Qin Yali

Detection of Chirp Signal by Combination of Kurtosis Detection and Filtering in Fractional Fourier Domain

The chirp signal has been used widely in radar signals. As a useful signal processing technique, the fractional Fourier transform (FRFT) is a way to concentrate the energy of a chirp signal. Therefore, the FRFT presents a potentially effective technique for detection of chirp signals. Compared with the common Wigner-Vill distribution (WVD) algorithm, the FRFT is a linear operator, and will not be influenced by cross-terms even if multiple components exist. Moreover, to solve the problem whereby weak components of the signal are shadowed by the sidelobes of strong ones, a new method of combination of kurtosis detection and filtering in fractional Fourier domain is proposed. In this way strong components and weak ones can be detected iteratively. The effectiveness of this combined method has been tested through simulation.

Considerations of dopant-dependent bandgap narrowing for accurate device simulation in abrupt HBTs

Heavy doping of the base in HBTs brings about a bandgap narrowing (BGN) effect, which modifies the intrinsic carrier density and disturbs the band offset, and thus leads to the change of the currents. Based on a thermionic-field-diffusion model that is used to the analyze the performance of an abrupt HBT with a heavy-doped base, the conclusion is made that, although the BGN effect makes the currents obviously change due to the modification of the intrinsic carrier density, the band offsets disturbed by the BGN effect should also be taken into account in the analysis of the electrical characteristics of abrupt HBTs. In addition, the BGN effect changes the bias voltage for the onset of Kirk effects.

A novel upstream transmission system of OFDMA-PON based on RSOA

The upstream transmission system is more challenge for OFDMA-PON than its downlink system due to various ONUs in the different locations. A novel cost-effective OFDMA-PON uplink system based on RSOA is proposed in this paper, where the complex synchronous operation in the receiver of the OLT is avoided because the signal is processed with separate OFDM-processors and each matched to its corresponding ONU in the coherent reception at the OLT. In order to save the precious wavelength resources, each wavelength can be assigned to the utilization of two ONUs for the loopback uplink scheme.