develop the IPNS method for joint DOA and polarization estimation based on a dual polarized array. Moreover, we propose an improved IPNS method based on the reconstructed noise subspace, which has higher resolution probability than the IPNS method. It is theoretically proved that the IPNS to power of sources is still valid when the eigenvalues of the noise subspace are changed artificially. Simulation results show that the resolution probability of the proposed method is enhanced compared with the methods based on the IPNS and the polarimetric multiple signal classification（MUSIC） method. Meanwhile, the proposed method has approximately the same estimation accuracy as the IPNS method for the weak source.

Low-Frequency Noise Properties of GaN Schottky Barriers Deposited on Intermediate Temperature Buffer Layers

Flicker noise and deep level transient spectroscopy were used to characterize defect properties of GaN films with different buffer structures. Results indicate improved properties with the use of intermediate temperature buffer layers due to the relaxation of residue strain in the films.

STATISTIC PROPERTIES OF NOISE FIELD OF MOVING SOURCE IN SHALLOW WATER AND ITS EFFECTS ON SIGNAL PROCESSING FOR THE NOISE RANGING SONAR

In this paper the properties of space- time correlation function of the noise field of moving source in layered statistic inhomogeneous medium are studied and the effects of random fluctuating boundary are considered as well.It has been shown, theoretically and experimentally, multi-path propergating effects cause the dispersion of the correlation function and fluctuations of the medium refraction index and the boundary cause the fluctuation of it.The effect of the movement of the noise source on the output of real- time correlator is equivalent to a low- pass filter added the drift of space- time correlation function.These properties of the correlation function cause grave degradation of the signal processing gain of noise ranging sonar system.The fluctuating and the distortion of conrrelation function made it difficult to realize the noise ranging.So in this paper, a method of space correlation ranging by a linear array of four points with short separation and long span and a technigue of dual- correlation signal processing are presented. By this, the influences of previously mentioned factors are greatly overcomed.Futhermore, for the long period and great delay fluctuation of the dual- correlation function output caused by internal wave, a method of limited memory Quasi- Kalman filtering is developed and the effective accurate ranging and tracing of noise ranging sonar are able to be tralized finally.

Graphene electrode with tunable charge transport in thin-film transistors

Graphene, a single atomic layer of sp2-hybridized carbon, has immense potential as a transparent conducting material in electronic applications owing to its superior properties, including optical transparency and high conductivity. Particularly, the tunable work function of graphene enables the integration of graphene electrodes with various electronic devices. To achieve high performance in graphene-based devices, effective charge transport between the graphene electrode and the semiconducting material needs to be optimized; this is closely related to the modulation of the Schottky barrier （SB）. In this study, we investigate the ~nable charge transport properties as a function of graphene doping in n-channel thin-film transistors （TFTs） in terms of the electrical characteristics and low-frequency noise （LFN） behaviors. Alkali metal carbonates tuned the work function of graphene, resulting in a dramatic decrease in the SB and an improvement of the carrier injection in n-channel TFTs. The electrical performance of the TFTs was evaluated by extraction of the field-effect mobilities and ratio of contact resistance to total resistance. Furthermore, the level of contact noise created by the barrier height fluctuation and relative contribution of channel noise and contact noise in the TFTs was investigated by LFN measurements to demonstrate the ~nable charge transport. Our findings therefore provide new insights into the tunable charge transport mechanism in graphene-based devices and reveal the immense potential of graphene as electrodes in high performance flexible and transparent displays.